The US electrical system

[Homer J Simpson]

From Technology Connections   https://www.youtube.com/channel/UCy0tKL1T7wFoYcxCe0xjN6Q/videos


I liked the ending the best.

[Tony_G]

Thanks for sharing - I think he does a good job generally on these.

That said, as an Australian living in the US for 25 odd years, I still miss having a switch on the socket...

TonyG

[GlennSprigg]

Wow!!!  As an Aussie, I was blown away by this....  EVERYONE including outside of the U.S.
should look at this video!  I always wondered how/if in Australia we have a heater, or clothes
drier or air-cond, running on 240v and drawing 15A, then on 120v in the U.S. then it must be
drawing 30-Amps!!?? That never sounded right??

And yes, outlets without 'Switches'??  Why??

[joseph nicholas]

The US system in not just US.  Its North American, including Canada and Mexico.

[ciccio]

I'm shocked by the 200 Amps main breaker.  Here in Italy a standard family has a 3.0 to 5.5 kVA contract, which means a 16 or 20  Amp breaker.
The new meters (the ones that allow for remote reading) are programmed for a maximum load of 3.3 kVA continous (in my case, with a 3.0 kVA contract) and it will trip if you drain more than the max for a long time (minutes?).
A contract with larger limits has higher costs.
I understand the US electric supply does not discourage customers from using a lot of energy (as long as they pay the bills), but in Europe a limited amouut of current to the users side allows for better planning of the network.

[ciccio]

I always wondered how/if in Australia we have a heater, or clothes
drier or air-cond, running on 240v and drawing 15A, then on 120v in the U.S. then it must be
drawing 30-Amps!!?? That never sounded right??

And yes, outlets without 'Switches'??  Why??

If you are in the US and  you have an heater in a room, (e-g- an electric stove), it will be powered via a ridicolus plug at 120 V. The plug will overheat and a fire will start, in the standard US home built with wood.
When I was in Seattle 20 years ago, I noticed a lot of firetrucks passing by, a lot more than was usual in Europe.
My US friend said: it's normal, Christmas is coming...

[themadhippy]

a maximum load of 3.3 kVA

What? my kettle nearly uses that paltry limit  up,i'd be buggered if i wanted toast with me coffee.

[duak]

I have a 230 V kettle that I use in the workshop.  It's not instant but the waiting time is shorter - No low torque water heating for me!  It's a Tefal and uses the same 120 V base as its domestic brethren.  I imagine a 120 V unit would incinerate its heating element on 230 V.

[Bassman59]

I'm shocked by the 200 Amps main breaker.  Here in Italy a standard family has a 3.0 to 5.5 kVA contract, which means a 16 or 20  Amp breaker.

The main breaker is right after the meter, and its outputs feed the two phases (the vertical bus bars). Each individual circuit has its own breaker. It's common to see a 50 A 240 V circuit for air conditioning, a 30 A 240 circuit for an electric dryer (and yes, I'd prefer a gas dryer which is cheaper to run, but the cost of bringing the gas line to my laundry room exceeds any savings I'd get ever), and a bunch of 15 A or 20 A 120 V circuits for various household use. Yes, I just described my house.

It used to be common to pull the meter to kill power to the entire house, but now the meters are locked down by the utility. The main breaker is the only way to de-energize the panel so you can work on it.

The new meters (the ones that allow for remote reading) are programmed for a maximum load of 3.3 kVA continous (in my case, with a 3.0 kVA contract) and it will trip if you drain more than the max for a long time (minutes?).
A contract with larger limits has higher costs.
I understand the US electric supply does not discourage customers from using a lot of energy (as long as they pay the bills), but in Europe a limited amouut of current to the users side allows for better planning of the network.

The idea that the utility can control your total draw and cut you off if you exceed some limit is a complete non-starter here. And for the most part, that sort of micromanaging the grid isn't really necessary. We have "tiered" pricing as a means of discouraging excessive use, so that up to some amount of usage you pay one price per kHh, above that to the next level you pay a higher price, and above that you get fucked.

In extreme cases, like in the deep summer where air conditioning puts significant loads on the entire grid, if the utilities cannot generate or bring in the necessary power, they will institute rolling blackouts. Customers are told that power will be off for some time and to plan for that outage.

[Monkeh]

The idea that the utility can control your total draw and cut you off if you exceed some limit is a complete non-starter here.

So that's why you have no fuses. There I was thinking it was just old infrastructure you refuse to improve.

[joseph nicholas]

Here we go again.  In all of North America, the newest utility meters can turn off the power to your house without even going outside the main power station, its all done remotely.  If the cops want to get you off guard to invade your home, all they need to do is cut the power to your house and you will come outside to see what the fuck is happening.  Gotcha, without every getting their hands dirty.  It's your world, more ways to have your liberties die.

[rstofer]

I always wondered how/if in Australia we have a heater, or clothes
drier or air-cond, running on 240v and drawing 15A, then on 120v in the U.S. then it must be
drawing 30-Amps!!?? That never sounded right??

And yes, outlets without 'Switches'??  Why??

If you are in the US and  you have an heater in a room, (e-g- an electric stove), it will be powered via a ridicolus plug at 120 V. The plug will overheat and a fire will start, in the standard US home built with wood.
When I was in Seattle 20 years ago, I noticed a lot of firetrucks passing by, a lot more than was usual in Europe.
My US friend said: it's normal, Christmas is coming...

That is just wrong!  I can't even imagine an oven or stove top that isn't running on 240V.  A typical stove top might have 2 ea 3kW heaters and 2 ea 1kW heater for a total of 8kW, probably more.  This would take at least 33 Amps at 240V and the typical circuit is probably 50A.  Based on 80% usage of circuit breaker ratings, a 40A circuit would be too small so it's usually 50A.  The clothes dryer is probably 30A at 240V.  Well pump, pool filter, HVAC also run on 240V.  I'm not talking about window mounted AC units, I'm talking central air and perhaps a 3200 square foot house.

Throw in a 1200W microwave, a 5 kW air conditioner, maybe a few kW for an arc welder plus, of course, the automotive EV charger and 20 kW wouldn't be a surprise.  That's the reason most service panels are 200A.  For a single family dwelling, 100A might prove to be too small.  I know I missed (or misstated) some of the loads.  It's a fact that people used to have me replace their 100A panels with 200A.  I didn't like doing residential work but sometimes the people were friends of friends, that kind of thing.

ETA:  I forgot to add in another 5kW for the oven!

The reason that the European countries have such low demand limits (the US has none, I have installed 400A residential panels) is that the system is underbuilt.  What's a 'contract'.  We connect to the utility (actually, they connect to us) and we use whatever we want.  If our load is too high, and there is some legitimate reason, they will simply run a bigger drop and probably install a bigger transformer.  They're in the business of selling electricity, not telling their customers that they buy too much.


When I had solar power (different house) an 8 kW array provided all the energy we needed.  At the end of the year (known as settle-up), I owed the utility nothing for electricity other than a non-negotiable meter charge of $5/month.  It's pretty clear that we exceeded 8 kW during the heat of the day but it all averaged out.

[themadhippy]

In all of North America, the newest utility meters can turn off the power to your house without even going outside the main power station

Not just limited to  america,but anywhere were smart meters are installed.However that aint the worst aspect of smart meters,with them the utility providers are now able to measure your  power factor and charge accordingly

clothes dryer is probably 30A at 240V.

7kw to dry yer clothes, aint you guys heard of washing lines

[rstofer]

In all of North America, the newest utility meters can turn off the power to your house without even going outside the main power station

Not just limited to  america,but anywhere were smart meters are installed.However that aint the worst aspect of smart meters,with them the utility providers are now able to measure your  power factor and charge accordingly.

But they're not doing it anywhere I have ever heard of.  More popular is Time of Use billing and, around here, that is pretty much a dead issue.  Individual customers can subscribe to that type of billing if it suits them, the rest of us just kiss it off.

[Monkeh]

I always wondered how/if in Australia we have a heater, or clothes
drier or air-cond, running on 240v and drawing 15A, then on 120v in the U.S. then it must be
drawing 30-Amps!!?? That never sounded right??

And yes, outlets without 'Switches'??  Why??

If you are in the US and  you have an heater in a room, (e-g- an electric stove), it will be powered via a ridicolus plug at 120 V. The plug will overheat and a fire will start, in the standard US home built with wood.
When I was in Seattle 20 years ago, I noticed a lot of firetrucks passing by, a lot more than was usual in Europe.
My US friend said: it's normal, Christmas is coming...

That is just wrong!  I can't even imagine an oven or stove top that isn't running on 240V.  A typical stove top might have 2 ea 3kW heaters and 2 ea 1kW heater for a total of 8kW, probably more.  This would take at least 33 Amps at 240V and the typical circuit is probably 50A.  Based on 80% usage of circuit breaker ratings, a 40A circuit would be too small so it's usually 50A.  The clothes dryer is probably 30A at 240V.  Well pump, pool filter, HVAC also run on 240V.  I'm not talking about window mounted AC units, I'm talking central air and perhaps a 3200 square foot house.

stove, noun, "A heater, a closed apparatus to burn fuel for the warming of a room."

Not a great leap to realise he's not talking about your kitchen stove.

The reason that the European countries have such low demand limits (the US has none, I have installed 400A residential panels) is that the system is underbuilt.  What's a 'contract'.  We connect to the utility (actually, they connect to us) and we use whatever we want.  If our load is too high, and there is some legitimate reason, they will simply run a bigger drop and probably install a bigger transformer.  They're in the business of selling electricity, not telling their customers that they buy too much.

Well, see, you pay for the provision and connection of a service capable of a particular load, and that's what you receive. If you want bigger, uhm, you'll have to pay for it.

contract, noun, "An agreement between two or more parties, to perform a specific job or work order, often temporary or of fixed duration and usually governed by a written agreement."

[alpher]

Here we go again.  In all of North America, the newest utility meters can turn off the power to your house without even going outside the main power station, its all done remotely.  If the cops want to get you off guard to invade your home, all they need to do is cut the power to your house and you will come outside to see what the fuck is happening.  Gotcha, without every getting their hands dirty.  It's your world, more ways to have your liberties die.

 
Have you ever been to this side of the pond?

[WattsThat]

In general, only commercial/industrial customers pay power factor penalties in the US. As for the time of use, you can still get off-peak metering for heating swimming pools and other high kw usages at reduced rates.

The earlier comment about being out of power with the kettle on and not being able to make toast reminded me of the “ten second toast” video.

[themadhippy]

More popular is Time of Use billing and, around here, that is pretty much a dead issue.

we've economy 7 or whatever its called these days,originally meant for night storage heaters ,charge them up with cheap off peak electricity during the night then hope theirs enough energy stored to keep the house warm during the day.Originally it was a separate meter and fuse board so only the heaters were supplied by off peak but now its all done with 1 meter and the whole installation is charged at the lower rated during off peak hours,if your nocternal it can save  you a few quid,the downside is the peak  rate is slightly more than the standard tariff

[bdunham7]

 (the US has none, I have installed 400A residential panels)

I doubt those McMansions ever actually pull that much power at once, but might one reason to get a 400A service might be to get approval for more breaker spaces?  I don't know if the code limits subpanels, but my 200A service is maxed out on breakers even with a 12-space subpanel and separate panels for the solar and the pool stuff.  If it wasn't for tandem breakers, I'd be screwed.  And yet there's almost no way to get my max current over 100A, even if I run the AC, charge the car and bake a cake all at once.

[rstofer]

We do have 120/240V single phase in the US.  Other countries have 240/415V three phase or perhaps the house doesn't get 3 phase, just 240V single phase.  I don't see why the video author is so amazed, it's been this way forever!  He would be more amazed to know that we got out of the 25Hz power business just recently in New York City.  Amtrak still uses it!

Why single phase?  Well, if you use earth for the high voltage return, you can string a single wire for miles and miles through 'fly-over' country to provide power to a house where the nearest neighbor is miles away!  You can still see poles with a single insulator and just a single conductor.

This arrangement is known as SWER - Single Wire Earth Return
https://en.wikipedia.org/wiki/Single-wire_earth_return

[Monkeh]

We do have 120/240V single phase in the US.  Other countries have 240/415V three phase or perhaps the house doesn't get 3 phase, just 240V single phase.  I don't see why the video author is so amazed, it's been this way forever!

.. did you watch the video at all?

[rstofer]

 (the US has none, I have installed 400A residential panels)

I doubt those McMansions ever actually pull that much power at once, but might one reason to get a 400A service might be to get approval for more breaker spaces?  I don't know if the code limits subpanels, but my 200A service is maxed out on breakers even with a 12-space subpanel and separate panels for the solar and the pool stuff.  If it wasn't for tandem breakers, I'd be screwed.  And yet there's almost no way to get my max current over 100A, even if I run the AC, charge the car and bake a cake all at once.

If they use marginally more than 200A, the next panel size is 400A and that is independent of breaker spaces. I think panels are limited to 42 circuits (poles) but you can buy 30 circuit, 24 circuit, any of a number of other sizes.

My incoming panel is 400A with just 2 pole breakers for feeders.  There is a 100A panel in the Laundry, another 100A panel in the Garage, a 50A panel in the shed and another in the Gym.  Lots and lots of 15A and 20A circuits.  We use gas for heating and the fireplace insert but the rest of the place is electric.

[rstofer]

We do have 120/240V single phase in the US.  Other countries have 240/415V three phase or perhaps the house doesn't get 3 phase, just 240V single phase.  I don't see why the video author is so amazed, it's been this way forever!

.. did you watch the video at all?

About the first exciting 30 seconds!

[Monkeh]

We do have 120/240V single phase in the US.  Other countries have 240/415V three phase or perhaps the house doesn't get 3 phase, just 240V single phase.  I don't see why the video author is so amazed, it's been this way forever!

.. did you watch the video at all?

About the first exciting 30 seconds!

Well that explains why you don't know what the video is about, doesn't it?

[duckduck]

 (the US has none, I have installed 400A residential panels)

I doubt those McMansions ever actually pull that much power at once, but might one reason to get a 400A service might be to get approval for more breaker spaces?

Just put in a bigger breaker for one breaker space and then run a sub-panel. This is sometimes done for a kitchen that is far away from the main panel, etc. It's cheaper / easier to run one big wire than a bunch of little ones.

EDIT:

I realize this doesn't directly address your question. I'm not sure how permitting is typically done for residential in the USA. It's by county and they all follow the National Electric Code (with various modifications). I assume that as long as everything meets code you can get as many amps and breakers as you can afford to install. Those damn breakers are US$50 each for modern combo GFCI/arc-flash ones (you might need 15-20 of the 20A ones) and US$1,000 for an average size residential load center / panel / breaker box. You'll be paying an electrician to do this work, too.

EDIT EDIT:

I've never heard of a power meter that can cut power by remote control until this thread. That seems a little scary to me for all kinds of reasons: fire safety, security, etc. My nest has two 120 V RMS phases that can easily supply 100 A each. That's a lot riding on a couple of switches that I can't physically inspect or secure from hackers.

EDIT EDIT EDIT:

I'm just gonna edit this post to death. I live in the Seattle metro area and I haven't noticed more house fires than when I lived in other (warmer) parts of the US.

EDIT EDIT EDIT EDIT:

Electromechanical spinning disk meter on my nest. I'm not a big fan of "smart" meters or "smart" anything else. Also, get off my lawn.

[rstofer]

If you are in the US and  you have an heater in a room, (e-g- an electric stove), it will be powered via a ridicolus plug at 120 V. The plug will overheat and a fire will start, in the standard US home built with wood.
When I was in Seattle 20 years ago, I noticed a lot of firetrucks passing by, a lot more than was usual in Europe.
My US friend said: it's normal, Christmas is coming...

That is just wrong!  I can't even imagine an oven or stovetop that isn't running on 240V.

stove, noun, "A heater, a closed apparatus to burn fuel for the warming of a room."

Not a great leap to realise he's not talking about your kitchen stove.

It never occurred to me to call a portable heater a stove.  Most of the portable heaters (also called space heaters) I have seen are on the order of 1.5 kW or about 12.5 Amps.  That is slightly more than a 15A breaker wants to provide on a full time basis.

Some come with 'tilt' switches to shut them down when they are turned over.

As to 'stove':
https://www.merriam-webster.com/dictionary/stove

Definition of stove (Entry 1 of 2)
1a: a portable or fixed apparatus that burns fuel or uses electricity to provide heat (as for cooking or heating)
b: a device that generates heat for special purposes (as for heating tools or heating air for a hot blast)
c: KILN

The stove is sometimes called a range but both terms are used in the US.  The term stovetop (one word) comes up when searching Home Depot:
https://www.homedepot.com/c/ab/types-of-stovetops/9ba683603be9fa5395fab90a04794ac

[james_s]

In all of North America, the newest utility meters can turn off the power to your house without even going outside the main power station

Not just limited to  america,but anywhere were smart meters are installed.However that aint the worst aspect of smart meters,with them the utility providers are now able to measure your  power factor and charge accordingly

clothes dryer is probably 30A at 240V.

7kw to dry yer clothes, aint you guys heard of washing lines

I've had a smart meter on my house for the entire 15 years I've lived here, recently it was upgraded to a newer style. In neither case did it have the ability to cut the power remotely, if they want to cut the power they have to either physically yank the meter or disconnect the feed at the distribution transformer. It's possible that US-style smart meters capable of remote cutoff exist but I've never seen one.

Just because the dryer circuit is 30A doesn't mean the dryer draws 30A. 5.5kW is typical of an electric clothes dryer. Clothes lines exist but they are rare here, electricity is cheap in most states, half to one third what it costs in the UK and a large number of residential areas have those horrid HOAs that ban clothes lines among other things. Obviously  urban city dwellers don't really have it as an option either.

[james_s]

If you are in the US and  you have an heater in a room, (e-g- an electric stove), it will be powered via a ridicolus plug at 120 V. The plug will overheat and a fire will start, in the standard US home built with wood.
When I was in Seattle 20 years ago, I noticed a lot of firetrucks passing by, a lot more than was usual in Europe.
My US friend said: it's normal, Christmas is coming...

That is just wrong!  I can't even imagine an oven or stovetop that isn't running on 240V.

stove, noun, "A heater, a closed apparatus to burn fuel for the warming of a room."

Not a great leap to realise he's not talking about your kitchen stove.

It never occurred to me to call a portable heater a stove.  Most of the portable heaters (also called space heaters) I have seen are on the order of 1.5 kW or about 12.5 Amps.  That is slightly more than a 15A breaker wants to provide on a full time basis.

Some come with 'tilt' switches to shut them down when they are turned over.

As to 'stove':
https://www.merriam-webster.com/dictionary/stove

Definition of stove (Entry 1 of 2)
1a: a portable or fixed apparatus that burns fuel or uses electricity to provide heat (as for cooking or heating)
b: a device that generates heat for special purposes (as for heating tools or heating air for a hot blast)
c: KILN

The stove is sometimes called a range but both terms are used in the US.  The term stovetop (one word) comes up when searching Home Depot:
https://www.homedepot.com/c/ab/types-of-stovetops/9ba683603be9fa5395fab90a04794ac

Ah, English, the US and the UK may both speak a language called "English" but there are substantial differences and context matters.

"Stove" in the USA is a kitchen stove, range, or what the UK would call a "hob". Except when it's not, "stove" also commonly refers to a wood stove which is a sort of fireplace used for heating rooms. You would never hear "stove" used to describe a portable space heater, which I've heard called an "electric fire" in the UK.

I believe the tilt cutout is a mandatory feature of portable heaters in the US, along with a thermal fuse. It was not always but it has been for decades.

I'm consistently surprised at the number of otherwise technical people in other parts of the world who are not aware that US homes have 240V despite the fact that our portable appliances and lighting are 120V.

[james_s]

I'm shocked by the 200 Amps main breaker.  Here in Italy a standard family has a 3.0 to 5.5 kVA contract, which means a 16 or 20  Amp breaker.
The new meters (the ones that allow for remote reading) are programmed for a maximum load of 3.3 kVA continous (in my case, with a 3.0 kVA contract) and it will trip if you drain more than the max for a long time (minutes?).
A contract with larger limits has higher costs.
I understand the US electric supply does not discourage customers from using a lot of energy (as long as they pay the bills), but in Europe a limited amouut of current to the users side allows for better planning of the network.

200A 240V is the standard service installed in the USA, I've seen 150 and even as small as 100A service in older houses but not anything built in the last 40 years.

Larger houses often have a 400A service with dual  panels. I've seen very large houses with a 600A service and three panels but that is not common.

[engrguy42]

Yeah, it's a bit of a surprise that, especially here in an "EE" forum people are surprised at how the electrical system in the US is configured. Geez, has nobody ever looked at that transformer on the pole in front of the house and wondered why the 3 wires are coming out? And nobody's ever opened up their main panel??

Anyway, it's only been like that freakin' FOREVER, so I guess I can understand the sudden revelation...

Regarding smart meters, yeah, there are some that can do what's called "DSM" (Demand Side Management) to curtail or shut people off, but as far as I know they haven't yet been widely adopted. Hell, some of us still have the old electromechanical spinning disk meters.

Anyway, the power company can just shut off the line serving your neighborhood anytime it wants, and that's probably by remote control (sending a signal over comm lines to the substation or an automated circuit opening device on the line serving your area), so not much difference. And they do that sometimes when bad stuff happens and have have to shut you off for some reason. Nothing new.

[tooki]

I'm shocked by the 200 Amps main breaker.  Here in Italy a standard family has a 3.0 to 5.5 kVA contract, which means a 16 or 20  Amp breaker.
The new meters (the ones that allow for remote reading) are programmed for a maximum load of 3.3 kVA continous (in my case, with a 3.0 kVA contract) and it will trip if you drain more than the max for a long time (minutes?).
A contract with larger limits has higher costs.
I understand the US electric supply does not discourage customers from using a lot of energy (as long as they pay the bills), but in Europe a limited amouut of current to the users side allows for better planning of the network.

LOL what? I live in a one bedroom apartment, and in my panel, I have 3x 13A circuits for outlets and lights, then 3x 13A for the washer, dryer, and dishwasher, and then 16A three-phase for the oven and stove (hob). And this is considered on the weak side by today’s standards here in Switzerland. (And this is in an apartment with central hot water and radiator heat, so not heated by my own electrical.)

[IanB]

So nobody has commented on his observation that 208 V provides 86.6% less power to heaters than 240 V? When in fact the ratio is 75%?

I would be bummed about that. 4500 W on the water heater at 240 V was reduced to 3380 W at 208 V.

I'm sure he meant to say 75% but somehow misspoke.

[NiHaoMike]

7kw to dry yer clothes, aint you guys heard of washing lines

Modern heat pump dryers are pretty efficient, some even run on a normal 120V circuit.

So nobody has commented on his observation that 208 V provides 86.6% less power to heaters than 240 V? When in fact the ratio is 75%?

I would be bummed about that. 4500 W on the water heater at 240 V was reduced to 3380 W at 208 V.

I'm sure he meant to say 75% but somehow misspoke.

The "2/3" 120/208V system is common in apartments and condos in densely populated cities. There, heating appliances running cooler keeps apartment owners happy by reducing maintenance costs.

[james_s]

So nobody has commented on his observation that 208 V provides 86.6% less power to heaters than 240 V? When in fact the ratio is 75%?

I would be bummed about that. 4500 W on the water heater at 240 V was reduced to 3380 W at 208 V.

I'm sure he meant to say 75% but somehow misspoke.

You can get 208V water heaters and room heaters, I don't know how often they actually get used in those applications but they are available. 208V is pretty much universal in larger apartment buildings, they're fed with 3 phase with 2 phases to each unit.

[Bud]

If you are in the US and  you have an heater in a room, (e-g- an electric stove), it will be powered via a ridicolus plug at 120 V.

It is a 2 phase 240v plug. Typically used by electric dryers and kitchen stoves.

[TimFox]

Just to clarify language usage in the US:
The typical appliance found in the kitchen for heating food is called a "range", and can be either electrical or gas-powered.  The usual range has a cooktop above an oven, possibly with a second oven mounted above the cooktop.  Here is a good discussion of options and fuels, along with the required electrical connections:  https://www.abt.com/learn/kitchen-range-buying-guide
In informal usage, this is sometimes called a "stove" or "cook stove", but it is rare in US usage to refer to a space-heating appliance as a stove.
The plug required for a 240V range or clothes dryer is large: the older style has only three prongs, but the newer ones have four prongs (NEMA 14-30).  A typical electric dryer pulls 30 A at 240 V.
An historical note:  the "Franklin stove", see  https://www.ushistory.org/franklin/science/stove.htm  , was an American invention (Benjamin Franklin, 1742) for space heating to improve efficiency over a traditional fireplace.

[themadhippy]

And in the uk
Range = somewhere cowboys  live or chavs shop
cooker = thing for cooking food with ovens. heating rings and maybe a grill
stove = can be a  heater or a cooker  if your posh,but more common  to break or smash, ,as in " I'll stove yer head in"

[filssavi]

Just as an addendum, 3kW single phase in italy is just the standard contract, the utility will happily give you more, if you ask.

Normal homes usually have a single phase system,  in that cases to avoid unbalances you can ask for up to 6 kW (each kW over the standard will cost 20-40€ more each month).
You can also ask to have a three phase feed, for which there are no additional costs, in that case you can usually have a lot more power (up to 100kW over which you have to connect to the medium voltage grid),

You are allowed to draw up to 10% more indefinitely, while for higher draws over the meter will trip.

So the low size of electric feeds has more to do with how the people use electricity than anything else. Mainly we don't need that much electrical power, clothes are usually air dried (dryers are getting more common but just barely), heating and cooking is done with natural gas. the houses are small enough that a 1/1.5kw A/C system is enough. etc.

I think things will start to change probably when electric cars will get more common.

[TimFox]

From the past participle of "stave", the verb "stove" means "to break in a stave or staves of (a cask or barrel) so as to release the wine, liquor, or other contents", and the mid-19th century stories of whaling referred to ships "stove in" by whales.  The generalization to heads is straightforward.
Yes, cowboys have a "home on the range (noun)", but what, pray tell, do you mean by "chavs shop"?

[IanB]

To add to the British perspective, a stove is generally a fixed device in which you burn wood or coal, for heating or cooking. If for heating it is usually qualified, as for example "a wood-burning stove". If the word "stove" is used by itself, it would usually be understood as a cooker, and a "stove-top" would be where you cook with pots and pans.

Under no circumstances would stove be used to describe an electric, gas or kerosene fueled space heater. Such a thing would simply be called a heater.

[richard.cs]

I imagine a 120 V unit would incinerate its heating element on 230 V.

It might survive better than you expect, a 240 V one wired wired between phases (so 415 V) seemed to work just fine, just boiled 3x quicker. 

200A 240V is the standard service installed in the USA, I've seen 150 and even as small as 100A service in older houses but not anything built in the last 40 years.

UK typical is 60-100 A, single phase, 230 V nominal, over 100 A you generally have to go to three phase but it is not common domestically.

[duak]

Good point Richard - root 3 times the voltage is 3X the power so 1/3 of the time.  240 V is about double 120 V so we're looking at 4X the power and 1/4 of the time - providing the delta T between the element and water doesn't get too excessive.

Apparently Lao Tzu said "the light that burns twice as bright burns half as long".  I expect 4X the power would reduce life by a greater factor.

History corner?: I  sort of understand why North America has a lower nominal line voltage of 110 to 120 V is due to the Current Wars.  Edison was into DC and Westinghouse and others were AC.  Somewhere along the way it was legislated (although lifted later) to limit AC.   A recent movie was based on it: https://en.wikipedia.org/wiki/The_Current_War   I don't think Europe went into the DC dead end.  Now can someone explain Japan's 100 V at 50 or 60 Hz?

Cheers,

[Gregg]

The North American standard of 120V line to a grounded neutral may have been deemed safer in the days of knob and tube wiring. 
Over a hundred years ago electricity in the home was mostly used for lighting and electric lights although crappy by our standards were far safer than gas lights.  A common wiring method was to run the hot line across the uninsulated attic staying off the wood about an inch by the ceramic ‘knob’ insulators. The wire had minimal insulation often rubber with a cloth cover and were routed through wood via ceramic tubes. Splices were in open air, sometimes soldered, sometimes just twisted together and covered with friction tape maybe with a layer of rubber tape if you had the premium installation.  A tap off the hot line was run through the ceiling to light fixtures and another wire routed down to the light switch on the wall where it switched to the neutral which was often located in the basement.  Outlets were wired similarly hot from the attic and neutral to the basement. 
Early services were often 30 amp 120 volt with two screw in fuses that could easily be bypassed with a coin.  The wire was often 14 ga powered via a 20 or 30 amp fuse because it was rated for free air to help dissipate heat.
Standards back then were minimal at best and many ways were found to make this system far less safe.   Things like blown in insulation, kitchen appliances, Christmas tree lights and electric heaters could easily over tax the system.  It wasn’t uncommon to have a homeowner install an outlet and run the neutral to a water pipe instead of the actual neutral wire.

[james_s]

Another factor that likely contributed to the voltage choice is that 120V incandescent lamps are substantially more efficient than 240V incandescent lamps. The lower the voltage, the shorter and thicker the filament is for the same wattage. A shorter, thicker filament has lower convective losses. A 240V 60W bulb is only slightly brighter than a 40W 120V bulb.

[richard.cs]

Another factor that likely contributed to the voltage choice is that 120V incandescent lamps are substantially more efficient than 240V incandescent lamps. The lower the voltage, the shorter and thicker the filament is for the same wattage. A shorter, thicker filament has lower convective losses. A 240V 60W bulb is only slightly brighter than a 40W 120V bulb.

Well, were more efficient, prior to the invention of the "coiled coil" filament in the 1910s. It's just a way of making a long thin filament behave convectively as a short fat one.

[rstofer]

The "2/3" 120/208V system is common in apartments and condos in densely populated cities. There, heating appliances running cooler keeps apartment owners happy by reducing maintenance costs.

120/208V 3 Phase 4 Wire is quite common for industrial and commercial applications.  Obviously, it is used for all small receptacle loads in both applications since the voltage between neutral and any of the 3 phases is 120V.
277/480V 3 Phase 4 Wire is the other common industrial supply and most large commercial and industrial lighting runs on 277V and the motors run on 480V.  Industrial applications will have both 120/208 3 Phase and 277/480V 3 Phase distributed internally.  The utility will provide just the 277/480V and the owners will use small transformers to create 120/208V 3 Phase where necessary.
120/240V 3 Phase 4 Wire is an oddball configuration (called 'wildcat' by some) where one transformer is the common 120/240V single phase and the second transformer provides the other 240V leg.  Between the neutral and the 2d transformer output is 208V and this leg is never used for a non-3 Phase application.  This is known as an open delta arrangement.  It requires only 2 transformers so the utility tends to like it but the 240V 3 Phase is a little low for larger motors.  The transformer delivering 120/240 single phase will be larger than the transformer providing just the 3rd phase for motor loads.

None of these 3 phase configurations are delivered to residential occupancies, as far as I know.  Those are strictly 120/240V Single Phase.

We have all kinds of transformer schemes.  For 3 phase transformers, the secondary can be either wye or delta connected.  Loads are usually delta connected and have no use for the neutral.  The neutral is always grounded, sometimes solidly, some times with a resistor.  These resistor grounded systems exist to limit fault current, most typically for large motor installations. 

In thinking about it, it's a real mess!

[richard.cs]

120/208V 3 Phase 4 Wire
277/480V 3 Phase 4 Wire
120/240V 3 Phase 4 Wire
120/240V Single Phase.

In thinking about it, it's a real mess!

There are too many different voltages, and too many of them are too similar to really be useful, e.g. 208/240/277 are all too similar to have significant advantage, but are different enough to be incompatible for many types of equipment.

[tom66]

The idea of 400A 240V service to me is just baffling.  In the UK it's rare to see any home over 100A 240V service, single phase, and many older homes have 63A or 80A service.  Some larger homes have 125A.

This creates a real hassle for EV adoption because there isn't enough local capacity to have two car chargers @ 32A each on someone's driveway.  Many DNOs (the local network operators) have designed the power distribution networks with the assumption that all customers will use an average of 4-5kW at peak.  That falls apart when people are charging their cars and heating/cooling their homes with heat pumps. Local upgrades are going to be necessary.

[richard.cs]

Many DNOs (the local network operators) have designed the power distribution networks with the assumption that all customers will use an average of 4-5kW at peak.

And the expected average for a house without electrical heating is 2 kW, this is the assumption used for network design. The UK approach with fewer larger transformers compared to the North American one does allow designing more for the average because there are more customers per transformer, but you still have to get that average right.

[GlennSprigg]

As a 'fun' diversion here...   
Many years ago in the bush, (I worked for that power authority), we would just string a 'clip' up
to the powerlines above with a pole, when out on the road. And connect it to a 're-wired' 30-Amp
kettle to make coffee. Took about 15 secs to boil !! Though it shook like hell,  haha...   

Also, in regards to effective energy management, ref a few times in this post...
I also worked more recently with a major company, ('Honeywell' actually!), where I was responsible
(amongst countless other things/equipment) for Energy Management systems in multi-story buildings.
Now, 'some' buildings owned & occupied by one company, are 'interested' in such savings...
However, multi-story bldg owners with MANY other companies residing within, would SCOFF at my
offerings of savings!!!  Why?... Because they would individually meter the whole bldg, and on-sell the
power to all the bldg customers!  Often making from $100,000 to $500,000 profit, JUST from re-sale
of electricity per year!!  They actually WANTED all their customers to be as in-efficient & wasteful as
possible!!  Always made me laugh, when the Govt was pushing for 'efficient' buildings... hahaha...   

[tooki]

The idea of 400A 240V service to me is just baffling.  In the UK it's rare to see any home over 100A 240V service, single phase, and many older homes have 63A or 80A service.  Some larger homes have 125A.

This creates a real hassle for EV adoption because there isn't enough local capacity to have two car chargers @ 32A each on someone's driveway.  Many DNOs (the local network operators) have designed the power distribution networks with the assumption that all customers will use an average of 4-5kW at peak.  That falls apart when people are charging their cars and heating/cooling their homes with heat pumps. Local upgrades are going to be necessary.

Don’t you have 400V three-phase service for major appliances? (Here in Switzerland, that is quite common.)

[duckduck]

As a 'fun' diversion here...   
Many years ago in the bush, (I worked for that power authority), we would just string a 'clip' up
to the powerlines above with a pole, when out on the road. And connect it to a 're-wired' 30-Amp
kettle to make coffee. Took about 15 secs to boil !! Though it shook like hell,  haha...   

Also, in regards to effective energy management, ref a few times in this post...
I also worked more recently with a major company, ('Honeywell' actually!), where I was responsible
(amongst countless other things/equipment) for Energy Management systems in multi-story buildings.
Now, 'some' buildings owned & occupied by one company, are 'interested' in such savings...
However, multi-story bldg owners with MANY other companies residing within, would SCOFF at my
offerings of savings!!!  Why?... Because they would individually meter the whole bldg, and on-sell the
power to all the bldg customers!  Often making from $100,000 to $500,000 profit, JUST from re-sale
of electricity per year!!  They actually WANTED all their customers to be as in-efficient & wasteful as
possible!!  Always made me laugh, when the Govt was pushing for 'efficient' buildings... hahaha...   

Love the kettle. I would watch from a distance    I have much respect for the people that build and maintain the electric lines. When I make a mistake I might burn up a fancy LED or a $6 opamp.

Off topic but apropos, there is little incentive to improve the fuel efficiency of cargo ships because most ships are leased (ball park of US$10,000 per day) and the lessee pays for fuel. The ship owners couldn't care less. Large shipping companies that buy their ships outright e.g. Maersk care very much about fuel efficiency because it directly affects their bottom line.

[schmitt trigger]

If people think that 120 volts is too low a voltage for the larger loads (a thought which I also share, BTW), in Japan it is only 100 volts.

[themadhippy]

Don’t you have 400V three-phase service for major appliances

As mentioned above 3 phase in domestic premises is rare in the uk.I can only think of 2 occasions ive come across it in 35+ years and both were much larger than the average  2up 2 down.

[IanB]

The idea of 400A 240V service to me is just baffling.  In the UK it's rare to see any home over 100A 240V service, single phase, and many older homes have 63A or 80A service.  Some larger homes have 125A.

I was curious when he talked about 200 A service in the video, and then he showed a "small" pole mounted transformer which presumably provided the supply. I know those transformers are bigger than they look when they are down on the ground, but I still wondered how many lots of 200 A it could supply before being overloaded?

[Gregg]

It seems that no matter what the local electrical standards may be, there always seems to be ways of making electrical devices work.
The larger the demand for electrical distribution built to a given standard, the better the selection and price due to scales of economy.  The differences do make for interesting discussion 

Perhaps a far more interesting topic may be why 60Hz or 50Hz became standard.

[james_s]

I was curious when he talked about 200 A service in the video, and then he showed a "small" pole mounted transformer which presumably provided the supply. I know those transformers are bigger than they look when they are down on the ground, but I still wondered how many lots of 200 A it could supply before being overloaded?

Those "pole pig" transformers are typically 20-30kVA, often they have the kVA printed right on them. They are big, typically 3'-4' tall and weigh several hundred pounds. They may supply from one house to 5 or 6 houses depending on the logistics, they try to avoid running 240V over runs of more than a few hundred feet.

[Monkeh]

I was curious when he talked about 200 A service in the video, and then he showed a "small" pole mounted transformer which presumably provided the supply. I know those transformers are bigger than they look when they are down on the ground, but I still wondered how many lots of 200 A it could supply before being overloaded?

Those "pole pig" transformers are typically 20-30kVA, often they have the kVA printed right on them. They are big, typically 3'-4' tall and weigh several hundred pounds. They may supply from one house to 5 or 6 houses depending on the logistics, they try to avoid running 240V over runs of more than a few hundred feet.

... a 30kVA transformer won't handle a single 200A service.

And we're the underbuilt ones?!

[tooki]

Perhaps a far more interesting topic may be why 60Hz or 50Hz became standard.

This paper has a quite comprehensive summary of the reasons: https://www.djtelectricaltraining.co.uk/downloads/50Hz-Frequency.pdf

[james_s]

... a 30kVA transformer won't handle a single 200A service.

And we're the underbuilt ones?!

I don't recall anyone saying anywhere is underbuilt?    Or do you just like being a dick?

I may have been mistaken in the rating so I just went and looked, the (pad mount, underground wired) transformer that feeds my house and I believe 3 others is 50kVA. This is as far as I know the continuous rating at max ambient temperature. A 200A service will *never* be pulling 200A continuously and it's typical to have 300A-400A cumulative in branch circuits off a 200A main, nobody is ever going to load them all up 100% at the same time. I've seen as small as 5kVA, I don't know what those are used for and at least as large as 75kVA. The only transformer of this type I've personally messed with is a 25kVA unit we used to step up 240V to 4800V to power a series streetlighting regulator, it was the smallest 4800V transformer we could find at the scrapyard.

Anyway suffice to say whatever we have here is clearly adequate, I've never seen my line voltage lower than 119V or higher than 123V at this house and it's extremely rare for a transformer to burn up outside of damage from a lightning strike.

[Monkeh]

... a 30kVA transformer won't handle a single 200A service.

And we're the underbuilt ones?!

I don't recall anyone saying anywhere is underbuilt?    Or do you just like being a dick?

https://www.eevblog.com/forum/chat/the-us-electrical-system/msg3104258/#msg3104258

I may have been mistaken in the rating so I just went and looked, the (pad mount, underground wired) transformer that feeds my house and I believe 3 others is 50kVA. This is as far as I know the continuous rating at max ambient temperature. A 200A service will *never* be pulling 200A continuously and it's typical to have 300A-400A cumulative in branch circuits off a 200A main, nobody is ever going to load them all up 100% at the same time. I've seen as small as 5kVA, I don't know what those are used for and at least as large as 75kVA. The only transformer of this type I've personally messed with is a 25kVA unit we used to step up 240V to 4800V to power a series streetlighting regulator, it was the smallest 4800V transformer we could find at the scrapyard.

50kVA makes more sense - at least it's capable of 200A. And yes, I get that in normal conditions you're not going to see full load from a single building, but it's not a 200A service if there isn't 200A behind it.

[Stray Electron]

7kw to dry yer clothes, aint you guys heard of washing lines

   Seriously, not since the 1960s. Besides with the now popular zero lot line subdivisions, there's NO room for one. I literally haven't seen a clothes line since probably 1968.

[tom66]

My clothes dryer uses 2.2kW and a total of ~2.7kWh to dry 8kg of clothes straight from the washing machine.

I don't understand how you'd need 7kW to dry clothes. One of the important things is to not overheat the clothes which damages fabrics and risks fire.   

[ciccio]

About NEW meters, I know (by experience) that the new electrical meters installed in Italy can be remote controlled (using some kind of signal over the power line) allowing the Utility Company to:
-read your meter, and bill you according to the (optional) tariff that changes day/night and workdays/weekends
-reduce the tripping current of the meter (if you forgot to pay a bill, the max power available will be reduced  from 3.5 kVA to 0.5 kVA for (I believe) 15 days, then to ZERO ).

Now they changed my GAS meter with a new one than can do the same things. It uses some kind of Wi-Fi (with some problems because most meters are installed in metal enclosures) and will allow for remote reading the meter and remote cutting off the gas supply.

Cutting the gas supply to a defaulting customer required physical access to the meter, that in old buildings is many times inside the house, and this created problems to the field technicians. Now the supplier can do this from their control room...

[bdunham7]

... a 30kVA transformer won't handle a single 200A service.

And we're the underbuilt ones?!

You'd have to understand what that rating means to make that statement.  Where I live, one 25kVA plated xformer is feeding 4 houses that were originally built 50 years ago with 100A service, but with many upgraded to 200A since.  If they need service, the utility company is swapping them out for 50kVA versions, but mostly they are still fine.  Using too large a transformer increases losses at low power, so they use low-Z oil-cooled transformers that can sustain massive overloads from their rated power.  IIRC, a typical xformer of this type can sustain a 175% continuous overload at 68F ambient and a 400% overload for an hour.  Or something like that. 

[bdunham7]

My clothes dryer uses 2.2kW and a total of ~2.7kWh to dry 8kg of clothes straight from the washing machine.

I don't understand how you'd need 7kW to dry clothes. One of the important things is to not overheat the clothes which damages fabrics and risks fire.

'merica.  Everything is bigger.  My first car had a 7.5 liter engine. 

[Halcyon]

Electromechanical spinning disk meter on my nest. I'm not a big fan of "smart" meters or "smart" anything else. Also, get off my lawn.

 

[free_electron]

I'm shocked by the 200 Amps main breaker.  Here in Italy a standard family has a 3.0 to 5.5 kVA contract, which means a 16 or 20  Amp breaker.

do you have any idea of the load of a 5 ton airco unit ? that thing pulls 30 to 32 ampere on a hot day ... throw in an electric water boiler, a 5 kilowatt oven (or a double one)  , a 3 kilowatt cooktop , a  2 kilowatt microwave, a 2 horsepower food disposal unit , a dishwasher, washing machine and electric clothes dryer,  a well pump , a 2 hp pool pump , 1kw saltwater chlorine generator,  ... yup you need that 200 ampere !

I just bought a new home. Planning to go solar... looking at a 16 kilowatt array with 4 battery units.... covers 120% of my usage.

[NiHaoMike]

do you have any idea of the load of a 5 ton airco unit ? that thing pulls 30 to 32 ampere on a hot day ... throw in an electric water boiler, a 5 kilowatt oven (or a double one)  , a 3 kilowatt cooktop , a  2 kilowatt microwave, a 2 horsepower food disposal unit , a dishwasher, washing machine and electric clothes dryer,  a well pump , a 2 hp pool pump , 1kw saltwater chlorine generator,  ... yup you need that 200 ampere !

The demand can be way reduced with smart engineering, even if 5 tons of A/C really is needed. (Hint: if your insulation is decent, it's unlikely unless you truly have a huge house.) The water heater isn't going to need to run at full capacity when the A/C is needed at all, plus one based on a heat pump reduces the power usage down to a few hundred watts. The oven is only going to draw full power during preheating, same with the cooktop. The microwave is only used for short bursts and the disposal for even shorter. Heat pump dryers also use much less power. The pool equipment doesn't need to run full time so a smart controller can run it when demand is low and/or energy is cheap.

[cliffyk]

At first I had a problem watching the video as I could not get General Trelane, the lonely Squire of Gothos out of my mind:



That and that it started out with the fellow prattling on sensationally about a bunch of stuff I learned in 8th Grade shop class kind of shot his credibility right off the bat. However once I saw where he was going it was not bad.

Maybe I missed it, but it did seem that he glossed over or did not emphasize that the so-caled "neutral" wire in our silly earth return split phase system is anything but neutral. It carries the full difference of the loads applied to each phase. If you draw 200 A from 120 V phase "A", and 100 A from phase "B", the "neutral" wire will be carrying 100 A--enough to be a BIG surprise for anyone believing it to be "neutral", and mucking about with it while the full phase load is unbalanced.

[CatalinaWOW]

All of these comments about service capacities in America are just snapshots in time.  I presume the same thing is true in the rest of the world.

I vividly remember a visit to my grandfathers house when an immense blizzard occurred.  It was electrified in the 1930s through an effort called REA in the US (Rural Electrification Association I believe).
When all power in the house went out I was sent out to check the fuses (old Edison base glass fuses), particularly to see if the main fuse had gone.  I reported back that the largest fuse I could find was 30 Amps and it couldn't be the main, so where was the main fuse.  Turns out that was the main and a surge had taken it out.

The house I grew up in was typical for its time (mid 1940s construction) and had 60 Amp service.

By the time I was starting to look at home buying 100 Amp service was common, but not dominant

Another twenty years and 200 Amp service is close to becoming standard.

While the values may be different I would bet that much of the rest of the world has a similar trajectory.  As worldwide wealth increases the number of electical gadgets, from kettles, to TVs, to hair dryers and computers and air conditioners is growing.

[cliffyk]

The first house we owned was a 3-room "winterized" summer cottage on a 50' x 80' lot (we paid $2700 for it in 1964)--it had a 30A "Edison" fused entrance, "knob and tube wiring", and an LPG floor furnace that you did not care walk on barefoot and gobbled up over 500 lbs. of propane / month in January and February. Taxes; IIRC were $65 a year...

[james_s]

My clothes dryer uses 2.2kW and a total of ~2.7kWh to dry 8kg of clothes straight from the washing machine.

I don't understand how you'd need 7kW to dry clothes. One of the important things is to not overheat the clothes which damages fabrics and risks fire.

I've never seen a 7kW clothes dryer. Mine is a big Maytag unit with a 5.5kW heater, many are around 4kW. The circuit capacity is 30A, that doesn't mean the dryer draws 30A. The next size down is 20A and that is insufficient for a 5.5kW dryer.

I think the wattage of the dryer is a rather useless metric though, what matters is the kWh required to dry a load of clothes. A lower powered dryer will consume less instantaneous power but all else being equal it will run longer. Seems like mine takes 30-40 minutes to dry a full load out of the washer, and it handles 2-3 times the load of a typical UK dryer. Bigger capacity machines are run less frequently, I doubt there is that much difference in consumption per item of clothing.

[NiHaoMike]

I think the wattage of the dryer is a rather useless metric though, what matters is the kWh required to dry a load of clothes. A lower powered dryer will consume less instantaneous power but all else being equal it will run longer. Seems like mine takes 30-40 minutes to dry a full load out of the washer, and it handles 2-3 times the load of a typical UK dryer. Bigger capacity machines are run less frequently, I doubt there is that much difference in consumption per item of clothing.

A heat pump makes a big difference there. Or even a heat recovery exchanger, for that matter.

[cliffyk]

My clothes dryer uses 2.2kW and a total of ~2.7kWh to dry 8kg of clothes straight from the washing machine.

I don't understand how you'd need 7kW to dry clothes. One of the important things is to not overheat the clothes which damages fabrics and risks fire.

I've never seen a 7kW clothes dryer. Mine is a big Maytag unit with a 5.5kW heater, many are around 4kW. The circuit capacity is 30A, that doesn't mean the dryer draws 30A. The next size down is 20A and that is insufficient for a 5.5kW dryer.

I think the wattage of the dryer is a rather useless metric though, what matters is the kWh required to dry a load of clothes. A lower powered dryer will consume less instantaneous power but all else being equal it will run longer. Seems like mine takes 30-40 minutes to dry a full load out of the washer, and it handles 2-3 times the load of a typical UK dryer. Bigger capacity machines are run less frequently, I doubt there is that much difference in consumption per item of clothing.

The "Whole Picture" is, for many, a difficult concept to grasp--this is why "waterfall" projects generally fail...

It's akin to Squire Trelane's (apparently due to a prior video); getting roasted for supposedly stating 120 VAC was "safe"--he did not, he said it was "safer" which is a factual statement...

[cliffyk]

I think the wattage of the dryer is a rather useless metric though, what matters is the kWh required to dry a load of clothes. A lower powered dryer will consume less instantaneous power but all else being equal it will run longer. Seems like mine takes 30-40 minutes to dry a full load out of the washer, and it handles 2-3 times the load of a typical UK dryer. Bigger capacity machines are run less frequently, I doubt there is that much difference in consumption per item of clothing.

A heat pump makes a big difference there. Or even a heat recovery exchanger, for that matter.

Do heat pump based clothes dryers exist? Interesting concept--our "new" (2 years old) R-410a based central HVAC system with heat pump (common here in Florida) can, in heat pump mode, produce a good flow (1600+ cfm) of 85° F air with an outdoor ambient of 40° F--below that 13.2 kW of coiled nichrome kicks in for "emergency" heat. We see the latter for usually < 100 hours/year...

The neat thing about the heat pump is of course that the heat is, like fossil fuels¹, free, I just pay to "pump" it in the direction I want it to go. I wish there were a market for that I pimp out this time of year. A practical, economical heat capture/distribution technology would be a winner--

---------------------------------
¹ - Leaving landowner subterranean mineral rights issues aside, oil, natural gas, coal, etc, are free, we pay for them to be extracted, refined, and distributed.

[Monkeh]

Maybe I missed it, but it did seem that he glossed over or did not emphasize that the so-caled "neutral" wire in our silly earth return split phase system is anything but neutral. It carries the full difference of the loads applied to each phase. If you draw 200 A from 120 V phase "A", and 100 A from phase "B", the "neutral" wire will be carrying 100 A--enough to be a BIG surprise for anyone believing it to be "neutral", and mucking about with it while the full phase load is unbalanced.

That the neutral can carry current is absolutely normal, not unique to your split-phase (which is not earth return, because you have a wire, not the earth) system. It is not neutral because it does nothing, but neutral because it is nominally at 0V.

[bdunham7]

If you draw 200 A from 120 V phase "A", and 100 A from phase "B", the "neutral" wire will be carrying 100 A--enough to be a BIG surprise for anyone believing it to be "neutral", and mucking about with it while the full phase load is unbalanced.

That is exactly what a neutral is supposed to do.  What big surprise would the neutral have?  3 volts?

[tooki]

7kw to dry yer clothes, aint you guys heard of washing lines

   Seriously, not since the 1960s. Besides with the now popular zero lot line subdivisions, there's NO room for one. I literally haven't seen a clothes line since probably 1968.

We still had one until 1992 (when we moved from USA to Switzerland), at a house built in the late 70s. My grandma (living in Florida) used one until she passed away in 2013.

Do heat pump based clothes dryers exist? Interesting concept--our "new" (2 years old) R-410a based central HVAC system with heat pump (common here in Florida) can, in heat pump mode, produce a good flow (1600+ cfm) of 85° F air with an outdoor ambient of 40° F--below that 13.2 kW of coiled nichrome kicks in for "emergency" heat. We see the latter for usually < 100 hours/year...

Yes. They’re exceedingly rare in USA (where just a handful of models exist, e.g. Miele), but in Europe, they’ve been the only type sold for several years AFAIK, in order to comply with energy efficiency regulation. Just as window air conditioners are cheap in USA due to economies of scale, heat pump dryers are available cheaply in Europe.

My apartment came with one from Bosch-Siemens, and it’s great. It doesn’t get as hot as a traditional dryer, making it gentler on the clothes, but the dehumidifying effect of the heat pump system makes it work just as fast. It uses less than 1KW.

[free_electron]

do you have any idea of the load of a 5 ton airco unit ? that thing pulls 30 to 32 ampere on a hot day ... throw in an electric water boiler, a 5 kilowatt oven (or a double one)  , a 3 kilowatt cooktop , a  2 kilowatt microwave, a 2 horsepower food disposal unit , a dishwasher, washing machine and electric clothes dryer,  a well pump , a 2 hp pool pump , 1kw saltwater chlorine generator,  ... yup you need that 200 ampere !

The demand can be way reduced with smart engineering, even if 5 tons of A/C really is needed. (Hint: if your insulation is decent, it's unlikely unless you truly have a huge house.) The water heater isn't going to need to run at full capacity when the A/C is needed at all, plus one based on a heat pump reduces the power usage down to a few hundred watts. The oven is only going to draw full power during preheating, same with the cooktop. The microwave is only used for short bursts and the disposal for even shorter. Heat pump dryers also use much less power. The pool equipment doesn't need to run full time so a smart controller can run it when demand is low and/or energy is cheap.

My warm water boiler runs at night for now. The airco runs pretty much full time.. Central valley gets hot in summer. I bake bread twice a week. cooking : three times a day. The problem is that there are moments , even if only for 5 minutes where peak power is very large. if your main breakers can't handle such a load it is going to get annoying very quickly. I have a heatpump airco system , but still the load is big. And then there's two electric cars that pull 30 ampere each. The pool pump and chlorine generator run 9 to 10 hours a day. You have to, otherwise the pool turns to soup. This is a saltwater pool , so it needs circulation to do the electrolytic conversion of the salt into chlorine and sodium. Pool is solar heated so that array needs circulation as well.

Cooking indian food is very involved. they don't do simple meals and run everything  on hot hot hot ( my wife is from india ) a 5 zone induction cooker pulls quite a load ...

Even the smallest homes in the us have 100 amp main breakers.

That's why i am going solar The system will give me more than 100 ampere off the panels on a bad day. Whatever is possible : dump it in the packs. Run the house at night off the packs and dump the rest in the cars. Everything else is going on smart controllers. if peak power is available on the array : use it. Run the 100 gallon water heater for the shower. run anything that can 'store energy' : water heater , pool heater , battery packs, cars. When the array becomes less productive : divert energy to large loads that are temporary : washing and drying.
As the array becomes less productive during the day : spin down the large loads and keep topping off the batteries ( if they are already full no problem. once it gets dark : shed the large loads. no running dryers ovens etc. cooking ok. Use the packs to run airco and the necessities : refrigerators and the stuff that needs to be on. keep dumping power into the cars if they require it.

the controller is self-learning and will adapt the load shift.

[tom66]

Do heat pump based clothes dryers exist? Interesting concept--our "new" (2 years old) R-410a based central HVAC system with heat pump (common here in Florida) can, in heat pump mode, produce a good flow (1600+ cfm) of 85° F air with an outdoor ambient of 40° F--below that 13.2 kW of coiled nichrome kicks in for "emergency" heat. We see the latter for usually < 100 hours/year...

Yes, we have those in Europe. They are relatively expensive because you need the equivalent of a 9000 BTU/hr A/C unit (~800W input power, 2600W output power) in the bottom of your dryer, plus all the associated complexities of a heatpump system, but they are considerably more energy efficient provided they are operating in a warm room.  And no, they aren't the only models available.  We have heat pump, condenser and vented dryers all available for sale.

The dryer we have is a condenser dryer, which is slightly more efficient than a straight vented arrangement as heat is recycled through the system and no heat is deliberately exhausted to atmosphere.  Cold metal coils (by shear thermal mass) condense the water in the hot humid air, which is then recycled through the machine.  A small pump moves that water into a disposal tank.  Humidity sensors detect when the humid air has become dry enough for the clothes to be considered "done".

Since my dryer is often operating in a cold garage (in summer clothes are hang-dried) I don't know if a heat pump would be much better.  It would depend on how efficient it is at extracting heat from a 5C room.

[tooki]

Relatively expensive? I’ve seen no-name heat pump dryers on sale here for $300.

(And it’s not like 9000BTU AC is that big. Those are routinely used as window AC units in USA, and don’t cost very much.)

Non-heat-pump condenser dryers use more energy than vented, not less: https://www.cda.eu/laundry/condenser-vs-vented/

They only made sense when you couldn’t have a vent. With the advent of heat pump dryers, are plain condenser dryers don’t make sense at all.

[tom66]

Are you sure?  The EU standards (Annex IV):
https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32012R0932

state that the 'standard' of each dryer should consume (@8kg capacity):
Vented - 4.1 kWh/cycle
Condenser - 2.30 kWh/cycle

The ratings get better at lower capacities, with the energy consumption of a 5kg vented dryer and 5kg condenser dryer only differing by about 20% or so, although the condenser still wins.  I'd be curious why there isn't a linear relationship, it might relate to the extra energy required by the condenser system, pushing the hot air through the internal condensation system might consume extra energy and give more opportunity for heat loss inside the machine perhaps.  The energy consumption of the tumble motor shouldn't be that high (100W or so.)

I have not seen a heatpump dryer for under £400 (~$500USD) here but then again, my current tumble dryer was a  road-side find (it had a blown fuse...)  I suspect that it may be more expensive to buy these types of dryers here as regulations for refrigerants may be more strict.  I would be surprised if propane is an acceptable refrigerant in such a device, which is common in cheap A/C units and refrigerators here.

There's probably the other factor that as you mention, condenser dryers are preferred as there is limited ventilation requirement, with no exhaust to atmosphere, especially important for flat dwellers.

[NiHaoMike]

Non-heat-pump condenser dryers use more energy than vented, not less: https://www.cda.eu/laundry/condenser-vs-vented/

In cold climates, vented dryers are the least efficient after accounting for heat lost from the building.

[duak]

I set up a little drying cabinet for delicates in the furnace closet.  The excess heat from the house's original furnace and hot water heater would dry laundry and remove the humid air by combusting it and firing it up the B-vent.  After replacing both units with closed combustion units, the furnace closet was cooler and had no natural venting.  I now had room for a dehumidifier that keeps the closet and most of the lower floor less humid than before, especially in the summer.  The dehumidifier doesn't run all the time even when drying laundry.  Three or four pairs of jeans or a few terry cloth towels will dry overnight as long as the circulating fan moves air around in the closet.

[AlbertL]

If you draw 200 A from 120 V phase "A", and 100 A from phase "B", the "neutral" wire will be carrying 100 A--enough to be a BIG surprise for anyone believing it to be "neutral", and mucking about with it while the full phase load is unbalanced.

That is exactly what a neutral is supposed to do.  What big surprise would the neutral have?  3 volts?

It depends on the nature of the mucking.  In a properly installed, intact system, touching the neutral and ground (earth) shouldn't yield any great surprise.  But getting in series with a neutral, or between an open neutral and ground, could expose one to essentially the full line voltage.  And opening a current-carrying neutral could produce a significant arc.

This leads into another interesting aspect of US distribution: the multi-grounded neutral.  The utility substation typically supplies three-phase distribution feeders from the wye-connected secondary of a step-down transformer.  The neutral of the wye is grounded at the substation, travels along with phase conductors, and is grounded at intervals along the line.  Transformers along the feeder make the final step down to customer delivery voltage, which is typically 120/240V single-phase (i.e. a center-tapped 240 volt secondary) or three-phase 120/208V or 277/480V wye.  The secondary neutrals of these transformers are connected to the feeder neutral, and grounded at the transformer location.  Finally, the neutral is carried to the customer's main service equipment, where it is again grounded, often at more than one location on the premises.

The two key points are (1) the neutral is common to both sides of the distribution transformers, and (2) the neutral is grounded (earthed) at multiple locations, some of them widely separated.

[Monkeh]

The two key points are (1) the neutral is common to both sides of the distribution transformers

This seems unwise. Also unlikely. HV and LV earths are normally kept separate for good reason.

(2) the neutral is grounded (earthed) at multiple locations, some of them widely separated.

And this is nothing unusual.

[AlbertL]

The two key points are (1) the neutral is common to both sides of the distribution transformers

This seems unwise. Also unlikely. HV and LV earths are normally kept separate for good reason.

(2) the neutral is grounded (earthed) at multiple locations, some of them widely separated.

And this is nothing unusual.

Using the same wire as the common grounded neutral for both sides of the transformer is standard US practice.  This brochure shows typical pole-mounted distribution transformers: https://www.eaton.com/content/dam/eaton/products/medium-voltage-power-distribution-control-systems/cooper-power-series-transformers/single-phase-overhead-transformers-catalog-ca201001en.pdf.  Note the ground strap connecting the center tap of the secondary to  the transformer tank.  And note that some of the transformers have just one primary terminal - in these models, the other end of the primary winding is internally connected to the tank, which has an external lug for connection of the ground wire.  The models with two primary terminals are intended for delta connections, but can be used in wye by grounding one of the terminals.  My neighborhood in fact has a mix of both types on its wye-connected feeder.  I think one reason for the common neutral is to limit the voltage rise on the secondary side if the primary and secondary circuits accidentally become connected; for example by a fallen wire.

The multiple ground points have the benefit of redundancy and lowered resistance, but can also hide the failure of one or more grounds, and cause undesirable "stray" ground-current paths.
 

[Monkeh]

Using the same wire as the common grounded neutral for both sides of the transformer is standard US practice.

Well, that's.. nice. We don't like bringing the primary into people's houses in the event of an earthing fault, so.. we don't do that.

To quote one technical spec on the subject:

i. All pole-mounted substations shall be designed with separate HV and LV Earthing Systems and shall be separated by at least 20 m.

ii. The HV Earth Electrode earth resistance shall not exceed 20 Ω in order to provide reliable protection operation. (Where surge arresters are installed, the HV Earth Electrode earth resistance shall not exceed 10 Ω).

iii. The LV Earth Electrode earth resistance shall not exceed 20 Ω to comply with ENA Engineering Recommendation EART-01-002.

iv. The HV Earth Electrode and Earthing Conductors shall be of sufficient size and surface area to safely carry fault current at that site (see sections 14.1 and 14.4).

v. EPR on pole-mounted steelwork can approach system phase-to-earth voltage, which in some situations might be close to 6.33kV. All LV equipment shall be suitably insulated and separated from HV equipment to prevent flashover during HV fault conditions.

That said, subject to certain conditions, ground-mounted substations may have an HV earth only (which is then shared). They're a little less damage prone, for a start..

[tooki]

Are you sure?  The EU standards (Annex IV):
https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32012R0932

state that the 'standard' of each dryer should consume (@8kg capacity):
Vented - 4.1 kWh/cycle
Condenser - 2.30 kWh/cycle

The ratings get better at lower capacities, with the energy consumption of a 5kg vented dryer and 5kg condenser dryer only differing by about 20% or so, although the condenser still wins.  I'd be curious why there isn't a linear relationship, it might relate to the extra energy required by the condenser system, pushing the hot air through the internal condensation system might consume extra energy and give more opportunity for heat loss inside the machine perhaps.  The energy consumption of the tumble motor shouldn't be that high (100W or so.)

I have not seen a heatpump dryer for under £400 (~$500USD) here but then again, my current tumble dryer was a  road-side find (it had a blown fuse...)  I suspect that it may be more expensive to buy these types of dryers here as regulations for refrigerants may be more strict.  I would be surprised if propane is an acceptable refrigerant in such a device, which is common in cheap A/C units and refrigerators here.

There's probably the other factor that as you mention, condenser dryers are preferred as there is limited ventilation requirement, with no exhaust to atmosphere, especially important for flat dwellers.

Well, I was sure, since until this thread, I’d never heard any claims of non-heat-pump condenser dryers being more efficient than vented. When I googled just now, the first result that had any statements about energy consumption agreed with me, hence why I posted it.

As for refrigerants, Switzerland is at least as strict as the EU, if not more. (Switzerland has arranged for itself the cushy position of enjoying most EU benefits while being subject to comparatively few of the responsibilities.) I know Switzerland follows EU appliance energy efficiency rules 1:1.

I have no idea what’s in mine, but you have me curious now. I’ll see if I can find out.

(Surprisingly to many outsiders, the US is also really strict on a lot of air quality stuff. In some areas, stricter than the EU, like vehicle exhaust. Unless the guy squatting in the White House gets his way, in which case we can soon expect 70s era smog there again.)

[GlennSprigg]

If you draw 200 A from 120 V phase "A", and 100 A from phase "B", the "neutral" wire will be carrying 100 A--enough to be a BIG surprise for anyone believing it to be "neutral", and mucking about with it while the full phase load is unbalanced.

That is exactly what a neutral is supposed to do.  What big surprise would the neutral have?  3 volts?

Nope!!  "Funny" things used to happen, (here in AussieLand) with say 3-Phase 'Star' (neutral) connected
supply authority transformers, (like the/our  11-kv ones). The Public never saw this, but 'Un-Loaded', you
would see very strange voltages, and often MANY hundreds of volts on the Neutral Star-Point!!   
Was lethal, until loaded/grounded.  Thinking back, it was never explained to us WHY, though...   

[cliffyk]

If you draw 200 A from 120 V phase "A", and 100 A from phase "B", the "neutral" wire will be carrying 100 A--enough to be a BIG surprise for anyone believing it to be "neutral", and mucking about with it while the full phase load is unbalanced.

That is exactly what a neutral is supposed to do.  What big surprise would the neutral have?  3 volts?

It depends on the nature of the mucking.  In a properly installed, intact system, touching the neutral and ground (earth) shouldn't yield any great surprise.  But getting in series with a neutral, or between an open neutral and ground, could expose one to essentially the full line voltage.  And opening a current-carrying neutral could produce a significant arc.

This leads into another interesting aspect of US distribution: the multi-grounded neutral.  The utility substation typically supplies three-phase distribution feeders from the wye-connected secondary of a step-down transformer.  The neutral of the wye is grounded at the substation, travels along with phase conductors, and is grounded at intervals along the line.  Transformers along the feeder make the final step down to customer delivery voltage, which is typically 120/240V single-phase (i.e. a center-tapped 240 volt secondary) or three-phase 120/208V or 277/480V wye.  The secondary neutrals of these transformers are connected to the feeder neutral, and grounded at the transformer location.  Finally, the neutral is carried to the customer's main service equipment, where it is again grounded, often at more than one location on the premises.

The two key points are (1) the neutral is common to both sides of the distribution transformers, and (2) the neutral is grounded (earthed) at multiple locations, some of them widely separated.

Yes, that was my point--disconnecting it, thinking it's harmless would cause a surprise...

[tom66]

A very dangerous condition can occur on TN-C-S electrical systems, which are very common in the UK.  A PEN connection, combined earth/neutral, is passed along with live in the supply cable.  PEN is split into neutral and earth at the main entry fuse.  Most UK homes do not have additional earthing (PME)

The risk is that if PEN fails due to cable damage, corrosion, poor maintenance etc then, although power to the building will be lost, the PEN can effectively float towards Live as any appliance that conducts current in the "off state" (think fridge compressors, heating elements, even some SMPSes) will pull that PEN node up via a low impedance node.  This will then mean if someone touches one of their now-floating appliances and an earthed device (such as water piping, or walks on wet ground outside while touching their PEN-earthed electric car) then they could receive a fatal electric shock.

This is a particular pain for EV charging installations, as far as I am aware there are only two ways to solve the problem:
- Earth rods until the impedance is below some nominal figure, which can often require 5+ earth rods to be drilled in to the driveway and fitted (expensive, time consuming)
- An EV charging station that isolates PE as well as L/N when power fails and only connects PE when the vehicle has been detected

It's for this reason PME is now standard at newer builds ... but again, one of those cost saving decisions made 50 years ago that bites us in the ass now.

[Monkeh]

A very dangerous condition can occur on TN-C-S electrical systems, which are very common in the UK.  A PEN connection, combined earth/neutral, is passed along with live in the supply cable.  PEN is split into neutral and earth at the main entry fuse.  Most UK homes do not have additional earthing (PME)

The majority of TN-C-S systems are PME. PME is distribution side, not customer.

This will then mean if someone touches one of their now-floating appliances and an earthed device (such as water piping

This is what bonding is for, see: equipotential zone.

or walks on wet ground outside while touching their PEN-earthed electric car

And this is a rather overblown concern IMO, but it is in fact proving to be a pain.

[richard.cs]

And this is a rather overblown concern IMO, but it is in fact proving to be a pain.

Well yes, it's not introducing a genuinely new risk, the general public was already hopelessly unaware of the risk of outdoor class I appliances with TNC-S earthing and happily bought all manner of earthed metalwork outdoors (outside of the equipotential zone), in addition to the various light fittings, outdoor taps and gas pipes (which now seem to default to running along outside walls) that form part of the installation more generally. The only difference with electric cars is that it's a new kind of class I appliance intended for use outdoors (rather than incidentally used as such), and lots of people have got in a bit of a panic about it. Class II cars would be possible, but it's now rather too late for that.

Generally the safety case for TNC-S in the UK has been looking progressively poorer for decades as the metallic water and gas pipes that used to provide free sub-Ohm backup earthing have disappeared, and the promised reliability of double-crimped neutral connections has not really been achieved.

[Gyro]

John Ward has a useful video on the subject (EV charger earthing)...  https://youtu.be/gZVx7GbAwlg

There are also an increasing number of chargers with earth fault detection, which do not require separate earthing... https://youtu.be/3-HEKqeSrwk

[helius]

The risk is that if PEN fails due to cable damage, corrosion, poor maintenance etc then, although power to the building will be lost, the PEN can effectively float towards Live as any appliance that conducts current in the "off state" (think fridge compressors, heating elements, even some SMPSes) will pull that PEN node up via a low impedance node.

The same situation in North America is called a broken neutral, and because of the split pole arrangement, does not cause power to the building to be lost! The tell-tale sign is when some of the lights dim or grow brighter in concert with a refrigerator or heater cycling on and off. Incandescents show the effect most because they run unregulated.

- Earth rods until the impedance is below some nominal figure, which can often require 5+ earth rods to be drilled in to the driveway and fitted (expensive, time consuming)

Measuring earth bonding also requires the installation of temporary grounding rods at some distance (100') to null the effect of local potential variations in the earth (caused by earth leakage). This is obviously complicated in a neighborhood with small subdivisions. And driving 10' grounding rods is no fun...

[Monkeh]

And this is a rather overblown concern IMO, but it is in fact proving to be a pain.

Well yes, it's not introducing a genuinely new risk, the general public was already hopelessly unaware of the risk of outdoor class I appliances with TNC-S earthing and happily bought all manner of earthed metalwork outdoors (outside of the equipotential zone), in addition to the various light fittings, outdoor taps and gas pipes (which now seem to default to running along outside walls) that form part of the installation more generally. The only difference with electric cars is that it's a new kind of class I appliance intended for use outdoors (rather than incidentally used as such), and lots of people have got in a bit of a panic about it. Class II cars would be possible, but it's now rather too late for that.

Generally the safety case for TNC-S in the UK has been looking progressively poorer for decades as the metallic water and gas pipes that used to provide free sub-Ohm backup earthing have disappeared, and the promised reliability of double-crimped neutral connections has not really been achieved.

Now, I could be wrong, but as far as I'm aware most electric cars do not connect the charging CPC to the chassis. That coupled with plastic handles and extremely high quality paint finishes leaves me entirely unconcerned about taking a belt off a car. Oh, that and like most people I walk around on a big sheet of rubber, not my bare feet.

I do, however, think we should never have used TN-C-S as an excuse not to properly control potential at the installation. It's a perfectly good system for ensuring a nice low impedance fault path for currents in normal operation without using lots of extra copper (or lead, or alu), but a poor excuse for not having good earthing at the property (and the American method of whacking a rod in quickly doesn't cut it).

[tom66]

Now, I could be wrong, but as far as I'm aware most electric cars do not connect the charging CPC to the chassis. That coupled with plastic handles and extremely high quality paint finishes leaves me entirely unconcerned about taking a belt off a car. Oh, that and like most people I walk around on a big sheet of rubber, not my bare feet.

You would unfortunately be incorrect.  The chassis of my PHEV VW Golf GTE is connected to the earth pin on the type 2 connector.  This means 12V battery earth and the Type 2 connector earth are the same.

While the paint on the vehicle provides some level of insulation (I was unable to measure a direct connection, although I of course did not press into the paint) parts of the car like the door locks and frame were found to be conductive in my tests.  It's possible to imagine someone stepping into their car and getting a shock that way. Also, the trailer connection if fitted would expose this, as would cigarette lighter/USB convenience socket or parts under the engine compartment.

I actually measured a direct connection from the alloy wheels to the protective earth if you want to talk about an interesting way to get a shock. I guess there are some bearings somewhere that are chassis connected.

[Monkeh]

Well, that's a shame. Roll out the earth mats (not that anyone wants to spend money on infrastructure).

[richard.cs]

Now, I could be wrong, but as far as I'm aware most electric cars do not connect the charging CPC to the chassis. That coupled with plastic handles and extremely high quality paint finishes leaves me entirely unconcerned about taking a belt off a car. Oh, that and like most people I walk around on a big sheet of rubber, not my bare feet.

Unfortunately most electric cars do have that CPC to chassis connection. I suspect only because it makes EMC design easier, or reduces costs over double/reinforced insulation, or even just because of an "earth everything" mentality. I agree there is no sound technical reason why it is required.

Personally I think plastic handles, paint and shoes make the risk small compared to other things (outside taps are the classic worry, often being associated with wet skin and bare feet). I don't worry at all when mine is plugged into a known TNC-S supply.

I do, however, think we should never have used TN-C-S as an excuse not to properly control potential at the installation. It's a perfectly good system for ensuring a nice low impedance fault path for currents in normal operation without using lots of extra copper (or lead, or alu), but a poor excuse for not having good earthing at the property (and the American method of whacking a rod in quickly doesn't cut it).

Fundamentally it is a poor system for that reason, and if we were starting from scratch today this is not where we'd end up. Personally I'd be inclined to go for something with an impedance-earthed neutral and then we could distribute a low-current CPC at negligible cost. This would be somewhat similar to UK HV distribution. Such a system allows RCD-like fault protection with much greater reliability than common 30 mA RCDs due to having a few tens of amps of fault current to play with, and gives negligible rise of earth potential during a fault.

From where we are today though I think that will never happen, we'd have to return to TNS or more likely give up on supplier earthing and TT everything - and that has problems with unreliable RCDs.

[tom66]

I think the reason for the CPC being earthed to battery negative is the sheer convenience of the communication interface of the pilot signal and cable detection. And for vehicles with DC-CCS, then they also need a communication bus with the charging station.  So you can keep all of this logic on the non-insulated side which reduces costs and complexity.

Of course the high voltage battery is always isolated from the rest of the chassis and this system is continuously monitored,  isolation drifting out of the specification will flag a service warning or disable drive.

[Monkeh]

From where we are today though I think that will never happen, we'd have to return to TNS or more likely give up on supplier earthing and TT everything - and that has problems with unreliable RCDs.

The reliability (or lack thereof) of RCDs is why I'm not a fan of TT systems. Although I suspect a lot of that has to do with the price point of them usually being used for secondary protection. Quality of protective devices is a problem which sorely needs addressing (more so than 'ooh, AFDDs sound good', and 'oh no, plastic boxes are bad in fires').

reduces costs and complexity.

Increases cost and complexity to the end user for the sake of the profit margin of the vehicle manufacturer, you mean. They know full well what earthing systems are in place, just like the manufacturers of bathroom fans know full well they'll be installed on 6A circuits.

[tom66]

Well the costs only come to users for countries where PME is not standard.  I don't know what the situation is in the rest of Europe but I imagine this would have been a consideration.

It's worth noting that in the Type2 standard the CP/PP signals are referenced to PE, and a secondary pain happens should there be a short that leads to the ~10mA DC current from these saturating a downstream RCD's current transformer, preventing it from operating correctly.

What this really is showing is how outdated our electrical infrastructure is. Frankly given all of this I'm shocked (no pun intended) that "granny chargers" (i.e. portable EVSE) are still permitted and sold with cars, despite the well known fire hazards.

[Monkeh]

It's worth noting that in the Type2 standard the CP/PP signals are referenced to PE, and a secondary pain happens should there be a short that leads to the ~10mA DC current from these saturating a downstream RCD's current transformer, preventing it from operating correctly.

Ah, yes, because we still use type AC RCDs in blissful ignorance of the loads around us changing. Well, those who even have RCDs, because spending money on your electrical installation is daft, "It's worked fine for all these years".

[richard.cs]

Frankly given all of this I'm shocked (no pun intended) that "granny chargers" (i.e. portable EVSE) are still permitted and sold with cars, despite the well known fire hazards.

The risk approaches for cars and electrical installations are so fundamentally different. All EVs could come supplied with a pair of yellow rubber washing up gloves and be connected to the mains with permanently-live M10 wingnuts and the majority of deaths would still come from allowing minimally-trained persons to manoeuvre tonnes of metal at high speed in public places rather than electrical shock.

It's very hard to argue that car manufacturer's should spend anything on electrical safety when they would save more lives spending that same money on improved brakes/seatbelts/airbags/etc., let alone that they should worry about TNC-S touch voltages.

[themadhippy]

IF were ripping out the  network and starting from a clean sheet we should spent a few quid on  distributing the neutral from the source to the point of use,would make things lot safer.

The risk is that if PEN fails due to cable damage, corrosion, poor maintenance etc

In the uk the biggest cause of failure of the bond from neutral to earth at substations was the same cause of train signalling failures, being tied to the towbar of a 4x4 or transit and driven off down the road at  high speed

as far as I am aware there are only two ways to solve the problem:
- Earth rods until.

Its a "problem" thats well document and covered in sevral parts of the uk wiring regs,put simply if your taking power outside the house dont take the earth,source it locally.

[IanB]

I'm a bit puzzled about the discussion of potential hazards from unexpected earth potentials.

Isn't it an important requirement that earth is bonded to all exposed metalwork (water pipes, gas pipes) in an installation?

If I could get a shock from touching my charging EV, couldn't I also get a shock from touching a garden tap for a hosepipe?

What is the difference between these cases?

[helius]

If I could get a shock from touching my charging EV, couldn't I also get a shock from touching a garden tap for a hosepipe?

What is the difference between these cases?

Conceptually they are the same: the metal object is bonded to the equipotential zone of the building, but you are standing on a section of earth that is outside and can be at a different potential in case of significant earth leakage, or if the building's link to earth is broken because of poor maintenance. People can and do get shocked by touching outside faucets, and worse problems are found around boats.

[tom66]

If I could get a shock from touching my charging EV, couldn't I also get a shock from touching a garden tap for a hosepipe?

Yes you could, but you don't tend to find two-tonne water garden taps parked on driveways accessible to the public, postman and neighborhood cat.

More seriously I think this is the reason plumbing tends to be grounded.

[TimFox]

Electricity and plumbing is not a trivial problem.  During the American invasion of Iraq, faulty grounding caused over 18 accidental electrocutions of Army and contractor personnel in new showers.  See
https://www.huffpost.com/entry/toll-rises--at-least-18-u_b_124863
When installing equipment in foreign countries with temporary portable Diesel generators for AC mains, I encountered ungrounded three-wire outlets.  Since all our low-power equipment used a conventional 3-prong IEC line filter at the single-phase mains input, the chassis of computers or other equipment ended up near half the mains voltage with respect to the heavy hardware that was grounded.  Even though the current through the victim is limited by the small capacitance of the filter, it can still cause one to fall off a ladder when surprised.

[AlbertL]

Figure 1-1 ("Multi-Grounded Common Neutral" Distribution System) on this page https://www.electrical-contractor.net/forums/ubbthreads.php/ubb/printthread/Board/15/main/16309/type/thread.html illustrates the system used by my utility, and which I think is the most common in the US.

So, here's a question: what would be the resulting voltage at the customer's premises (bottom of the drawing) in the case of an accidental short between the ungrounded side of the distribution transformer primary (7200V) and one end of the 240V secondary?

[duckduck]

Non-heat-pump condenser dryers use more energy than vented, not less: https://www.cda.eu/laundry/condenser-vs-vented/

In cold climates, vented dryers are the least efficient after accounting for heat lost from the building.

In cold climates all appliances are 100% efficient

[CatalinaWOW]

Non-heat-pump condenser dryers use more energy than vented, not less: https://www.cda.eu/laundry/condenser-vs-vented/

In cold climates, vented dryers are the least efficient after accounting for heat lost from the building.

In cold climates all appliances are 100% efficient

Not an outside vented cloths dryer.

[helius]

So, here's a question: what would be the resulting voltage at the customer's premises (bottom of the drawing) in the case of an accidental short between the ungrounded side of the distribution transformer primary (7200V) and one end of the 240V secondary?

Which end, the side linked in-phase with the primary, or the other side?

[richard.cs]

So, here's a question: what would be the resulting voltage at the customer's premises (bottom of the drawing) in the case of an accidental short between the ungrounded side of the distribution transformer primary (7200V) and one end of the 240V secondary?

Just looking at the diagram I would say it depends on the saturation behaviour of the distribution transformer when it sees 7200 V on its secondary winding, and the impedance of the HV line and neutral at that point. Overall the secondary winding probably looks mostly like a short to the HV, and the shared neutral is probably pulled up to around half the HV line voltage. Clearly it should draw enough fault current to trip the HV, but until that happens I don't think I'd want to be touching any line, neutral or earth at any of the six consumers shown, including the ones on other transformers.

An impedance-earthed star point on the HV source would be much nicer.

[james_s]

I've never heard of that happening although I suppose anything is possible.

Back in the 90s a high tension line fell on a 7200V line and resulted in a substantial overvoltage in my friend's neighborhood. It blew out a bunch of light bulbs and fried some of their electronics.

[IanB]

I've never heard of that happening although I suppose anything is possible.

Apparently it can happen that the 7200 V line can fall onto the telephone or CATV line strung lower down the pole, and cause problems (occasionally fatal) in connected homes.

[richard.cs]

Apparently it can happen that the 7200 V line can fall onto the telephone or CATV line strung lower down the pole, and cause problems (occasionally fatal) in connected homes.

We don't share telephone etc. with HV poles here (UK), poles can have HV and LV or LV and signal stuff (but is possibly discouraged now?) but not HV and signals. Generally we have less overhead distribution in urban areas compared to what I have seen of the USA, and near-zero overhead HV in towns.

We have a lot of overhead LV and overhead telephone in older suburban areas, but all but the most rural newbuilds have all the cabling underground. Likely more to do with maintenance costs than safety, all the urban overhead LV was installed when labour was a lot cheaper.

Typical UK suburban area with overhead LV (note that line and several others is fed from a ground mounted transformer ~50m away via that PILC cable): https://goo.gl/maps/ruSgiQZ6PCM4PnNu9
A few hundred yards away it's been updated to aerial bundled cables: https://goo.gl/maps/Rxujc9uwFYUqKMDs5
Typical UK rural setup with a small pole mount transformer and HV and LV sharing that pole: https://goo.gl/maps/Ph3DQrHQmp7W6wMh7

[TimFox]

In residential areas of Chicago, with alleys between rows of houses, there are usually poles along the alley that carry the overhead power line, pole transformers, telephone, and cable lines.  Typically, though, they are fed from underground cables.  Total underground distribution is typical in industrial parks in the suburbs.  If you want to see a sky extremely polluted with overhead wires, go to urban Japan.

[themadhippy]

If you want to see a sky extremely polluted with overhead wires, go to urban Japan.

Their mere amateurs,try Thailand Cambodia or Vietnam to see how the professionals do it.

[james_s]

Apparently it can happen that the 7200 V line can fall onto the telephone or CATV line strung lower down the pole, and cause problems (occasionally fatal) in connected homes.

We don't share telephone etc. with HV poles here (UK), poles can have HV and LV or LV and signal stuff (but is possibly discouraged now?) but not HV and signals. Generally we have less overhead distribution in urban areas compared to what I have seen of the USA, and near-zero overhead HV in towns.

We have a lot of overhead LV and overhead telephone in older suburban areas, but all but the most rural newbuilds have all the cabling underground. Likely more to do with maintenance costs than safety, all the urban overhead LV was installed when labour was a lot cheaper.

Underground wiring is far more expensive to install and maintain than overhead. While it's true that it isn't as prone to damage in wind storms that knock trees down it's not immune, a root ball from a fallen tree can really do a number on underground wires. It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry and have relatively few trees though.

[TimFox]

A big advantage of underground wire in my part of the country is less problems with ice storms.

[AlbertL]

So, here's a question: what would be the resulting voltage at the customer's premises (bottom of the drawing) in the case of an accidental short between the ungrounded side of the distribution transformer primary (7200V) and one end of the 240V secondary?

Which end, the side linked in-phase with the primary, or the other side?

Good point - I hadn't considered the phasing aspect.   I think in the electrical power world they call that "polarity" even though it's referring to AC.

[james_s]

Underground certainly has advantages, but it's not a panacea. Every time we have a big storm, especially the once in a decade kind a bunch of people start moaning that we should redo everything to underground. They have no clue how much it would cost and think it will solve all the problems, but it won't.

[richard.cs]

Underground wiring is far more expensive to install and maintain than overhead. While it's true that it isn't as prone to damage in wind storms that knock trees down it's not immune, a root ball from a fallen tree can really do a number on underground wires. It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry and have relatively few trees though.

I am with you on more expensive to install but unconvinced on underground cable maintenance being more expensive than overhead, at least in a UK-like climate. Sure it costs more to actually do the repair but it is rare. Here underground cable faults are more often from people digging them up by accident* than by tree roots and similar though it does happen. Failures not caused by digger buckets are often poorly installed joints or places where the cable sheath was nicked on installation leading to eventual to water ingress. I don't see why the cables themselves would be considered vulnerable to flooding? They're waterproof and often installed below the water table anyway. A majority of all the underground cables ever installed in the UK are still in service, thousands of miles of 1950s lead-covered cable still in-use. In comparison we loose lots of overhead cables every time there's a storm and routine maintenance is needed too - regular tree cutting, replacement of the poles every 30 years or so, etc.

Generally I expect our electricity suppliers to do the cheapest thing, and they seem to have settled on putting new cables underground by default in urban and suburban areas. This may be influenced by them being fined for customer minutes off supply, so powercuts have a significant financial cost.

*Yes someone pays to fix these (and other expenses incurred as a result), but it's not the cable owner.

[TimFox]

Yes, everything in engineering involves a trade-off between installation cost and operating cost.  It depends on how much it costs to repair ice-storm damage, and often it occurs, and if the power company is liable for consequent damage.  New York City banned overhead wires sometime after a serious blizzard in 1888, although there are still some areas in the city (annexed thereafter) with overhead wires.

[themadhippy]

It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry

meanwhile in the uk we run 400KV cables under the towpath and use the canal water to keep the cables cool

[IanB]

Generally I expect our electricity suppliers to do the cheapest thing, and they seem to have settled on putting new cables underground by default in urban and suburban areas.

In the UK I would think this is more about planning consent than cost. When there is a new development every detail has to be negotiated with the planning authority, and I would assume that "all cables are underground" is high on the list of requirements.

Weirdly, not long ago the National Grid were upgrading a substation near where I grew up (I used to fall asleep every night to the transformer hum floating miles across the countryside--but I digress), so anyway they were upgrading the substation and they actually did a public consultation about the design of a new switch yard--air insulated circuit interrupters or gas insulated interrupters. The air breakers were bigger, required more land area, but were cheaper and easier to maintain, while the SF6 breakers were more compact and had a smaller footprint, but were more expensive. People voted for the SF6 design, and they accepted the result of the poll. I was surprised they actually did that consultation exercise.

[james_s]

It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry

meanwhile in the uk we run 400KV cables under the towpath and use the canal water to keep the cables cool

How many junctions, switches, fuses, and transformer vaults are down there under the canal water? How much does it cost to maintain them? Do you think the UK possesses some magical technology that North America lacks? Keep in mind the entire country is smaller than some of our individual states, there has got to be a lot less electrical infrastructure, vastly fewer km of cable.

This is one source I came across: "According to the May 2011 paper “Underground Electric Transmission Lines” published by the Public Service Commission of Wisconsin, “The estimated cost for constructing underground transmission lines ranges from 4 to 14 times more expensive than overhead lines of the same voltage and same distance."

Underground lines have their place, they have advantages, but they also have disadvantages. Because of that we typically use underground in cities and modern suburbs but the long runs between towns are usually overhead.

[richard.cs]

meanwhile in the uk we run 400KV cables under the towpath and use the canal water to keep the cables cool

How many junctions, switches, fuses, and transformer vaults are down there under the canal water? How much does it cost to maintain them? Do you think the UK possesses some magical technology that North America lacks? Keep in mind the entire country is smaller than some of our individual states, there has got to be a lot less electrical infrastructure, vastly fewer km of cable.

This is one source I came across: "According to the May 2011 paper “Underground Electric Transmission Lines” published by the Public Service Commission of Wisconsin, “The estimated cost for constructing underground transmission lines ranges from 4 to 14 times more expensive than overhead lines of the same voltage and same distance."

Here we make a distinction between "transmission" at >100 kV, "HV distribution" generally at 11 kV and 33 kV, and "LV distribution" at 400 V (all line to line).

The vast majority of our transmission network is overhead - at these voltage levels underground becomes very expensive, but in urban areas both HV and LV distribution tends to be underground, and there is very little suburban HV distribution.

Underground lines have their place, they have advantages, but they also have disadvantages. Because of that we typically use underground in cities and modern suburbs but the long runs between towns are usually overhead.

Well yes, we tend to do that too, noting that "long runs" are always at higher voltages. The point I was making is that this kind of thing: https://goo.gl/maps/rqwRZZQkqCgEUxqQ6 with HV distribution on poles in a urban area just does not exist here at all.

[tom66]

There are some 275kV cables that run under an office estate I used to work at in Leeds.  I'm not sure why they ended up there but I recall National Grid was pissed that someone had built an estate over this underground line.  They had assumed they would always be able to dig to access the cable!

[themadhippy]

How many junctions, switches, fuses, and transformer vaults are down there under the canal water?

none ,but then again no mention of those factors was mentioned by the claim

It's also far more prone to damage from flooding

The added advantage is no road closures if a fault does occur,and the heat from the cables keep the tow path frost free

with HV distribution on poles in a urban area just does not exist here at all

https://goo.gl/maps/zkvizUUCEwnNckxJ8

[Monkeh]

with HV distribution on poles in a urban area just does not exist here at all

https://goo.gl/maps/zkvizUUCEwnNckxJ8

Well, they're not poles..

[james_s]

The added advantage is no road closures if a fault does occur,and the heat from the cables keep the tow path frost free

I don't see how they avoid road closures if there's a fault, here they typically have to close at least a lane to excavate a faulty underground cable, sometimes it's quite a major project. There have been a few cases where underground transformer vaults have caught fire or exploded and left a crater in the street. If it's an overhead line the fault is usually a large tree falling across the line (and the road) so the road is closed while crews clear the tree, repairing the power lines doesn't normally require any sort of closure, they just park the utility truck on the shoulder and get to work. It doesn't really happen very often though, just when a big storm rolls through at which point there are often road closures all over from downed trees, most of which don't involve power lines.

Somebody posted this a few days ago https://www.youtube.com/channel/UCpJWHeFjOjoDrHLIPqIHgwA
He's based in Canada but their system is pretty much the same as what we use here in the US. Older and rural areas are typically exclusively overhead, newer, urban and/or more upper class areas that can afford the cost are usually underground.

[themadhippy]

I don't see how they avoid road closures if there's a fault

here in the uk its  rare to find vehicles on canal towpaths,maybe its different in america

[IanB]

here in the uk its  rare to find vehicles on canal towpaths,maybe its different in america

Speaking of which, I wonder how they get motorized vehicle access to maintain their poles? Or for that matter the transmission tower visible on the other side of the canal? In California transmission and distribution lines tend to be placed along a vehicular right of way. In the UK they seem to get plonked down anywhere across the countryside.

The pole in the foreground appears to be burnt. Lightning strike perhaps?

https://goo.gl/maps/MhbJjs7dMU1i61JF9

[themadhippy]

Lightning strike perhaps

more likely local scrotes trying to set them on fire

[AlbertL]

with HV distribution on poles in a urban area just does not exist here at all

https://goo.gl/maps/zkvizUUCEwnNckxJ8

Well, they're not poles..

Love the towers in the middle of the roundabouts!  That must have taken some serious coordination between the utility and the road authority.

[Monkeh]

with HV distribution on poles in a urban area just does not exist here at all

https://goo.gl/maps/zkvizUUCEwnNckxJ8

Well, they're not poles..

Love the towers in the middle of the roundabouts!  That must have taken some serious coordination between the utility and the road authority.

I think it's far more likely they built that entire estate around them to save costs. They're actually gone now anyway. At least 8 years gone.

[themadhippy]

They're actually gone now anyway. At least 8 years gone.

Have they? Another childhood memory gone.

[richard.cs]

with HV distribution on poles in a urban area just does not exist here at all

https://goo.gl/maps/zkvizUUCEwnNckxJ8

Well, they're not poles..

This is the transmission vs distribution distinction I was trying to make. We have >100 kV lines on towers passing through some urban areas because at those voltages underground just gets crazy expensive, but the general power distribution for that area, at moderate HV voltages of 11-33 kV (we used to call this "medium voltage" / "MV") is underground. Scrolling way back we were discussing shared HV and LV on poles, etc. and this is something we never get on those kind of towers.

Also it's not a pole

Speaking of which, I wonder how they get motorized vehicle access to maintain their poles? Or for that matter the transmission tower visible on the other side of the canal? In California transmission and distribution lines tend to be placed along a vehicular right of way. In the UK they seem to get plonked down anywhere across the countryside.

In this case probably either by driving carefully along the towpath which might just have enough gap between poles and water, or by boat. A lot of distribution poles here are across farmland and and accessed with offroad vehicles.

The pole in the foreground appears to be burnt. Lightning strike perhaps?

https://goo.gl/maps/MhbJjs7dMU1i61JF9

This is 33 kV distribution, and I think the black areas on the pole are just places where the wood preservative is darker.