house outlet ac power

[mcz]

The conductor thickness comparison was mostly an exercise to illustrate how much more copper is needed for those higher currents. It is a lot. (P=I²*R losses)

I can see it was an exercise, but clearly an incorrect one which is why I corrected you. Obviously higher current requires more copper, there is no way around this. This is not related to 1-phase vs. 3-phase. Your example supposedly showed that 3-phase requires lower mm^2 per A - in other words, better utilization - but I showed that your calculation is incorrect, and now you just changed the goalpost to match the reality that the 1-phase 75A use case actually carries more current, which is indeed true.

If you need x A, then you need x A. Single-phase system has optimum copper use, since the current in incoming conductor and return path is always automatically equal.

Perfectly balanced 3~230V equals 1~400V system regarding losses, AFAIK, so it does a bit better. But you could as well use the 400V in a single phase system, or do what our US. of A friends do and use a center-tapped transformer to power "small" trivial loads with lower voltage, and big loads with higher.

[...]

Well, in the end it is a certain amount of power that is heating your house/water, not current.
If we assume for simplicity and easy comparison that your 75A circuit is 3 times a 25A single phase coming in (and it is the same phase) that just gets paralleled that gives you 6 times a conductor of a certain size.
The according 3-phase system (at the same power -> 3x25A but 3 phases) gets rid of 2 return paths leaving you with just 4 wires of the same size. And again, no bigger sized neutral in use here.

Whether you use the available power is up to you. Just because in your example the 25A rating is particularly shitty doesn't mean the concept as a whole is bad.

[JohanH]

In other words, in 3*25A nominal systems it's completely possible and usual that some of the wires carry 30-35A (beyond the design current) while the total is still just say 50. This leads to poor copper utilization. While in 1-phase house wiring, copper utilization is always optimal and geez, if you don't need 75A, then don't wire for 75A.

Maybe farming and industrial needs have influenced the shift to 3-phase here. I remember in my youth, a lot of farmers installed electrical motors for dehydrating grains, conveyors etc. I remember one particular example on a farm where the 3*60A main fuse sockets always expanded due to the high current and eventually began sparking and then popped a fuse. It was solved by changing to industrial grip type fuses. This particular motor was so big so it could be seen around the village when they started it (every evening), due to the lamps always dimming a bit. That again was solved by a larger distribution transformer in the village. There were single phase connected houses here in the past, but I haven't heard of any with larger than 25A mains. The "upgrade" that was offered was always 3-phase, not larger mains fuses.

Now the 3-phase heat pumps have been in a bit of bad situation because of the situation you describe. I've read many examples of their inverters going bad due to one phase breaking in the house. Solution for those would be larger mains fuses and/or phase protection at the pump that breaks all phases if one goes missing. So actually I'm glad I get by with a one-phase compressor, less troubles.

[JohanH]

Here in the Southern parts it works fine, but I do switch to oil, below approx. -17 (when COP < 1.5). Still, one of the most important things overlooked by those installing air-to-water units is the total surface area of the distribution (radiator size, or in-floor heating vs. not having one). It completely changes the game. If you need to run 60degC water into the system at mere -10degC, you can't win. Even ground source would struggle to give good savings but it at least somehow works. But the whole game changes if you run 30degC water in massive radiators or in-floor heating. I invested 3000€ in the heat pump and another 600-700€ into upgrading radiators and it's working well and based some modeling and approximate measurements I'm expecting SCOP significantly exceeding 2. The radiator upgrade pays for itself in a year or two. Such "small" details are hugely important.

Yes, I upgraded radiators as well when switching from oil to ground heat pump (the bigger the better). In-floor heating would be best, but this is an old house, so not that easy to convert. Now it gets to 55-60 ℃ at -25 ℃, so kind of fine. Those temps are rare, but happens about once per winter.

Some statistics I've checked/calculated from the heat pump:

COP 4.4 at 0 ℃. Heat output 2.4 kW, electrical power 0.54 kW.
COP 3.9 at -15 ℃. Heat output 4.5 kW, electrical power 1.16 kW.
(this must be momentary numbers, my notes are a bit messy)

With a newer house with better insulation and only in-floor heating, those numbers would be better.

Edit. Looked up my notes and it looks like SCOP improved from 3.2 to 3.7 due to the larger radiators. In 2021 SCOP was 3.7. These numbers are quite reliable, because I've a separate energy meter at the pump and the pump itself has its own flow sensor, calculating total heat output.

[nali]

Yeah, well for us here, the incentive has been always there and is purely economical, because energy price have had near 1:1 parity between electricity and burnable fossils, thanks to cheap electricity and heavily taxed fossils; causing the COP of the heat pump to translate into money savings almost directly. This is one of the few things we have the right way here, IMHO. The fact that in UK or US you get natural gas (or even oil) for so much cheaper than electricity per kWh, that installing heat pumps makes no financial sense, is just... nuts. Especially since the conditions for air source heatpumps would be just excellent in the UK. We run 'em here even though they are pretty marginal, and they still make financial sense... or made, before the subsidies caused hyperinflation in their install prices.

Well in the UK there is a masive disparity between domestic gas & electricity prices. A quick look at my last year's bills which is a standard domestic tariff* gives gas:3.3p electric:19.7p per kWh which even at optimal CoP makes it more expensive to run. Add to that the cost of installation means there's simply no incentive to retro-fit.

There is a govt grant to offset installation, but you need to use an approved installer (expensive) so expect to pay a 5-figure sum.

*(We're planning moving house so not much point signing up to new tariffs just now. I do want to move to heatpump but I'll evaluate that as part of the whole package when housemoving)

[Zero999]

Yeah, well for us here, the incentive has been always there and is purely economical, because energy price have had near 1:1 parity between electricity and burnable fossils, thanks to cheap electricity and heavily taxed fossils; causing the COP of the heat pump to translate into money savings almost directly. This is one of the few things we have the right way here, IMHO. The fact that in UK or US you get natural gas (or even oil) for so much cheaper than electricity per kWh, that installing heat pumps makes no financial sense, is just... nuts.

How is it nuts?

A good proportion of our electricity is generated using natural gas and other fossil fuels, so it's obviously going to be more expensive, than gas. Electricity being the same price as gas makes no sense. It's like in the USSR when bread was cheaper than grain, at one point, so farmers fed it to their animals. This just shows the insanity of too much state interference in the market.

Because if you turn natural gas into electricity in modern combined cycle facilities and use at least some of the waste heat for district heating with combined total efficiency of, say, 60% (this is a fair approximation, much better numbers have been reported), and then use this 60% to run heat pumps at COP=3, total efficiency (from chemical energy in gas, to heat output inside houses) is 180%. Add renewables to the mix and it only gets better. This is why.

The point you totally miss is extracting free energy. It's similar to PV; the only reason not to install it is, if install costs exceed the savings. Artificial market structures like super-cheap fossils and expensive electricity affect that natural balance of energy choices which should be based on minimizing burning fossils and maximizing extraction of free energy.

This is, if bread was miraculously falling off the sky, it would make sense to feed it to animals, even if small amount of effort would be required to collect and distribute that bread.

If you think it from climate viewpoint, price should be in relation of the CO2 emissions per kWh. The emissions from grid energy are roughly similar to that of locally burning natural gas. (Roughly, because it's really a moving target). Hence the price should be similar. Not exactly the same, but 3x difference in favor of burning fossils is, I repeat, just nuts.

If natural gas is three times cheaper per kWh than electricity, this leads to massive waste of energy due to ignoring heat pumps, which could provide a lot of basically "free" energy.

Finland's tradition of similar price per kWh between fossils and electrical energy (which, on average, has lower CO2 footprint than locally burning fossils) is not only logical and fair, it leads into natural incentive to make energy efficient choices. Now this is partially thanks to the nanny state which I pretty much hate, and we have many of those USSR-like sick mechanisms you mention, but approximate energy price parity is not one of those; this is one of the very few areas where the system accidentally succeeded. Maybe because no one has thought about it, it's not planned, it's more of a coincidence.

Also don't underestimate the amount of politics that went into the cheaply available natural gas! It's an indirect incentive as well. That is the part I call nuts.

Similarly, some countries have sources of cheap oil available to them thanks to political choices of extracting it, or starting wars to gain access to it. We never had this kind of source.

Yes it's more environmentally friendly to use a heat pump, but it's more expensive. The fact that gas has to be taxed to make the price equal to electricity in your country proves this. I'm all for cutting CO₂ emissions, but I'm against everyone being poorer and higher taxes more. If the UK achieved net zero CO₂ emissions tomorrow. It would make absolutely sod all difference to the global climate, with Russia, China and the US emissions dwarfing the UK. The only people who would benefit is our big fat government.

I wonder if gas powered heat pumps would be a better alternative, assuming they're a thing? The installation cost would  be high, but they're bound to be more efficient.

[SeanB]

Rural single phase is very common, SWER means you only have to run a single bare 11kV overhead aluminium conductor, and put the transformer by the load, and add in the big earth mat under the transformer, with the secondary having a separate earthing rod a few metres away. Thus you find there being a product from Alsthom in supplying a single phase 22kW motor, which is a common item to use, as 63A is about the largest load you can get off the most common cheap rural tariff, for a 15kVA supply, and not needing a supply conductor upsize.

3 phase yes is cheaper in conductor if you only consider conductor size, but if the supply also means you need 3 conductors installed, instead of one, then single phase is cheaper for rural use, especially as there is no difference in conductor size at 11kV.

[BeBuLamar]

If your house only have 2400W like someone said you're in big trouble.

EDF in France go down to a 3kW supply agreement.

You mean you can only have 3kW to power your house? Wow. I was thinking of getting a backup generator for my house and I think I need a 20KW unit to do that.

[Capernicus]

If your house only have 2400W like someone said you're in big trouble.

EDF in France go down to a 3kW supply agreement.

You mean you can only have 3kW to power your house? Wow. I was thinking of getting a backup generator for my house and I think I need a 20KW unit to do that.

I thought it was 10A for the whole house - before it starts to brown out.   (or the safety goes off.)

[JohanH]

You mean you can only have 3kW to power your house? Wow. I was thinking of getting a backup generator for my house and I think I need a 20KW unit to do that.

What kind of house is that? Levitating? Just kidding. I think I would get by with a 3 kW generator (worst case). But that would mean no sauna or car engine heaters. We have about 2 kW continuous power consumption with short peaks of 6-7 kW in the winter. Total year consumption 16000 kWh. And I would imagine it's a typical house around here (maybe a bit on the smaller side).

[Zero999]

If your house only have 2400W like someone said you're in big trouble.

EDF in France go down to a 3kW supply agreement.

You mean you can only have 3kW to power your house? Wow. I was thinking of getting a backup generator for my house and I think I need a 20KW unit to do that.

I thought it was 10A for the whole house - before it starts to brown out.   (or the safety goes off.)

Don't be silly. An electric kettle normally uses around 10A, which is 2400W, at 240V. In the UK, the maximum current per plug is 13A, which is roughly 3kW, although some appliances can draw a little more, for a short period.

[Capernicus]

So its per plug,  not for the whole house!!

I didn't know that.     So what if I get two plugs and power one thing off it,  do i get 20A??

[themadhippy]

So what if I get two plugs and power one thing off it,  do i get 20A??

Theoretically yes, practically  you stand a very good chance of being dead

[Zero999]

So its per plug,  not for the whole house!!

I didn't know that.     So what if I get two plugs and power one thing off it,  do i get 20A??

No, the device will only draw as much current as it needs.

Connecting two plugs together is very dangerous. Don't do it. If someone disconnects one of them, it will have mains voltage, on the exposed pins.

[IanB]

An electric kettle normally uses around 10A, which is 2400W, at 240V.

This is the second time I have seen this said recently. But if you go here, for example, the majority of listed products are 3000 W:

https://www.currys.co.uk/gbuk/household-appliances/small-kitchen-appliances/kettles/336_3156_30244_xx_xx/xx-criteria.html

3000 W is cunningly designed to max out a 13 A plug, since 3000/240 = 12.5.

[Capernicus]

So its per plug,  not for the whole house!!

I didn't know that.     So what if I get two plugs and power one thing off it,  do i get 20A??

No, the device will only draw as much current as it needs.

Connecting two plugs together is very dangerous. Don't do it. If someone disconnects one of them, it will have mains voltage, on the exposed pins.

It would be good to power a 120db block party rave out of your house tho.  (with your custom amplifier.)

[John B]

It's called a Darwin extension cable.

[themadhippy]

It's called a Darwin extension cable

We call em widow makers

This is the second time I have seen this said recently. But if you go here, for example, the majority of listed products are 3000 W:

https://www.currys.co.uk/gbuk/household-appliances/small-kitchen-appliances/kettles/336_3156_30244_xx_xx/xx-criteria.html

try widening your shopping net,just like homebase aint the only seller of showers,currys aint the only seller of kettles,theirs plenty of kettles rated at 2-2.5kw as there are showers rated less than 8.5kw.

[IanB]

try widening your shopping net,just like homebase aint the only seller of showers,currys aint the only seller of kettles,theirs plenty of kettles rated at 2-2.5kw as there are showers rated less than 8.5kw.

Why would I want to buy a kettle less than 3000 W? It will boil slower. It would be just as dumb as buying a shower less than 8.5 kW.

But since you are taking issue, please show me a UK retailer of your choice where most kettles listed are not 3000 W? You can pick Argos, Tesco, John Lewis, Amazon, any popular retailer of kitchen goods. Not just some of the kettles, most of the kettles.

[Siwastaja]

Here in the European market of crappy Schuko plugs and some tradition for 10-16A fusing per whole circuit of outlets, kettles are typically around 1.5-2kW. I just checked mine, which is 1650W, but this isn't too bad if you are making just 1-2 cups of tea at a time. Visiting Japan, I remember kettles designed for the 100V plug and these were well below 1kW.

Basically here, anything beyond 2kW does not come with a plug, but would require a permanent installation by an electrician!

European stoves also tend to have lower power burners compared to UK or USA; if you want to actually fry something (instead of slow boiling), better preheat the pan on the stove for 3-4 minutes, and then fry small amounts at a time. It's not always like this, of course, higher power appliances are available, but you can't take the US-style 230V 40A stoves for granted. But we get by, laughing at the strawman of the USA supposedly being limited to 110V and no power beyond ~1kW anywhere.

[Zero999]

try widening your shopping net,just like homebase aint the only seller of showers,currys aint the only seller of kettles,theirs plenty of kettles rated at 2-2.5kw as there are showers rated less than 8.5kw.

Why would I want to buy a kettle less than 3000 W? It will boil slower. It would be just as dumb as buying a shower less than 8.5 kW.

But since you are taking issue, please show me a UK retailer of your choice where most kettles listed are not 3000 W? You can pick Argos, Tesco, John Lewis, Amazon, any popular retailer of kitchen goods. Not just some of the kettles, most of the kettles.

I have a kettle rated to much less than 3kW. I think it's around 1kW, from memory. I like it because it's much smaller than my 3kW kettle and I can boil 1 cup of water.

The main reason for having a low power kettle is for situations where there isn't much power available, such as when running it off an inverter, or at a campsite, where you might not have enough power available for a 3kW kettle.

[Siwastaja]

Many kettles suffer from poor ratio between min/max water volume. You need to boil 2 cups and waste half of the hot water. And when you get a few visitors and want to make 5 cups, you need to do it in two batches.

I'm sure with clever design one could design a kettle which could boil you just one cup of water, but could also do 1.5 liters, and do all that with high peak power (say 3kW).

[JohanH]

I'm sure with clever design one could design a kettle which could boil you just one cup of water, but could also do 1.5 liters, and do all that with high peak power (say 3kW).

Induction should solve this. A quick google search shows something like this:

https://www.cnet.com/tech/computing/this-crazy-kettle-heats-only-the-water-you-need/

[IanB]

I'm sure with clever design one could design a kettle which could boil you just one cup of water, but could also do 1.5 liters, and do all that with high peak power (say 3kW).

I do currently own and use a 3 kW kettle with a capacity of 1.7 liters that also can boil one cup of water:

https://uk.russellhobbs.com/adventure-kettle-23910

I like it because it has no plastic windows that can leak.

The main reason for having a low power kettle is for situations where there isn't much power available, such as when running it off an inverter, or at a campsite, where you might not have enough power available for a 3kW kettle.

Granted.

[IanB]

European stoves also tend to have lower power burners compared to UK or USA; if you want to actually fry something (instead of slow boiling), better preheat the pan on the stove for 3-4 minutes, and then fry small amounts at a time.

Ouch. That would be frustrating for anyone who likes cooking.

I have a gas stove with literal burners, and out of curiosity I measured the heat output of a burner on the maximum setting a little while back. I found it was about 1000 W, which was lower than I thought it might be.

[mcz]

European stoves also tend to have lower power burners compared to UK or USA; if you want to actually fry something (instead of slow boiling), better preheat the pan on the stove for 3-4 minutes, and then fry small amounts at a time.

Ouch. That would be frustrating for anyone who likes cooking.

I have a gas stove with literal burners, and out of curiosity I measured the heat output of a burner on the maximum setting a little while back. I found it was about 1000 W, which was lower than I thought it might be.

Interesting. My dad has a gas stove and the bigger burners are rated 4.5kW. I think my (induction) stove burners go from 2.2kW max to 3.3kW max, depending on the size of the thing. Dunno what the US equivalents are.