House mains electricity issues

[Monkeh]

As others have noted, in the USA, neutral is bonded to earth at the service entrance (and no where else). In older homes the earthing was often done using buried water pipe instead of a dedicated ground rod.

Which is not relevant.

[mtdoc]

As others have noted, in the USA, neutral is bonded to earth at the service entrance (and no where else). In older homes the earthing was often done using buried water pipe instead of a dedicated ground rod.

Which is not relevant.

I was responding to and clarifying Mechatomers unqualified statements:

neutral SHOULD NOT be connected intentionally to earth wire

and

earth wiring is and should be an isolated system from mains L and N, its sole purpose is only for protecting your arse. and any devices/metal connected to it. if you see an earth wire is connected to water or copper pipe, not because the pipe will be used as earth return path, but meaning that, that pipe is to be protected from live connection

Which as stated are not fully accurate.

[IanB]

It is of course interesting how earthing systems vary from one country to another. For example, descriptions of protective earthing in the UK tend to say the neutral is bonded to earth "at the substation". However, here in the USA it is fairly traditional that there is no substation. Very often the transformer is in a metal can at the top of a wooden pole outside the house. It is far away from the ground and in any case wood is not a very good conductor. This state of affairs probably has a bearing on the different traditions in the two countries.

[Mechatrommer]

I was responding to and clarifying Mechatomers unqualified statements:
...
Which as stated are not fully accurate.

in your 110V dry country only... in 220V wet country, you may be surprised if you get a shock, people died. maybe you can learn from 220V country code conduct and make your own proper substation (proper return path through RCD in the house. what i linked and stated is in accordance to our energy committe guideline, not some found by luck method. you country doesnt enforce it not necessarily means it is safe or valid... ymmv..

These Guidelines are based on the Electricity Supply Act 1990, The
Electricity Regulations 1994, MS IEC 60364:2003 Standard: Electrical
Installations of Buildings, MS 1936:2006 Standard: Electrical Installations
of Buildings – Guide To MS IEC 60364, MS 1979:2007 Standard:
Electrical Installation of Buildings – Code of Practice.

go figure i dont have time for...

[Ian.M]

In the UK, for domestic consumers, EITHER the supply company provides an earth (TN-S or TN-C-S systems) OR it does not, making the earthing system entirely the consumer's responsibility (TT).   Any Earth-Neutral bond on the supply side of the meter (TN-C-S), is the supply company's responsibility, as all the L and N terminals up to the meter are sealed with tamper-proof seals, so any such bond has to have been approved by the supply company before they applied the seals.  OTOH there should *NOT* be an Earth-Neutral bond after the meter - the installation either uses the Earth as supplied by the supply company or the L and N *MUST* pass through a RCD and then a local Earth electrode system (TT) can be used (and in some cases - e.g. feeds to caravans & boats - is required even if the incoming supply offers an Earth terminal).  This differs considerably from American practice where IIRC it is more or less standard to have an Earth-Neutral (or in American Ground-Neutral) link in the main panel, but it is prohibited in sub-panels or elsewhere downstream of the main panel.   

[mtdoc]

Because there is a variety of earthing systems employed in different  countries (and no, the US is not unique) I think it is important to qualify statements and not assume that readers know that what one reads may not apply to their country. That in itself could prevent someone from doing something dangerous.

Oh and FWIW, many parts of the USA are very wet and there is a National Electrical Code that is very safety focused and strictly enforced in most juristictions.

[Monkeh]

Welp, now we're off the rails and rolling downhill.

[Mechatrommer]

i dont know, but if one (non competent) take earthing at his own hand, there could be a tremendous waste of energy if there is short L to E, without any meter or panel telling or tripping it (you only know it from the bills you pay next month), there could be also fire hazard, not to mention the earlier mentioned life threatening issue. maybe the 110V countries took this lightly as death toll is probably on low side 

[james_s]

The transformer that supplies my house and the one next door is in a small cabinet in the bushes near the sidewalk, this is typical of neighborhoods with underground power.

I don't know what constitutes "wet" but here in the Northwest corner of the US there is an area classified as rainforest, and the area I live is wetter than average, notorious for gloomy gray skies and drizzle. The climate here in the Seattle area is very much like that in much of the UK. It's a big country and when it comes to climate we have a little of everything.

[james_s]

i dont know, but if one (non competent) take earthing at his own hand, there could be a tremendous waste of energy if there is short L to E, without any meter or panel telling or tripping it (you only know it from the bills you pay next month), there could be also fire hazard, not to mention the earlier mentioned life threatening issue. maybe the 110V countries took this lightly as death toll is probably on low side 

We have 240V too, although it's 120-0-120 center tapped. It's not possible to bypass the meter or the breakers by messing with the earth ground. You could tap off the live conductor and wire something between that and a separate ground rod driven into the yard and the meter will still register. If there's a potential way to steal electricity, you can bet somebody has tried it. The power companies are not stupid, they don't make it easy.

[Mechatrommer]

I don't know what constitutes "wet" but here in the Northwest corner of the US there is an area classified as rainforest.

i was refering to atmosphere relative humidity where probably it will affect your body and finger conductance. heavy rain may not necessarily affect average daily RH. one thing for sure, wet hand on a live wire is much more painfull than a dry hand.

If there's a potential way to steal electricity, you can bet somebody has tried it. The power companies are not stupid, they don't make it easy.

stealing around here is easy, just do the job before the meter (tap both L and N), i'm guessing in coutries where N is non existence, just tap the L before the meter, no? but well, i'm not into stealing stuffs.

[james_s]

During times of heavy rain the RH goes way up, at times it can get almost tropical feeling when we have the occasional summer rain storm.

I suppose it would be possible to tap off before the meter, I don't think the grounding scheme would affect that though. Pretty sure they have ways of detecting it too although I don't know for sure as I don't mind paying for my power. I think it's mostly people who are growing drugs and need large amounts of power to run grow lights that try to bypass the meter. Excess power consumption is one of the things that tips off the authorities.

[Nusa]

It is of course interesting how earthing systems vary from one country to another. For example, descriptions of protective earthing in the UK tend to say the neutral is bonded to earth "at the substation". However, here in the USA it is fairly traditional that there is no substation. Very often the transformer is in a metal can at the top of a wooden pole outside the house. It is far away from the ground and in any case wood is not a very good conductor. This state of affairs probably has a bearing on the different traditions in the two countries.

Actually those USA pole transformers should be grounded to earth at the pole. If you take a close at a transformer pole you'll probably notice the wire coming down it, probably under a wood molding that both protects and camouflages it.

Now back to your regularly scheduled program about UK-specific electrical safety and laws.

[CatalinaWOW]

It is interesting how many of the comments on this thread are recital of code, and how few discuss the thoughts behind the code.  After reading the links and the thread a beginner should begin to understand that the intent of the earth/ground connection is to minimize hazard under fault conditions.  While it is implied, none of the comments or references directly states that there is an underlying presumption that those protected are standing on a surface that is likely to be at earth potential.  If this surface is conductive and a potential appears between the case of the equipment and ground bad things happen.

The different systems in the UK and US likely are at least partly the result of geography and climate.  In the soils of the UK, with the generally damp climate there is likely to be a low impedance between any service location and the bonding point at the substation.  The surface that the protected person is standing on is very likely to be at the same potential as the bonding point, even if it is dozens or hundreds of meters away.   This is true in large parts of the US, but unfortunately very untrue in other, also large parts.  Dry soils and/or those with little ionic or metallic content can have extremely high impedances.   I have observed potentials of half the line voltage between the local dirt and a bonding point a couple of hundred meters away.  This is likely the reason for the requirement for local bonding.  Those same soil conditions make it very challenging to actually get an earth connection.  Fortunately they also are a strong limit on the fault currents that can develop through body contact with the floor so it is a somewhat self compensating problem.

There is no substitute for following local code requirements.  They are the result of decades of experience in what works and what does not.  But I find it easier to understand and remember the code requirements when I have some understanding on why they have occurred.  Simple things like wire size relations to current flowing in a circuit are obvious, but some are more subtle.

[Elf]

I suppose it would be possible to tap off before the meter, I don't think the grounding scheme would affect that though. Pretty sure they have ways of detecting it too although I don't know for sure as I don't mind paying for my power.

People do seem to try a lot of ways to steal power:

• Grappling hooks: https://www.wired.com/2010/06/military-bat-hook-sucks-free-power-from-overhead-lines/ (military version of an urban legend of people tossing grappling hooks onto overhead lines)
• Induction: http://hackaday.com/2017/04/10/wirelessly-charge-your-phone-from-high-voltage-power-lines/
• Meter bypass: https://www.youtube.com/results?search_query=meter+bypass
• More meter bypass (screwdrivers!), jumper cables: http://www.news4jax.com/news/local/thousands-stealing-power-from-jea-their-neighbors
• More jumper cables: http://www.eastvalleytribune.com/business/utility-providers-boost-efforts-to-stop-theft-of-electricity-water/article_10b3438a-6234-11e0-8db1-001cc4c002e0.html

Of course, my all time favorite:

[CatalinaWOW]

It is interesting that none of the power thieves I have seen documented even approximate the appropriate electrical code in their connections.  While code installations are clearly safer, the death rate among power thieves is not so high as to discourage the practice, or to improve their methodology.  I have seen reports of death and injury among power thieves, but it isn't all that common.

[james_s]

One can often get away with some really sketchy stuff. I have certainly rigged up temporary stuff that would make an electrician cringe. That said, I learned some of that stuff from my uncle who was a licensed commercial electrician. The power cord with alligator clips on the end for example.

When it comes to power thieves, I don't think they're typically the sharpest tools in the shed. Brilliant people tend not to need to resort to such petty crimes even if they do lack honesty.

[RGB255_0_0]

Brilliant people tend not to need to resort to such petty crimes even if they do lack honesty.

If they had brains they'd be bankers or lawyers.

[drussell]

...but even RCD/GFCI devices do not protect you from 2-wire appliances being mis-used.

Yes they do...  The way they work is to measure the current flowing in and out of the line and neutral (or line and line on a North American 240v circuit) using a balanced current transformer arrangement.  Any significant current flowing (here usually about 5ma) in the circuit that does NOT return via the other wire must be flowing through something else outside the intended circuit one way or another, so it trips.

It has nothing to do with the earth conductor.  It doesn't measure the current on the ground wire, it measures the difference between the current in the two current-carrying conductors.  Eg., if you somehow leak more than 5ma from your 2-wire hair drier to the sink faucet, it will trip.

Am I misunderstanding your use of "mis-used"?

[Seekonk]

When I bought my house I went in the basement a found a one foot section of water pipe suspended from a wire.  In the middle there was a clamp that had a big yellow tag. It said in bold letters, Do not remove this wire or clamp.  Always read and follow safety instructions.

[RGB255_0_0]

...but even RCD/GFCI devices do not protect you from 2-wire appliances being mis-used.

Am I misunderstanding your use of "mis-used"?

[P90]

http://www.dailymail.co.uk/news/article-3004108/Shocking-moment-passers-refused-help-fatally-injured-South-African-man-burst-flames-stealing-copper-wires-electricity-substation.html

[CatalinaWOW]

As others have mentioned, those stealing power are often not in the top tier of intelligence.

Those who steal copper generally make the power thieves look like geniuses.

[P90]

Do they still use those silly ring circuits in the UK?

Nothing silly about them - and no reason to sidetrack the tread further either.

Actually you're right, it's not silly, it's plain outright stupid and adds unnecessary complexity to the installation and testing. Relying on a100% functioning ring circuit to carry 32A over 2.5mm2 wire is asking for trouble. Yes, but you have fuses in your plugs, bravo...
As for sidetracking the "tread," it's mains wiring and switch related...

[Nusa]

...but even RCD/GFCI devices do not protect you from 2-wire appliances being mis-used.

Am I misunderstanding your use of "mis-used"?

Two things wrong with those videos.
a) They didn't demonstrate that it was a working GFCI device with the test button on the outlet.
b) In these days of plastic sinks and plastic drainage pipe, they were testing in ungrounded pools of water. Easiest electrical return path is still the neutral in the cord. Drape a wire from a grounded metal object into the water and I bet it trips immediately. Understand the wire is a stand-in for your body.