The real reason why North America uses 120v instead of 240v.

[themadhippy]

Why not have 120V be 2x 60V to ground? Wouldn't that be the safest way to have 120V?

We do in the uk.ok its 55-0-55v ,it mainly used on construction sites.

[Monkeh]

My guess is that the vast majority of electrical shock fatalities are in industrial settings.  480 VAC and much higher.

So unless there is data that breaks our household electrical shock fatalities the data is meaningless to the discussion.

Of the 13 I mentioned in England, 7 were in homes - no 480VAC in homes. Actually, no 480VAC at all, not that shocks between phases are common.. In 2020, there were 14 - 4 of them in homes.

Of the 126 workplace fatalities in the US, 13 examples were given. Three were almost certainly only 120VAC, a fourth highly unlikely to be greater than that. The others vary, several are likely to have been 120VAC and a few more, 277VAC (one phase of 480VAC, because again, contact between phases is unlikely). Contact with overhead lines is remarked to be the most common cause, however, but the voltage of those is unspecified. 120VAC lines are much lower down than higher voltage supplies, of course..

As a curious aside which I'm tempted to contact the ONS about, in 2018 a 7 year old boy was electrocuted at a pub in Essex by faulty outdoor lighting. This age group does not appear in the released data..

[AVGresponding]

My guess is that the vast majority of electrical shock fatalities are in industrial settings.  480 VAC and much higher.

So unless there is data that breaks our household electrical shock fatalities the data is meaningless to the discussion.

Of the 13 I mentioned in England, 7 were in homes - no 480VAC in homes. Actually, no 480VAC at all, not that shocks between phases are common.. In 2020, there were 14 - 4 of them in homes.

Of the 126 workplace fatalities in the US, 13 examples were given. Three were almost certainly only 120VAC, a fourth highly unlikely to be greater than that. The others vary, several are likely to have been 120VAC and a few more, 277VAC (one phase of 480VAC, because again, contact between phases is unlikely). Contact with overhead lines is remarked to be the most common cause, however, but the voltage of those is unspecified. 120VAC lines are much lower down than higher voltage supplies, of course..

As a curious aside which I'm tempted to contact the ONS about, in 2018 a 7 year old boy was electrocuted at a pub in Essex by faulty outdoor lighting. This age group does not appear in the released data..

Larger homes often have 3-ph supplies in the UK.

[Monkeh]

Larger homes often have 3-ph supplies in the UK.

I wouldn't say often, and many DNOs actively refuse to supply such. And still not 480VAC.

Mind you, there's the far rarer option of a split-phase supply.. never say never, I guess.

[mcovington]

Do countries that use 240V have two out-of-phase 120V lines (like the US actually has), or do they just have a single 240V line?

It is single phase 240 V, but wiring and appliances are supposed to assume that both line and neutral conductors are live, and each has to be equally insulated from any exposed parts that could be touched.

We certainly have the safest plug and socket system in the world I think. That is our saving grace.

Are you referring to the UK, Australia, or somewhere else?   The tiny plugs in the US certainly don't give me a lot of confidence.

[mcovington]

Why not have 120V be 2x 60V to ground? Wouldn't that be the safest way to have 120V?

I like that idea -- with GFCIs (residual current devices) on both sides.   Hmmm...  Currently existing American appliances would all work, I think.

[mcovington]

Why not have 120V be 2x 60V to ground? Wouldn't that be the safest way to have 120V?

We do in the uk.ok its 55-0-55v ,it mainly used on construction sites.

Interesting.  With American-type 120V tools?

[AVGresponding]

Larger homes often have 3-ph supplies in the UK.

I wouldn't say often, and many DNOs actively refuse to supply such. And still not 480VAC.

Mind you, there's the far rarer option of a split-phase supply..

I would, and I've worked in a few. When you get to the size of 10+ bedrooms and multiple wings and/or sub-buildings, it's common, and necessary. And 3-ph in the UK is most commonly 400VAC (nominally, actually more like 415, blame weird EU harmonisation attempts, just like the "230" in the UK is more likely to be between 240 and 250), not 480. Some specialised use cases exist of course, ie railway signalling at 650VAC 1-ph etc.

[TimFox]

Why not have 120V be 2x 60V to ground? Wouldn't that be the safest way to have 120V?

We do in the uk.ok its 55-0-55v ,it mainly used on construction sites.

Interesting.  With American-type 120V tools?

I encountered the 110 VCT transformers during an installation in UK:  it seems to be mandated when a long extension cord is required from the wall to a power tool.
The connectors used are quite different from normal UK or US plugs.
The local workers did not use these extra transformers very often, using cordless power tools (battery operated) when possible to meet the safety regulations.

[themadhippy]

it seems to be mandated when a long extension cord is required from the wall to a power tool.

nope,its just to  reduce the risk of a fatal shock on  damp building sites

The connectors used are quite different from normal UK or US plugs.

compared to  domestic stuff yes,but fairly common else were and come in a wide variety of voltage and current ratings

[mcovington]

it seems to be mandated when a long extension cord is required from the wall to a power tool.

nope,its just to  reduce the risk of a fatal shock on  damp building sites

The connectors used are quite different from normal UK or US plugs.

compared to  domestic stuff yes,but fairly common else were and come in a wide variety of voltage and current ratings

Where can I see a picture of one?

[IanB]

it seems to be mandated when a long extension cord is required from the wall to a power tool.

nope,its just to  reduce the risk of a fatal shock on  damp building sites

The connectors used are quite different from normal UK or US plugs.

compared to  domestic stuff yes,but fairly common else were and come in a wide variety of voltage and current ratings

Where can I see a picture of one?

https://en.wikipedia.org/wiki/IEC_60309

[Zero999]

Do countries that use 240V have two out-of-phase 120V lines (like the US actually has), or do they just have a single 240V line?

Europe to a large part has 3 phase 230 V. So 3x230 V to ground and ~400 from phase to phase. Some smaller private installations only get 1 phase.

Then that would be 400V three phase. 230V three phase would be 133V to neutral, which is uncommon.

[JPortici]

Do countries that use 240V have two out-of-phase 120V lines (like the US actually has), or do they just have a single 240V line?

Europe to a large part has 3 phase 230 V. So 3x230 V to ground and ~400 from phase to phase. Some smaller private installations only get 1 phase.

Then that would be 400V three phase. 230V three phase would be 163V to neutral, which is uncommon.

In italy there should still be some areas in Turin and Rome with three phase 230V, no neutral (residential utilities are connected between two phases)
however the last i heard of it is that they started converting to the current 400V 3phase + neutral

[Nusa]

Do countries that use 240V have two out-of-phase 120V lines (like the US actually has), or do they just have a single 240V line?

It is single phase 240 V, but wiring and appliances are supposed to assume that both line and neutral conductors are live, and each has to be equally insulated from any exposed parts that could be touched.

We certainly have the safest plug and socket system in the world I think. That is our saving grace.

"we" and "our" have no meaning when you don't identify where you are. You don't have the country code set on your identity, so we don't even have an assumption to go with.

[PlainName]

And I agree that it isn't easy to draw conclusions from the data - but I find it unlikely that the most commonly accessible voltage is in fact safer when fatalities are 20-30x higher for only 6x the population.

The UK stats are all W86 ("Exposure to other specified electric current") and W87 (""Exposure to unspecified electric current"), and roughly half are "Trade and service area" and "Industrial and construction area". So they are likely 240V but with a high probability of 120V (constructions, etc). There is W85 ("Exposure to electric transmission lines") which doesn't appear in the stats, so we are talking all low voltage.

By contrast, the US stats include people snipping primary distribution lines (5+kV). Their stats include much higher voltages than the UK ones. If there is any question, it is why the UK seems not to have had any high voltage fatalities (unless the selected stats excludes them, in which case it's apple vs oranges).

[Monkeh]

And I agree that it isn't easy to draw conclusions from the data - but I find it unlikely that the most commonly accessible voltage is in fact safer when fatalities are 20-30x higher for only 6x the population.

The UK stats are all W86 ("Exposure to other specified electric current") and W87 (""Exposure to unspecified electric current"), and roughly half are "Trade and service area" and "Industrial and construction area". So they are likely 240V but with a high probability of 120V (constructions, etc). There is W85 ("Exposure to electric transmission lines") which doesn't appear in the stats, so we are talking all low voltage.

By contrast, the US stats include people snipping primary distribution lines (5+kV). Their stats include much higher voltages than the UK ones. If there is any question, it is why the UK seems not to have had any high voltage fatalities (unless the selected stats excludes them, in which case it's apple vs oranges).

The W85 numbers are.. minimal. 2 in 2013, 4 in 2014, 3 in 2016, 6 in 2017 (rough year.), 2 in 2018, 2 in 2019, 2 in 2021.

[AVGresponding]

Why not have 120V be 2x 60V to ground? Wouldn't that be the safest way to have 120V?

We do in the uk.ok its 55-0-55v ,it mainly used on construction sites.

Interesting.  With American-type 120V tools?

I encountered the 110 VCT transformers during an installation in UK:  it seems to be mandated when a long extension cord is required from the wall to a power tool.
The connectors used are quite different from normal UK or US plugs.
The local workers did not use these extra transformers very often, using cordless power tools (battery operated) when possible to meet the safety regulations.

Generally speaking, 240V tools are not permitted on construction sites, regardless of cable length. Using battery tools is usually a matter of convenience, but for heavier tasks, the leaded 110V stuff gets used. Better to put wear on the gearbox of the hired SDS hammer drill than my own battery one!

[PlainName]

The W85 numbers are.. minimal. 2 in 2013, 4 in 2014, 3 in 2016...

One interpretation might be that the higher the voltage the safer it is! But I think it's more likely that anyone going near that stuff is trained to a high standard and using equipment appropriate to the environment.

[mcovington]

A couple of thoughts:

- Maybe people working on 240V are more careful.

- The US has more sparsely populated places, farms, and (presumably) DIYers.

[jmelson]

Older houses, especially attics and crawlspaces, along with barns, seem to be the among the most dangerous places.

Yup, poking around inbasement ceilings and inside walls of houses with knob and tube wiring, you will find bare conductors all over the place where you least expect it!
Jon

[Gyro]

Generally speaking, 240V tools are not permitted on construction sites, regardless of cable length. Using battery tools is usually a matter of convenience, but for heavier tasks, the leaded 110V stuff gets used. Better to put wear on the gearbox of the hired SDS hammer drill than my own battery one!

That really ought to be discriminated as 55-0-55V rather than 110V. In the case of accidental contact you'd only get hit with 55V, it would take holding one wire in each hand to get a 110V shock. It's almost SELV.

[AVGresponding]

Generally speaking, 240V tools are not permitted on construction sites, regardless of cable length. Using battery tools is usually a matter of convenience, but for heavier tasks, the leaded 110V stuff gets used. Better to put wear on the gearbox of the hired SDS hammer drill than my own battery one!

That really ought to be discriminated as 55-0-55V rather than 110V. In the case of accidental contact you'd only get hit with 55V, it would take holding one wire in each hand to get a 110V shock. It's almost SELV.

It's easier to just refer to it as 110V, and in the cases of CPC failure, class 2 devices (many drills etc are this now) and festoon lighting (where there is no CPC) for example, that's exactly what it is.

The inclusion of a CPC would make it PELV, not SELV, and it would have to be under 50V between any two conductors to meet the criteria for either.

[mfro]

Just to fire up discussion: German statistics list 32 deaths caused by electricity  in 2019, 7 of them in industry/commerce (that is: professional) environments.

US population is (roughly) four times that of Germany, UK about 20% less.
 

[tom66]

In italy there should still be some areas in Turin and Rome with three phase 230V, no neutral (residential utilities are connected between two phases)
however the last i heard of it is that they started converting to the current 400V 3phase + neutral

I know Belgium is similar, in rural areas.
Apparently some electric vehicles cannot charge off such 230V 3ph, they require a neutral (they will charge on the slow charger, but not on a wall box.)