US verses Europe

[bphgravity]

Most of us here are aware that the US and European systems differ in several ways. My question concerns the difference in typical residential voltages and the hazardous consequences.

With most of Europe employing systems at 220V to ground verses the US standard of 120V to ground, you would automatically assume the potential of shock, electrocution, and fire would also be twice as high.

Statistics show otherwise. The number of deaths per year due to exposure of energize equipment is roughly the same and the number of fires in homes due to electrical failure is much lower in Europe than it is here in the US.

I then assumed it must be due to the age of the electrical systems here, yet many of the European countries developed their electrical systems at the same the US was. And many of their structures are much, much older. I then assumed it must be the total number of users of electricity but that doesn't explain the numbers either. While typical US homes due have a few more TV's and computers per resident, the numbers are not all that much greater.

So the question is, why are US systems so inherently dangerous. Due they protect persons and property differently than we do here, or is it have nothing to do with the system at all and have to do with something we Americans are doing different than Europeans?

 

[iwire]

Re: US verses Europe

Bryan sorry to go OT I was under the impression they use 220 but it was still only 110 to ground.

 

[iwire]

Re: US verses Europe

Back to your question.

You found the deaths are about the same which suggest the people are the same.

You found the rate of electrical fires was much lower.

My thought is this, the Europeans do not routinely blame fires of unknown origin as 'electrical fires' as seem to be the practice here in the states.

It seem Americans hate the word 'unknown' on a form so some other word like electrical fits nicely.

Just a thought..

Bob

 

[rbalex]

Re: US verses Europe

The bulk of European residential distribution is 220/380, 4w. Depending on the country (or locality in some cases) each home receives 1 or 2 phases of the three phase system. Also depending on the country some types of loads (e.g. water heaters) in a given area are restricted to specific phases. This permits the local utility to shut down part of a residential area for energy conservation without shutting down everything.

We would probably classify the bulk of the wiring as NMC with a 500V rating.

When the US first started regulating voltages it was believed 150V was the lowest lethal voltage and we decided to go with 80% (120V) of that as the standard residential value. Electrocutions (as opposed to lethal burns or fires caused by short-circuits) have been documented as low as 60V.

Statistically, there is virtually no difference between 120 or 220 Volts to ground with regard to a properly installed and maintained system.

Edit" added "...or fires..." to the parenthetic

[ November 14, 2005, 07:38 PM: Message edited by: rbalex ]

 

[jes25]

Re: US verses Europe

I think Europe in general is more regulated. Installs here that are compliant are just as safe but unqualified persons operating without permits is a REAL problem. If I had my guess 90% percent plus of the people buying millions of dollars of Electrical products at your typical big box retailer are unqualified or unlicensed.

 

[bphgravity]

Re: US verses Europe

Originally posted by rbalex:
...Statistically, there is virtually no difference between 120 or 220 Volts to ground with regard to a properly installed and maintained system....

This is what I don'tunderstand. Using the formula provided in the IEEE Std. 80, maximum shock duration would be half that in Europe as it would be here.

US: .116 / (120/1,000) = Approx. 1 second
EUROPE: .116 / (220/1,000) = Approx. .5 second

This is assuming a contact resistance of 1,000 ohms.

Even systems that are installed properly have failures, and accidents and mistakes do happen. It just seems counter-intuitive to me that Europe doesn't have more problems. Actualy, it makes me wonder why we have so many.

I like Bob's idea that insurance companies and the like are quick to blame electricity when they truely don't know the cause of fire or death. That seems very probable and would explain the inflated numbers in the US.

Thanks for your thoughts.

 

[c-h]

Re: US verses Europe

Much of it could be due to different reporting standards. Do we know of all accidents? I doubt it.

Perhaps the voltage is a red herring. It could be less importantant than the conditions. Maybe a wet person exposed to a voltage higher than e.g. 100V always dies. Despite the fact that you're "more dead" at 240V than at 120V, it really doesn't make any difference. (Just a theory, I have no evidence to back it up!)

If you're in a dry room, 240V will rarely kill you unless you touch something grounded. In my experience, you might not even notice it.

The shock duration reasoning you describe is behind the European requirement for disconnection of a ground fault in 0.4 s for 240V and 0.8 s for 120V. (The values fit nicely with your calculation.)

Another possible reason is that modern electrical equipment in Europe is often designed(*) to be safe to touch even if you open it. Some of the latest outlets are safe even when hanging out of the box without cover.

*I didn't say required. It just happens to be made that way.

[ November 15, 2005, 11:05 AM: Message edited by: c-h ]

 

[rbalex]

Re: US verses Europe

Bryan,

Actually my point was that the probability of an accident occurring is about the same at either voltage with respect to fires although the would probably be true with electrocutions.

With regard to electrocutions, even though the apparent severity of 220V is definitely higher, the probability of death is about the same - burn damage is probably higher. I don't know any accurate statistics and I doubt they are relegated to more than "high," "medium" or "low" voltage anyway - if that. Residential stats are far less rigorous than industrial.

 

[LawnGuyLandSparky]

Re: US verses Europe

I worked with a gent from Ireland who worked extensively there, as well as England. They've been using GFCI's on ALL of their ring mains and anything similar to our convenience receptacle circuits long before the US ever required them.

 

[ramsy]

Re: US verses Europe

.. the number of fires in homes due to electrical failure is much lower in Europe than it is here in the US.

Heat may have something to do with this.

1) The same power is available with less Amps on 220/440vac systems. V-drop burns the same heat in Watts, but it could be easier to oversize conductors that run a bit cooler with 1/2 the amps.

2) The Lower fundamental frequency of 50 HZ means a bit less hysteresis heat and harmonic spectrums are also lower. Combined with less current THD to begin with, lower frequency harmonics may take longer to reach flash-over temperatures due to skin effects over 1000Hz.

3) Since European branch circuits don't use grounding, conduit body & box fill is less without all the EGC pigtails. ECG's don't count in fill calcs with NFPA 70 370-16, but still take up space. Maybe nixing ECG's arn't much in heat prevention, but the simpler wireing may be harder to screw up.

4) When things do go wrong, heat ignition must overcome the wider barriers designed for twice the voltage, in insulation and devices. Broader barriers may disipate more heat below the ignition point.

If higher rates of electrical fires do exist in the US, European eletrical services could be intrinsically safer.

Considering their intrinsically simpler metric system, foods that digest easier, and a church that pays taxes, it seems the relatively well designed electrical system was no accident.

 

[iwire]

Re: US verses Europe

Originally posted by ramsy:
.. the number of fires in homes due to electrical failure is much lower in Europe than it is here in the US.

We have talked about this before and this is not an easy thing to compare.

Here in America we are quick to report the fire was 'electrical' when the actual cause is unknown.

 

[jimwalker]

Re: US verses Europe

When we do have electrical fires it usually is because of handyman type work and not code compliant.Or from stupid things like cords under carpet.

 

[wyatt]

Re: US verses Europe

I'm no expert but in europe the outltes have 2 110v legs so the odds that some one gets shocked with 220v is low you would have to be touching both legs at the same time. more likely the get one leg to ground. as for fires they have a lot less timber frame construction more brick and morter. and fewer outlets and electrical applances. they use more gas,oil and even coal to heat homes, water, and to cook. I'm not sure but in Germany youn can't work on electrical things if you are not a tradesman. IMO electecal fires here are more caused by DIYers and uncertifed workers.

[ December 13, 2005, 06:27 AM: Message edited by: wyatt ]

 

[hardworkingstiff]

Re: US verses Europe

Originally posted by wyatt:
I'm no expert but in europe the outltes have 2 110v legs

I don't think that's true Tony. I think they have 220v to neutral/ground and 380v between legs. They use a 3-phase distribution system exclusively and don't offer a single-phase service (I believe, not positive).

 

[petersonra]

Re: US verses Europe

Originally posted by jimwalker:
When we do have electrical fires it usually is because of handyman type work and not code compliant.Or from stupid things like cords under carpet.

do you know this as a fact, or is this just a personal belief?

I would buy the second statement since there is evidence to support that position, but am not so sure about the first.

I have seen no evidence to support the idea that unlicensed work is responsible for any substantial number of fires. It may be, and logically, one might infer it is, but that is not evidence.

 

[c-h]

Re: US verses Europe

Ramsy,

1) The same power is available with less Amps on 220/440vac systems. V-drop burns the same heat in Watts, but it could be easier to oversize conductors that run a bit cooler with 1/2 the amps.

Yes. A 20A circuit for lights and receptacles in Europe is much less likely to actually see 20A than one in the US. (Unless you use up the extra headroom gained by reducing the number of circuits.) The wire is often slightly smaller.

3) Since European branch circuits don't use grounding, conduit body & box fill is less without all the EGC pigtails.

No pigtails with wirenuts, but the EGC is there. In many countries is is an insulated conductor, not a bare wire like in NM-B. This could reduce the risk of arc. On the other hand, the boxes tend to be plastic which is not very fire resistant.

4) When things do go wrong, heat ignition must overcome the wider barriers designed for twice the voltage, in insulation and devices. Broader barriers may disipate more heat below the ignition point.

I've looked at the cable specifications and found that the insulation thickness of NM-B and corresponding European cables is about 0.5 mm in both cases. Contrary to what one would think, the voltage rating of the European cable is not higher. The thinnest cable used for buildings has a rating of only 300V to ground (500V line-to-line) compared to the American 600V. (In all fairness, 450/750V and 600/1000V is the norm for larger wire sizes.)

Perhaps the higher voltage reduces the risk of sustained arcing by tripping the breaker quicker. (Higher voltage equals higher fault current, if everything else is equal)

hardworkingstiff,

I think they have 220v to neutral/ground and 380v between legs. They use a 3-phase distribution system exclusively and don't offer a single-phase service

Spot on. Except for the exceptions , single phase is simply one leg from the 3-phase distribution network. Most large services are 3-phase. Large single phase services are only common in Britain as far as I know.

 

[hardworkingstiff]

Re: US verses Europe

C-H

So what do houses get? A service that is 220-volts (2-wire)?

"Spot on", you from Europe?

 

[jimwalker]

Re: US verses Europe

I have seen diy type work far to often and for 2 years i was employed by an EC that did work for one of the major disaster relief companies.The topper was a job where mr home owner added recess cans he found in the dump.The frame was gone as well as the j box and of course no ic.He nailed them in place with 12 penny nails and open sliced,no ground.He did use wire nuts.Some others were 30 amp fuses for lighting (minor damage)and then there was a remodel that they used lamp cord between romex,no wire nuts or even tape.I had the advantage of seeing at least 20 major fire jobs.Not all from electrical.

 

[c-h]

Re: US verses Europe

Originally posted by hardworkingstiff:
So what do houses get? A service that is 220-volts (2-wire)?

Yes, very common. In some regions 3-fase (4-wire) is brought to pretty much all houses.

"Spot on", you from Europe?

Right on. Darn, these different English languages befuddle me.

 

[JimPhillips_66]

More Electrical Fires in US vs Europe

More Electrical Fires in US vs Europe

About 30 years ago I was told by some people that fuses are safer than circuit breakers, and this still applys.

I remember an article in EC&M Oldies but Goodies, stating that ONLY 25% of the circuit breakers failed!!! I could not believe that someone would publish that, but there it was.

Europe uses Fuses, WHY DOESN'T THE INDUSTRY ADMIT IT.