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# An unanticipated fire hazard

## An unanticipated fire hazard

#1
09-29-03, 10:55 PM
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An unanticipated fire hazard

I've known for some time now that the Europeans use 230 volts and that we Americans use 120 volts for most household items and 240 volts for large appliances. Even though I've never really given it much thought, I've always imagined that the US system is somewhat less efficient than the European system because of the lower voltage and higher amperages that our electrical devices have use to compensate for the lower voltage. But I was talking to an electrician the other day and he told me that this is not really the case between the breaker box and the transformer. According to him, if all the 120 volt loads that are connected to one hot leg exactly matched the loads that are connected to the other, it would be as if half the loads were connected in series with the other half. At the same time, you would find that the neutral is not carrying any current at all. In the real world, some of the current does have to pass through the neutral since the loads being imposed on both legs are not perfectly balanced. But most of the current that's delivered to our homes comes as 240 volts through the hot wires because of this effect. This would also explain why a double receptacle circuit with a shared neutral wire doesn't have to use a neutral wire that can accommodate the amperages of both 120 volt hot wires.

Could this also mean that a double receptacle circuit connected to two individual breakers on the same leg could overheat the neutral wire?

Robert

#2
09-30-03, 12:55 AM
cem-bsee
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There are a many voltages used in other countries, even within the same country, just as here.
First part of statement has some erroneous statements. It is most desireable to have loads balanced on each phase of a panel. Say, refrig on A, freezer on B. Where it is important is when unit heaters, such as baseboards are used. Larger appliances are connected across both phases @ 230v.

Multiwire circuits need each phase/ hot wire on a different bus bar of the panel to advoid overheating of the neutral; normally from different sides of a panel. Thus, across each receptacle there is probably 230v!

#3
09-30-03, 06:38 AM
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Could this also mean that a double receptacle circuit connected to two individual breakers on the same leg could overheat the neutral wire?
Absolutely!! That's why it's illegal.

#4
09-30-03, 11:21 AM
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The reason that the US systems are superior to the Europeon systems is the most important of reasons----- protection from life-threating hazards, specificaly electrical shock, which in almost all situations is caused by Voltage-to-Ground.

In the US systems, the maximun Voltage-to-Ground, whether the system is 120/240 3-wire, single-phase, or 120/208, 3-phase 4-wire, or whether the circuit-voltage is 120 or 240 volts, is 120-Volts-to- Ground.In Europe, the V-T-G is 240 volts which is extremely hazardous.

The concept of "efficiency," as applied to power-consuming electrical loads such as motors, is the ratio of Output-Power/ Input-Power and is a "design" matter. A 120-volt lamp-ballast could be more efficent than a 480-volt ballast.

When you have achieved 100% efficiency you have solved the problem of Perpetual Motion.

#5
09-30-03, 12:22 PM
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Originally posted by cem-bsee
First part of statement has some erroneous statements.

Originally posted by PATTBAA
The concept of "efficiency," as applied to power-consuming electrical loads such as motors, is the ratio of Output-Power/ Input-Power and is a "design" matter. A 120-volt lamp-ballast could be more efficent than a 480-volt ballast.
I was always under the impression that lower amperage (requiring higher voltage for the same amount of power obviously) was always more efficient than higher amperage. If this is not the case, then why don't electric utilities just get rid of all those expensive and unsightly transformers and send 120/240 volts all the way from the power plants to our homes?

Robert

#6
09-30-03, 01:22 PM
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Yes, lower amperages are more efficient (all other things being equal). The difference when running your average television is so small, however, as to be mostly irrelevant. And of course, most of the big power draws in your house are 240-volt anyway.

As I'm sure you already know, sending 240 volts from the power plant would be very highly impractical. In fact, we often have people in this forum who want to send power 1000 feet to a barn or dock, and that is fairly impractical too.

It's all in the numbers. We must make a balance between safety and efficiency, and we do pretty well at it. The way we get both 120 and 240 with relative safety and efficiency in North America is really a quite clever design.

#7
09-30-03, 01:32 PM
frenchsparky
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In the US systems, the maximun Voltage-to-Ground, whether the system is 120/240 3-wire, single-phase, or 120/208, 3-phase 4-wire, or whether the circuit-voltage is 120 or 240 volts, is 120-Volts-to- Ground.In Europe, the V-T-G is 240 volts which is extremely hazardous

just before you start this mess here !!!!!!

i do live in France the voltage system is 200/ 415 volts let me make it clear here the line to ground is 200 volts and line to line is 415 volts ( both 1 and 3 phase system)

and the frencty is 50 HZ in north american system is 60 HZ but really in fact if we increase the HZ to your system the voltage will rise same as 277/480 volts !!

the voltage is very common in most european area useally 200 to 240 volts line to ground and line to line is from 400 to 460 volts area . majorty of hevey devices use hook up on higher side and yeah sometime you will see 3 phase stove or dryer or water heater but it do varis depending on location

hope i get it some detail straght here

merci marc

#8
09-30-03, 03:06 PM
CSelectric
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Originally posted by cem-bsee

Multiwire circuits need each phase/ hot wire on a different bus bar of the panel to advoid overheating of the neutral; normally from different sides of a panel. Thus, across each receptacle there is probably 230v!
Just curiuos, but what type of panels are you using? Outside of the old Pushmatics, I can't think of a panel that phases from side to side. Generally it is odd/even going from top to bottom.