110-120v V 220-240v

[HogF]

Which is the better system? Is the american standard safer because it is lower voltage or practical as some appliances such as cookers and tumble driers dont work as well on it and require a separate 220v supply. Do all american homes have dual voltage wiring? Also american building regs permit ordinary wall switches and sockets in bathrooms, surely 120v would be just as lethal in that situation?

[Pinotage]

I think the higher voltage has to be better. The Americans wanted a higher voltage but were not allowewd to. Initially when public mains electricity was first about to be installed the authorities were worried about the risks and restricted the voltage to 100v with a 10% margin of error. The electricians wer so confident they used 110v. And ever sincethen they've been stiuck with it. But other countries that followed the American lead decided to use a higher voltage. And if you've ever waited for an electric kettle to boil in America, then you'llbe joly glad the UK doesn't use 100v

[KARL]

As a rule, a lower voltage is potentially less harmful to living creatures (us included) and also less likely to cause fires. The reason is that, when something is subjected to electrical current going through it at any given voltage, the amount of that current will be governed by the resistance it encounters. All bodies have an innate resistance. Higher voltage will drive more current and this is why high(er still) voltage is so dangerous. The lower the current, the less energy transmitted and the less heat etc. created. The downside of low voltage is that you have to build in lower resistance in order to increase the current to transmit more energy (or create more heat). This means you need thicker cables and the situation becomes impractical, even for relatively modest loads (dryers, etc.). Japan uses 115V and Saudi Arabia has announced it will favour 110V.

[HogF]

Thanks for that guys. Am I right in thinking that the 110v going into a house would be single phase and that in order to have 220v available in the house a second 110v phase would have to be laid on from the main cable (outside)?

[chrislangham]

USA system has 208 volts across each phase in three pahse system. Most of their wiring uses 2 phases of 110 Volt The main problem with safety is that USA systems tend to allow circuit protection devices in the neutral conductor