240v Wiring ?

stupoty said:
Yeah like wreck says it might be polerised Live Neutral if it's a ground referenced neutral system you should read 240volts across live and earth and 0volts across neutral and earth. easy way to check for reversed wiring. Most installations in the UK only switch the Live so it's quite important its round the right way.

Stuart
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Here in the USA, for typical single phase house wiring, hot to the grounded (neutral) conductor will be 120v. Hot on one leg to hot on the other leg of the service line will be 240v. The 120v 2 prong plug are normally polarize. One stab on the plug will be larger than the other. Both 2 & 3 prong plugs connection screws are color coded. Green = ground. Brass = Black. Silver (white screw) = white.
 
ARKnack said:
Here in the USA, for typical single phase house wiring, hot to the grounded (neutral) conductor will be 120v. Hot on one leg to hot on the other leg of the service line will be 240v. The 120v 2 prong plug are normally polarize. One stab on the plug will be larger than the other. Both 2 & 3 prong plugs connection screws are color coded. Green = ground. Brass = Black. Silver (white screw) = white.
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Interesting, thats almost the reverse of the way we have 110volt (yellow site power boxes generaly or from a generator) which is a step down transformer from a single 240v live to a centre tapped 110 volt out put that is described as phase and phase, the earth tap ends up 55volt away from each. It's main use is on building sites hear in the uk.

It's them little differences that keeps it interesting :)

Stuart
 
stupoty said:
nteresting, thats almost the reverse of the way we have 110volt (yellow site power boxes generaly or from a generator) which is a step down transformer from a single 240v live to a centre tapped 110 volt out put that is described as phase and phase, the earth tap ends up 55volt away from each. It's main use is on building sites hear in the uk.
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First I ever heard of that. Interesting. They're clearly attempting to reduce the shock hazard while retaining the fault protection.
 
John Hasler said:
First I ever heard of that. Interesting. They're clearly attempting to reduce the shock hazard while retaining the fault protection.
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Yeah exactly that, it's also isolated via the transformer, it's all the yellow cables you see draped around scafolding in the UK supplying the lights and tools. Like you say most faults will only give you 55v shock.

https://www.tool-net.co.uk/p-411230...Lc30yzj1movfGQz-na2JyBKTr02mjtxIFDhoChz3w_wcB

I always wonder about using them in reverse to get 440v for powering a 3 phase VFD (sorry off topic, bit late)

Stuart
 
Here's my two cents' worth on the subject: UL listed &/or NEC compliant 120-volt plugs & outlets are made with silver-colored terminal screws for the neutral wire, brass for the hot leads & green-colored for the ground lead. Three pole, 240-volt, [single-phase] outlets & plugs don't use a neutral lead so both 240V terminals are brass. Same with 3-phase outlets & plugs. If a 240 or 480-volt, single or 3-phase device requires a neutral it will have an extra terminal with a silver screw. This removes confusion about the meaning of left & right. And if you ever use the white wire for one of the hot leads, particularly on wiring away from the panel, identify it as being hot & not a neutral by wrapping a little black, red or other colored tape [other than green] on the hot white wire.
 
Wreck™Wreck said:
3 phase AC also has no polarity, it merely alternates 120° between each leg.
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That isn't technically correct. With 3 phase having the phases out of order will reverse the motor so it does matter. Of course the only thing that will happen is it will turn the opposite direction, and fixing it is swapping two or the phases.
 
On my 240 volt plug and outlet, one of the blades is vertical and the other is horizontal. the third one (ground) is the half round one on the bottom. Is this a 240 plug and outlet?
 
John,
Thanks for the info... I'm gonna' print that and file it...
Bill
 
Keith Foor said:
That isn't technically correct. With 3 phase having the phases out of order will reverse the motor so it does matter. Of course the only thing that will happen is it will turn the opposite direction, and fixing it is swapping two or the phases.
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I think were getting into symantics (which is a fun hobby of mine as thats what words are for :) )

Polarity can only discribe a system of two opposits as wrek wrek says so we have to call three phase somthing else, maybe "phase order" is a better term for 3 phase.

This is intended to be light hearted as aposed to be pernickity :)

Stuart
 
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