# 240v Wiring ?



## planeflyer21 (Mar 17, 2016)

Howdy all.

This afternoon I wired up a plug onto a lead smelting pot, following the instructions on the plug box:  green to ground, white to neutral, black to hot.  Looking from the wire to the back of the plug, green on the bottom, white on the left prong, black on the right right prong.

Looked at the plug on the lathe and it was the same:  white on the left prong, black on the right prong.

Never one to leave well enough alone, I pulled apart the 50A outlet for the welder.  Lo and behold, it is wired so that the black (hot) wire goes to the left prong, white on the right prong.

My question is this:  with two hot wires coming to the outlet, does it matter which one is grounded?  Does it matter how your plugs are wired?

I've always been under the impression it makes a difference.


----------



## pdentrem (Mar 17, 2016)

240 has 2 hot wires while 120 has only 1 hot & 1 neutral. 240 plugs are not polarized unlike the 120 ones. At least that is my understand of that. The 3 phase at work is a different animal again if it has a neutral or not.
Pierre


----------



## John Hasler (Mar 17, 2016)

planeflyer21 said:


> white to neutral, black to hot.


Wait a minute.  This is a 2-wire (plus ground) 240VAC circuit?  If so you have no neutral.  You should have two hots (black and red, usually) and green ground.


----------



## jim18655 (Mar 17, 2016)

If you used a 3 conductor cord then the only thing you need to worry about is the location of the green ground. The black and white don't matter. You did use a 240v plug - right? That would have the blades horizontal, for lack of a better description. The receptacle is the same way, doesn't matter which side is white or black. If you used non-metalic cable put black tape on the white to designate it's live. If in conduit you should have pulled two colors for the hot wires.


----------



## ARKnack (Mar 17, 2016)

Doesn't matter. Both lines are hot. Left or right, both the same. As long as green wire goes to the green screw.  A white neutral is not required if you do not have 120vac requirement. You normally can not find Red/Black/Green power cord. You should use a black felt marker and paint the white wire black indicating that it is a hot wire. I hope you are using a proper 240vac plug and not a 120vac plug.


----------



## TOOLMASTER (Mar 17, 2016)

it will flip 60 times a second all by itself ;-)


----------



## jim18655 (Mar 17, 2016)

Seconds


----------



## planeflyer21 (Mar 17, 2016)

Thanks everyone!

Don't need to start something on fire.  I'd never hear the end of it.



John Hasler said:


> Wait a minute.  This is a 2-wire (plus ground) 240VAC circuit?  If so you have no neutral.  You should have two hots (black and red, usually) and green ground.



My apologies.  That was the terminology on the Pass&Seymour legrand box.  

Jim18655 and ARKnack, yes, I'm using a 6-15 plug.


----------



## Wreck™Wreck (Mar 19, 2016)

pdentrem said:


> 240 has 2 hot wires while 120 has only 1 hot & 1 neutral. 240 plugs are not polarized unlike the 120 ones. At least that is my understand of that. The 3 phase at work is a different animal again if it has a neutral or not.
> Pierre


A polarized 110 wall plug assures that the "neutral" is connected to the grounded (for want of the correct term) leg, you may have noticed that many modern hand tools do not have a distinct ground connection, also alternating current at the US standard 60 hz  changes polarity every cycle, or 120 times per second.
3 phase AC also has no polarity, it merely alternates 120° between each leg.


----------



## stupoty (Mar 19, 2016)

Wreck™Wreck said:


> A polarized 110 wall plug assures that the "neutral" is connected to the grounded (for want of the correct term) leg, you may have noticed that many modern hand tools do not have a distinct ground connection, also alternating current at the US standard 60 hz  changes polarity every cycle, or 120 times per second.
> 3 phase AC also has no polarity, it merely alternates 120° between each leg.



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


----------



## ARKnack (Mar 19, 2016)

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



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.


----------



## stupoty (Mar 19, 2016)

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.



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


----------



## John Hasler (Mar 19, 2016)

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.


First I ever heard of that.  Interesting.  They're clearly attempting to reduce the shock hazard while retaining the fault protection.


----------



## stupoty (Mar 19, 2016)

John Hasler said:


> First I ever heard of that.  Interesting.  They're clearly attempting to reduce the shock hazard while retaining the fault protection.



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


----------



## Wireaddict (Apr 10, 2016)

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.


----------



## Keith Foor (Apr 10, 2016)

Wreck™Wreck said:


> 3 phase AC also has no polarity, it merely alternates 120° between each leg.



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.


----------



## Bill W. (Apr 10, 2016)

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 Hasler (Apr 10, 2016)

Bill W. said:


> 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?




https://frentzandsons.com/Hardware References/plugandreceptacleconfiguratio.htm


----------



## Bill W. (Apr 10, 2016)

John,
Thanks for the info...  I'm gonna' print that and file it...
Bill


----------



## stupoty (Apr 10, 2016)

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.



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


----------



## Keith Foor (Apr 10, 2016)

stupoty said:


> 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.
> 
> ...


Yes, I believe that you put it to words better than I.


----------



## Wreck™Wreck (Apr 10, 2016)

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.


Correct the the legs change polarity 60 times per second in the US, if one had a device that was effected by polarity that operated at a frequency higher then the line I should imagine that problems would occur. A simple induction motor is not such a device.


----------

