Wiring Colours - Black, White & Green - which is neutral

[Athos]

Hi

I have purchased an electric treadmill which was cheap because it has a broken socket (casing crushed and connections snapped).

I am going to replace the socket and plug with a three core in-line connection, but the treadmill's internal wiring colours has me confused.

Leading into it's transformer it has Green and yellow (Earth, simple enough) then black and white with an in-line switch in the black.

Some websites say the US colouring is white or grey for neutral, but I think I was taught at school that switches always go in the neutral so you're less likely to electrocute yourself when touching the switch.

Can anyone offer any guidance, please.

Many thanks in advance.

 

[Steve]

This has gotta be a wind up.

You switch the LIVE!!!

What does the data plate say about the machine's rating? Voltage hertz, things like that.

If its destined for the American market, its doubtful you can use it here without replacing the transformer (if this is what it is)

 

[wingcoax]

Sure this thread has been on before, A couple of weeks ago/

 

[Athos]

I bought the treadmill yesterday and I haven't posted this question before, if this forum is similar to others you can check the history of posts each user has made - which is one other concerning a noisy washing machine, to which I received very helpful answers and was hoping for the same again, not to be derided for not knowing something.

It's been a fair number of years since I learnt basic circuits in physics and my uncertainty on where the switch should why I've sought help. I apologise if this has incurred your wrath.

I've looked at multiple websites and have found conflicting information on wiring colours and so I am trying to find a definitive answer before plugging the machine in.

The machine has been previoulsy used in the UK, all that's happened since then is the previous owner tried to move with the power lead still plugged in and damaged the socket. The face plate on the transformer indicates 240v 50-60 Hz. There is no labelling to identify the black, white and green inputs nor the black and white DC outputs. The machine's brand name is Pro-form.

I would appreciate a proper answer, please.

 

[Steve]

I would get in touch with the transformer's manufacturers then, for a definite answer.

In all honesty, it normally does not matter which way around you wire live and neutral AC - they alternate 50/100 times a second anyway. BUT if you are introducing a switch it MUST interrupt the LIVE.

If you only interrupt the neutral with a switch, the machine will still be live, but appear dead. I hope you can see why this would be dangerous for anyone that wants to open the thing up.

 

[Colin Brenton]

Hi Athos,

The standard in the US is;

Green for earth / ground / CPC

White for neutral

Black for phase / live

It is important to switch the phase line, so that when switched off, not only is the circuit broken, not part of the system after the switch is at a potential relavtive to earth.

This assumes that the neutral is within a few volts of ground, as should be the case in Europe. In the US I belive that 220v is dervied from two phases of 110 each, 180 degrees out of phase. In this case neither line is at ground potential, and both should be switched.

Do check that the machine is suitable for use in the UK before starting

Hope this helps,

Colin

 

[Athos]

Thank you very much, Steve and Colin.

It now makes perfect sense, and as always in these situations, I can't think why I thought otherwise.

Thanks again.

 

[Steve]

This assumes that the neutral is within a few volts of ground, as should be the case in Europe. In the US I belive that 220v is dervied from two phases of 110 each, 180 degrees out of phase. In this case neither line is at ground potential, and both should be switched.

Colin, please dont confuse things by introducing unnessecary information.

The majority of appliances in the US run on 110v AC single phase and neutral - neutral being tied to earth at the substation, and the basics of the modern domestic circuit wiring is similar to ours (different colours and standards though). Many homes there though, have a split phase supply for appliances such as washing machines and electric dryers. In these cases they still have a neutral. The voltage between each phase and neutral is still 110v, but the voltage between phases is about 220v.

A similar system is used in parts of Europe, and is used to supply electric cookers on supplies that, if single phase only, would become overloaded with such a load. One has to remember that much of Europe is not as developed as the UK, and their electric system, whilst having the same standards as everyone else, is usually a lot older than ours, particularly in rural parts.

 

[Colin Brenton]

How was that irrelavent information?!

The first part related to the colour code that was asked about, the second to why you shouldn't fit a switch in the neutral wire, answering the second part of the OP's question...

 

[Adam_151]

I beleive steve was on about the point that they use a 220v split phase/centre grounded supply for some fixed equipment in a domestic was irrelevent, as normal plug in appliances run on 110v with the neutral earthed

Anything with white and black is 110v... the other phase is red where used (and we won't mention the blue )

 

[Colin Brenton]

Yes, I see your point, fair enough.

Electrical wiring being reasonably recent, it makes you wonder why so many differences between countries, really.

 

[Paul_C]

Anything with white and black is 110v... the other phase is red where used (and we won't mention the blue )

As a general rule that's so, but remember that an American 3-core flexible cord comes with black/white/green cores as standard. Although white is usually the neutral or grounded circuit conductor, it's an allowed exception to use white as a "hot" line in a connection cord where only 240V plus ground is required.

Where the neutral is required to provide both 120 & 240V, then the cord would be 4-wire: black/white/red/green.