Ask Me Help Desk - Red, White and Black

Hi,

I have a Red wire (3 reds twisted together, a white wire and a black wire (2 blacks twisted together) coming out of the ceiling.

With the light switch turned off I get continuity, on my meter, when I check the black and red wires together.

I get nothing across the black and white wires with the switch off but do get continuity with the switch turn on.

So, I am thinking I connect the two wires for the lamp to the black and white wires and cap off the red.

The lamp has a red and a black wire. I am looking to connect the black to black and red (of the lamp) to the white coming out of the ceiling (capping off the red).

In this configuration the lamp turns on and off at the switch.

Hope this is correct - and huge thanks for your help... don't want the house to burn down :-)

Are you located in USA?

Melbourne , Australia... so replies will be for guidance only

I don't know Australian wiring code, wire colors or practices, therefore I am hesitant to reply.

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I get nothing across the black and white wires with the switch off but do get continuity with the switch turn on.

That, of course indicates that the switch interrupts those two wires.

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With the light switch turned off I get continuity, on my meter, when I check the black and red wires together.

I don't think that is meaningful. More meaningful to do voltage checks.

How many switches control this light?

In US, when we have multiple switches controlling a fixture we call them 3-way. In EU I belief they are called 2-way. What do you call them?

Do you have multiple switches for this light?

Do voltage checks between red and black, between red and white and between black and white. Also do voltage check between each color and ground. Voltage check have to be done with power on, hope you are comfortable with that.

You could also remove switch(s) covers and look at wiring connections there to determine circuity.

Thanks for the help - it is really helpful.
Aus voltage is 220VAC - just like the UK.

[I] get 220V across black and red whether switch if on or off (3 reds twisted together and 2 black twisted together.

No current across black and white switch turned off, 220VAC across black and white switch turned on.

Only 1 switch for this light.

See this web site. It appears to me that black is neutral. It also appears to me that Australia has have a real mess as for as wiring color codes, one for equipment and one for building. Not only that but you have old and new for each.

Electrical Wiring Colour Codes

You said

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a white wire and a black wire (2 blacks twisted together) coming out of the ceiling.

Does that mean you have a white wire and two black wires all twisted together? Or does it mean that you have a white wire and that you have two black wires twisted together?

I think you are going to have to use logic and not wire colors to determine how things are wired. In Australia apparently red is hot or live and black is neutral. Power comes in on the live, goes through the appliance and goes out on the neutral. That is a completed circuit. Switches are used to interrupt that circuit. Switches are always put in the live side, never in the neutral side.

Can't figure out how the white is being used.

Remove the switch and see what wire are being used.

Switches for ceiling fixtures can be wired a couple of different ways.

The first is to bring the power to the switch box then take it to the ceiling fixture. This is called feeding the switch. The incoming live is connected to one side of the switch, the outgoing live is connected to the other side of the switch. The neutrals are connected together. So you have power coming to the switch box, going through the switch (when on) and going to the ceiling fixture.
If wired this way the switch box should have two blacks (neutral) connected together and two reds connected to the switch.

The other way is to run power to the ceiling fixture. A switch loop (one wire to take power from the ceiling to the switch another to bring it back to the light. No need to take neutral to the switch.) is used to control the light. This method has the advantage of being able to take uninterrupted power to other fixtures. If this method is used there should be only two wires in the switch box, both connected to the switch.

So pull the switch and tell me what you have there.

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[I] get 220V across black and red whether switch if on or off (3 reds twisted together and 2 black twisted together.

That would be correct. You are measuring the difference in voltage between live and neutral.

Doing a voltage check between each wire color and the ground should also tell you which wire is live.