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I have a very OLD wiring so it isn't clear how to install my new switch per the provided wiring diagram.

I have 2 COMBINATION SWITCHES, each has a switch and a pilot light on them housed in a single junction box. The old switches are brown, I want to replace them with white switches.

1

2

The old switches were wired with 3 wires, black, white, plain copper. I don't know that the plain cooper was to a ground screw or not. In the old switch the copper wire was attached to a screw that WAS NOT GREEN but was a single screw on the right side of the old switch.

I don't know how the old switch compares to the new switch. I only know that the old switch was wired with the black and white wire on the top/bottom of the two screws on the left side of the switch and the plain copper wire was wired to the one screw on the right side of the switch.

I wired the 1st new replacement switch as follows:

  1. Black Wire to Brass Screw on switch
  2. White Wire to Silver Screw on switch
  3. Plain Copper Wire to Black Screw

I replaced the first old switch as above in 1, 2, 3 with the new switch. Turned on power, switch worked as expected (pilot shows on when the switch is on, pilot off when switch off).

Then I replace the 2nd switch exactly at the first and it tripped the circuit breaker.

How do I wire using the 3 existing wires (Black, White, Copper) to the new 2nd switch in order without causing the circuit breaker to trip when it is used?

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Are there any other wires in this box or is that it? Are the wires going to each switch out of the same cable or not? A clear picture of the wires coming out of the box would be helpful. Do you have a multimeter or preferably a non-contact voltage tester? –  bcworkz Feb 3 at 23:24
    
Black and white wire from same source going into one switch. Black and white wire from another source going into second switch. There is a green covered and a plain copper wire connected with a NUT and it looks like the plain copper that goes to each switch is coming out of the connected nut. –  user19680 Feb 4 at 0:07
    
I have a simple voltage tester with two probes, one red one black. If I attach the black to one wire and the red to the other wire, the voltage tester will light up with the voltage when the power to that is on but it is off now –  user19680 Feb 4 at 0:10
    
I am thinking I need to put the plain cooper to the green screw on both the new switches, would that be correct. Then just need to figure out where the black wire goes to on the other side of the switch? –  user19680 Feb 4 at 0:11
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Sounds like the old setup was using the grounding conductor (bare) as a grounded (neutral) conductor. This is NOT appropriate. –  Tester101 Feb 4 at 13:23
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2 Answers 2

It sounds like the old switches were hooked up using the bare copper grounding conductor as a grounded (neutral) conductor. This is NOT the proper way to wire this switch. To wire the new switches properly, you'll have to install an additional wire between the switch and the load.

It sounds like you have a situation like this...

Current Wiring

But what you need, is something like this...

Required Wiring

About the Device

The device you're trying to install has 5 screw terminals. On one side it has 2 COMMON terminals, which are likely either black or brass in color. This side also contains the GROUNDING terminal, which is likely green and located kind of off by itself.

On the other side of the device, there are two screw terminals. The first is the LOAD terminal, and is likely brass in color. The other terminal is the GROUNDED (neutral) terminal, and is probably silver in color.

COMMON

The COMMON terminals are used to supply power to the device. It's typical for only one of the terminals to be connected, but possible that both can be used.

GROUNDING

The GROUNDING terminal is used to connect the device to the equipment grounding system.

LOAD

The LOAD terminal is used to supply power from the switch, to the light or other load that is being controlled by the switch.

GROUNDED

The GROUNDED terminal is used to complete the circuit so the pilot light can be illuminated.

Internally, the switch looks something like this...

enter image description here

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Thank you, yes it seems I would need another wire to be able to use the pilot. Thus I gave up on using the combination switch with pilot and just put in 2 plain switches and will cover them with a switch guard so that no one accidentally turns on the attic light or fan unless they mean to. I had found out that the white wire from one of the cables was the live wire and the black wire from the other cable was the live wire. I think This is what caused the originally tripping of the circuit breaker. –  user19680 Feb 6 at 1:11
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I'm not sure what caused your breaker to trip; I'd need more details about exactly how you wired thing. (If you could upload a pic of what tripped the circut, and of the old switch that would help a lot.)

I can't imagine someone using deciding to use the bare copper wire as the hot, or to carry the load, so would feel safe to assume it's properly wired as a ground and connect it to your green screw.

Further, it sounds like your current wiring set-up doesn't distinguish between the load and a direct connection to neutral. As long as you aren't using CFLs this is probably fine. Thus, you likely want to run a jumper between them. Going by the figure in step 4 you can attach a short wire between A1 and B1 (the brass and silver screws).

This leaves you with two possible configurations white to 'common' and black to 'A1' or vice versa. Both was may work to complete the circuit, but I'd start with white to common.

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Why would you jumper brass and silver terminals? That will bypass the pilot, rendering it useless. Something is messed up here for one setup to work and the other to trip breakers. This indicates reversed polarity or switched neutral somewhere. The wire colors cannot be trusted. Until it can be established what's hot, what's neutral (if any) and what's switch legs, I don't think we can safely establish a proper installation. –  bcworkz Feb 3 at 23:21
    
@bcworkz Assume the switch is down stream of the load. Electricity Flows in via common and would exit to neutral both the silver and brass (A1 and B1). Same is true if it's upstream. However, you are correct if the resistance of the pilot is too high, then one is left with the less ideal situation of jumping silver to green. –  virtualxtc Feb 3 at 23:29
    
The two old switches were wired exactly alike. I have attached pictures of the old switches. The NEW switch has BRASS / Silver screws on one side of switch an Black/Green screws on the other. –  user19680 Feb 3 at 23:59
    
@user19680 there doesn't appear to be any pics, you might need to try again. –  virtualxtc Feb 4 at 0:01
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