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Multiple "pilot" wires for heaters at the electrical box. How to figure out which is


The heating system in my house uses electric heaters. Each heater has a "pilot" wire that runs to the electrical box, along with the load and neutral wires.

The pilot wire is connected to the control system, which then sends a signal to each heater to turn it on, off, daytime, day-time.

The control system has two "zones", and so the pilot wires can be grouped into areas of heat. (ie: Zone 1 = bedrooms / Zone 2 = everything else)

The problem is that I have no idea which pilot wires are for which heater. They are not labeled.

Is there any way I can figure this out? For example, I thought about putting a 9v battery on one end of the wire and then a multi-meter to check for voltage... but I need two wires for that, and the pilot wire is only a single wire.

Any ideas?


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Buy a long length (say, 100 feet) of #14 to #22 insulated wire (the #22 or #20 costs less and you can get that at Radio Shack too).

Turn off the power. Disconnect one end of a pilot wire from everything and connect it to the wire you bought. Go to the other end, laying out the wire you bought as you go. Use the ohms (or continuity) function of your multimeter between the wire you bought and the suspected other end of the pilot wire. (Or use the 9 volt battery and the volts function of the multimeter.)

The second end of the pilot wire does not have to be disconnected from everything else.

It will probably be easier if you connect the first end of the wire you bought up at the radiator and do the meter tests down at the heat control panel. This way, after stringing the wire you bought once, you can try all the pilot wire ends one at a time quickly to find out which one matches.

It doesn't matter whether you leave the 9 volt battery (if you use that method) connected at the first end of the wire you bought, or you hold the battery in your hand while using the meter at the second end.
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