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-   -   thermostat wiring trouble ( 10-28-2007 06:50 PM

thermostat wiring trouble
I have a new thermostat unit I am wiring, i am stumped! on the old white rodgers 20 year old mercury switch it had one wire that is white and was connected to two screws an E and a W2. which post should i screw that one wire to if it has two designations?

TurningColorz 10-31-2007 06:51 PM

On a two wire system, you can't do any harm by hooking it up wrong.
One wire is ground, the other hot. When shorted, the furnace should come on.
If there's a "w2" on the new thermostat, the white wire should go there.

Good luck,
Mike -

J. V. 11-01-2007 01:03 PM

Mike...How can one wire be hot and the other be ground and the thermostat work. To make an electrical circuit it must be completed back to the source. Ground wires carry no current unless there is a ground fault.
Also, two wires that have polarity reversed can cause failure of the device. This is usually found in DC circuits.

To try and answer the question.
You do not have enough wires to for your new thermostat. Your old thermostat only had two wires correct? That means the old thermostat was just a switch. on/off. The newer thermostats are smarter and require more wires that your old one did.
Try to find a single pole switch type of themostat or get an HVAC guy out there.

TurningColorz 11-01-2007 04:17 PM

Thanks J.V.,
You're right, "hot" and "ground" were the wrong terms to use.
Maybe "in" and "out" would be more accurate?

Either way, as J.V. points out, your thermostat is a simple switch and connecting the two wires will "close" the switch.
I'm only assuming there are really 2 wires on the new thermostat, although only the white wire is mentioned in the original post.


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