No Power from C-wire with my old furnace

Problems related to residential installations.

No Power from C-wire with my old furnace

Postby dalumberjack » Fri Jan 06, 2012 11:26 pm

Hi everyone.

I am trying to run a C-Wire for my thermostat for a wireless module as it seems only two wires were ran before since it was an old mercury switch. Here are the pictures of my situation.

As of right now, I have the red wire connected to the C-Wire on both the furnace board and the Tstat. I how ever am not getting any power from it for some reason. I am a little lost when it comes to this old furnace so any help is greatly appreciated.

My furnace is an old Old GE Day and Night furnace. Also, for some reason the BBCode is turned off so I can't post links to the picks or the actual pick in the thread. Guess you have to cut and paste the links. Sorry. And as you can tell the site is removing the word photobucket from the link so you cant even copy and past the link. Don't know what else to do.

*.*/albums/cc513/dalumberjack/IMG_20120106_184510.jpg

*.*/albums/cc513/dalumberjack/IMG_20120106_184520.jpg
dalumberjack
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- No Power from C-wire with my old furnace

Postby Silverjwj » Sat Jan 07, 2012 9:54 am

Hook the red wire to the R on the t stat and white to the W. Then at your furnace or gas valve make sure it's e same. Could be any color wire just make sure they connect to the same letter. R and w is for heat.
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- No Power from C-wire with my old furnace

Postby Silverjwj » Sat Jan 07, 2012 9:58 am

Also you want to make sure it's the right thermostat for the application. Is it A 24 v or millivolt thermostat that's needed.
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- No Power from C-wire with my old furnace

Postby Freon » Sat Jan 07, 2012 12:30 pm

Can you tell us the make and model of the thermostat/wireless system? I think, not knowing the thermostat, that at a minimum you'll need 3 wires. The R terminal at the furnace is the source of the 24 volts, AC. In the old thermostat, you were simply connecting the 24 volts from the red wire (connected to the red terminal at the furnace and thermostat) to the W wire at the thermostat thru the mercury switch and thereby sending the 24 volts to the W terminal at the furnace causing the heating cycle to start.

Your new thermostat may need to be powered by the 24 volts and that will require the addition of a wire from the C terminal at the furnace to the C terminal at the thermostat. Be sure all power is off when doing any wiring.
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