Question about Heating & Cooling
I have two systems - a FHW oil fired heating system and a central A/C system on the thermostat. Instructions say common 24vac must come in from the A/C side, not the furnace side. This works fine under normal circumstances. But, I have a portable generator and a Gnerac panel wired for 10 circuits. The A/C system is not on the Generac panel; the furnace is. When I have a power outage and hook up my generator, my furnace had power, but my thermostat does not. Honeywell has been of no help on this, other than for one person to say that in no way can you take the 24vac common to the thermostat from the furnace. I have asked about several options, but cannot get them to reply. For example, put an A/B type switch off the therostate 24vac common with the ability to switch it to feed from either the A/C or the furnace. Can you comment and do you have any practical suggestions short of ditching this thermostat, which I really like otherwise?
A common is basically a ground. If you had to you could run your common to an electric outlet on the ground wire. Not recommended but I have done it and it will work. I'm a southern a/c guy with no oil furnace experience but if your furnace isn't sending 24 volts to the tstat it's not going to matter if it has a common because you will have lost your 24 volts when your a/c is off. If your furnace does send 24 volts to the tstat then I don't see why you could not get the common from the same spot, even if you run your common straight to ground. Good Luck
Posted on Mar 10, 2017
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Posted on Jan 02, 2017
9 TIMES OUT OF 10 THE COLORS ARE THE SAME. MATCH THEM UP. FIRST LABEL THE WIRES ON THE ORIGINAL STAT, AND PUT THEM IN THE CORRESPONDING PLACE ON NEW ONE.
Posted on Oct 27, 2008
I had the same set and problem. I had a RC wire which is the power to the AC. But didn't have an RH wire which is the power for the heat. To fix this just use the jumper wire and insert it in with the RC wire and hook it up to the RH. Fixed my problem.
Posted on Oct 16, 2009
You need a specific thermostat for a Wall Furnace it is a Millivolt Thermostat and not a 24v standard thermostat....usually it will work anyway however if the powerpile (generator produces millivolts from the pilot light) is weak it may not be producing enough...or the Pilot light may be dirty and lazy...won't produce enough millivolts ...or you can have bad or dirty contacts or connections....or a combination of any of the above.....a 24v Thermostat and particularly a non-mercury thermostat has too much resistance in it for a millivolt system....as your Wall Furnace (other than the fan) runs on less than 1 volt
Posted on Oct 31, 2009
This does not sound like a thermostat problem. I would be looking for a zone valve or circulator pump problem.
Posted on Nov 12, 2009
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