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Honeywell therostat wiring help

Have issue with long delays and heat and air coming on together. Wired exactly what they told me to do. replacing old Honeywell mercury with new digital.
jumpered E and AUX


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Re: honeywell therostat wiring help

Don't assume the wires at the thermistate are correct.

I had similar and had to go all the way back to the heat/AC controller board. I found the colors weren't attached per spec so was fighting the origional installation at the new thermistat.

Also some digital won't control mutizones proerly

Posted on Dec 19, 2007

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A thermostat is a switch. It connects 24vac from one terminal to another depending on the request. The 24vac comes from a transformer, usually located in the furnace and connects to the R terminal. Since you are using RH and RC without a jumper between it means there are two transformers, one in the furnace for heating (RH) and one in the air conditioner condenser used for cooling (RC).
Your old thermostat was probably mechanical and did not have a C (24vac common) terminal. Your new thermostat requires power to operate therefore needs a wire connected to a C terminal. I would get rid of the transformer you added and look for an unused wire in the bunch at the thermostat. If it's there connect it to C on the thermostat and to C on the furnace. Remove any jumper from R to RC or from RH to RC depending on your thermostat and connect wires same as the old thermostat.

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Recheck your connections.The wire colors may not have been wired in the standard way when HVAC system was installed. I remember the instructions on my Honeywell thermostat(replaced mine about 2 months ago) stated that you should look at the wire LOCATIONS on the 'stat you're replacing and tag the wires according to this,not the wire color(too late in your case).You'll have to verify the wires.Disconnect them(don't worry about noting where they were as it's not right anyway).Using an A/C voltmeter,locate the hot feed to the 'stat(ground one lead of the meter at a nearby outlet and look for 24v on any of the wires).Tag it as "feed".Now,touch this to each wire until you find one that turns on the ventilation blower and tag it.Try the other two,one of them should turn on the outside A/C condensor unit(this is the A/C wire).The remaining wire's gotta be the furnace,but verify anyway.This should be enough to get you back on track(don't feel bad,the instructions in my 'stat confused me a little,even though I've replaced mine a couple times before).PS- I think the blower fan wire goes to the terminal with the little factory jumper wire-this is so you can set it up to run the same fan in heat or A/C(factory setup) or remove the jumper to run a seperate fan for each(highly unusual setup but possible)

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1 Answer

I installed the Honeywell RRH230B, wired exactly as the one I replaced, but can't get the fan to run continously when switched to fan rather than auto. In fan mode, the fan goes off with the furnace when...

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1 Answer

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1 Answer

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