Help with Honeywell Thermostat Wiring


Old 01-03-09, 10:19 AM
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Unhappy Help with Honeywell Thermostat Wiring

Gang...I just got back from holiday vacation and noticed that my current Honeywell Thermostat (T8411R) was not working. The digital screen was blank, as if it was not getting power. By the way, this model does not use a battery. No matter what I did, nothing helped. So, I figured that the thermostat was burned out. So, I just got a new one, a Honeywell RTH6400, yet this is not working either.

On the old system, my wiring was set as follows:
G,C,R,Y,W2,W2 jumpered to E, and O

On the new system, I have it wired as follows:
G,W2(going to W),O (going to W also), Y, and R. According to the directions, C is not used.

At this stage I am wondering if I have it wired correctly (which is the more likely story), or if there is another issue altogether with the heating system altogether. Any ideas? Thanks everyone.
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Old 01-03-09, 01:43 PM
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You sure there isn't a typo? I can find no information for a Honeywell RTH6400 here on their web site.

Sorry I am a gas heat man and don't have much expertise on heat pumps but it seems to me that in order to have power to the thermostat you would have to have a "c", common connection. Do you have 24VAC between "R" and "C" wires? You should have. If not your old thermostat is probably OK and the problem is in your indoor unit or an open thermostat wire.

You should have 24VAC between the "R" and "C" wires at you indoor unit. Make sure you have 115VAC (or perhaps 230VAC) on one side of the unit's transformer and 24VAC on the other. Does you furnace have a circuit board if so, check for a blown fuse.

Last edited by xpogi; 01-03-09 at 02:00 PM.
Old 01-03-09, 10:31 PM
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This t-stat will not work on your system.. It's the wrong type of t-stat. YOu need stat that support back up heat, the one you got does not. and with the two wires together is going to turn on both heat pump and back up at the same time.

You need to use either the Honeywell RTH7500 or RTH7600.

But as X pointed out, it may not be your t-stat.. It can be your system that has lost power or your low voltage side of the system has gone out.

You need to take some reading to see what your problem is.
Old 01-04-09, 09:50 PM
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Any update for us Mike of what you may have found for your issue?
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