New Honeywell RTH6580WF Thermostat

Problems related to residential installations.

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New Honeywell RTH6580WF Thermostat

Post by santa6tom » Sun May 17, 2015 2:08 pm

I installed this thermostat for my central air gas single stage heat/AC unit which has a General 90 50A50-131 controller. Previous thermostat was a White Rogers battery unit, model 1F80-51. Thermostat wiring is 4-wire red, blue, white, green. Unfortunately, I did not maintain a record of how the original was wired on either end. I installed the new thermostat a few months ago during winter in Iowa. It worked fine for heating. Tried to run AC last night. Nothing seemed to happen. Switched it to cool, dropped the target temp below actual a couple of degrees. Nothing. This morning the compressor was running, but no fan circulating. Compressor was iced up a bit. Shut everything off.

At the furnace controller the available contacts are "C", "Y", "W", "R", "G". Currently have green wire going to "C", red going to "R", and white going to "W". Blue is wire nutted to a red coming from what appears to be a transformer two-wire cable. The white from this two-wire cable is also connected to "C". At thermostat, red is connected to R & Rc via factory installed jumper, blue to "Y", green to "C" and white to "W".

Where'd I go wrong?

Thanks for any help.

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- New Honeywell RTH6580WF Thermostat

Post by Freon » Thu May 21, 2015 10:42 am

Forget wire colors. Just make sure whatever wire you have connected to the furnace terminal is the same wire connected to the corresponding thermostat terminal. And make sure there isn't a different colored wire splices into the circuit. Here is what should connect to what.

At the furnace controller the available contacts are "C", "Y", "W", "R", "G".
C is the Common and goes to the common terminal of the Thermostat
Y is the AC condenser and goes to the Y terminal of the 'stat.
W is the Heat and goes to the W terminal of the 'stat.
R is the 24 volts AC power and goes to the R/Rc terminal of the 'stat.
G is the fan and goes to the G terminal of the Stat.

USUALLY and I emphasize this word, White is the heat wire color, Green is the fan color wire, Red is the 24 volts power color and Blue the Common color and Yellow the AC compressor color. But anyone could have wired it not to convention.

Did your compressor ice up or did the evaporator coil in the furnace ice up? Connecting G (fan) to C (Common) would mean your furnace fan shouldn't run and the indoor evaporator coil would ice up.

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