Old Honeywell T8085 - http://www.hvacmechanic.com/ Forums
Original message
| ianr
 |  "Old Honeywell T8085"
, posted Sun 17 Aug 10:27  
Hi,
I just brought house with old Honeywell T8085 thermostat with 19110AJ wallplate. I was trying to switch out for a RTH8500.
The old wall plate has:
R
W
2 C - according to old manual the drive the clock
Unmarked terminal - with a white wire connected to it
I connected to RTH8500 as follows:
R to R
W to W
Unmarked to Y
The system as heat and AC controlled by switch in basement. I can see in the zone control board (TROL-A-TEMP MASTEROL MARK V) that the outputs to system are R (Rc and Rh are jumpered together), W, Y, G. The fan has switch in basement also set to auto.
But the inputs from thermostats are market T5, T6, T7 on the zoning board so no clue what maps to what.
At moment when the thermostat calls for AC nothing happens. It works fine with old thermostat still so i must be doing something wrong, any ideas?
Any help much appreciated,
tks ian
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Replies:
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| ianr
| "Re(1):Old Honeywell T8085" , posted Sun 17 Aug 21:29
Hi,
thanks v much for the diagrams it is working now. Turned out I had it ok but the jumper between R and Rc on the new themostat had fallen off - once i noticed that and patched wire all is working well. The Y is not marked on the old wall plate but it is Y wire - which make sense looking at plate contacts and the wire colors going into zone controller.
cheers ian
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