Thermostat wiring

Asked March 27, 2016, 9:41 AM EDT

I am replacing an old thermostat that uses "G, O, Y-W, C, R" but can not identify the "O" on the new thermostat. The new one has either "RC, R,W,Y,G,C" or "RC,R,O/B,Y,G,C". I assume "C to C", "G to G", "Y to Y", "R to R", but then I don't know where the "O" is to go? Also, Y-W have a jumper, what do I do on the new thermostat. Old model is ICM (AN7814) and new is Honeywell (TH8320U1008). Condo has large exchanger in closet that uses cold/heat supplied for entire building. Pictures provided.

Palm Beach County Florida

1 Response

Some old thermostats use the letter O for a contact, others use the letter B for the same function. So, the new thermostat labels the connection "O/B".
The new thermostat should have came with some instructions. for the wiring. But, I think it is acceptable to jumper the Y and W like the old thermostat.