REPLACING THERMOSTAT ON HEAT PUMP - http://www.hvacmechanic.com/ Forums

Original message

RONNIEJ

70.242.135.242

"REPLACING THERMOSTAT ON HEAT PUMP" , posted Sat 26 Apr 01:48

I am replacing a Robertshaw thermostat which used all 10 wires to a Honeywell thermostat which only has a place for 9 wires.

My system is a 2 stage (I think because it has aux or emergency heat) heat pump with electronic air cleaning filter.

The new thermostat has on 9 connectors labeled
Rc R O/B Y G C L E AUX

My old used all 10 wires
C L R Y2 Y1 E W2 G O B

what wire do I not use or where do I connect 2 wires?

Thanks
Rhonda

Rhonda

Replies:

Houston204

98.196.66.53

"Re(1):REPLACING THERMOSTAT ON HEAT PUMP" , posted Sat 26 Apr 15:25

If your system requires seperate O and B terminals your new stat will not work.

More information would help verify this.
The model of your old and new stat would be a good start.

Do you have a motorized zone damper system? This is almost the only time that I have seen both reversing valve terminals used. 2 stats connected to one furnace might indicate a motorized zone damper system. The make and model of this would be of assistance.

What brand is your outdoor unit? Most brands use the O terminal. Rheem and Ruud use the B terminal for the reversing valve.

"Tip of the Day" Remember to remove power first.

RONNIEJ

70.242.135.242

"Re(2):REPLACING THERMOSTAT ON HEAT PUMP" , posted Sun 27 Apr 13:46

Old stat is Robertshaw 9520
New is honeywell 7500 series like you show

Heating / cooling unit is a Goodman AE2410A with electronic cleaner.

I was told by the Honeywell tech line that the thermostat would not work, but they could not tell me one that would work and to call a
repairman.

Thanks

Rhonda

Houston204

98.196.66.53

"Re(3):REPLACING THERMOSTAT ON HEAT PUMP" , posted Sun 27 Apr 18:22

What model number is your outdoor unit? (You listed a fancoil number)

Goodman does not use the B terminal for the heatpump reversing valve, it uses O. I'm confident that it isn't connected to anything at the other end.

If this is the case the Honeywell Visionpro TH8320 is compatible with your system.

White Rodgers has some stats with seperate O and B terminals and 2 stages of cooling.

"Tip of the Day" Remember to remove power first.

Houston204

98.196.66.53

"Re(4):REPLACING THERMOSTAT ON HEAT PUMP" , posted Sun 27 Apr 22:29

Be sure to write down your old terminal = color combination before removing your old stat. The color used for C, E, and Y2 vary greatly.

"Tip of the Day" Remember to remove power first.