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jet · Nov 11, 2005, 10:14 PM

Currently have a Honeywell T841A1712 Multi-Stage Heat pump thermostat. I am changing to a Honeywell RTH7500D. All is good except that the manual states "If the old thermostat had wires on W1, Y1, and W2, some modification is required. Call your loca heating and cooling contractor for assistance."

What kind of a modification would be necessary and is it worth the cost. The Thermo cost me $105. Really can't spend any more $ on this. I will return it if need be.

Old description

Wiring is so:
On Old
R - red wire
O - orange wire
Y1 - has a yellow wire connected
W1 - is bridged to Y1(no direct wire attached to terminal)
E - Blue wire
W2 - white wire

Taken from HERE!!

PLease let me know if there is a way to wire this properly.

Thank You

labman · Nov 12, 2005, 06:27 AM

I don't know enough about heat pumps to help much. Maybe one of the newer people here will do better. You need to worry less about the old thermostat and more what the heat pump asks for. How are the terminals marked at the other end? You may also look at the instructions for heat pump and any schematic you find around it for what signals it needs. If it needs power to W1 in the high heat rate and the thermostat provides power to W1 when it calls for the high heat rate, then connect the same wire to both W1's.

Where did you buy the thermostat? If somebody there can help you a little, they might be much happier than having you return it. Honeywell and whoever made the heat pump may be able to help through their dealer, tech service, or website. You could even do a search on the thermostat part numbers and maybe turn up some information.

jet · Nov 12, 2005, 08:34 AM

I will get in the attic today and find that information. Thank You for the help that you have given, I really appreciate this.