I am trying to replace a fairly old Honeywell Heat Pump Thermostat whose only marking is T 841 A 1712. The new thermostat I'm trying to install is a Honeywell RTH7500. Here are the wires (coming from 2 cables) that are hooked up to the old thermostat:

Cable 1:
X - Red
E - Blue
G - Green
O - White

Cable 2:
R - Red
W2 - Blue
W3 - White
Y - Yellow
B - Brown

The installation guide for the RTH7500 is throwing me off because it says "if your old thermostat had a Y1, W1, and W2, stop now and contact a contractor." Now, I don't have exactly this...instead I have a Y, W2, and W3, which I assume is equivalent. Any ideas for how to wire up my new thermostat?

Thanks,
Mal

 

We need more info here.

What is the model # and make of both indoor and outdoor unit?

 

The heat pump:
Payne
BDP Company
Model: 517B030010HPFC
Product: 517BN0030010ABAE

The A/C:
Bryant
Model: 661CJ030-E
Product: 661CJX030000AEAA

Have I provided the necessary information?

 

Must be an older equipment? I am not able to pull the model's..

You will have to let me know what you got for letters on the furnace (or air handler) that the t-stat's wire goes to.

Also, if the heat pump has letters on the board or wire.

 

Maybe I got that wrong. The outdoor unit, which looks like an A/C, is the Bryant, and the unit in the garage, that has a bunch of duct work coming in and out, is the Payne. No idea which is actually the heat pump. As far as I know, the Payne is original equipment in my 1981 condo. Would the serial number for either unit help to identify? Over on hvacmechanic.com, I learned the issue is that I have two leads for the heat pump reversal valve (b and o) when most units have just one.

 

That is the Heat Pump.
That is the Air Handler, or Furnace if it's gas.

No, I'd like you to take the covers off on the air handler/furnace and make notes of what colored thermostat-wire went on what letter, and post back here.

Also, for the outdoor unit as well.

 

Today I'm finally installing my RTH7500 thermostat, but I'm still having issues. Over on HVACMechanic.com, we determined that while my old thermostat had O and B wires, I only need to connect the O wire (for the heat pump reversal valve) to the RTH7500 since that's what my Bryant heat pump uses. But I'm still having issues with the installation. I can't figure out what to do with my W2 and W3 wires. Here's how I'm connecting the wires:

Old -> RTH7500
-----------------
R -> R
O -> O/B
Y -> Y
G -> G
X -> C
E -> E
W2 -> ?
W3 -> ?

So I'm pretty close to getting this thing installed, but I can't figure out what to do with W2 and W3. Any ideas? It's getting cold over here...

Thanks a ton!

 

I would put W2 with the other wire on E, and W3 on Aux.