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Need help wiring up a new thermostat

3043 Views 9 Replies 6 Participants Last post by  sktn77a

I have an old Friedrich Thermostat (still uses mercury) running my heat pump furnace. I bought a new Honeywell thermostat and im confused on where to put the old black wire, along with the W1 and W2. In the instructions it says that if I have both a Y1 and W2 and W3 wires that i should ask for help.

Here are the wires my old, existing thermostat has:

F- White wire
Y-Yellow wire
W1- Green
W2- Blue
#5- Black. (New thermostat does not have a #5, whats this wire for??)

NEW thermostat terminals:

Rc (R and Rc terminals are jumped)

In the instructions it says that the "W/Aux" terminal can be used for W, W1, or W2. But I cant put BOTH of my w1 and w2 wires in that terminal can i?

Thanks everyone for looking and for the help.
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You need a 2 stage heat thermostat

Sent from my iPhone using DIY Forum
Ok thanks.

On the package it says "Works with heat pumps w/ Auxillary" so I figured this meant it was a two stage thermostat.
Yes, it should work if its designed to run a heat pump with auxilliary heat. Don't the instructions that came with the stat give any insights (this is a pretty standard set up)? As to the black wire, no idea. :(
Yeah the instructions came with a diagram and all of the different possible wire/terminal combinations that may be used with different manufacturers...but I have both a w1 and w2 wires and only one terminal. Unless I can just join w1 and w2 together and put them in the same terminal.
Does the old thermostat have a emergency heat function? Does the new thermostat have an E terminal. What is the model of the old and new thermostat?
Yes the old one has emergency heat setting. Old thermostat is a friedrich. Not sure of the model. New stat is a Honeywell RTH2410B.

Does not have an E terminal but it does have a terminal that says "not used."
Need to see where the W1 and W2 wires go in your air handler. That stat is not designed to control stage aux heat.
From the link above:

"On a heat pump system the compressor ("Y" terminal) is activated for both heating and cooling the only difference is that to switch to cooling the O terminal is activated to reverse the outdoor unit"

I think the thermostat will work with your system but you need to post the exact model number to figure out the wiring and, as Been says, check which wires go where in your furnace (you can't always go by the color). I think I know how this would work, but I'm reluctant to tell you something that could damage your compressor!

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