thermostat installation-Honeywell

Old 05-17-07, 06:04 AM
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thermostat installation-Honeywell

I am upgrading from an old honeywell T841 thermostat to a new Honeywell digital TH5220D.
My Heat Pump is a Carrier 38YCB from 1996
On the old T841 thermostat the wires are attached as follows:
The Yellow wire attaches to Y.
The Green attaches to G.
The Orange wire attaches to O.
The red wire attaches to R.
The brown wire attaches to X.
The white wire attaches to W2.
On the Heat pump unit the wire connections are the same except the brown attaches to C at the heat pump.
The new TH 5220D has the following terminals and designations:
Rc for 24VAC power from cooling transformer.
R for 24VAC power from heating transformer.
R and Rc are bridged together.
O/B for changeover valve.
Y for compresser contactor (stage 1)
G for fan relay
AUX for auxilary heat relay
E for emergency heat relay
L for sends output when set to emergency heat.
C for 24VAC common. C is optional with batteries.
How do I connect the new thermostat.
Old 05-17-07, 05:42 PM
Jarredsdad's Avatar
Join Date: Oct 2002
Location: Troy, VA
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Simple - original manual

Everything is pretty much the same as far as wiring.
R to R
Y to Y
G to G
X goes to C
W2 goes to aux
O goes to W O/B

Jumper E to Aux for em heat to work.

Look at page 4 of your installation book. What you call W is for conventional. Below that is O/b for heat pumps. You address this during programing.

This maybe the install manual for your old stat, you didn't give the entire model number so there is no X terminal.


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