Old Lennox thermostat wiring conversion

Old 10-25-20, 02:38 PM
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Old Lennox thermostat wiring conversion

I'm trying to replace an old Lennox mercury thermostat but the wiring codes do not match those on the new UWP mounting system (Honeywell RTH6360D); I'm not even sure this model can work w/ the wiring I have (see image of original Lennox thermostat mounting plate wiring pattern). The numbers on the original Lennox thermostat control panel are T872R1131 7933H and the number on the mounting plate is 0672L1144.

1. Can the Honeywell RTH6360D thermostat work as a replacement?

2. If so, what is the conversion for the wiring pattern from the original mounting plate to the new system (see image of UWP mounting system for reference)?

3. If not, what brand/model is recommended as a replacement thermostat?

The current wiring pattern is as follows:

Code/Wire Color(s)
M/magenta-ish (or reddish)
Y/red AND orange

Original Lennox thermostat mounting plate showing wiring pattern.

UWP Mounting System for Honeywell T3 Programable Thermostat Model RTH6360D
Old 10-25-20, 07:20 PM
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Welcome to the forums.

Tentative wiring. Your system may have an indoor transformer and an outdoor transformer. They are supposed to be replaced with one larger one. You could try the stat without changing the transformer.

A ------> yellow -------> cap off
Vr -----> white --------> R (1 wire)
R ------> black --------> O/B
F ------> brown --------> G
V ------> blue ----------> cap off
M ------> red -----------> Y
Y -------> orange ------> AUX/W2

You need to program the stat for advanced features.....
200 ----> 2 = heat pump
205 ----> 7 = air to air heat pump


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