Honeywell Thermostat CT31A1003 and multistage furnace

Old 10-27-13, 05:03 PM
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Honeywell Thermostat CT31A1003 and multistage furnace

My mother has a Lennox G61v furnace installed in 2010 and a Honeywell thermostat CT31A1003 installed just recently. She is elderly and prefers the manual thermostat. She did have a digital thermostat but the display went crazy and she hated it anyway. My brother installed the manual thermostat and when the switch was flipped to heat the furnace came on no matter what the temperature and it could only be shut off at the switch in the basement. We called a technician and he said it had been wired all wrong. Now, my mother can cause the heat to turn on and off by pushing the lever on the thermostat up or down, but the heat will not go on or off by itself. Without waiting around to see if it would cycle on and off by itself, the technician assured us that everything was now working properly. I see he set the anticipator at .8 which is the proper setting for a high efficiency furnace. I will call him back but only if he does not charge again.

I have seen on the internet that this thermostat is not for multistage furnaces. Could that be the problem?

Thank you.
Old 10-27-13, 06:32 PM
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It is too bad that your mother is so stubborn as that two-stage furnace would both save her in fuel costs and keep the house more comfortable with a proper multi-stage thermostat.

IF a two-stage thermostat was originally installed with the new furnace then you need to make a few changes in the wiring compartment of the furnace in order to use a single stage thermostat. Not knowing exactly how the thermostat is currently wired I cannot help much but here is the instruction manual for that thermostat.

Note that ONLY the white and the red wires should be connected and no others to the thermostat. At the furnace ONLY the white should be connected to W1 and ONLY the red should be connected to R. There is also a DIP switch setting that I will have to look up for you that changes the second stage to a timed operation rather than temperature signal.

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