We have a Frigidaire model B3BM-024K-A HVAC system. It is all electric. A few days ago, my husband replaced the old thermostat with a Honeywell RTH6300B programmable one. My husband wired it according to the instruction. It has a problem: the heat will not switch off automatically when the desired set temp. has been reached. It will not even stop when we manually switches to Off.

What could be the problem and how do I fix it?

Thanks in advance,
Confused Housewife

You must first check to be sure the Honeywell thermostat is compatible with your electric furnace. Call or e-mail Honeywell to confirm you are OK to go ahead. If they say the stat is fine have your husband tell them exactly how he connect the 4 lead wires. One or more is wrong and he may have missed a jumper that is recommended in some installation.

We have a Frigidaire model B3BM-024K-A HVAC system. It is all electric. A few days ago, my husband replaced the old thermostat with a Honeywell RTH6300B programmable one. My husband wired it according to the instruction. It has a problem: the heat will not switch off automatically when the desired set temp. has been reached. It will not even stop when we manually switches to Off.

What could be the problem and how do I fix it?

Thanks in advance,
Confused Housewife
Thanks for the prompt response. We have been trying to contact Honeywell via email and phone support. In both cases, we could not get an answer. I talked to them today to check if the thermostat is compatible, but the lady who answered was reading off some manual instead of giving me a straight answer. Is there an online site I can go and find the compatibility myself?

The literature that came with the Honeywell should outline what iis can and can not be used with. However, unless you have some good background it is going to read like double speak. Your next chance might be with the store where you bought the stat. They sometimes have very knowledgeable people who can help you pick the correct stat. I have little experience with electric furnaces but recall that they are a bit picky regarding what stat to use. Forced hot air systems are a little easier to work with.

Is this a electric furnace depending only on resistive elements for heat, or is it a heat pump? Northern heat has prepared some excellent material in a sticky at the top of the H&C forum, https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html Start with how to identify a heat pump. There is plenty of material there to solve most problems.

Frankly, from what I see here, Honeywell's record on tech service is very poor.

There is an installer manual that came with your furnace, not the owners manual. You have to go into the setup and tell it what kind of system you are controlling. Assuming all the wires where hooked up properly.