Gas and Oil Home Heating Furnaces - Kenmore Furnace/Thermostat Problem

Recently tried installing both a Honeywell and a Noma digital thermostat with a Kenmore, model NTC5075BFC1 (bought through Sears in Canada & beleive it might be made by Heil but not sure),mid efficiency furnace with the same results (bought through Sears). In both cases the exhaust flue fan starts cycling on and off as soon as you put power on to the furnace after the installation is complete and it cycles on and off after the heating cycle has shut down. It is a 4 wire , 24 V system. The present thermostat is a mercury bulb type with a timer mechanism that works normally without this cycling. The wiring is the normal red,white,green and yellow leads and I checked the correctness right back to the fan control circuit board. Any ideas?

What model T-stat do you have now from Honeywell?

Lot of times, when you have "power stealing" t-stat, it will make the furnace run funny..


Post back on the t-stat model, and we can go from there.

Model CT3200A

OK, The 3200 is battery powered. On the thermostat base there is a fuel switch. Make sure it is set to "F" & not "E". Also make sure the heating system type screws are set correctly. See page 7 of your owners manual. After checking these settings & re-confirming the wiring, if the stat still doesn't work properly I suggest taking it back to the place of purchase.

I take it from your reply that with being battery powered that the "power stealing" is not an issue?

Correct, BUT: Some thermostats just don't seem to be compatible with some furnaces. I have no idea why.

I did take the Honeywell back and got another one the same but the same result. Took that back and oicked up a Noma programable with the same 4 wire configuration, fuel selection; only difference was that only 4 terminals available with only a R terminal , no Rc so it must have been jumpered internally. The same constant cycling of the flue exhaust fan occurred. I've been reading the next thread posted after this one of the same subject and they seem to be concentrating on the "power stealing" and fluctuating 24 V voltage as the cause of my problem. If the presence of batteries rules this out then I'm stuck.

Some thermostats, even if they have batteries, are of the power stealing type. The batteries in those are there to save the program if the power goes out or the switch is turned off. Honeywell lists your stat as battery powered.

Can anything be done to overcome this power stealing thing?

Your stat is NOT a power stealing type, at least according to Honeywell's web site. Go to a HVAC supply house & get a thermostat. Forget these "retail" ones.

Thanks for the time and advice.

One last question. What is the difference between a thermostat from a HVAC supplier and a "retail" one. I presently have a Honeywell T8132A installed by the HVAC company that installed our new AC which is obviously from a supplier as per the plain packaging; the Honeywell CT3200A that I've been having trouble installing at the father-in-laws is a "retail" which has the fancy packaging. On the Honeywell website both are listed and both have the same features listed and no apparent differences. What would be the difference?

Honestly, I have no clue what the difference(s) is/are but I seem to encounter far more problems with stats from a retail store than the "professional" ones. May be just a local quirk but maybe not.

Have you tried leaving the tstat out of the circuit and install jumper on r & w for test purpose only.

That's next; thanks.