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pete0403 03-25-2013 12:33 PM

Heating Cycle Rate, mid efficiency.
Hi All,

I have a Lenox G50UH-36A mid efficiency furnace controlled by a Honeywell thermostat. I noticed my furnace short-cycling all the time and decided to try to lower the heart cycle rate from the recommended 5 cycles per hour to 3. I didn't notice any temperature swings but did notice the furnace acting a little strange.

It didn't seem to always fire up and down in the proper sequence and sometimes it seemed like one cycle would run into another. For example the blower would still be running from the previous cycle and the inducer world kick on for the next cycle. Or everything would shut off with the flame leaving the heat exchanger to cool down without the blower.

I've put the thermostat back to 5 now but does this sound like a normal reaction to this change in cycle rate? I'm really only concerned with energy savings and wear on the furnace components.


yuri 03-25-2013 01:11 PM

how old is the tstat? sounds very strange 2 me. sounds like your tstat is malfunctioning now and sometimes just playing with them can cause them 2 act up. the only other scenario is the circuit board is acting up but the odds of that happening with you changing the cycles is very slim. I have seen hundreds of those furnaces with never that symptom. get a new Honeywell Focus Pro tstat from HDepot and try it.

beenthere 03-25-2013 04:23 PM

Yep, going from 5 to 3 CPH won't in itself cause what your describing. Almost sounds like you have a power stealing thermostat like the T8400C.

pete0403 03-25-2013 07:41 PM

It's an rth7600. I just noticed another issue with the furnace. There was an error indicating an open primary or secondary limit switch. I took the primary out and cleaned/tapped it and now it's working again. Maybe that was my problem if it was intermittent before?

I'll try setting to 3 again and see what happens.

beenthere 03-25-2013 07:52 PM

Check your air filter. it may be dirty.

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