Fan cycles on and off between heating cycles.
The Temp in house is 67 and Heat setting is set to 67 the reading on the thermostat never changes, but the heat kicks on and off. Between heat cycles the fan cycles without the burner being on. I have a Honeywell Programmable Digital Thermostat set on 67 Hold 2-3 years old. I have two one upstairs and one down. I tried swapping the two, no change. My heating unit is a Janitrol about 19 years old 1986 model. I have had five Technicians to the house, the first one replaced the Fan limit control. The settings on the new one are 150, 110, and 50. All the other techs said it was out of adjustment.
I observed the cycle pattern last night
3:32 am Burner turns on
3:33 Burner still on, Fan turns on
3:36 Burner turns off, Fan still on
3:36 Fan turns off (within the same minute)
3:39 Burner NOT on, but Fan turns on
3:40 Fan turns off
3:44 Burner turns on
3:45 Burner still on, Fan Turns on
3:47 Burner turns off Fan still on
3:48 Fan turns off
3:51 Burner Not on, but Fan turns on
3:52 Fan turn off
3:58 the above pattern starts again
Other than very short cycling, the blower operation appears normal. Blower operation is determined by plenum temp. Different fan limit settings can reduce cycling of the fan if you so choose. Burner short cycling can be reduced by the thermostat setting, assuming the burner is functioning right in the first place.
appears you are stating Limit at 150 fan on at 110 and fan off 50 if this is correct than fan will probably run almost constantly. Is this a Honeywell L4064 by chance?? If so I would probably set Limit around 180 fan on 140 fan off 95-100 if counterflo set 5 degrees less for off temp. I would normally say to call a dealer to make adjustments. However after 5 I don't know what to say. Why didn't the other 4 techs make adjustments???
[Edited by mike3 on 02-01-2005 at 12:52 AM]