Heater Fan Cycles On - http://www.hvacmechanic.com/ Forums
Original message
| bertbren
 |  "Heater Fan Cycles On"
, posted Mon 21 Jul 19:09  
I recently had a comp roof installed replacing wood shake. Now, in the afternoon when it is warm, the fan on my attic installed furnace cycles on, blowing heat from the attic into the house. I have an attic fan installed and set to 90 degrees. How high can I set the furnace fan setting to keep it from tripping due to the attic heat. The furnance is a Payne Mod 80 H-13
Bert
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Replies:
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| yuri
| "Re(1):Heater Fan Cycles On" , posted Mon 21 Jul 19:37
You cannot adjust the furnace fan setting. It is built into the circuit board (timed on). Your unit is actually tripping the limit control which is non-adjustable and may be as low as 160-170 deg F. Hard to believe it gets that hot inside there but it must. Shut off the main power to the furnace and the problem is solved unless you have A/C with it.
Yuri
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| | bertbren
| "Re(2):Heater Fan Cycles On" , posted Mon 21 Jul 19:50
The attic is 110 degrees by accurate measurement. Does this mean that possibly the limit control switch is defective? Can it be replaced?
Bert
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| | yuri
| "Re(3):Heater Fan Cycles On" , posted Mon 21 Jul 21:49:
We have had a few posts recently with exactly the same symptoms so it sounds very coincidental to me. Horizontal units tend to have lower limit control settings and I don't know what yours is. Some furnaces "ride" short cycle on the limit control in the Winter due to poor airflow etc and that will make them weak/inaccurate which may be your problem. Have very few attic units where I am but I have seen plenty of horizontal furnaces. Try replace the limit as it is a cheap part if you can get it. Less than $50. When the limit opens the circuit board starts the fan to "cool" off the heat exchanger. Gone for the night now, will check in tomorrow. Good Luck
Yuri
[this message was edited by yuri on Mon 21 Jul 22:01] |
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