Dayton Furnace Cycle Prob. - HVAC - DIY Chatroom Home Improvement Forum

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Old 12-30-2007, 05:50 PM   #1
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dayton furnace cycle prob.

hello, first time user of forum. i have a dayton gas furnace, unit cycles about every 10 seconds, first burners will ignite and after 10 sec. they will extinguish and blower fan will kick in, blower will run for 10 sec. and then shut down and burners will ignite again for 10 sec. and extinguish, then blower kicks in again for 10 sec. and shutsdown. this sequence keeps repeating until i turn the thermostat off. then approxiamately after about 15 minutes i turn the thermostat back up and the furnace operates good for about 5 minutes, after 5 min. the cycling that i described above starts up again. model # 3e437b i have no idea how old it is. furnace was cleaned 6 months ago and i was told the heat exchanger and burners were in good shape. please if anyone can help i would greatly appreciate it, thanks


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Old 12-31-2007, 08:37 AM   #2
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Sounds like a couple of things. Do you know what a fan limit switch looks like? Does the top of the furnace itself seem overly hot, like the flue is blocked? Do you have an old mercury thermostat?


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Old 01-01-2008, 07:19 PM   #3
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hey bigMikeB, thanks for answering my post

yes i can see the fan limit switch and it looks like it is set at 102 degrees
the top of the furnace doesnt seem overly hot or anything, but i will get the flue checked out. and we have a UPM programmable digital thermostat model # THM301M... UPDATE AFTER MORE DIGGING, FURTHER INFO... firewall that the fan limit switch is attached to gets very hot after about 5-10 minutes, (unable to put hand on "hot")I mean VERY hot. I dont have a flue, I have a pvc pipe extruding from my roof with the end of the pipe doing a 180 and pointing straight down, when furnace is running there is visible exhaust coming from pvc pipe outside

Last edited by firefighter23; 01-02-2008 at 05:50 PM. Reason: more info
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Old 02-01-2008, 10:34 AM   #4
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dayton furnace cycle problem

I just noticed your question and "firefightet23" caught my eye. I've been in the fire service for over 30 years. I'm a board director now. If the furnace was recently serviced, your problem could be too much primary air. That will make many furnaces short cycle because of getting super hot. Make sure the air on each buner is properly adjusted.
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Old 02-01-2008, 05:57 PM   #5
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Be certain the flue is not restricted. Why it runs longer the second time around could be the initial heat from it trying to maintain fire is causing a draft after warming up the cold vent. Once draft is established, the furnace will run longer. I seen this when spiders spin webs in the vent near the cap during the off season.
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