Heating, Air Conditioning, Fridge, HVAC/cofortmaker nat gas heating unit


I just purchased a house with a cofort maker gas hot air unit. I replaced the inducer motor assy (very noisy).It is a horizontal mount 75K BTU The limit switch sometimes pops and no flame,then I reset it..then it will run for days or hours and trip again. Unit built in 1998. I checked the 2 inch inlet and outletfor blockedge. I am loosing my mind.Return is in the ceiling(wrong place)but is clear.. Obviously an over heat problem in the chamber caused by what? Thank You...

 You are not re-setting a limit switch, they do not make limits that are manual reset.  What you are re-setting is either a flame roll out or a stack switch.  If the switch is around the burner compartment it is a roll out.  If it is at the outlet for the flue gases it is a stack switch.
 I would guess it is a roll out switch.  Which means there is some kind of restriction in the flow of combustion air.  You say you checked the 2" PVC.  Did you check it all the way to the termination outdoors?  And did you check the screen inside the burn compartment where the air flows from outside to the burn chamber?  Ususally is is leaves, bee's, birds or mice that make nests or the dead bodies clogg the air flow.
 If you know which one is the inlet, you can actuall remove the pvc and run it for a while, drawing air from the attic.  That is also where you need to follow the path of the air into the burn chamber for a clogged screen or leaves or something.  If it is clear and it runs with the pvc inlet pipe removed then it is clogged somewhere in the pipe.
 If it still does not run without tripping the switch, the next thing is to check for obstructions in the water drain system and then the heat exhchangers themselves ( there are 2 or them )
 You really need to get a tech out, as you are in an unsafe condition both for your home and for the equipment.I strongly urge you to have a complete tune up by a N.A.T.E. qualifiled tech.  Due to the age of the furnace if this is addressed and timely maintenance is preformed you can get 10 plus years out of your furnace.  If you don't, you take a chance on damaging the furnace to the point of a very large bill to repair it and due to the age that means a new one.

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john t. borgman


I am in Portland Oregon at Ben's heating 503-233-1779. I work days, so I can only answer early in the day or later in the evening. I only answer public questions for residential equipment. I am very well versed in gas, electric and heat pumps and will only answer residential applications. I have been known the past decade or so, by my employers as the guy you send when no one can figure it out. Trouble shooting is my special. I understand the physics behind air flow, refrigerants and electricity. I understand programmable t-stats, zone controls, economizers, fossil fuel kits and the engineering thought process in the wiring and construction of residential equipment


I was lucky enough to start in this field almost 30 years ago as an installer, for a company that installed the best duct systems I have ever seen, even to this day. The best ,as far as understanding the way air really flows through a duct system, from the return air to the very last supply register . They also had great pride and the duct work was put in, not only to last 50 years, but to look exceptional. Then as I started doing service work, I was again fortunate that I found a 3 year engineering class being put on be a man that was the educational director for the Entire united states for a society called " the Refrigeration Service Engineering Society " And for the next 3 years I schooled at night and practiced what I learned during the day, a great advantage over schooling and then trying to remember it years later.. Versed in duct design manual J heat gain/loss calculations.

Refrigeration Service Engineer's Society

I have 2 inventions that have gone through the process and been recorded at the National Institute of Standards and Technology from start to finish and thus been invited to national innovation workshops by the dept. of Commerce and the dept. of Energy. They are waste heat recovery devices that N.I.S.T approved as valid and am currently looking for marketing partners to get this product into the hands of consumers and make a BIG difference in Energy savings for every Household and Eatery and take a big bite in the the peak hours power consumption that face our Utilities companies.

factory training in Lennox ,Rheem, Ruud ,Trane, Tempstar ,Carrier, Day&Night, Payne, Bryant, Coleman, Intertherm, York, Goodman, Ultra boilers, Unico, Mitsubishi,Sanyo, Taylor, Nicewonger, Navien. Associates degree in Refrigeration Engineering. Certified with Energy Department, Check-me Program, P.T.C.S (performance tested comfort systems ), have N.A.T.E. certifications in gas, a/c & heat pump.

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