Please Help w/Ducane Furnace


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Old 01-17-09, 11:35 AM
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Please Help w/Ducane Furnace

Greetings. I have a 5 year old Ducane hot air furnace MPGA10084. Recently I have been having to go downstairs and reset the rollout switch.....maybe once per day. I called a local company. First visit cleaned the burners and changed the filter which was only a month old. Problem persisted. Then came back and changed the rollout switch. Now everytime it cycles I have to reset the switch. I'm already into this for $250 between the two visits. Now they say it's the draft inducers which is about $200 for the part only. They can't give me any guarantee that will solve the problem. I'm not confident I have the right company on the job but don't want to start fresh now. To make things worse, I'm leaving tomorrow for 8 days and we have single digit temps here in Philly. The only thing I notice is the flames on other heaters seem to shoot more powerfully out of the burners and into the holes on other units I've seen. I am mechanically inclined so can follow directions well. What can I check? Should I just replace the draft inducer? Thanks.
 
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Old 01-17-09, 12:03 PM
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Causes of flame rollout switches opening might include an inducer motor not turning on or powering up completely, a cracked heat exchanger. plugged heat exchanger, defective pressure switch among others.

Poor gas pressure on one furnace? Perhaps.


What I would do is to take the cover off the furnace and camp out in front of it as someone repeatedly turns the thermostat down to shut the furnace off then turn it up to start the ignition process and let that continue a while before doing it again. You would be looking to observe anything that's happening that irregular or out of the ordinary, and especially to observe that flame rollout switch opening.

If you go through that cycle oh, 30-40 times without the rollout switch opening, I'd switch to turning the thermostat up to 85 degrees and again watch the furnace for any irregularities in how it operates. Time how long the burners stay on before it shuts off.


With intermittent problems, a good repairman will take the time to replicate the problem by running the equipment until it fails so you have a chance to diagnose the actual problem, rather than guessing and very likely being wrong.

After you identify the actual problem, more than likely you are going to be in a position to apply to have the money you spent on the incompetent repairman refuned to you.



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Old 01-17-09, 12:44 PM
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Observe for any flame irregularity (like a waver or dance) that only occurs just as main house air circulation blower comes on. That would indicate a bad heat exchanger

Make sure outside exhaust vent not partialy obstructed with ice or ?.

Also make sure condensate line does not have water in it at secondary exchanger, that is compromising ability of furnace to draw in fresh air and draft properly and might cause flame to leap out to get to fresh air. Blow the condensate line out both ways, through the trap and back into the secondary exchanger. If you blow out the trap, fill it with fresh water so exhaust gases do not enter the house.

Is there any partcular reason that may lead you to believe the inducer motor is not working 'up to speed'? I'm not fond of replacing parts based on a guess.

Make sure replacement roll out switch was located in same location and is of same temp rating as what is required, - and not something perhaps generic used off his truck.
 
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Old 01-30-09, 07:07 AM
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Hello guys. I looked at the rollout switch. Temp. rating is 250. Does that sound correct?

Also, service guy wanted to change out the draft inducer for $350. Said he was absolutely sure that was the problem. I actually went ahead and changed it out myself. Still same problem.

From what I can see, the flame on the right side dances around the igniter and heats up that side which has the rollout switch on it.

The small rubber house that runs off the inducer motor had no water in it. Also, nothing in the pressure switch either.

Condensate line is clear.

What next?
 
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Old 01-30-09, 10:02 AM
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Please provide the model number of the furnace from the rating plate in the burner compartment. Also the make and model of the ignition control module.

That the flame rollout switch opens repeatedly suggests that it is being hit by flame backing out of the furnace. Since it's failing every time it cycles, I'm surprised this isn't being caught and observed by your repairman, and even by you.


I'm supposing the furnace has a sealed combustion system with a cover plate that has a viewing port for observing the burners while they operate. You should be observing the burners operate with that cover plate in place, and looking for any evidence that the flames are backing out of the furnace toward the flame rollout switch.

Also, while the furnace burners are on, try pulling the rubber hose off the pressure switch, which should cause the burners to shut off. That would test to verify that the pressure switch is working the way it should and that the furnace isn't plugged up in some way.
 
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Old 01-31-09, 07:04 AM
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check the gas pressure after the gas vavel
 

Last edited by Shadeladie; 11-28-14 at 04:48 PM. Reason: Removed quote
 

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