York Furnace Roll Out Switch keeps tripping

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Old 11-20-10, 03:24 PM
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York Furnace Roll Out Switch keeps tripping

Hi Everyone -- Any advice appreciated!

My 5 year old York furnace works fine sometimes, other times the roll out switch on top of the burners trips which makes the fan run endlessly. Two companies have come to check it out and - naturally - the furnace functions properly while the repairman is here. The heat exchanger is okay, and there don't appear to be any flame roll outs. Also, the vent is ok. Both said that the furnace is in good shape, and they can't find a problem.

I go down and re-set the switch whenever it trips, but there has got to be some other way to fix the problem.

Should I have the roll out switch replaced?
Any other ideas?

Thanks!
Single girl, New homeowner
 
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Old 11-20-10, 06:10 PM
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It's far more likely that you are having an intermittent flame rollout problem than that the switches are bad.

Is there any pattern to the flame rollout switch opening? How often does that happen?


Do you get a good view of the burners by taking the front cover off?


If so, I'd cycle the furnace on and off a couple of hundred times or until you catch a failure or irregularity of some kind.

Usually such problems manifest themselves when the burners turn on, but they could happen while the burners are operating or when it shuts off.


I don't suppose the repairmen used a manometer to measure the air pressure being presented to the pressure switch. If they had they might have noticed that the pressure was inadequate or marginal, but not bad enough to cause the pressure switch to open.

Do you have natural gas or propane?
 

Last edited by SeattlePioneer; 11-20-10 at 06:27 PM.
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Old 11-20-10, 08:54 PM
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Thanks for the response! It's happening more and more frequently (to the point where I just cut the power to the furnace and don't have heat now so that the fan blower isn't blowing cold after it trips)

Today the furnace was on for about 15 minutes and turned off appropriately when the set temp was reached. Since then the roll out switch has tripped every time the heater has come on -- usually after about 5 minutes or so, but sometimes immediately and sometimes after 15 minutes or so.

Yes, I get a good view of the burners. Will take your advice and cycle through (with a repair guy) until he can figure it out. Not sure if he used a manometer. I'll ask about that. Its natural gas.

Thanks again!
 
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Old 11-20-10, 10:32 PM
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A gas furnace depends on a flow of combustion air into the furnace to burn the gas, then the flow of those combustion products through the heat exchange and through the vent and chimney to the outdoors.

If something is plugged up or not working properly, that flow is interrupted. At that point you have gas from the burners burning and looking for air --- which causes the flames to back out behind the burners and cause the flame rollout switches to trip.

If this wern't related to the burners, the rollout switches would randomly trip when the burners aren't lit.

Have you heard any squealing or labored operation from the inducer motor that starts when the thermostat calls for heat? If that fan slows down because the bearings are going bad it could be a cause of the problem, along with a plugged heat exchanger, plugged chimney or vent.

I don't think I ever replaced a flame rollout switch.


That leads me to conclude that the odds are about 99% that a flame rollout condition is occurring.

Usually I'd expect the pressure switch to detect that failure and turn the burners off before a flame rollout could affect the switches ---- that's why I'm supposing you have enough draft through the furnace to keep the pressure switch closed but still allow the rollout condition to occur.

That suggests that measuring the pressure the pressure switch sees would verify a partial plugging condition.

The more frequent occurrence of the condition suggests it's getting worse fast.


That's my theory anyway. Careful observation is going to prove me right or wrong before long.
 
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Old 11-21-10, 12:31 PM
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Thanks Seattle Pioneer!

I've scheduled a different repair guy to come out this week and have printed your response/advice. Will post again after the fact to let you know what happens.
 
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