Payne P8U error 31


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Old 12-30-11, 02:11 PM
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Question Payne P8U error 31

Continually getting error 31. Removed pressure (diaphragm) switch and it sounds like it is free. Put meter on it and blew in tube and the switch operates. Hooked up to rubber hose to furnace and metered switch, it opens and closes as it should when combustion chamber fan comes on. I have no way of checking all the vent piping from the basement out through the roof. Water heater vent joins vent after out put of furnace and all seems to be fine with that so I am assuming the vent piping is all clear and it all appears to be. I'm at a loss???? Thanks on advance for any help!
 
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Old 12-30-11, 02:26 PM
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Does this furnace have PVC vent piping?
 
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Old 12-30-11, 02:45 PM
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No......all metal piping. All vent pipe appears to be about 9" diam all the way through to the roof. It sticks out of the roof at least 2 ft. ( live in Minnesota).

Just had vent fan all apart and all looks clean in as far as I can see and fan blades are perfectly clean. Which would make sense as it is tripping the pressure switch fine.

There appears to be a small component wired in series with the pressure switch that is mounted on the combustion chamber near to the diaphragm/switch. Don't know what it is...?
 
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Old 12-31-11, 03:48 AM
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that is a blocked vent switch and it should have a small red button in the middle of it. Push it in. NOW, if that was tripped the furnace should operate, but if it was tripped it tripped for a reason. (Blocked Vent)
 
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Old 12-31-11, 12:27 PM
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Thank you so VERY much! Yes, I reset the switch and it is working. I will have an HVAC person check the venting on Monday. I am confused as the water heater uses the same ducting and vents without any problem. I am questioning whether the 40-50 mph winds might have done it....at any rate I will have it checked out. Thanks again, I sincerely appreciate you sharing your knowledge. Have a Happy New Year!
 
 

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