Payne GAW Furnace Tripped Auxilary Limit

I have a Payne GAW type furnace in a rental property (Carrier three wire pilot, heating and cooling fan relay on the circuit board and counterflow furnace)

The auxilary limit in the fan compartment at the top of the furnace was tripped, causing the fan to run continuously and the burners to fail to ignite.

I cycled the furnace through the ignition sequence several times and everything worked fine.

I cleaned the burners, pilot burner and pilot orifice.


I wrote this off as a fluke, but I'd be glad to have any opinions on likely causes of the problem.

I can think of several, including a circuit board intermittently failing to turn on the fan when it should and a pilot burner allowing the main burner to cycle on and off without the fan being switched on.

Any other bright ideas?

 

I'm sure you already asked your tenant, was there a power failure?

 

There was no power failure, although after the problem occurred the tenants shut off the power.

But absent a voltage spike damaging something, a power failure would not cause a problem with this furnace. The furnace would cycle back on itself when power was restored.