Hypothetical Furnace question

[Jimi]

I have two forced air furnaces...I have a gas one in the house, and an old oil burner I use to heat my shop in the backyard. The other day I was close to my gas furnace in the house and heard some squeaking as the fan was turning. On inspection I found that the allan screws had become loose holding down the drive pulley and the pulleys had become out of alignment causing the belt to squeak. It was a simple fix, tap the pulley back in place and tighten the screws. This brings to mind a question. If the furnace threw a belt during it's heating cycle, would it not crater the heat exchanger? Like...there is no air going through it, and the motor would be still running so the furnace would think everything is fine, right? Is there a thermostat to kick the burners off in the event the heat exchanger reaches a critical temperature in case something like this happens? Thanks for any replies...Jim

[jazon48]

Yes.

My furnace has two devices, a low draft detector and high firebox temperature detector.

The high firebox temperature detector failed and shut the furnace down six years ago. The repair guy said they do that now and then.

Jason

[udarrell]

Yes, there is a high temp limit switch that will open the circuit to the gas valve or oil burner.

- udarrell

[Gerald Newton]

Some hot air furnaces use a air flow switch for this. It is a switch mounted on the air plenum with a little flat piece of metal inside the plenum.

[Jim]

? Is there a thermostat to

[Tekkie®]

posted for all of us...

WOW that's a LONG time to be cold. Why don't you get it fixed?