"Jimi" wrote in message
...
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
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.