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

On Jan 25, 2:49 pm, "Jimi" wrote:
. . . .(snip). . . Is there a thermostat to kick the
burners off in the event the heat exchanger reaches a critical temperature
. . .? Thanks for any replies...Jim

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

Jimi wrote:

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


Yes, there is a high temp limit switch that will open the circuit to the
gas valve or oil burner.
http://www.udarrell.com/oil_furnace_heating.html - udarrell

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http://www.udarrell.com/

"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.

? 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.

Thanks to all that replied...It sets my mind at ease knowing that there is
something to prevent that from happening....have a good week...Jim

posted for all of us...

The high firebox temperature detector failed and shut the furnace down
six years ago.

WOW that's a LONG time to be cold. Why don't you get it fixed?
--
Tekkie Don't bother to thank me, I do this as a public service.