# Wood furnace blower thermostat?



## asdf (May 23, 2011)

I have a basic wood furnace with a blower. There is a Honeywell thermostat type thing mounted on the furnace and I was wondering how it is supposed to work. It has a dial with off/on/off which appear to be set at 100/150/200, but the blower runs regardless of the temp. Any help is appreciated. Mark


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## Allen W (Aug 2, 2008)

I would guess one on position would be full time for the fan and the other on position would be controlled by the temperature switch.


ETA I misread last night and thought you had two on positions. The one one my furnace has a push/pull button for continues fan or thermostat controlled fan. It could have got to hot at some point and as a fail safe will run all the time.


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## agmantoo (May 23, 2003)

The 100/150/200 is the temperature that the furnace has to reach BEFORE the fan comes on. The fan will run continuously until the stove temperature drops below the set point.


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## asdf (May 23, 2011)

Ah, thanks guys. The blower was wired to the always-on circuit, not the thermostat controlled side.


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## Allen W (Aug 2, 2008)

Doesn't do much for staying warm when the fire is low does it?


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## Ross (May 9, 2002)

Its called a fan limit switch and uses a bimetal coil to operate. The 100 is fan off the 150 fan on and the 200 is limit. Now the limit should shut off the electric damper if it has one, if not its meaningless. You can change the fan on and off somewhat but go much below 100 and it will feel like cool air blowing and go much over 150 and you risk cracking the furnace. It may have a fan on switch built in too that you pull off or push on.


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## asdf (May 23, 2011)

Update - thanks for the info. I couldn't figure it out until the short elsewhere led me to discover that the thermostat was being bypassed due to the short. Now working as expected.


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