How to wire furnace fan to run without heat?

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How to wire furnace fan to run without heat?

Postby bgilbert » Mon Nov 15, 2010 2:11 pm

I want to be able to run my 500 year old furnace fan without the heat. FAN ONLY operation. I just replaced the old mercury switch? thermostat for a digital unit. I bought it in hopes of being able to run fan only operation. Evidently I only have a 'two wire' furnace or the like..? Google wasn't much help... Thanks. Oh and it might not be 500 years old, but it's an old house with an older furnace.
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Re: How to wire furnace fan to run without heat?

Postby BILTIT » Mon Nov 15, 2010 2:14 pm

Do you want the fan to run continously or controlled by the thermostat somehow?
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Re: How to wire furnace fan to run without heat?

Postby bgilbert » Mon Nov 15, 2010 2:21 pm

BILTIT wrote:Do you want the fan to run continously or controlled by the thermostat somehow?

Continuously. Most newer thermostat's have the option of fan only or auto. This way I can circulate the new found heat from the LP heater I recently bought.
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Re: How to wire furnace fan to run without heat?

Postby Richie O » Mon Nov 15, 2010 3:25 pm

Your furnace thermo wires should be low voltage and only 2 wires to the thermostat. If you want " fan only " you will need more wires then what you have.Then there will be some additional wiring to do at the furnace to get it to work. ( relay and such ) What I would do is wire a 110 switch where its easy to do so and hook into the fan circuit directly.
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Re: How to wire furnace fan to run without heat?

Postby jimferguson » Tue Jan 17, 2012 4:03 am

I think 2 wires are are there, connected them to R and W. now test the furnace by turn "ON" furnace, the furnace will started running and the fan turns on and blows the hot air around the house. I think even now fan is not working then you need a different wire to make the fan individually.

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Re: How to wire furnace fan to run without heat?

Postby 49COE » Tue Jun 05, 2012 4:50 pm

You could always just stop paying your gas bill. ;)
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