Furnace Fan

[lvfd50]

I have a Bryant furnace and no AC. I also have a programmable thermostat that has a switch on the bottom for the fan with two positions, Auto and ON. Currently if the furnace kicks on I have the fan switch at auto and the fan kicks on as it should. I would like to be able to move the switch to ON and turn the fan on constantly. Currently if I move the switch to ON it doesn't do anything. I was wondering if anyone knew how I should wire this so that it will do what I want? What terminal on the thermostat goes to what on the furnace? or can I jump somthing on the thermostat to make this switch work? Thanks for any help.

 

[pgmr]

You need a wire from the thermostat to the furnace dedicated to fan control. It's usually the "G" terminal. See http://wiki.xtronics.com/index.php/Thermostat_signals_and_wiring for more info.

 

[dave11]

I'd be surprised if it hadn't been wired to do what you want when it was installed. Most people want the option to run the fan as you describe.

Did you try taking the thermostat off the wall and checking for a loose wire? Many of them use tiny screw terminals that don't hold wire well. you might see if the wire has come loose.

 

[Redox]

How old is the furnace? Most sold in the last 20-30 years have a fan relay already built in. Check where the thermostat wire connects to the furnace. If you have a G terminal, it's probably ready to go. Connect R to G and the fan should run. If you only have an R and W, you can add a fan relay to it.

Chris