how to turn on furnace fan

Old 05-27-10, 05:14 AM
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Location: Westchester County, NY
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how to turn on furnace fan

Hey guys,

I have this furnace: Join Luxaire Heating and Air Conditioning, residential and commercial HVAC products. I want to turn on the fan by itself (without heating) in order to refresh the air. How would I do that.

The thermostat is only 2 wires so I don't think it has the ability to do that. (I selected FAN on and nothing happened). So can I go down to furnace itself and manually turn on the fan? I'm guessing it involves shorting some wires or something of that sort.

Also, does anyone know if I live the fan on, will it help dehumidify the air? Thanks
Old 05-27-10, 05:44 AM
Join Date: May 2010
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You need to run a new thermostat wire from your thermostat to the furnace. 18/5 would be preferred.
You would then do this:

At the furnace: connect the red wire to "R"
connect the white wire to "W"
connect the green wire to "G"
connect the yellow wire to "Y"

At the therm: connect the red wire to "RH"
put a jumper between "RH and RC"
connect the white wire to "W"
connect the green wire to "G"
connect the yellow wire to "Y"

Now your thermostat will control the fan when you switch "FAN" to ON.
In AUTO, it will be controlled by the fan control baord in the furnace.
The fan control board is located inside the blower cabinet.

If you want to dehumidify, you will need to install central air off the furnace. The wiring as mentioned is set up for A/C operation as well as heating.
Old 06-06-10, 10:24 PM
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Open the furnace and locate the t-stat wire terminal strip.

Mount a single pole single throw switch outside of the furnace (even a standard light switch in a box will do fine) and connect it to terminals G and R.

If you want the fan to run on high speed, place a jumper between G and Y. (blower speed can be adjusted if need be - the dip switch setting info might printed on the blower access panel, inside)

The alternative is to run a new wire (3 or more conductors) and connect the G terminal to the t-stat.

Running the fan in itself won't take out humidity, but it will reduce the temperature differential between rooms.

Dehumidification options:

- Whole house dehumidifier (Example: Humidity Control | Home humidity controls | Healthy Climate Whole-Home Dehumidifiers | Lennox Residential)

- Portable dehumidifiers

- Central A/C

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