How can I cycle HVAC fan?


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Old 06-15-14, 12:33 PM
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How can I cycle HVAC fan?

Have White-Rodgers 50A55-843 controller. Would like to short terminals and run fan a certain amount each day in cooling season. Since "cool" and "heat' terminals on board are both connected to fan wires, I assume I have different speeds for heating and cooling.

A. Can I short "cool" to "line-H" without causing any other problem?

B. Can I assume this would need to be disabled b4 going to heating mode? I guess I should not apply "line-H" to both fan wires.??:

thanks, Tom
 
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Old 06-15-14, 01:19 PM
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Why not just turn it on at the stat?
 
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Old 06-15-14, 02:10 PM
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http://www.emersonclimate.com/docume.../0037-6265.pdf

The low voltage terminals would be safer to jump (if you only have 2 wires between the thermostat and the furnace).

R to G will give you fan operation.

R = 24 volts
G = fan
W = heat
Y = cooling fan speed
C = 24 volt common.

Connecting C to R will damage the transformer if a low voltage fuse is not present on the control board.

I would look into pulling 6 conductor wire between the stat and furnace if you only have 2 conductors. A programmable stat would be better than jumping wires.
 
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Old 06-16-14, 12:15 PM
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Skaggsje: That is what we are doing, but I am tired of doing this. Would rather automate.
 
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Old 06-16-14, 12:23 PM
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Houston204: Thanks for info; I never bothered to think about shorting stat wires. I have 6 wire cable & programmable stat, but stat does not allow for fan only programming. Just nosy: Which fan speed would R to G give me? Or is it dependent on whether stat is set for heat or cool?
 
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Old 06-16-14, 06:13 PM
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Yes, High speed for cooling and medium for heat.
 
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Old 06-16-14, 07:24 PM
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R to G gives you heating speed with most modern furnaces. It gives you cooling speed with old furnaces that use a Fan Limit control.

While this would be a strange question if you were in the Houston area...
Do you have air conditioning as well as heating? If not, you could program your stat for cooling and connect the stat to your Y and G terminals at the furnace. This would give you programmable fan control.

Something else that you might consider...
Some thermostats offer programmable fan operation.
 
 

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