Use main HVAC blower for comfort instead of variable speed fan


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Old 05-21-16, 12:16 PM
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Use main HVAC blower for comfort instead of variable speed fan

At my old house, I had a high efficiency HVAC unit installed that had a variable speed fan that would run almost continuously throughout the day for air circulation and comfort. When my son bought his new (to him) house, he installed a new thermostat that lets him set the time his blower motor can run without starting up the AC or furnace.

I told him he should set it to run 50% to 70% of the time cause I liked how our unit kept things comfortable but, now that I think of it, I don't know if it's a wise thing to do for the main blower to be switched on and off like that all day and night.

Is there any concern for harm to the unit doing things this way?

My only other reason for not doing this is the main blower is noisier than my high efficiency unit.
 
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Old 05-21-16, 02:10 PM
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I think starting is hard on a motor. I would either run it in traditional mode where the fan only runs when the thermostat calls for heat or AC or just turn the fan on and let it run continuously.
 
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Old 05-22-16, 05:47 AM
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When compared to a standard 3 or 4 speed blower motor the electronically-controlled variable speed blower motors use significantly less electricity. You WILL notice an increase in electrical consumption (and a bigger bill) if you run a conventional motor all or most of the time.

Now you MIGHT be able to slow down the conventional motor to where it uses less electricity (still more than the ECM motor) and also reduce the noise level BUT you need to measure the rise in temperature across the heat exchanger while the furnace is in operation. The ratings plate (inside the burner compartment usually) will state the maximum temperature rise allowable and this must not be exceeded.

Also, if you are running air conditioning then the blower should be stopped whenever the A/C compressor is stopped. Otherwise it will have a tendency to increase the relative humidity in the house rather than decrease it.
 
 

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