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  1. #1
    Join Date
    Feb 2004
    Massillon, Ohio
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    Red face Heatpump, Blower fan speed

    Hi Guys!
    I have an Amana dual fuel heating system ( heatpump with nat. gas aux. heat ) My question is about the Variable speed blower. In the heatpump mode is the blower running at AC CFM's? Does the main control board recognize it as being in the heating mode and adjust the speed to the same speed as it would be using the auxillary heat? Would it be advisable to change the dip switches to a lower cfm setting to get a warmer heat? It sounds like a 767 taking off all the time, it's set at 1200 cfm on cooling.
    Thanks, John

  2. #2
    Join Date
    May 2000
    Indianapolis, IN, USA
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    If the compressor is on, either heating or cooling, you need the same speed. If 3 ton, then 1200 CFM is right. If the furnace is firing, you need the speed to keep the heat exchanger at the right temp. That could be more, the same or less than compressor speed. If 1200 CFM sounds like a jet taking off you have serious duct sizing issues.

  3. #3
    Join Date
    Feb 2007
    Central MD, Carroll County
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    rule of the thumb 400cfm per ton of cooling, 450 cfm for heat pump in heating, 300cfm per ton fossil fuel (I think). However I agree with baldloonie about cfm selection if you lower your cfm in heat mode you could have to high of a delta t and have other complications as a result. I know on the york affinity your aux heat has its own seperate cfm selection which you can adjust for your fossil fuel or strip heat package. Pretty sure you can as well on the amana. So yes the board does recognize these functions. But vfd motors are designed to accomodate to differences in static pressure in the ductwork if your having that much of noise issue you have some ductwork issues that need to be resolved. Also some vfd motor boards blink the amount of cfm ie 1 blink is 100 cfm. Or you could check your heat the tried and true way. Through cfm calculations its simple cfm=heating output divided by 1.08 x ^T example you have a 100,000 btu furnace its 90percent eff your output is 90,000 90,000/1.08 and lets say a 6o^T 90,000/1.08 x60
    90,000/64.80 youd be moving apx 1388 cfm hope this helps.

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