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what speed for central air?

are the same in any motor.

Closer to the neutral the faster the speed


  • Dave_118
    Dave_118 Member Posts: 17
    what speed for central air?

    we have a Trane 3-speed air handler that we run on low speed for heat in winter. What is best speed for a/c?
  • bill_71
    bill_71 Member Posts: 46

    what hp is the motor? what size is the a/c? speed should be selected to give the proper amount of cfm per ton of cooling..rule of thumb 400 cfm per ton
  • Brad White
    Brad White Member Posts: 2,393
    It depends...

    Sorry but it is true... The speeds are relative and incidental. The questions you need to know are, in rough terms, how much air are you moving and and what inlet and outlet conditions? What tonnage are you running?

    Low speed for winter makes general sense as you do not need to move much air at those higher delta-T's (supply air to room air temperatures). Saves kW's too.

    With cooling and absent knowing all of your variables, try each speed and measure the temperatures across the coil.

    Too high and you may not dehumidify too well. Too slow and your coil may freeze up especially if it is too humid.

    Ideally, your inlet temperature should be close to your space temperature (assuming you are not ducting in any outside air).

    Your supply air, for best dehumidification, should be about 53-55 degrees depending on what space condition you are trying to maintain. (SpacePak or Unico High-V systems are different and run much colder. Not what I am describing here.)

    Try each setting and watch it for about 20 minutes through some cycles and see what happens.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Dave_61
    Dave_61 Member Posts: 271

    I'm wondering which the speeds even are....they are marked A, B, and C. The unit is a TWE unit. Does anyone know what speeds each of the letters correspond to? (Low, medium, high)
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