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checking airflow

moter amp goes up . He didnt say what moter he had but .


  • rick_30
    rick_30 Member Posts: 4

    Iam going to look at a job 2 story colonial .basement too cold Owner shut dampers in basement .Suction line icing when unit runs .How can I check the airflow on the ahu without a manometer. Ican check the deta t ,but with the different effficiencies are their different rules of thumb.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    As far as the delta-t across the evaporator coil goes, you can still expect the range to be between 17 and 20 degees when the RH in the space is at 50%. If the humidity is higher than 50%, the delta-t would be expected to be lower, while lower RH would result in a higher delta-t.

    I would check the amperage of the blower motor on the air handler and compare that amperage to the nameplate. Be sure that the service panels are in place when checking the amperage.

    Excessively low amperage draw by the blower motor is an indication that there is indeed reduced airflow through the duct system.

    As the airflow is reduced, the motor does not work as hard and the amperage draw falls. '

    Good luck and let us know what happens.
  • don_172
    don_172 Member Posts: 1

    look for one central return in basement area...with stat on the second floor could be the reason for freezing as well.

    I just dont know how you guys do it...I mean to go on a call without a magnehelic guage is like trouble shooting a refrigerant circuit without a temperature probe.

    Please buy the guage and see for yourself how much money the tool can bring in.
  • billygoat22
    billygoat22 Member Posts: 124

    There's several ways to check airflow.

    Temperature rise method using the electric heater or clocking the gas meter or fuel oil firing rate (collect oil in bucket timing the flow rate)
    pitot tube
    esp charts

    I don't think the anenometer method is all that accurate, though, temp rise is supposed to be +/- 5%, pitot 2% if used correctly
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