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    mdgorham's Avatar
    mdgorham Posts: 1, Reputation: 1
    New Member

    Jul 14, 2008, 12:11 PM
    My compressor is rated for 19 amps, running 11.7, good or bad?
    I just had a technician out to do a tune-up on my heat and air conditioning. He tested the amperage on my compressor, fan motor and blower motor. They were all below the rated amperage. Is that a good thing or bad? Also, does anyone know what a reasonable cost to recharge freon in a 4 ton unit would be?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert

    Jul 14, 2008, 01:42 PM
    It depends upon the

    Temperature out of the condenser
    Temperature of the air going into the condenser
    Temperature of the air into the evaporator
    Temperature of the air leaving the evaporator
    Suction pressure
    Liquid line pressure
    Suction line temperature
    Liquid line temperature
    Calculated superheat/subcooling

    If you have all the above information I can get you close.

    There is no reasonable cost. All areas of the country charge different amount for labor and materials and how much refrigerant is used in the process.

    Low amp draw usually means the machine is not working very hard BUT it could be other items also
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
    Uber Member

    Aug 21, 2009, 06:49 AM

    Hvac, how about Altitude? Just curious.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert

    Aug 21, 2009, 07:17 AM
    Here is a older Unico spec sheet for air flow at altitude. Something tells me 6% loss difference at 5000 for most refrigerants.

    Depending upon circumstances flash gas can be a problem at altitude. The flash gas causes a decrease of COP (coefficient of performance).

    Cap tube systems can be stinkers at altitude.
    If checking the refrigerant charge then consult a temperature pressure chart corrected for the altitude in which you are servicing the capillary tube system.
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
    Uber Member

    Aug 21, 2009, 07:36 AM

    Thanks, Take Care
    pcampion's Avatar
    pcampion Posts: 19, Reputation: 3
    New Member

    Aug 24, 2009, 07:20 PM

    You probably have anywhere from 5-7 pounds of Freon in the system. If it was low on charge, expect about 2-3 pounds max to be added (unless you have a major leak) I believe R-22 costs around $6-7 per pound and most contractors are charging double per pound and sometimes triple (that would be on the higher side) The time should take no longer than 1-2 hours, so figure the service charge and hourly rate.

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