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  1. #1

    Smile American Standard

    I had a call yesterday on a cooling problem. The first thing I noticed was that the condenser was extremely dirty. It was an Allegiance 12 model number 2A7A2048A1000A (for those who care), R22 system.

    After cleaning the outdoor coil I took some pressure/temperature readings:

    Ambient 95 degrees

    Discharge psi=298/131 degree saturation temp

    Suction psi=55/30 degree saturation temp

    Sub-cooling=17 degrees

    Super heat= 12 degrees

    TXV metering device

    That is as far a I got before the storm hit, my initial evaluations based on pressures alone would be low charge. However, with sub-cooling at 17 degrees that changed that thought. Just to verify the condition of the evaporator I measured superheat to ensure that the TXV wasn't starving it.

    My course of action this afternoon is to look at air flow across the evaporator (low heat load). I plan on looking at the coil, filters, blower, delta T, and FLA of the IBM. If I am properly charged and both the suction and discharge pressures are low this should mean that I have a low heat load across the evaporator.

    I would be interested in your thoughts on this matter.

  2. #2
    Join Date
    Dec 2004
    Chicago area
    those stats look fine, other than a evaporator mis match. But, with a txv, it should cool fine.

  3. #3
    Join Date
    Jul 2006
    sub cool is a little high and your not moving enough air

  4. #4
    I took the air handler apart to gain access to the supply side of the coil and the blower, then I took the delta T and had 26 degrees. Upon closer inspection I noticed that a piece of plentum board, probably left behind from the installation, was laying under on side of the blower. The customer had complained about an occasional thud, I suspect that the blower under the right conditions was trying to eat the insulation board, giving him the thud.

    The problem this guy had was one blower wheel , on one side, was nearly completely clogged and the evaporator was extremely dirty. Once I cleaned the blower wheel and the evaporator, the pressures went to: suction 66, discharge 300 and the sub-cooling was still at 15-17 degrees, and the delta T went to 22 degrees.

    This reminds me of the article "How much refrigerant do I need to add to make my blower blow harder," what had happened is another guy came out looked at the pressures and added more refrigerant, overcharging the system in order to correct an air flow problem. This just stacked liquid up in the condense and prohibbited the condensers ability to reject the heat.

    I removed about 18 ounces and the sub-cooling value went to 13 degrees. Thanks for the input and have a good day!

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