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  1. #14
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    In heat mode. The outdoor coil is the evap. So the VS blower inside isn't causing the high low side pressure.
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    How many times must one fix something before it is fixed?

  2. #15
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Outdoor Temp Indoor Temp Rise
    65 degrees 33 degrees
    60 degrees 31
    55 degrees 29
    50 degrees 27
    45 degrees 25
    40 degrees 23
    35 degrees 21
    30 degrees 19
    25 degrees 17
    20 degrees 15
    15 degrees 13

    This is a generic chart. If you have an oversized indoor unit, the temperature rise will typically be a couple of degrees cooler. Different brands vary some as well. But it is a good starting point for a heat pump with the strip heat help off.

    Note: There does not seem to be a way to make the columns line up right.
    Remember, Air Conditioning begins with AIR.

  3. #16
    Join Date
    Jul 2010
    Location
    Northern Virginia
    Posts
    25
    Yeah the concept of heat pump is neat, in heat mode outside unit is Evap. Yesssir !

    Thanks for the chart Kevin. This absolutely will help me diagnose heat pumps better (with elements off). I just got to learn so much its unbelievalbe ! Infact there is so much to learn in this industry, I love it!

    Next is to master boilers...we don't have many here, well I say maybe 25-30 percent, but everytime I get a call to do a pm on a boiler it makes my day

  4. #17
    Join Date
    Sep 2002
    Location
    I don't know
    Posts
    2,903
    The problem with relying on temp rise alone is that the airflow greatly varies - you can't assume that the installer set the blower speed correctly.

    Superheat/subcooling, compression ratio, indoor airflow, and amp draw theoretically can tell you exactly what's happening in the system.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  5. #18

    panels

    if you take ampdraws, pressures with panels off of condensing unit,ive gotten some crazy pressures and draws.air flow across coil is important right?pros i am asking your opinion

  6. #19
    Join Date
    Jul 2010
    Location
    Northern Virginia
    Posts
    25
    hvacmac7, you are right. once the panel is off, the pressures do generally go high. I never take pressures with panels off. I think its the air volume that goes through the coils is not enough and hence impacting the pressures in the coils and amping of the compressor.

    *air flow and air volume are two different measurements*

  7. #20
    Join Date
    Jun 2008
    Location
    Cincinnati, Ohio
    Posts
    2,176
    Quote Originally Posted by hvacmac7 View Post
    if you take ampdraws, pressures with panels off of condensing unit,ive gotten some crazy pressures and draws.air flow across coil is important right?pros i am asking your opinion
    Think about it. Where does the airflow go when you take the panel off? Why do you want the airflow to draw across the coils? Remember what is required for the vapor-compression cycle to work.

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