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  1. #1
    Join Date
    Sep 2008
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    Charging a heat pump with big outdoor but small indoor coils

    Hi everyone. Nice to find this forum. I recently have problem charging a heat pump that has a relatively small indoor coil. I charged the unit per rating plate using the subcooling method in cooling mode. For some reasons, the subcooling is not very sensitive to the charge. I had to add 2 lbm to increase 2 °F subcooling!!! I ended up adding lots of charge to the system to get to the rating plate pressure. The unit seemed working fine in cooling mode. However, when the unit switched to heating mode, I noticed a significant high head pressure, like 550 pisg at 47 ambient. I removed lots of refrigerant out to get the pressure below 400 psig.

    I am thinking the problem is the indoor coil is too small for this outdoor unit. Does anyone know of any other way to charge this kind of system?

  2. #2
    Join Date
    Jan 2004
    Location
    PA
    Posts
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    let me guess.
    You installed a 13 SEER outdoor unit, on an old 8 SEER or less indoor coil.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Feb 2007
    Location
    out in the country
    Posts
    633
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    yep, it sounds like a mismatched system
    I never let schooling interfere with my education... Mark Twain

  4. #4
    Join Date
    Sep 2008
    Posts
    2
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    Exactly, the indoor coil is decade old, but the outdoor unit is quite new. Didn't know that would cause this charging issue.

  5. #5
    Join Date
    Jan 2004
    Location
    PA
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    Yep, it makes trouble.
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    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Aug 2006
    Location
    Ohio
    Posts
    2,185
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    Please please please say it isn't R-410.

  7. #7
    Join Date
    Jan 2004
    Location
    PA
    Posts
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    Is it ok to say its R410A
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    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Nov 2004
    Location
    South Carolina
    Posts
    1,841
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    Quote Originally Posted by ggaaxx View Post
    Exactly, the indoor coil is decade old, but the outdoor unit is quite new. Didn't know that would cause this charging issue.
    time to call " Joe the HVAC guy" Obama would approve

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