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  1. #1
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    95

    Compressor pump down

    My Carrier Infinity has a 50psig low pressure cutout. When the tech did a pump down a couple of weeks ago, to replace my evaporator, I noticed that he didn't bypass the cutout, and I don't think he even let it get to 50psig before manually flipping the breaker. He did appropriately recover any remaining 410a.

    When he was back today, I asked him about that and he says that he doesn't bypass the low pressure cutout, because of the risk.

    This was also the same tech that told Carrier he had no problem pumping down the compressor (Carrier was trying to rule out compressor issues).

    My question is, if you don't let the compress pump down below the 50pisg cutout, can you really say that a compressor successfully passes a pump down test?

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Yes and he followed proper procedures by pumping down and recovering the excess.

  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,347
    I second second opinion's opinion. Your tech did the right thing. I don't bypass safeties, either, unless absolutely necessary, and only temporarily.

    A compressor does not need to be pumped down to test how well it pumps. Compression ratio is good for that.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    Jan 2008
    Location
    Newark, DE
    Posts
    10
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    Last edited by beenthere; 08-14-2012 at 08:36 PM. Reason: Non Pro * Member

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by tighttommy View Post
    I just want to clarify for my own knowlage, regardless of safeties, an infinity unit has a scroll compressor, which has no internal valves. a pump down test isnt necissary, because it is used to test if the valves hold on a recip compressor. so if it moves refrigerant at all then it should be fine, all you would be testing is if the check valve holds. All things being equal, checking amp draw and superheat, subcool would be more infomative.
    Well you are partially right, this Infinity has a two stage reciprocating compressor. Your are correct on the scroll scenario no pump down required.

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