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  1. #1
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463

    scroll internal check valve

    How many of you have seen multiple copeland scroll issues with discharge check valves failing to holdback during off cycle causing on/off cycling on low pressure. This kills contactors and start relays, caps etc.. I've had multiple compressors on different units w/ the same problem. Low temp 404a application. Units are 18-24 months old and out of warranty, customer is ticked that unit runs fine just kills wiring and components when load is satisfied. ZF15K4E model. Not a cheap compressor to replace.

    I advise my customers of the high future replacement cost of scrolls and sell mostly semi-hermetic due to the ready access and rebuild cost.
    Last edited by codgy; 08-07-2010 at 05:19 AM. Reason: additional info

  2. #2
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,195
    You can get external check valves that braze into the discharge line rather than replacing the compressor.

    I agree that semi hermetic compressors are the way to go if you can convince the customer to spend a little more up front.

  3. #3
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,080
    I've found this on two units with Copeland scrolls.

    One is a 4 HP R22 high temp, the other is a 6 hp R404A low temp. Both are Heatcraft units.

    Heatcraft recommended installing an external check valve or adding a delay on break time delay.

  4. #4
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463
    Already did the delay on break to prevent short cycling. This application is cold plates w/ only 20" between cpr and compressor w/ pressure control as the thermostat, this screws up the discharge check valve being external due to to much gas bleeding into suction. Only 10 psi diff. on control to maintain temp. Thought about moving pressure control to entering side of cpr then maybe external check valve would work.

  5. #5
    Join Date
    May 2010
    Location
    Oxford, UK
    Posts
    336
    I've had this problem on some copelands too, fitted a check valve in the discharge pipe and alls been well since.
    Some other makes of scrolls need an external check valve as they don't have one as part of the compressor, so i don't see much wrong in fitting one in your example.

  6. #6
    Join Date
    Sep 2002
    Posts
    11,543

    A suction check valve might last longer

    And sometimes it is easier to install a suction check valve.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  7. #7
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,288
    If you read the literature they say it's a low leak check valve. But say it's ok to use with pump down. I have seen many leak through. And we always end up with a check on the discharge.

  8. #8
    Join Date
    Sep 2002
    Posts
    11,543

    I think it has no seal at the seat - just metal to metal

    I think the scroll discharge checks are just a metal-to-metal seal because isn't it's primary function to prevent back-spin on shutdown?

    A metal-to-metal design discharge check valve would also be cheaper to make and have no high temperature issues.

    PHM
    ---------



    Quote Originally Posted by ascj View Post
    If you read the literature they say it's a low leak check valve. But say it's ok to use with pump down. I have seen many leak through. And we always end up with a check on the discharge.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  9. #9
    Join Date
    Sep 2007
    Location
    Denver , Co.
    Posts
    109

    " you want how much for that compressor" (cough cough)

    Quote Originally Posted by craig1 View Post
    I agree that semi hermetic compressors are the way to go if you can convince the customer to spend a little more up front.
    Craig you speak the truth , fortunately the margin on new cond units is the same lol. cause selling hot water in hell aint easy lol
    Outlaw guns? only outlaws will have guns
    Those who live by the sword are SHOT by us who don't.

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