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Thread: DDR VALVE

  1. #1
    Join Date
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    DDR VALVE

    Can I replace the DDR valve with a OLDR valve on a Margaux rack? If so, what are the deciding factors wether to use an OLDR or a LDR? It seems to me a few years back I heard that you had to come back in with a DDR on a Margaux rack!!

  2. #2
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    In order to get the condensed defrost gas back to the liquid header on a HG defrost rack we need to establish a pressure difference between the hot gas (or Kool Gas) and the liquid header.

    There are two basic methods to accomplish this. One is the discharge method where you have a differential regulator (DDR) after the tee for the HG header. The other is the liquid method where you install a differential regulator (OLDR) in the liquid line upstream of of the liquid header.

    They both accomplish the same thing, although the liquid method is probably a bit more energy efficient because the discharge method increases the compressor discharge pressure above that of the condenser. The liquid method however will cause a loss of apparent subcooling due to the pressure drop in the liquid feed, so its probably best you have a mechanical subcooler when using the liquid method.

    Otherwise, the difference is the DDR energizes to fully open and the OLDR de-energizes to open.

    http://sporlanonline.com/90-50.pdf

  3. #3
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    Quote Originally Posted by icemeister View Post
    In order to get the condensed defrost gas back to the liquid header on a HG defrost rack we need to establish a pressure difference between the hot gas (or Kool Gas) and the liquid header.

    There are two basic methods to accomplish this. One is the discharge method where you have a differential regulator (DDR) after the tee for the HG header. The other is the liquid method where you install a differential regulator (OLDR) in the liquid line upstream of of the liquid header.

    They both accomplish the same thing, although the liquid method is probably a bit more energy efficient because the discharge method increases the compressor discharge pressure above that of the condenser. The liquid method however will cause a loss of apparent subcooling due to the pressure drop in the liquid feed, so its probably best you have a mechanical subcooler when using the liquid method.

    Otherwise, the difference is the DDR energizes to fully open and the OLDR de-energizes to open.

    http://sporlanonline.com/90-50.pdf

    Or in plain English DDR's are de energized during defrost and OLDRs are energized during defrost.
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  4. #4
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    Quote Originally Posted by crackertech View Post
    Or in plain English DDR's are de energized during defrost and OLDRs are energized during defrost.
    You have a knack of cutting through my mumbo-jumbo.

  5. #5
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    Quote Originally Posted by icemeister View Post
    You have a knack of cutting through my mumbo-jumbo.


    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


    Educational forums are open.

    If you would like to submit a link or an article or other related info to the EF. click here

  6. #6
    Join Date
    Mar 2006
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    18
    Only if the return gas fron the liquid line does not return to the discharge line. I have seen a lot of margaux racks return to the discharge line (Food Lion). If you have tees and check valves on all your liquid lines attached to another header use a DDR.
    The largest room in the world is the room for improvement.

  7. #7
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    Quote Originally Posted by legend View Post
    Only if the return gas fron the liquid line does not return to the discharge line. I have seen a lot of margaux racks return to the discharge line (Food Lion). If you have tees and check valves on all your liquid lines attached to another header use a DDR.
    This may well be what NANOTECH is concerned about.

    Good info!

    I've never run across a rack set up like that, but it would certainly work...as long as you have a DDR.

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