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  1. #1
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    mp39 walk in cooler with water cooled cond

    Went on a call for unit shutting down, and in the customer's words "no water coming out of the drain line" of a pump-and-dump, water-cooled condenser. WRV was sticking, so I backed off the spring a bit and it opened. Now he's happy because there's water dumping, but I digress. Then I noticed freezing at the txv. No noticeable drop across the filter drier, so

    what would be ball park pressures and superheat/subcooling numbers for an MP39 system?
    with domestic water at the condenser inlet, 72* water temp.
    It's great to be alive and pumping oxygen!

  2. #2
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    Whats the outgoing water temp?
    ___________________________________________


  3. #3
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    Quote Originally Posted by DPSwitch View Post
    Whats the outgoing water temp?
    Well, it depended on where I set the head. But I don't know where to set the SC/SH, so setting the head pressure and the subsequent LWT was sometimes low, and sometimes it was very hot to the touch. The reason I played with it so much is because there are other issues. The TXV also has a problem, so I was trying to push it around and get the suction up. It's freezing up at the TXV, and producing 8-20psi suction.
    The WRV is coming out because it had stuck closed. But when I set up a new one, should I go for a 4-7* temp rise in LWT? The other issues are on my "recommend" list also, so we'll see what they want to do.
    It's great to be alive and pumping oxygen!

  4. #4
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    I'd set the WRV to maintain 90° condensor saturation. So around 120 head.

  5. #5
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    Jul 2008
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    South Shore,Long Island
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    According to "Heatcraft" instillation manual water cooled units should operate at a pressure correspondent to 105*F. condenser temperature which is 154#.

  6. #6
    Join Date
    Nov 2006
    Location
    Ontario
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    The water valve might not be the problem. What was the discharge pressure upon arrival ? Why was the unit not tripped on high pressure control ? or was it ? Low gas charge would cause low discharge pressure and therefore a closed wrv. Check more thoroughly your pressures and SH.

  7. #7
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    Dec 2006
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    Middle Tennessee
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    *

    Quote Originally Posted by kbghdg View Post
    I'd set the WRV to maintain 90 condensor saturation. So around 120 head.

    seems a little low to me!



    .

  8. #8
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    Quote Originally Posted by Airmechanical View Post
    seems a little low to me!



    .
    I think your right. I should have said 95 saturation. But after reading burnerfixer's post even that maybe wrong. The last WCC i worked on. I could have sworn the valve was set to 180 psi( r-22) and clearly marked as its correct setting. Oh well, live and learn!

  9. #9
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    Thanks for all replies. It got away from me. I figured we'd be back there by now on the recommendation quote, and time keeps on slippin...into the future.
    So in reply to your posts I (if we EVER get to return) will set that valve up as suggested, and will see what 150-180psi head gets with suction and liquid
    .

    coolaide--The original head pressure was tripping the dual pressure switch, requiring manual reset. It was hitched until I applied sudden thwack and then seemed to respond as expected. That was the reason for recommending replacement of WRV.
    It's great to be alive and pumping oxygen!

  10. #10
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    Dec 2006
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    Quote Originally Posted by The Doctor View Post
    and will see what 150-180psi head gets with suction and liquid
    .
    .
    I like kbghdg's answer better!

    Would you like 150/180 head on a R12 system??, sounds like an overload or condensing problem to me try the 120-130 range!
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