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  1. #1
    Join Date
    Mar 2003
    Location
    Brooklyn, Ohio
    Posts
    102

    Water source heat pump

    I have a McQuay heat pump M/N CCH120AETS. The compressor seems to intermitently shut down and not restart until the power is reset. When i went out I found the following>>>suction 70# discharge pressure250#.suction line temp at comp 75deg. hot gas discharge temp180degr. cond water temp in was 86 and 100 out. not sure what design water temp rise should be.
    it was running and stayed running the whole time I was there.

  2. #2
    Join Date
    May 2007
    Posts
    732
    I'm not familiar with that model number, but we service some water-cooled McQuay AHUs. Those units have condenser delta T of 10F at full load, so I would be looking for an explanation of why your equipment has a 14F delta T. May be OK, I'm just saying.

    I'd also be looking at refrigerant charge and TXV performance, superheat seems high. If high SH were due to high load it seems like the suction pressure would be higher.

    Have you tried to get the documentation online?

  3. #3
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    How large of an area is this unit serving. What is the flowrate through the condenser.

  4. #4
    Join Date
    Mar 2003
    Location
    Brooklyn, Ohio
    Posts
    102
    I found out comdenser water temp rise should be 10 to 14..so i think with high subcooling and high superheat it may be a txv or metering device as it looks like a fixed orfice.

  5. #5
    Join Date
    Jan 2010
    Posts
    6,058
    Go to McQuay's web site. You will find all kinds of info.

  6. #6
    Join Date
    May 2006
    Location
    toronto
    Posts
    46
    depending on your room temp i would lower the head pressure, if your room temp is 72 to 75 i would like it runing at 210 head

  7. #7
    Join Date
    Mar 2003
    Location
    Brooklyn, Ohio
    Posts
    102
    going back tues. going to check the water flow thru condenser then perhaps add a little refrigerant. the evap almost seems to be starving a bit.

  8. #8
    Join Date
    Apr 2005
    Location
    where the beer flows like wine
    Posts
    2,871
    14F temp rise is normal in cooling mode, place the unit in heating mode and see what it does. I hope the reversing valve isnt leaking (internally) these things are a pain to replace.

  9. #9
    Join Date
    Mar 2003
    Location
    Brooklyn, Ohio
    Posts
    102
    I added 1# R22 which brought the superheat closer to 12. My discharge pressure fell inline with the entering cond water temp. i am having the maintenance clean the evap coil as it does have some grease on it. I ended up with a 20 degree temp drop across the evap.

  10. #10
    Join Date
    Mar 2011
    Location
    Southern California
    Posts
    17
    Sounds like it was undercharged to me. I'd do a leak test and if you can't find one, isolate the water and test for a leak in the condenser loop. If you get a positive hit in the condenser, you can submit to replace the unit.

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