HP Problem
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Thread: HP Problem

  1. #1

    HP Problem

    I have a straight forward split DX system running on R407C, that serves a critical IT comms room. The other unit in this room is currently awaiting a new compressor and so this unit must remain on at all times.
    System trips on HP despite condensor coil being unblocked and cond fan running at full speed.
    Suction Pressure is 65 Psi, ambient approx 21 C.
    Discharge in excess of 4OO Psi.

    I have bypassed HP switch and removed approx 1Kg charge and now the system is running at 45/345 Psi....ie both the suction and discharge have reduced, though discharge is still too high.
    Off coil duty is approx 6-8C with room temp of 22C.

    I originally thought the system could be overcharged, and still might be though i am unable to reclaim all refrigerant until the other unit is repaired.

    Any ideas as to why HP ???

  2. #2
    Join Date
    Nov 2006
    Location
    New Hampsha'!!!
    Posts
    274
    are you positive that the condensor is clean? or does it look clean? what is you ambient for the condensor? you have a problem that you have created too by taking that refrigerant out now your coil is what around 15*F with 45 suction pressure???? hahts that -9 c?
    Last edited by refrige-nate; 06-26-2008 at 04:15 PM.
    dont worry what people think, they dont do it often

  3. #3
    It looks clean, and ive seen worse..system is approx 4yr old and runs on R407c refrigerant, common in the UK.

  4. #4
    Join Date
    Oct 2004
    Location
    Metro ATL
    Posts
    454
    Superheat and subcooling numbers would be helpful if you could. Without them any advice will be a WAG.

  5. #5
    Join Date
    Dec 2004
    Location
    toledo, ohio
    Posts
    179
    Can the coil be split? If so the outside of the coil may look clean but between the coils can be a blanket of dirt.

  6. #6
    Join Date
    May 2007
    Location
    maryland, baltimore
    Posts
    135
    shine a light through the coil, have seen very clean looking coils that were completely packed with dirt and pollen. hold your hand over the condenser fan and feel the air flow, if the air is mostly around the edges of the blade the air is being sucked down through the center. Check the compressor motor to see if the hp is from being overheated. Have never worked with R407 but have seen fractionated 404a with similar problems.

  7. #7
    thanks for replies...
    the air is being blown out around edges of cond. fan ....and not through centre..

    what does this mean ?

  8. #8
    Join Date
    May 2008
    Location
    Jax Fl.
    Posts
    1,943
    Usually Perimeter-only air flow on a prop fan means there is restriction on the intake to it, I would guess the coil is the restriction. It would be worth hitting it with a pressure washer/fan spray nozzle. Be careful not to angle the spray or it will flatten the fins.

  9. #9
    Join Date
    Mar 2008
    Location
    North Queensland, Australia
    Posts
    1,051
    Sounds to me like you may have air in the system.
    at present you're running -6C coil temp. Your evap will ice up and you won't have any A/C.
    can you run a water hose over the condenser?
    how big is the system? Would it take long to decant it, vac it out then recharge it with fresh gas? Or just to valve off the inlet of the receiver and the suction service valve and decant the condenser and vac it? 400 PSI head sounds like more than just a dirty condenser to me.
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  10. #10
    Join Date
    Sep 2006
    Location
    Southern California
    Posts
    86
    I agree w/ slatts, Possible air or Nitro in there. Disable the compressor and let the condenser fans run awhile then check your liq. line temp. versus sat. temp. should coincide, if not you got non-condensables.

  11. #11
    Join Date
    Sep 2006
    Location
    Southern California
    Posts
    86
    Quote Originally Posted by toy501 View Post
    I agree w/ slatts, Possible air or Nitro in there. Disable the compressor and let the condenser fans run awhile then check your liq. line temp. versus sat. temp. should coincide, if not you got non-condensables.
    should coincide w/ ambient

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