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  1. #1
    Join Date
    Jul 2007
    Location
    South Jersey
    Posts
    1

    Question High suction pressure

    I am working on a split system...the problem is that the unit has a high suction pressure of 80 and the head pressure is 220, discharging 61 degree air and returning at 76 degrees. The unit does not have an expansion valve. What could be causing this problem? This is an air cool unit. Any help would be greatly appreciated.

  2. #2
    Join Date
    Aug 2002
    Location
    Southern NJ
    Posts
    962

    Wink

    Wow..many questions. What was your SH/SC readings? Was the area that this system serves very hot? There are a number of things that could cause this.........
    I love to Cook...HVAC is a hobby that pays the bills!

  3. #3
    Join Date
    Apr 2007
    Location
    Philadelphia
    Posts
    2,193
    returning at 76??
    what was your superheat?
    try to give as much info as possible to help us help you when posting.
    model and serial, tonnage, brand, SH SC. application (Resi,comm.)

  4. #4
    Does The Condenser Have A Good Ventilation, Or It Is Too Hot?
    I Think The Condenser Unit Does Not Work Well

  5. #5
    Join Date
    May 2006
    Location
    Western NY
    Posts
    4,366
    Is this a resi/light commercial unit with fixed orfice metering device? If it is, you need to check the superheat. You'll also have to obtain the manufacturer's charging table. Tell us what you have and we can help you better.
    "Nearly all men can stand adversity, but if you want to test a man's character, give him power."
    -Abraham Lincoln

  6. #6
    Join Date
    Mar 2006
    Posts
    6
    i take it we are talking about a hermetically sealed compressor.Generally they are capable of pumping at a ratio of 4 to 1.with a high suction and a low dishcharge pressure(be sure you are reading dishcharge pressure and not liquid pressure) it doesnt sound like your suction pressure is abnormal at 61 degrees dishcharge temp and your delta t looks ok ,the only thing i see is the low dishcharge pressure,but that is relative to ambient temp.

  7. #7
    Join Date
    Jun 2005
    Location
    Ohio
    Posts
    1,720
    First things first.
    Perform a compressor efficiency test. See if it will pump down, how far into a vacuum, and does it hold the pressure differential or equalize?
    76* return, 80# suction, and 220# head don't add up. Is it a newer hi-efficiency condenser?
    jogas

  8. #8
    Join Date
    Jan 2004
    Posts
    1,176
    Could it be because it is a 2 ton unit on a 5000 square foot house.

  9. #9
    Join Date
    Mar 2005
    Location
    Pacific Time Zone
    Posts
    4,223
    What is the refrigerant? R-22 I would assume?

    Of course what are the superheat and subcool readings?

    What size is your indoor coil and what size is your outdoor coil? (I've had a recent experience with a high efficiency unit 3 ton outdoor and 5 ton indoor that causes higher than normal suction pressure readings).

    What is your outdoor temperature at the time of these readings?

    What is your db/wb humidity readings? Perhaps you are drawing out much more latent than sensible heat and thus the higher suction?
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  10. #10
    Join Date
    Apr 2007
    Location
    lake grove, ny
    Posts
    63
    Quote Originally Posted by winbarro View Post
    I am working on a split system...the problem is that the unit has a high suction pressure of 80 and the head pressure is 220, discharging 61 degree air and returning at 76 degrees. The unit does not have an expansion valve. What could be causing this problem? This is an air cool unit. Any help would be greatly appreciated.
    is it a ductless unit?? if it is did you check the condensor for the txv??
    observation is key..

  11. #11
    Join Date
    Jun 2004
    Location
    BR,LA
    Posts
    256
    80 + 15 = 95
    220 + 15 = 235
    235/95=2.47
    2.5 to 1 compression ratio

  12. #12
    Join Date
    Jan 2001
    Location
    MN
    Posts
    115
    Is your condenser and evaporator the same size? Is the evap. over sized?
    I am here to make money for me and the company, I only guarantee one of 'em.

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