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Thread: Screwed Up Unit

  1. #1
    Join Date
    Dec 2000
    Location
    flourtown pa.
    Posts
    57
    Got one for you. Skymark unit, 3 ton,
    Walked in on this one, unit had problems since install with screws thru piping. Was repaired then after about a month it burned out compressor. Replaced Copeland Scroll, TXV, Lig Drier. Pressure test , evacuated.
    Problem, weighed in 4lbs 13oz R-22 per unit data.
    H.P. 375, S.P. 101, Suction Temp 62f.
    Condenser coil was cleaned.
    I think the condenser coil is internally blocked at inlet.



  2. #2
    Join Date
    Jun 2004
    Posts
    420
    With head and suction both that high, it's probably overcharged. Is that 375 discharge or liquid pressure?

  3. #3
    Join Date
    Feb 2004
    Posts
    534
    Superheat and subcooling??? need to check SH and SC this should tell if your overcharged. That 375 is that head pressure or LL pressure?

    [Edited by service guy on 08-21-2004 at 04:58 PM]

  4. #4
    Join Date
    Aug 2002
    Location
    Greenville SC
    Posts
    431
    Do not always trust Data Plate's for the correct charge.
    Seen alot of them that were wrong.

  5. #5
    3 ton unit with 4lbs 13 oz. should not be that far off on charge. I'd place my money on blocked cond. coil. I'd back off on charge to see what the numbers looked like, but i think at lower pressure your temps still wont be right.

  6. #6
    Join Date
    Jul 2004
    Location
    Houston
    Posts
    129
    Check your liquid temp if not 5 deg. over ambient then you have condensor restriction. If subcool good and high superheat check operation of txv(if equipped). May have bad suction valve in compressor if high superheat. Had a cap tube the other day 325 head with 95 suction 40 superheat bad suction valve bleeding pressure.

  7. #7
    Join Date
    Apr 2004
    Location
    Michigan
    Posts
    295
    I think some manufacturers put a refrigerant quantity on the nameplate because they have to, but I've seen some that weren't even close to what the charge should be.

  8. #8
    Join Date
    Apr 2004
    Location
    Rossville, GA
    Posts
    104
    I had a problem like this before and found return air pulling unconditioned air @ 90 degrees. Have you checked your delta tee? Can you pump down the compressor or dropout your evaporator motor to test suction valve performance.........

  9. #9
    Join Date
    Apr 2003
    Location
    Florence , Alabama
    Posts
    24
    The condenser could be dirty on the second row . I am prity shure your suction valve is ok . You did say it was a scrol . they dont have valves . Just a check valve in the discharge line . I would check the return line to evaperatore first , it could be sucking from ceiling . High suc. equals high head . This may not be the prob. I also would sugest checking superheat and subcooling .

  10. #10
    Join Date
    Apr 2003
    Location
    Florence , Alabama
    Posts
    24
    I just looked at your post agin . 62 suction temp and 101 suc. pres. thats alot of superheat.

  11. #11
    Join Date
    Apr 2003
    Location
    Florence , Alabama
    Posts
    24
    i am sorry no superheat.

  12. #12
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    to me replacing the compressor is like installing a whole new system so i treat it that way from my own experience, when i first started i didnt have the proper guidence, my boss wanted me to learn on my own so to speak, if i was really intersted in the trade i would find my own info, why pay extra $$$ for my extrs time on the job when he could assist and would take more profit i have no idea but i'm glad he chose that way of teaching/learning cause ireally love this stuff, on a compressor switch out i go ahead with a full inspection and cleaning, clean the evaporator, clean the condensor, pump the evap condenssor and lineset individually with nitro get all the old oil out of the system, change the piston in the evap if orfice type,as you said was a txv so leave out and pump coil with nitro and i have yet to have a problem this way,

    all and all with what you changed thus far i would say some of the distributor tubes from the txv to the evap are clogged, check the temp on each distibutor line and rows on the coil, if temp is the same on all tubes your good if not pump nitro backwards from suction line to liquid line on coil to try and get whatever is stuck in there out, if temp still isnt equal replace evap

  13. #13
    Join Date
    Oct 2002
    Posts
    970
    I think you got some air in there, liquid line is cool to the touch, right? change the oil in that pump, son

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