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  1. #1

    Confused

    carrier 34 ton rtu, two 17 ton cicuits. Replaced A circuit compressor ran for two days and grounded. Compressor was changed again ran for 1 week and grounded. I went to the site yesterday replaced compressor. Flushed system, purged two large cylinders of nitrogen through sytem, replaced LL
    drier, triple evacuated and pulled system down and held at 400 microns, charged with factory charge of 24 lbs., started unit Running 300 head, 90 suction, 20 superheat,
    my main problem are my amp readings. Voltage is consistent
    485, 487, 487, all wiring has been checked and ohmed out
    RLA is 26.5 compressor is running at 28, 29, 32 amps fully loaded can't get amps or pressures down, any ideas?????

    I just got involved on the last compressor. My SH is 20
    and my subcooling is 7-9, it is a TXV system. My delta accross my evap. coil I have not taken yet I can't get the machine running propperly. My oil has been fine 1/8 to3/8


    [Edited by carriertech1 on 07-07-2004 at 08:17 PM]

  2. #2
    Join Date
    Sep 2002
    Location
    Hampton Roads, Virginia
    Posts
    1,627
    Does it have TXV's, probably at that tonnage, if so what is the subcooling, If all coils are clean, airflow OK, I would say overcharged, don't always believe factory charge on data plate.
    "Profit is not the legitimate purpose of business. The legitimate purpose of business is to provide a product or service that people need and do it so well that it's profitable."

    James Rouse

  3. #3
    Join Date
    Oct 2003
    Location
    UTAH
    Posts
    145
    how much oil did you drain out of old compressors? you should drain same amount of oil out of new compressor as you do out of old if oil charges match up. High amps probably caused by oil charge. What was your split btw?

  4. #4
    Join Date
    Jun 2004
    Posts
    72
    You should of done all of the steps that you took on the last compressor before you let the first compressor back into service. What were the pressures, amps, subcooling or superheat, temps, etc.. on the first one?
    Generally the weighed in refrigerant listed on the nameplate are correct, but you should always do your pressure, temp. checks before leaving the site.
    Use what you learned, sometimes we do this for so long that we get really complacent in our jobs, and just change parts. I've done it and it came and bit me on the a@#, don't let it happen to you.
    Get back with temps, press, delta T, and whether its a TXV or Cap system in order for us to help U out.
    12-14deg. superheat, 10deg subcooling should get you close to what you want. Read the post in "For your interest" in the main page and look for charging by super heat or subcooling to help you out or refresh your memory banks.

  5. #5

    carrier 34 ton rtu

    I just got on the job on the last compressor
    my superheat was running 20 and my superheat at 7-9
    degrees. I did not check the sight glass but my oil levels have been fine 1/8 to 3/8. I have not even got to a delta T because I have not got the unit running propperly

  6. #6
    Join Date
    Jun 2004
    Location
    Virginia
    Posts
    52
    First thing I would like to know is what took the first compressor out?Was it grounded too?Sounds to me like either a voltage problem or a slugging problem.I would install some kind of phase monitor that reports under and over volts.Maybe a problem with the building and not with you at all.whats the oil pressure diff.?maybe your not returning oil for some reason.Although with those pressures I doubt it.non-condensables?Just some thoughts I had.

  7. #7
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,993
    I see no mention of a suction line drier. Did this system have acid in it? Was the oil black?

  8. #8
    Join Date
    Jun 2004
    Location
    Richmond Virginia
    Posts
    1,078
    Pressures are always affected by your temperatures. What was the outdoor ambient and what was the temperature split. I see that you said you didn't get to the Delta T but that is a must to know. If your return air temp is 90 degrees your pressures are going to be high. The harder the compressor is pushing (discharge), the higher the amps will be. What concerns me most is that you have not mentioned an oil sample. On that size system, you should always take an oil sample to see what clean up measures are going to be necessary. Simply purging and replacing a drier one time may not be adequate. Also, whenever you encounter a high discharge pressure take a reading of the discharge line temp as well. You are probably at a high enough temp that your oil is breaking down. I would start by cleaning the condenser coil and taking an oil sample.

  9. #9
    Join Date
    Dec 2002
    Posts
    9,871
    Hi head with lo subcooling equals air flow restriction over condenser. Are the fans running in the right direction? Is the condensor dirty? Also treat this circuit as a hi acicidic burnout. Installation of changeable drier cores on both hi and lo side would be the ticket.

    [Edited by rob10 on 07-07-2004 at 09:49 PM]

  10. #10
    Join Date
    Aug 2003
    Posts
    242
    Need to know return temp, supply temp, & ambiant temp. If your ambiant and return temps are very high and your cond coil is dirty, you will overamp.

  11. #11
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    Whats the other circuit readings ?

  12. #12
    Join Date
    Jun 2004
    Location
    Richmond Virginia
    Posts
    1,078
    Originally posted by onesidedcoin
    Whats the other circuit readings ?
    An excellent point! Compare the two and you will know whether you have a system problem or just a problem with the one stage.

  13. #13
    Join Date
    Aug 2002
    Location
    manitowoc wisconsin
    Posts
    4,943
    You did not say weather or not you replaced the motor starter with the comp.Also you said all wires ohmed out but did you test the under load?why the high head?Are the fans all coming on as designed?Is the coil clean?There is alot of info in the carlyle handbook that might help you out too. http://www.carlylecompressor.com/PDFs/PSG/PSG.pdf
    Take your time & do it right!

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