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  1. #1
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,564

    clearing oil from oil logged evap

    I have a customer with a True reach in that had the CPR valve fail closed. The resulting low flow rates caused the compressor to run out of oil and ruin the rods and pistons.

    When I tore down and rebuilt the compressor it was missing about half the oil. Since there was no leaks, I'm assuming the oil must be in the coils and piping.

    I can easily blow out the condenser, but is there a way to clear out the evaporator without removing the cap tube?

    I know the oil will return once everything is working right, but then the compressor will be overfilled. Additionally I wanted to switch it to POE and R-404a (it had a 502 drop in in it.) so I don't want all that mineral oil in the system.

  2. #2
    Join Date
    Apr 2001
    Location
    Over Here
    Posts
    1,105
    Quote Originally Posted by craig1 View Post
    When I tore down and rebuilt the compressor it was missing about half the oil. Since there was no leaks, I'm assuming the oil must be in the coils and piping.

    I can easily blow out the condenser, but is there a way to clear out the evaporator without removing the cap tube?
    Short answer, no. With all the work you are doing to that relic (if it is was originally an R-502 system), are you really that attached to the cap tube?

    There is the textbook answer, and then there is the real world answer to refrigerant and oil retros. It is almost impossible IMO to acheive the correct percentage of POE to mineral oil ratio needed to textbook it without exceeding practical repair cost on that older unit, unless this is a 'labor of love' project.

    That said, I am not a fan of original cap tube and R-502 retrofit refrigerants due to the differing 'consistancies' of the replacement refrigerants. My choice would be to install a TXV, but then you would need to look at requirement for small receiver, etc... Which again exceeds cost of 'textbook' repair, as you may just as well install a complete new skid designed for R-404 with a receiver.

    Is the relic worth it? Take their money for the repair, and you surely will be back indefinitely until you finally get tired of working for free. But then again, I can't set my eyes upon the unit you are working on to really help you here.

    Good luck.

  3. #3
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,478
    Since you're planning on doing all this work, you should replace the existing cap tube anyway...even though the cap tube size is about the same for R502 and R404A.

    Actually, pulling the cap tube from the evaporator isn't that big a deal, whereas replacing it usually involves running it up the inside left hand corner of the box for a True.

    I'd simply pull the cap tube, braze in some 1/4" copper and backflush using some reclaimed R22 (or whatever) up the suction line and into an evacuated recovery cylinder. About 10 lbs or so should do it. Then reinstall the cap tube into the 1/4".

    On the True freezers, I've found it helps to drop the LH end of the evap coil for better access to the cap tube.

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