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  1. #1
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    I ran into a r12 walk in freezer. Box normally at 0 degrees f but it was at 20 degrees. Sight glass wasnt full so i evactuated recovered exc. I recharged with mp66 to full sight glass. Condenser is clean, evaporator is clean, fan is good. Ive got a 6 degree temp change at the evap. Line temperature at the txv bulb is 22 degrees. Line temp at the suction service valve is 32 degrees. Suction pressure is 15 pounds. High side pressure is 148 with a 94 degree line at the reciever. The lowest ive been able to get this thing is around 20 box temp and i was there all dam day but they periodicly did have to go in the box for product. There isnt much of a load in the box and whats in there is still frozen. This is a 4 by 4 box with about 8 foot eight foot ceiling height. Hvac sure is a heap easiar than the refer stuff. The temp does barely creep downward but i mean it does it slowlyyyy. This is a chinese restrant and i think the owner is getting ansy..im faily positive i saw him polishing one on those samarai swords like john belushi use to swing on snl.

  2. #2
    Join Date
    Nov 2003
    Location
    Wisconsin
    Posts
    458
    Haven't looked at my p/t chat, but off the top of my head, don't believe your compressor can maintin the pressures necessary for mp66. Unit just not up to the challenge pressurewise.. Volumetric efficiencies just not there.

  3. #3
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Ive been thinking the same thing rango but this is an r12 system and im using a r12 drop in. My low side pressure just goes to high when i clear the site glass. I have no idea what to do with this system. They claim its always maintained 0 degree box temp. I keep waiting for my low side pressure to drop and it does but oh so slightly...something just isnt right. If i cant use mp66 then what in the world do i use?

  4. #4
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    12 is what I'd use, but I know that's not always possible.

    I'd go to 404a with a valve and condensing unit replacement.

  5. #5
    Many freezers first turn into coolers, then they die. Shut the valve on the receiver, see if the compressor pulls down to -25 or -30 or so, if it doesn't, the compressor valves are shot. Try 409-A for a drop in refrigerant if the compressor is good.
    Hey cockroach, don't bug me! ©

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  6. #6
    Join Date
    Jan 2002
    Posts
    1,895
    chinese resturant ? what kind of shape is the box itself in ? mp66 is a little better than 409 for a freezer but I agree with dave thats if the box itself is in decent shape

  7. #7
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    I had already closed off on the suction service valve and could only pull down to 10 inch vacume and thats with the compressor sounding like it was gonna tear apart...ive had a sneaky suspicion that the compressor was inefficient...but dam its sure difficult to safely say thats the main cause...i mean if i change that thing out and i get the same results im out some cash. 409a is like already very similar to mp66 with the exception to having a higher head...ive already got 66 and mp39 jeeze i cant put out another 230 for such a similar refrigerant. Them dupont guys really put it to us when they quit making the r12. They are probably licking their lips over all the r22 alternatives there gonna come up with and charge us 250 a pop for.

  8. #8
    Well Ok then, no problem use the mp66, but you need a new compressor.
    Hey cockroach, don't bug me! ©

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  9. #9
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Thanx diceman ive had that suspicion from the start but wasnt totally confident in it.

  10. #10
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    The only thing was Ive been drawing specs amps on the compressor and thats what shook my confidence some...i would figure i would be high or low on that.

  11. #11
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    If your amps are ok, ohm out your windings. More than 8-9 ohms on your start to common, compressor looks shaky.

    If pump is ok, check your fan delay. That coil needs to fill with liquid before the fans load it up.

    It is also possible that Samuri Refrigeration Man paid a visit and opened that TXV.
    A Diamond is just a piece of coal, that made good under pressure!

  12. #12
    Amps sould be slightly lower but not always a good indication.
    If you shut off the service vavlves and it doesn't pull down to close to -30, the comp is shot. Very common on freezers to do that, seem to be working somewhat, but can't pull down all the way.
    Hey cockroach, don't bug me! ©

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  13. #13
    I agree the compressor is suspect, but make sure you've got good distribution in the coil. Superheat can look great, but if only part of the coil is wet you won't get full capacity.

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