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Thread: Dunham Bush

  1. #1
    Join Date
    Mar 2004
    Location
    New England
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    224
    I have got an APCX230-OO chiller with remote air cooled condensor we are new to this unit.System has been trippig out for years on safteys when unit has low load and outside temp is below 65°.I installed tattle tails across safteys ,unit tripped on high oil temp the other night control cuts out at 185°.Changed the oil about 4 weeks ago oil was dark brown ,open drive compressor.Wih the unit running @50% load oil temp is 148°,refrigerant level of indoor receiver is half full.I have not been able to see its operation with a low load and cooler outdoor temps.Any ideas?

  2. #2
    Join Date
    Oct 2001
    Posts
    6,966
    are all your condenser fans coming on at the start,and see about putting a time delay jumper on the LP for low load starts on cool days...also megerohm the windings on the compressor(s) and do and acid test if you still have oil samples from the pull.check the charge on the next hi-load day with all your condenser fans running,amps,line temps.O/A temp into the condenser at full compressor load hi/lo readings!verfy the chiller controller is it for return water or dicharge water when you set it?

  3. #3
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    Oil was tested no acid,open drive compressor no motor problems.unit run great loaded problem is running it unloaded with lower outside air temp,condensor fans are staging

  4. #4
    Join Date
    Sep 2002
    Location
    Hampton Roads, Virginia
    Posts
    1,602
    Originally posted by onesidedcoin
    I have got an APCX230-OO chiller with remote air cooled condensor we are new to this unit.System has been trippig out for years on safteys when unit has low load and outside temp is below 65°.I installed tattle tails across safteys ,unit tripped on high oil temp the other night control cuts out at 185°.Changed the oil about 4 weeks ago oil was dark brown ,open drive compressor.Wih the unit running @50% load oil temp is 148°,refrigerant level of indoor receiver is half full.I have not been able to see its operation with a low load and cooler outdoor temps.Any ideas?
    Does it have a hot gas bypass?, If it is really tripping on high oil temp I'm thinking not enough compressor cooling because the suction temperature is to high.
    "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

  5. #5
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    Yes it does have hot gas by pass and I have believed that it is a compressor cooling issue.It also has discharge regulating valve and a bypass regulaing valve.Sounds like under unloading conditions 10% hot gas kicks in ,discharge regulating valve and a bypass regulaing valve cause R22 stores out in condensor ,hot gas bypass prevents low pressure manual reset control from tripping.The IVC condensor fan staging is pressure and temperature.The first fan come on @ 160psi/100diff the second fan cyles with the first @ 40°/6°diff and the third @60°/6°diff.


  6. #6
    Join Date
    Sep 2002
    Location
    Hampton Roads, Virginia
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    1,602
    Originally posted by onesidedcoin
    The first fan come on @ 160psi/100diff the second fan cyles with the first @ 40°/6°diff and the third @60°/6°diff.

    Are you sure about 160psi/100psidiff, thats low, this is R22 right?
    "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

  7. #7
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    Yes it is R22 and yes I find the setting troubling but the is what is listed on wiring print and also note is not to tamper with setting from Dunham Bush. But I think it is a miss print from 1987 that no one has changed.

  8. #8
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,356

    D/B APCX...........

    The D/B APCX air-cooled packages typically have liquid injection oil cooling that are very sensitive to having a solid column of liquid to work right. It's possible that during your low load/lower ambient conditions that the condenser is flooding sufficiently to cause the receiver level to drop and lose a good feed to the liquid injection. Could be a plugged filter or strainer too.

    The discharge pressure and bypass (receiver pressure) regulator are your flooding controls. Make sure that they aren't in a battle with the fan cycling controls. If the fan controls are set too low, you can flood the condenser unnecessarily and run out of liquid. This would be my first guess.

    The HGBP is usually a fixed solenoid valve controlled by slide valve position switches set way below 50% load. I don't think that's coming into play here.

    Poodlehead Mikey would know all this better than me. Hey Mikey! Where' you at?

  9. #9
    low head pressure at low ambient or low load conditions will
    trip out unit constantly. raise the head pressure to around 200 lbs and you should be ok.
    test it chaeck oil pressure at 160 lbs then raise it to 200 lbs and see if pressure doesn't come up. also make sure your unloaders and hotgas is set properly.
    do not let unit run unloaded for extreme periods of time
    try to make it loadup every so often.

  10. #10
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    My concern on the head pressure is the oil pump pressue it is an open drive pump.Oil pressure is on the high side.her is a shot of the equiment. http://www.pbase.com/onesidedcoin/founders

  11. #11
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,356
    What's it shutting down on then.......is it high oil temp or low oil pressure?

    The oil pressure is the net difference between oil pump discharge and compressor discharge pressures. So long as you maintain adequate discharge superheat you should have good quality oil to pump.

  12. #12
    Join Date
    Mar 2004
    Location
    New England
    Posts
    224
    It shut down last Thursday morring 12:30 AM on high oil temp.

  13. #13
    Join Date
    Dec 2003
    Location
    Kenilworth New Jersey
    Posts
    230
    High oil temp is actually high dischagre temp on the air cooled screws as the location fo the bulb or sensor will tell you. Check all the obvious stuff dirty condensers and fan cycling settings etc. and you`ll find the answer.

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