Dunham Bush

[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?

[maxster]

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?

[onesidedcoin]

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

[klrogers]

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.

[onesidedcoin]

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.

[klrogers]

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?

[onesidedcoin]

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.

[icemeister]

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?

[airworx]

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.

[onesidedcoin]

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

[icemeister]

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.

[onesidedcoin]

It shut down last Thursday morring 12:30 AM on high oil temp.

[h2045]

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.

[twcpipes]

Is the liquid injection solenoid (8sol) opening and is the oil TXV feeding? And if so, is there a solid liquid head to the TXV?
I have an old catalog showing the low discharge temp switch
(8tas) has to be made for the solenoid to energize. Is the oil heating up under low loads with the slide valve backed off?
Thanks, tom

[mathias]

I am ex Dunham-Bush service rep and Icemiester is right!!! All screw chillers are very critical to discharge superheat and your problem is high oil temp - check that expansion valve to the oil and your oil cooler!!!!!

[onesidedcoin]

I gave the customer a quote on changing the fan staging.
The building has 3chillers ,1apcx (air cooled)2 pcx chillers (water condersors) that heat and cool the building the third the one the apcx the one with problems is used during the summer months to reduce run time on the other two chillers.During the day the load requires two chiller to be on line but at night the load drops to the point were each chiller is at 10%.