HELP.....Chiller

[NZPOMME]

Right I have a Berluga water chiller, thats been playing up on the oil pressure switch so I replaced the oil switch today with the coms cable and transducer, but the switch is still tripping out? what I have in 55 psi oil pressure, and 3/4 sight glass of oil, Its a copeland hermitique and ave been pulling my hair out about this and the pressure switch is a like for like (copeland sentronic 085-0172-03) and information regardin this would be great help!!:rolleyes:

[Tesla]

Hey NZPOMME welcome to our forum
I thought a POME was a Prisnor Of Mother England sent to Australia?
A common problem with chillers is that due to lo loads for extended periods or shortage of refrigerant the oil will tend to log in the cooler (they rely on refrigerant velocity for oil flow). they usually need a good four hour running at full load to pull the oil back. Oh and of course make sure it has a full refrigerant first (fixing any leaks). The glass may look full but could be a percentage of refrigerant. Can you obtain a manual for this chiller? This is a common problem that I had but don't work on many chillers these days, if you take all your temps and pressures then post them it would be helpful.

[Grizzly]

Follow the link.
http://www.hvacrinfo.com/cope_ae_bulletins/TAE1275.PDF
Grizzly

[Emmett]

Please provide as much information on the system as possible, refrigerant, discharge, suction pressures, temperatures,etc.

[install monkey]

maybe read the oil pressure scale on the switch to see what the set diff is and compare oil pressure to suction pressure(sump) ensure ur reading is higher than what the switch is meant to trip at, maybe the oil picup filer is choked, is the crankcase heater working, is the 90sec-2min delay operating correctly

[NZPOMME]

hey, been back today, suction pressure 20 psi, oil pressure 75 so the gives us diff off 45, its 3/4 sight glass full aand Running on R404A!! Its really weird because it stops and starts but then will running for about a week then stop!!

[install monkey]

whats the oil pressure switch set at? wind the pressure switch up slowly with the comp running to see if the set pressure is too close to the operating pressure.
mabe the oil pump is worn and not pumping as well as before.try winding the pressure switch down slightly to accomodate the nusience trip, is the crankcase heater working? maybe an oil change is due
hey, been back today, suction pressure 20 psi, oil pressure 75 so the gives us diff off 45, its 3/4 sight glass full aand Running on R404A!! Its really weird because it stops and starts but then will running for about a week then stop!!

[Magoo]

the suction at 20 psi/ -33'C R404a evaporating seems low.

[Grizzly]

Tesla may have something?
It depends whether the problem is poor or fluctuating oil flow/ levels?
Or poor gas flow which relates to gradual loss of oil out of comp and low gas flows.
You could try raising your head pressure set point.
And see what happens?
Also check the LWT sensor for accuracy and system charge.

As Magoo points out the evaporating temp/pressure seems low!
Have you a bocked or partially blocked evap?
Or even a liquid line obstruction (what's the filter like?)
IM'S points also need to be eliminated.

It's time to go back to basics I am afraid and do a plant log that at least would maybe identify if
there was another area involved?
Good Luck Grizzly
Grizzly

[Tesla]

Magoo & Grizzly you are correct.
NZPOMME - You need to do your homework please.
We need all system parameters measured under steady state conditions for accurate diagnosis.
HP
LP
HP temp
LP temp
Liquid pressure and temp
Water in temp
Water out temp
Ambient
Air/Water on cond temp
Air/water off temp
Oil press
Liquid line sight glass
Oil glass level
Current
Current rating.
You wrote 20psi which clearly indicates short of refrigerant or restriction. You will need to just set up some measuring instruments and take measurements over a period of time, I will usually do it for an hour taking all measurements every 10 minutes. sometimes I will override the controls on a cold day and enable the heating to create a load so the chiller can run for a decent time. Then check the results. Accurate measurement is important, there maybe an electronic display which will give most of them but don't rely on old fitted gauge readings. All of the measurements listed above are important and can tell us many things like if there is too much chilled water flow etc. From my bitzer app PT chart tells me 20psi is around -26degC which is too low for any chiller.
+40% of faults I have attended happen like this - there is vibration which leads to a leak which leads to loss of refrigerant which leads to oil not returning to compressor which leads to low oil pressure, then some people keep resetting which leads to compressor failure and it can get worse. But there could be other problems like compressor components failure, Metering device failure, undersized condenser, AHU control failure etc.