Freezer Room.

[sacoolman]

I recently had to change the compressor.The system still uses R22.I recovered the gas and re-used it.The unit had a Dorin Mod: K280CC and I had to install the new model H280CC.
I had to flush out the synthetic oil in the new compressor and add mineral oil.The same quantity.
A few days later I went to check on the unit,and found the compressor low on oil.I topped it up.Was called back and found the oil level on minimum.As the oil separator was looking old,I changed it and charged the separator as per manufacturers instruction.I once again topped up the compressor.
Yesterday went back to check and found the oil level down to minimum again.The pipe run is approx.7m.
I have done other repairs on other units and not encountered this situation before.
Can anyone give me an idea what I have overlooked?Do these Dorins run with such low oil levels?Help, please people.

[Magoo]

What was the reason of first compressor failure. Possibly suction is over saturated and compressor is carrying oil over faster than oil separator can cope with.
Relate more compressor operating conditions, temps and pressures.

[sacoolman]

Thanks for the reply.The first compressor had been operating for the past 10 years trouble free,but it started siezing on start up in December last year and operating noisy, ran for a few weeks.Seized completely.Oil level normal.
It has a liquid separator on the suction.No frost back on the suction at the compressor,I will take the pressure readings,but they were normal for ambient temps.
Thanks again.

[cadwaladr]

well the oil must be going somewhere question is where,probably the evap i have heard of other guys putting a little mineral oil in to help,is there a suction accumalator on this plant if not i would fit one is the crankcase heated?

[sacoolman]

Hi,thanks for the info.Went there today.Checked out the tube from the separator to the compressor for possible blockage,ok.Added more oil and left it for the weekend.On start up had a suction pressure of 1,5 bars and head of 13 bars.The room temp was -16ºC and the ambient at the time was 26ºC.There is a suction accumulator installed.I installed a crankcase heater when I did the compressor change over.Where the oil is going is a mystery,I thought the oil separator was supposed to prevent oil loss.

[D.D.KORANNE]

Suction accumulator will have u bend in it with a hole for oil return . Some times the hole gets blocked with debris , causing oil build up in suction accumulator and no oil return .

[sacoolman]

Thanks very much,had not thought of that one.Will go check it out.Thanks once again.

[chemi-cool]

Usually, oil does not return due to a low refrigerant velocity. Check the TXV strainer, Accumulator [D.D.KORANNE is right about that]

R-22 can run on synthetic oil just as good as on mineral oil.

Try to increase head pressure, it helps some times.

[sacoolman]

Thanks,chemi-cool.I will try anything.Will let you know results.Regards.

[Magoo]

Something in system from original installation has changed/ happened to cause to original compressor to fail, and subsequent oil carryover from new compressor. You have not related any pressures or temps at compressor.

[sacoolman]

Hi,there.You were right.Installed new accumulator,cut open old one and found the hole partially blocked.Added oil to normal level in compressor and let it run for a few days.Alls well.
Thanks to D.D KORANNE for the tip,saved my sanity for now.Regards.

[sacoolman]

Thanks to everyone who gave their advice.Nice to know there are people who give out their knowledge and dont ask for anything in return.Thanks once again.

[Tradewinds]

Just wondering how much oil you have added and where the old oil is now? If the seperator wasn't working then it may have carried over into the rest of the system and can reduce your cooling capacity.
Just a thought.

Glad you found the fault.

[sacoolman]

I added the amount specified by the oil seperator manuf.The suction accumulator had about 750ml inside.
All is back to normal for now.Regards to all.

[claud]

My freezer room has been running for 8 years without any problem and without being serviced. In our December heat last year, however, it struggled for the first time to maintain its temperature, so I had it regassed and it was fine again.

With our ever-rising electicity prices, I had a refrigeration mechanic come out and give me advice and he was horrified and astounded that I had never had it serviced since it was built. My theory is that if it doesn't have a problem, don't "fix" it! He said the least I should do is to change the synthetic oil that has been in there all along.

Is he correct? And any advice on how to reduce power consumption? I store ice cream in it.

[monkey spanners]

Depends on the size and make of compressor, we have a couple of 15hp Frascolds on a freezer room we change the oil in every 18 months or so, but also lots of smaller compressors that never get an oil change.

Did it actually need any more refrigerant when you had it re-gassed or did you just have some put in anyway?

After eight years it would be worth checking over the system for the condition on the pipe work and insulation, all the wiring, contactors, relays etc, motor bearings, defrost heaters, crankcase heaters, etc and no doubt the condensers could do with a clean, filter driers could be changed, superheats checked, safety switch calibration. In fact the more i think of it theres lots to check over.

With regular customers i would give the system a general check over and put right what i find wrong. I might spend most of one visit on the condensing unit and the next checking over the wiring, and the next something else but in your case i would want to give it a good check over to get an idea for the condition and wear and tear on things.

Its often cheaper to maintain things than to wait till they fail big time and also possibly lose stock due to the temperature not being maintained.

Energy saving would be to keep the condensers clean, and the systems refrigerant charge and superheat at the correct level. If it is much cooler at night time there you could run the room cooler at night when the system would be more efficient and warmer during the day when its less efficient. Not sure on any effect this would have on the icecream you would need to look into that.

Jon

[claud]

[
Many thanks fo your elaborate answer, Jon.

Yes, it did need refrigerant in December and after it was re-gassed it was cooling perfectly again.

Not sure of the size of the compressor, but the freezer room is 3 by 2 by 2m. Do you think the oil in this size compressor require changing?

The temperature would need to be held constant or else ice crystals form.