Oil Pressure Cutout

[ironmen]

hey guys
I know we have talk about this before on a previous forum, just got a couple of questions and maybe someone can help;
1. Lack of oil in your compressor when starting does it cause the oil to foam as if there is liquid in your compressor?
2. example if there is liquid washing up oil in your compressor and cause it to go out on safety switch, after couple of hours all the oil should be back in your compressor with the system off. if not there is still very low oil and as soon as you start the system after the time delay it cut out again. it's not intermitent, it goes out straight away on oil pressure after reset. my understanding is there is no oil return, either you are loosing oil somewhere or the separator is not functioning properly. That's why during start up you see oil foaming in your system due to lack of oil, correct me if im wrong

[Grizzly]

i.

Personally I would not associate oil foaming with low oil pressure but rather the presence of refrigerant.
Have you tried checking your crankcase heater to see if it is working?
Does the lower half of the comp feel warm?
Incidentally you don't tell us much about the compressor or your system, so I am just guessing.
I don't know whether it is related?

But on larger recip you can get the situation where whilst it is running at low load or unloaded for long periods.
The oil is carried over but there is not enough swept volume (Read gas flow)within the system to return the oil.
So you could add a little oil to give a working level and "Force the comp to load up.
Leave it running for a suitable period not just 5 Min's and hopefully if that is an issue your oil should return.
Whatever the case your oil will not return of it's own accord whilst the system is not running.
At least I have never heard of a system doing that!
To be able to assist more "We" need some more info please.
How old is the equipment and if old when last serviced would be a start.
Cheers Grizzly

[yorkman_gr]

oil foaming = refrigerant in your oil
So u have to check your superheat , you have to check the carter heater if working, check the return from your oil separator to the compressor, some times inside the oil separator remain to much ***** which is coming back to the compressor through the return line causing the oil in the carter to foam, once your compressor is in full load oil should be return back to the carter.
Also foaming can caused by broken suction or discharge valves, or leaking internal relief valve
Just i give u some starting points to check

[yorkman_gr]

PS: and off course like Grizzly said we need some more informations about the installation and the type of the compressor, because some times answering to a general questions is not at your benefit, because the guys in here based the answer by assuming or supposing
.
Yorman

[ironmen]

Its a copeland semihermetic compressor with no unloader,installed on a 110kw split ductted air conditioning unit with two stage.the one thats got the fault ,compressor just been replace recently due to a burnt out.its a 12 years system.

[Grizzly]

Check your system operating pressures and temps as suggested by yorkman_gr.
You may just have superheat / expansion valve issues. It is sounding more serious the more you tell us.
How often have you changed the oil and filters since the burn out?
Grizzly

[yorkman_gr]

proceed as Grizzly said also check your airflow , insufficient airflow can cause liquid coming back at the compressor, also very important you have to check your oil for acid, you will burn the new compressor if the oil remain acid, and liquid filters

Yorkman

[yorkman_gr]

PS: Once we talking about air one more possibility is that to much oil remain at your evaporator coil, that is also a cause of liquid flooding back at the compressor, just try to create heat load across your coil to increase the velocity and return some oil back to the compressor

[ironmen]

I recently clean the coil it was fully clogged.someone before replaced that compresspr without asking why that compressor fail and i dont think if a quality repair been done on that systen in the past.

[yorkman_gr]

ok so i guess is always the possibility that this compressor can have higher capacity then the previous one, just check what me a grizzly advise before, check your superheat and please check your oil for acid, and if everything seem to be ok then just measured your evaporation temperature and your air inlet, if i remember well, the difference between this two should not go more then 15 degrees, because higher difference means lower suction pressure=oil emigrate easier from the compressor=small superheat=liquid coming at the compressor=foaming at the oil=the humidity is freezing up at your coil= low suction pressure

Yorkman

[yorkman_gr]

ironmen sorry for all this PS man but i am getting old.
one more thing i just realize. You said is semihermertic copeland with out capacity valve, how do they arrange the capacity of the compressor if only one coil is working? i assume that the capacity of the compressor matching the demand of two coils so how they match the demand from one evaporator coil with the same compressor and with out any kind of capacity regulation?

[ironmen]

Hi yorkman,each compressor got its own evaporator.

[yorkman_gr]

oh ok ironman i am sorry i understand wrong but please let us know how you doing with your problem

[serviceman]

solenoid valve operating correctly? when the compressor does pumpdown?

[yorkman_gr]

hi serviceman did you got on your e-mail the manual that i have send for the screw chillers solid state starter?

[serviceman]

hi yorkman thanks ¡

[yorkman_gr]

cool man any time hope it will helps