oil pressure differential switch shut down

[tarcau mihai]

Hello guys!
We have a problem with a rack with 4 compressors copenland semihermetics....during the night the system is shutted down by the oil pressure differential switch....when we went to check we found that the compressor which stop the system it was with low oil level...we add arround 600 ml and it was ok the level....after 4 days the system was stopped again by the same reason...our question is where is the oil?and if is on system why is not returning back?we check for leaks but is look that there are not any...have anyone any sugestion?
Regards Mihai

[taz24]

Hello guys!
We have a problem with a rack with 4 compressors copenland semihermetics....during the night the system is shutted down by the oil pressure differential switch....when we went to check we found that the compressor which stop the system it was with low oil level...we add arround 600 ml and it was ok the level....after 4 days the system was stopped again by the same reason...our question is where is the oil?and if is on system why is not returning back?we check for leaks but is look that there are not any...have anyone any sugestion?
Regards Mihai


If it is just one compressor that is tripping you need to check the oil management for that comp.
What regulates the level of oil in the comp?
Is it a float?
or is it a sensor and solenoid valve?

Checck the filters in the compressor and in the line to the compressor are clean.

Cheers taz.


.

[tarcau mihai]

tks Taz for your quick replay...in this system are 4 compressors but 2 of them are not working for a while....the capacity is enought with 50% wich we have cause is not too hot in this time here... both compressor are tripping but not on the same time....we check to see if is correct the settings and we check also the oil filters..everithing is look fine but the oil is go away from them to the system...there are 4 evaporatores and all of them are working fine....can remain the oil in one of themand if yes ,why?
Regards Mihai?

[chemi-cool]

If there is no oil leak, adding extra oil will not solve any problem,

Is there oil level float on compressors?
Did you check oil filter on that compressor?
Did you check oil pressure for oil pump function?
Are the evaporators above or below the rack?


Lokks to me that the problem is oil return to the compressor, have it checked.

[tarcau mihai]

Re: oil pressure differential switch shut down
<hr style="color: rgb(153, 153, 153);" size="1"> If there is no oil leak, adding extra oil will not solve any problem,

Is there oil level float on compressors?
Did you check oil filter on that compressor?
Did you check oil pressure for oil pump function?
Are the evaporators above or below the rack?


Lokks to me that the problem is oil return to the compressor, have it checked.



Chemi Cool , the compressors are without level oil float,oil filters are clean,oil pressure pump ok(with oil),oil pressure switch set at o.7 bar+ suction pressure,the evaporators are at same level with the rack...also we think that the oil is not returning ....
Which is the best way to flush the evaporators without opening the systems?
I had the same problem 4 yrs ago with a Grenco chiller on cruise ship...on that time the chiller stop for low oil level..we add like 100 liters of oil in oil separator but the level didn't rise on sight glass...all the oil remain in evaporator..later we found that the evaporator has leaks ....but here no leaks!....
Regards Mihai

[intense baz]

Does this compressor have a crankcase heater and if so is it working correctly?

[tarcau mihai]

Does this compressor have a crankcase heater and if so is it working correctly


don't have also crankase heater....

[tarcau mihai]

don't have any heater on carnkase!

[chemi-cool]

Oil return with refrigerant, there a few things to do'

Open the TEV to increase the refrigerant flow,
You can add 1\2% of R12, you can increase head pressure, you can add a 3\8 pipe from the lowest point of the evaporator to the entrance of the liquid accumulator.

Can you give more details like size of compressors, working temp. head pressure, etc.etc.

[Porkington]

Get the Pack working back to full capacity.

[andywill]

Check the oil return line from the oil seperator to see if it is cold or warm(Whilst Running). If it is warm then the float inside the seperator is ok. Does the oil return line have a sight glass you can check for oil flow. Does the oil seperator have float that you can access or is it sealed "ie no bolts"
I have replaced many oil floats in oil seperators due to floats falling off and needle valves sticking...You should NEVER have to add oil to a system that has been running ok for a long period of time unless you have added extra equipment, suffered a leak or done an oil change...

[tarcau mihai]

Oil return with refrigerant, there a few things to do'

Open the TEV to increase the refrigerant flow,
You can add 1\2% of R12, you can increase head pressure, you can add a 3\8 pipe from the lowest point of the evaporator to the entrance of the liquid accumulator.

Can you give more details like size of compressors, working temp. head pressure, etc.etc.
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ok it's look that i have a lot of quick feed back answers regard of my problem...this rack was installed two yrs ago and is 2nd hand from Germany...is working with 4 semihermetics compressors Copenland but i don't know exactly the capacity of each compressor(kw) i will check this Monday morning...the sequency controller is Wurm brand modell dcc-910 controlled by suction temperature sensor...the evaporators temp is -10 degrees C...the guy who's mantain this rack is a good friend of mine and from one month i start to work with him here home in comercial refrigeration business ...two compressors from four are not working(damaged) but with other 2 is enought for the system(controller require just one ,sometime two compressors to run 25-50%) but we are affraid that in summer time we will need more load(75-100%)...system is working with R22, head pressure 13-14 bars..system is without oil separator...i was thinking that the space where are installed the compressors is too cold during the night (8-10 degrees C)and this can be a reason why the oil is not returning to compressors....
Monday morning we will try flush each evap to see what is gonna happen,if the oil will return to compressor...is a good ideea to close the liquid valve by each evap ,heat the evap with a heat gun and then to reopen the liquid to flush the evap?????????
all the best Mihai

[Gary]

Whenever you have parallel compressors there must be some means of equalizing the oil levels, or the returning oil will go to whichever compressor is running and whichever compressor is not running will not get the oil.

Apparently this system does not have an oil distribution system (separator, reservoir, floats, etc.) to equalize the oil levels.

Are the crankcases joined (pipes running between compressor crankcases to equalize the oil levels)?

[tarcau mihai]

Whenever you have parallel compressors there must be some means of equalizing the oil levels, or the returning oil will go to whichever compressor is running and whichever compressor is not running will not get the oil.

Apparently this system does not have an oil distribution system (separator, reservoir, floats, etc.) to equalize the oil levels.

Are the crankcases joined (pipes running between compressor crankcases to equalize the oil levels)?
<!-- / message --> <!-- sig --> __________________


I agree with you Garry ,but this rack don't have separators,reservoirs,floats,joints between compressors to equalise the oil level.....what do you suggest me to find where is the oil ?
all the best Mihai

[Andy]

Hi Tarcau:)

If you don't have any separator or floats you will need a means to balance the oil levels in the crankcase (oil balance lines between the compressors to balance the oil level).

To return the oil, shut the valve on the liquid receiver, pump the system down, let some heat build up in the rooms with the fans (a few degrees c higherv than normal).

Open the liquid valve and the compressors wil have decent load to return the oil themselves.

If this is a recuring problem, add a solinide on the liquidline, shut once a night with a time clock, to harvest the oil.

Kind Regards Andy :)

[tarcau mihai]

Thks Andy for your suggestion,i will do this tomorrow morning..
Regards Mihai

[Gary]

Oil return is the least of your problems. If there is no equalization, returning the oil all at once could overfill/slug one or more compressors and destroy them.

[Gary]

It seems highly unlikely that any rack manufacturer would design a rack without oil equalization. Possibly the equalization system has been removed?

Who manufactured the rack? Does the rack have a model number?

[taz24]

I think you need to go back to the begining.
How old is the pack (rack)?
Has it worked ok before now?

If it is an old pack, what has changed for it not to work?

If it is a new pack, who built the pack?

taz.

.

[tarcau mihai]

2476
Hello guys...as you can see from picture that is the rack...is very old and has worked before in Germany..2 yrs ago was installed here and running with not any problem...just from one month it start to look that don't want to work anymore..maybe is tired after 20 yrs of work...

cheers Mihai

[Porkington]

Never again will i slag off Radfords!!!! :D

[Gary]

Does the condenser have fan controls? If so, what are the settings? Possibly the head pressure is dropping too low at night.

[tarcau mihai]

<!-- / icon and title --> <!-- message --> Never again will i slag off Radfords!!!! :D


What do you mean?

[tarcau mihai]

yep Gary ,the fan condenser have 2 speeds .Low speed when the compressor start and high speed when the system reach 16 bars...
Regards Mihai

[Gary]

yep Gary ,the fan condenser have 2 speeds .Low speed when the compressor start and high speed when the system reach 16 bars...
Regards Mihai

At what pressure do they switch back to low speed?

[tarcau mihai]

Gary
I realy don't know this,but i guess around 14 bars ...you think that the condensation pressure it could be a reason which the oil is leaving the compressors?2 strong winter the system has been worked like that....i know that normaly for compressor installed in a lower temp those should have oil heaters for crankase ...
Regards Mihai

[Gary]

If it gets very cold at night, even dropping to low speed may allow the head pressure to get too low to push the refrigerant through the coils and flush out the oil. If that is the case, then you may need to disconnect the low speed, switching between high speed and off.

[taz24]

<!-- / icon and title --> <!-- message -->Never again will i slag off Radfords!!!! :D


What do you mean?

Radfords were a pack manufacturer.
He is comparing your pack to one of those ;)





2476
Hello guys...as you can see from picture that is the rack...is very old and has worked before in Germany..2 yrs ago was installed here and running with not any problem...just from one month it start to look that don't want to work anymore..maybe is tired after 20 yrs of work...

cheers Mihai


Looking at the comps they are different sizes, which allows for the different duty levels on the pack at different load levels.
What controls the compressor loading and unloading?

Cheers taz.

[tarcau mihai]

the controller is a Wurm brand ,model dcc-910 and a temp transmiter conected on common suction side..
Mihai

[Andy]

Hello tarcau,

This pack looks like a Linde Pack.

The oil is balanced by needle regulating valves fitted to the bottom of the suction header. These block with dirt over a period of time.

Please check for these valves and adjust them open to clear the blockage.

Also this design is very dependant on refrigerant charge, please check that the plant has enough gas.

Maybe a good idea to check superheat at the evaporator outlets. The dirt in the needle valves on the suction header may also be in the expansion valves.

Hope this helps.

Kind Regards Andy

[kyaw htoo]

Hello guys!
We have a problem with a rack with 4 compressors copenland semihermetics....during the night the system is shutted down by the oil pressure differential switch....when we went to check we found that the compressor which stop the system it was with low oil level...we add arround 600 ml and it was ok the level....after 4 days the system was stopped again by the same reason...our question is where is the oil?and if is on system why is not returning back?we check for leaks but is look that there are not any...have anyone any sugestion?
Regards Mihai
My sugestion is to check the oil return line,especially the solenoid v/v and strainer.And check the oil level of the other 3 .

[moyoyo]

Hello guys!
We have a problem with a rack with 4 compressors copenland semihermetics....during the night the system is shutted down by the oil pressure differential switch....when we went to check we found that the compressor which stop the system it was with low oil level...we add arround 600 ml and it was ok the level....after 4 days the system was stopped again by the same reason...our question is where is the oil?and if is on system why is not returning back?we check for leaks but is look that there are not any...have anyone any sugestion?
Regards Mihai
Hi member.I am also a machanic here in Africa and i want to be your friend and get to know more about the A/C.
Would you welcome me into your world?
Peace.
Awal.

[tarcau mihai]

you're very well come here on this forum !
you can share with us you're knowladge in hvac and refrigeration...
Well come to the forum;)

[lanzy]

May I ask which supplier provides this oil pressure differencial switch?

[tarcau mihai]

i guess that is danfoss,but i'm not sure...i didn't pass to our clinent from 2 weeks since we add some oil to the compressor...
Mihai

[abet_meneses]

Mihai,

if that is a linde comp rack and if the gas is adequate, checking the superheat of various evaporators according to standard may eliminate that oil problem.

regards

[rbsguzman]

Hi My name is Robert and me and my guys deal with this kind of problem at least 10 times a week in different stores.
First you have to check what type of regulation you have there.
Hi pressure oil regulation= A temprite oil separator and oil reservoir built in one piece.
Low pressure oil regulation= An AC&R (Henry) oil separator and a separate oil reservoir
Most of the times on hi pressure oil regulation you will find a pressure regulating valve which tend to fail
not keeping a 30 psig differential between the suction and the RV outlet ,also if you severe humidity in the rack that surely will clogge the OF-303(oil filter) and the oil will be forced to go to the evaporators and takes a lon time to come back
The only way to fix that problem is to replace the liquid line drier at least 3 times (RCW -48 sporlan) cause oil filters will absorb 5 times moisture faster than the RCW-48 liquid line drier. On low pressure oil regulation make sure the float in the oil separator is completely clean. If there is any particles such as grinding wax or metal fragments from compressors then you have to used a suction filter screening to catch any fragments left when oil comes from any systems being on defrost, also make sure that the Oil check valve (OCV) is maintaining 20 PSIG over the crakcase pressure.You mentioned 4 compressors and each one has an oil regulator, and each compressor oil level is controlled individually so defective oil regulators must not be the problem because is happening in the entire rack and if you have a Temprite oil separator make sure that the filter is clean

[Andy]

Hi My name is Robert and me and my guys deal with this kind of problem at least 10 times a week in different stores.
First you have to check what type of regulation you have there.
Hi pressure oil regulation= A temprite oil separator and oil reservoir built in one piece.
Low pressure oil regulation= An AC&R (Henry) oil separator and a separate oil reservoir
Most of the times on hi pressure oil regulation you will find a pressure regulating valve which tend to fail
not keeping a 30 psig differential between the suction and the RV outlet ,also if you severe humidity in the rack that surely will clogge the OF-303(oil filter) and the oil will be forced to go to the evaporators and takes a lon time to come back
The only way to fix that problem is to replace the liquid line drier at least 3 times (RCW -48 sporlan) cause oil filters will absorb 5 times moisture faster than the RCW-48 liquid line drier. On low pressure oil regulation make sure the float in the oil separator is completely clean. If there is any particles such as grinding wax or metal fragments from compressors then you have to used a suction filter screening to catch any fragments left when oil comes from any systems being on defrost, also make sure that the Oil check valve (OCV) is maintaining 20 PSIG over the crakcase pressure.You mentioned 4 compressors and each one has an oil regulator, and each compressor oil level is controlled individually so defective oil regulators must not be the problem because is happening in the entire rack and if you have a Temprite oil separator make sure that the filter is clean

Hello rbsguzman:)

Sorry to sink your boat.

These packs were made for Linde Refrigeration, no oil separator, no floats and usually no oil balance lines, just an oil return reg valve hidden on the suction header, which will block up if the dirt builds up in it.

Check the gas and if thats ok open up the valves, flush them then return them to the original setting.

Kind Regards Andy:)

[dogma]

pull out the strainer at the oil pressure switch and give the spring a little pull. same prob the other day and that fixed it.

[tarcau mihai]

Hy guys ..thks for your replay,but since i add last time some oil the costumer didn't call us ,but i feel that soon he will do it..Andy i will check that hidden reg valve ,you're right can be this one reason....
Regards Mihai

[round_the_rack]

Hy guys ..thks for your replay,but since i add last time some oil the costumer didn't call us ,but i feel that soon he will do it..Andy i will check that hidden reg valve ,you're right can be this one reason....
Regards Mihai
Mihail,
Please do report back when you return to the customer site. I'm curious as to what you find. I encountered a similar problem a couple months ago with a low-temp rack that had been neglected for months (years actually). The problem turned out to multi-faceted. The oil filter for the rack was clogged, 2 of 5 oil level controls were bad, all 5 internal oil screens were clogged, and one oil pump was shot.:confused:

After dedicating 2 days to diagnosis and repair, the rack is now purring along nicely. I wonder at times what the previous fridgie did with his days.:D

[moideen]

Hy guys ..thks for your replay,but since i add last time some oil the costumer didn't call us ,but i feel that soon he will do it..Andy i will check that hidden reg valve ,you're right can be this one reason....
Regards Mihai
hi mihai,

Did you check andes suggestions. do fast. I am waiting for your last result?
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Regards
moideen
:)

[dogma]

Thats why we should all use Dry Nitrogen when braizing and replace the oil after the inital 12-24hrs of operation.


Does anyone do an oil change on a new install?



_Dogma_

[750 Valve]

None of the majors do it here, in this age of accountant run companies it is just an additional expense (especially given the higher cost of POE oils). On a new installation I am more a fan of testing the oil before changing, if its good then there is no reason to waste the money, if however it is acidic, moisture laiden or has a large amaount of metal in it then yes by all means change it before leaving the site.

On all refurbs we change oil until its clean.

[dogma]

I don't see it as an aditional "expense" when you are certain the "new" system is clean and any swarf from the manufacture of the compressor is removed.

It's an advertising investment when your system out lasts the competitions.

no??