Bitzer oil problem

[HARRY 7]

I have a heat pump water chiller with two bitzer screw
CSH8561-125Y-40D.The one compressor shows alarm with loss of oil.I cannot see oil in sight glass.Where do you beleive that the oil have gone?R407C in the system.

[Gingerair]

Hi Harry
You'll have to give more info, but if the loss occurs in heating possibly the condenser..

[NoNickName]

Have you tried looking around, above or below? If no oil is on the walls, ceiling or floor, then it must be in the circuit.

[HARRY 7]

Hello guys:). There is no oil outside the system.
The chiller is working in cooling.
LP= 4 bar
HP= 16 bar

[NoNickName]

Is there a liquid receiver? How big it is?

[HARRY 7]

Hi nonickname.There is only a suction acumulator.

[NoNickName]

Hi nonickname.There is only a suction acumulator.

Quite normal in a heat pump, but it should be excluded in cooling mode. Anyway, the oil is inside of it.

[HARRY 7]

The system stops from oil alarm.
What should i do?Fill with oil and monitor the system?

[NoNickName]

No, don't add any oil. The oil is in the system. You just need to drain it out the accumulator.

[charlie n]

If he drains the accmulator, it may fill again. You need to find out why the accumulator filled, or you need to add an oul return tube from the bottom of the accumulator to the suction pipe near the comnpressor if thereisn't a proper oil return design now.

[HARRY 7]

Hello guys.Thanks for replies.
There is a return line in suction accumulator.

[HARRY 7]

Could that problem appeared if the system is overcharged?

[NoNickName]

I think that this problem is more likely to happen in a system with low suction superheat.

[HARRY 7]

Maybe you are right nonickname:).
But what is the solution??I cannot drain the accumulator.

[NoNickName]

Warm up the accumulator and start the compressor, crossing your fingers that it doesn't seize. Eventually some oil will start returning.

[HARRY 7]

I have to bypass the oil floter control.How much time should i do that??

[NoNickName]

Least possible.
Listen up: you are going to trash the compressor, you know that, don't you?

[HARRY 7]

Yes nonickname.Any other option??

[NoNickName]

Drain the oil.

[Andy]

Yes nonickname.Any other option??

Hello Harry,

add enough oil to bring you to the minimum operating level.
Run the plant on either cooling or heating, the cycle that you have no oil problems in.
Watch the oil level until it reaches the highest running level that you can see.
Stop the plant, drain the oil.
Start the plant run allow the oil level to rise again. Repeat until you take out the oil you put in.

If the problem is in heating limit the amount of heating time and add an oil harvest or a perriod of cooling to bring back the oil.
Best check what way the condenser is circuited as an evaporator during heating, this may be a problem, or as nonickname state you may need to fit the suction accumulator on the evaporator is of the four way reversing valve.

Kind Regards Andy D

[HARRY 7]

Hi Andy.Thanks for reply.
I will add oil and check the operation.Do you know where i can find oil CPI SOLEST 170??

[Eeram]

If there is a drain line on the suction accumulator, install a 3/8" solenoid valve in the line and bring it back to the suction before the compressor.

Let the solenoid valve only be energised when the compressor is running.

If this does not help, install an oil seperator in the discharge line with the oil return line before the compressor suction fitting. Install a solenoid valve in the oil return line.

Install an unequal repeating timer to operate the solenoid valve. 3 seconds on, 10 - 15 seconds off. This circuit must also be in operation only when the compressor is running. Had the same problem and got this information from Bitzer South Africa.

Another alternative is to raise your condensing temperature by about 10 deg. C, to try to get the oil back, even through the suction accumulator. This is only a temporarily solution, as you want to keep your condensing temperature to design criteria.

Try your local Bitzer office/agent for oil or go to CPI Engineering.

Please remember! If there are no oil leaks, the oil is in the system. Do not add oil that can overfill a system. Monitor your oil levels for the first few days and remove excess oil.

Good Luck!

[HARRY 7]

Hi Eeram:).As i said before there is a line that connects the bottom of the accumulator with suction before compressor but without a solenoid valve.There is another one compressor in circuit with no problem.The compressor stops from oil level alarm.So i have to put oil in system to start.

[RANGER1]

Not sure if its same set up , but had similar problem & found main oil line to compressor solonoid suspect .
When cycled off oil migated into compressor & suction line

[Gingerair]

If you fit a solenoid in the oil return line from the accumulator also fit a sight glass after it so that oil flow, or lack of it can be observed..

[Eeram]

Are the two compressors controlled by one controller? Are they running as lead & lag? What capacity control do they use?

[HARRY 7]

They are controlled by one controller.They work both together or one at a time.Their capacity is minimum 50% and above.

[lma]

How many expansion valves / liquid line solenoid valves do you have in your system ?

[HARRY 7]

I have one expansion valve for cooling,two for heating.No liquid line solenoid valve

[lma]

suspecting some sort of restriction on or near the expansion valve... does the oil return when the system is off ? or is it constantly low ?

[HARRY 7]

Hi Ima.No it doesn't return.

[lma]

Nonickname gets it right when he says the oil is in the system.(if it was there originally and there is no visible trace of it coming out). question is where ?.... was leaning to the idea of an overcharged system...the expansion valve closes sharply, oil migrates from compressor to condenser as the suction side moves to very low pressure.. but has to be ruled out as normally if that was the case.. the oil would return back to the compressor in the off cycle..

[lma]

unless the expansion valve itself, depending on the cycle you are using, was blocked or restricted

[Magoo]

I am more inclined the problem is at the oil separator, either the check vav after oil separator is allowing liquid to develop in separator during off cycle or else the separator heater is not keeping the oil hot, the oil will disappear into system real quick with either problem.

[HARRY 7]

There is no oil separator in system maggoo.
That bitzer model has an internal one.

[NoNickName]

Yes, there is a separator, which incidentally is built in. Magoo advices are good.

[Eeram]

The compressor with the oil problem, does it run lower on capacity than the other one? Still needs to know how the controller operates.

Are they both running, then one compressor cycles off and the one with the oil problem runs and goes down to 50%?

What is the oil pressure and what is the discharge/condensing pressure?

Can you tell the operating hours of these compressors?

[HARRY 7]

That is what i meant nonickname it has a buid in separator.
Magoo i will check what you said.Eeram the compressors run together ,one stops the other continues until it catches the set point.Then when the temp rises the other begins to work.The controller distributes the time and starts exactly the same.The minimum working capacity of both compressors is 50%.I do not have the working hours of the compressors.The working pressures of machine are:
LP:60PSI
HP:230PSI
R407C

[Gingerair]

Just to clarify Harry,
Is it a common discharge & suction lines, inc one common suction accumulator, for both compressors ??

[HARRY 7]

Hi Gingerair!Two different circuits.;)

[Gingerair]

Ok, so you've got 2 completely independent circuit's, 2 x condensers, 2 evaps or 1 x split evap ?

Is the oil in the faulty system definitely the correct type ?

Is the oil heater working ?

Does the oil loss occur in both heating & cooling ?

If you're going to run the compressor that looses oil, make sure the oil level is above the min level before starting. Do not do this too many times as any excess oil will have to be drained.
Also do not either start or allow a compressor with excess oil in to run..
As i said, if you can't get the 'missing' oil to return, don't keep trying to run the compressor.
You're then going to have to drain it from wherever it is in the system, even if this means a decant..

:)

[HARRY 7]

2 independent circuits,1 evaporator split to two circuits,two condensers.Oil heater is working.Oil loss occured in cooling.Oil is the correct type.The above pressures are in cooling.The system stops from oil level control.

[Gingerair]

Does the oil loss also occur in heating ?

Is the oil loss a new problem or has it always occurred ?

How fast is the oil loss when the comp runs ?

Your going to have to start taking temperatures & pressures to check that the plant is operating correctly..

[HARRY 7]

It is the first time the alarm occured.I cannot see oil in the oil sight glass,even if the machine is stopped.The pressures of the system are the above for about 1 minute of work until it stoppes from alarm.

[lma]

Are the pressures for both machines or only the machine which has the oil problem ?

[lma]

Sorry... Have you checked the pressure indicated is coming from the circuit having the oil problem ?

[HARRY 7]

The pressures are from the faulty system.

[Peter_1]

TEV's or EEV's as expansion valves?
Brand of machine?

[Peter_1]

Is the oil alarm coming from the special screw-Kriwan?

[HARRY 7]

Hi peter.There is an oil level mechanism in the side of the compressor near the sight glass.

[Peter_1]

The Bitzer screws I've seen had an oil pressure control but not an oil level.

[Gingerair]

I think it's a oil level switch.

Harry, have you checked the superheat in cooling, both at the expansion valve & compressor suction ??
Are you familiar with how to do this ??

[HARRY 7]

Here you can see in bottom the oil level switch.
Yes gingerair, i know how to do this,but the compressor works only for one minute,then it stops.

[lma]

Hello Harry,

add enough oil to bring you to the minimum operating level.
Run the plant on either cooling or heating, the cycle that you have no oil problems in.
Watch the oil level until it reaches the highest running level that you can see.
Stop the plant, drain the oil.
Start the plant run allow the oil level to rise again. Repeat until you take out the oil you put in.


Kind Regards Andy D


Makes the most sense to me.... you need to obtain more information in the safest possible way and that means... add the oil and run the system and see the behaviour.... does the oil run out again ? does it trip on the oil pressure switch ?if it does .. at what temperature does it happen ? ...

[oldesky]

I think Andy might be on the money. If the oil comes back on cooling you may need to check condenser design for cooling and or put a timer set to bring on the cooling mode occasionaly to return the oil.

[HARRY 7]

Hello to everybody.I went to the chiller today.I put oil in the system about 20lt.[The compressor takes 22lt].
The oil level switch was reset,but i cannot see the oil level in the sight glass.I was watching it during the filling.What could had happened?

I started the system for about twenty minutes,still no level in sight glass,and have the
below measurements in heating:

HP=260PSI
LP=42,4PSI
SUPERHEAT AT SUCTION VANE=9C
SUBCOOLING AT FILTER DRIER=8.7C
ENTERING WATER=37.7C
LEAVING WATER=39.7C
DISCHARGE TEMP=80C
OUTDOOR TEMP=10C

I checked the oil return from the accumulator.No restriction or oil there.

[JFK]

Hi Harry,

Just a concern have your problem solved?

[Peter_1]

I'm interested too Harry

[HARRY 7]

Hello guys!Sorry for not answering!I put oil in compressor but the alarm was still engaged.So i replaced the oil level switch and the problem solved!Thanks everybody for the help!