Screw compressor MYCOM, problems with the refrigeration system

[andrey7474]

Hi there.
I’ve got some problems with my refrigeration system. I will try to describe the situation.
Equipment: Screw compressor MYCOM FM160 L
We have replaced the compressor with a new one because the old compressor has worked for 13 years.
Before replacing the compressor we had a problem with low superheat. We thought the problem was in the evaporator because of the blend of oil and refrigerant. We’ve changed the oil (about 300 Litres) and filled R22 (about 350 kg). I must notice that the amount of oil and refrigerant we added based on documentation. Practically, we filled the system up completely as a new one. Of course, we evacuated the system beforehand. However, we got the same problem after starting the compressor. Superheat is low, the suction pressure is low and, at the same time, the discharge temperature is getting too high after an hour of working.
I have a few things to think about: 1. We filled too much oil in the system. 2. There is a lack of refrigerant. 3.Evaporator is dirty and because of that refrigerant evaporates much worse.
I was adding R22 to the system but its level in the evaporator decreased after a few hours of working again. I’ve checked oil filters. It is okay. The oil is clean.
Tomorrow, I’m going to pump down a small amount of oil from the system.
I would appreciate any thoughts and opinions about my situation.
Best regards.
Andrey7474

[RANGER1]

Andrey,
I think more information required.
What type of evaporators & type of level or tx valve control
running conditions suction, discharge, oil pressures & temperatures
What type of oil cooling
what type of oil return from evaporator/s

Low suction pressure, low superheat, no heat transfer

High discharge temperature could be high oil temperature, or not enough oil injected into rotors.

300 litres of oil for such a small compressor does not seem right.
100 to 150 litres sounds more realistic

See what you come up with

[andrey7474]

Thanks for replaying, RANGER1.

Please find below a part of the manual instruction with a description of the process.

Relatively of the amount of oil that we filled in the system: I must admit we filled a bit more because I can see a full sight glass because of that I'm going to pump down the oil tomorrow
to be able to see the oil level in the sight glass.

Accordingly the discharge temperature- yes, the oil temperature is high so discharge temperature is getting high respectively.
Level in the r22 receiver is low.

PART OF MANUAL INSTRUCTION

In the compressor is the gas compressed from 0,7 bar to app. 15 bar. At the discharge pipe is oil separator installed. Here the oil is separated from the gas and drained back to the compressor oil reservoir. Extra oil separation is done in 2 fine mist filters installed from the cover at the oil reservoir. The pressure drop across the filters is monitored by the differential pressure between two transmitters. The oil separated from the gas in these filters, is drained back to the compressor through the solenoid valve. The gas is condensed in the R22 condenser and flows to the receiver. The liquid R22 to R22 evaporator is sub-cooled in the heat exchanger. The subcooler also acts as an oil return system from the R22 evaporator. Through valve is a small amount of R22 passing the heat exchanger, thus boiling out the oil contained in the R22. The oil flow can see in sight glass before entering the refrigeration compressor suction pipe.

Oil pressure for compressor lubrication is obtained through the difference in pressure between discharge pressure oil cooler and compressor suction pressure. The oil filter is installed between the oil cooler and the compressor. In case of too high a pressure drop across the filter must the filter element be renewed.

The oil cooler is using R22 as cooling media. By gravity is the liquid from the R22 condenser flowing to the oil cooler. The piping of the refrigeration unit is manufactured in such a way that the condensed R22 always is flowing to the oil cooler as first priority. Excess liquid is flowing to the receiver. In the oil cooler is the R22 evaporated and the gas is returned to the condenser.

The oil level in the compressor oil receiver must be checked regularly, and refilling must be done when necessary. Normal level is between ¾ in upper sight glass and 1/4 in the lower sight glass. A level switch is stopping the compressor in case of low level
R22 evaporator (CO2 condenser)
The refrigerant level in the R22 evaporator (CO2 condenser) is controlled by level control valve. The valve opening is controlled by the R22 level in the evaporator monitored by level transmitter. The valve has its own PID setup screen.


R22 condenser and receiver
In the R22 condenser is the R22 liquefied using cooling water as cooling media. The condenser is a shell and tube exchanger type. The condensed R22 is flowing to the receiver. From the receiver the liquid R22 is led back to the CO2 condenser.
The receiver is accumulating the condensed R22. The level must be visible from sight glass. From the receiver the liquid R22 is led back to the evaporator.

[RANGER1]

Andrey,
Thanks for description, understand a fair bit more now.

So to go through it

You checked enough refrigerant in liquid receiver sight glass & level is low.
You mention high oil temperature, so important level correct.

You need to add more refrigerant, as liquid receiver has to have level for thermosyphon oil cooler as is the priority before it can send refrigerant to evaporator, which will also be low.

Instruction suggest keep adding oil if level low, if you do this problems will occur, it must be balances perfectly.
Whatever compressor passes out of oil separator must be returned in oil return.
I recommend change coalesces in oil separator as high priority if you have not done already.

Good luck, hopefully you had a good pressure test & leak check before adding new refrigerant & filter driers.

[andrey7474]

Thanks a lot, RANGER1.

Only one thing I'd like you to make clear for me. You write "I recommend change coalesces in oil separator as high priority if you have not done already." Do you mean that I will check or change two filters in the oil separator?

Andrey

[RANGER1]

[QUOTE=andrey7474;330256]Thanks a lot, RANGER1.

Only one thing I'd like you to make clear for me. You write "I recommend change coalesces in oil separator as high priority if you have not done already." Do you mean that I will check or change two filters in the oil separator?

Andrey,
I suggest install new coalesces in oil separator, unless you know history.
Probably change every 2 years for reliability.

[andrey7474]

Okay. Got it.

Thanks for helping. I really appreciate your help.

Andrey.

[andrey7474]

Hello.

I have to continue this topic because the problem is still available.

Today, I've pump down a small amount of oil from the oil receiver to see oil level in the sight glass. Also, I've filled 136kg of R22 up to the system. As a result of all my action- my refrigeration unit has been working for 8 hours. I had low suction pressure, low level in R22 receiver, not high superheat and at the and I got high oil temperature on the suction line to the compressor.

what should I think about? Where is a big amount of R22? I have no idea. I didn't find any visible leakage or big/small oil spot. I evacuated the system before filling it.

I've already added about 500 kg of R22. I understood that it is a big amount of refrigerant but....
maybe the problem is in the oil?

I would appreciate any help.

Best regards.

Andrey.

[RANGER1]

Hello.

I have to continue this topic because the problem is still available.

Today, I've pump down a small amount of oil from the oil receiver to see oil level in the sight glass. Also, I've filled 136kg of R22 up to the system. As a result of all my action- my refrigeration unit has been working for 8 hours. I had low suction pressure, low level in R22 receiver, not high superheat and at the and I got high oil temperature on the suction line to the compressor.

what should I think about? Where is a big amount of R22? I have no idea. I didn't find any visible leakage or big/small oil spot. I evacuated the system before filling it.

I've already added about 500 kg of R22. I understood that it is a big amount of refrigerant but....
maybe the problem is in the oil?

I would appreciate any help.

Best regards.

Andrey.

Andrey,
With more refrigerant is system improving?
You mention high oil temperature at suction of compressor, I don't understand what that means, must be translation issue.

Can you give us all pressure & temperature readings like suction discharge & oil pressure/temperatures.

500 kg is a lot of R22 & you are questioning yourself as to where it is.
If you can see level in liquid receiver, then fair chance it has level, but I think you say level low, is that correct?
Evaporator has modulating liquid level control valve, can you see level, ice formation, liquid valve modulating, or is it just fully open.
Sometimes ice formation on vessels & columns exposed can indicate levels(unless lots of oil).

Do not expect superheat on a flooded evaporator system.

Without knowing how big vessels are holding refrigerant, cannot guess how much you need, assuming no big leaks.
If adding more refrigerant is helping system run better, maybe more is required if level in liquid receiver & evaporator low & you have looked hard to be confident.

More oil in system only takes up room where refrigerant should be.
Upsets heat transfer, whether in evaporator or oil cooler.
Process of elimination.

[andrey7474]

hello, RANGER1.

First thing first, I have found the old documentation where it was said R22 in the system 800kg.
Evaporator has R22 volume 800 litres
R22 receiver- 220 litres
Condenser R22 -225 litres
Oil separator- oil volume-320 litres
oil cooler(shell tube heat exchanger) -40 litres
So now you can imagine the R22 volume in all system

I can see the level in R22 receiver but I know that it's too low.
R22 Level in evaporator almost 0%. The regulating valve fully opened.
Suction pressure 0.1 bar
oil temperature 63-67°C
Discharge pressure 10.5 bar
Discharge temperature 83-85°C

Looking at these parameters and getting new information about the volume of R22(800kg) I think I should add more refrigerant to the system.

What is your opinion?

Andrey.

[RANGER1]

hello, RANGER1.

First thing first, I have found the old documentation where it was said R22 in the system 800kg.
Evaporator has R22 volume 800 litres
R22 receiver- 220 litres
Condenser R22 -225 litres
Oil separator- oil volume-320 litres
oil cooler(shell tube heat exchanger) -40 litres
So now you can imagine the R22 volume in all system

I can see the level in R22 receiver but I know that it's too low.
R22 Level in evaporator almost 0%. The regulating valve fully opened.
Suction pressure 0.1 bar
oil temperature 63-67°C
Discharge pressure 10.5 bar
Discharge temperature 83-85°C

Looking at these parameters and getting new information about the volume of R22(800kg) I think I should add more refrigerant to the system.

What is your opinion?

Andrey.

Add more refrigerant, without a doubt.

[andrey7474]

Hi there.

I'm still having a problem with the refrigeration system.

I have added about 300 kg of R22 and started the plant. R22 level increased but still, a bit low in all vessels. The refrigeration unit has worked quite stable for 8 hours.

I must say that I had a low superheat and low suction pressure but the oil temperature, discharge temperature, and discharge pressure were okay.

After 8 hours of working R22 level in the evaporator was getting decreased. level control valve was fully opened, but the R22 level was low.

Can I have a problem with heat transfer in the evaporator? Low superheat and low suction pressure is indicator of that, but at the same time I don't have R22 in the evaporator. really, I can't understand it.

Now, I'm pressurizing the evaporator and R22 condenser to make a leakage test.

I hope it will be okay... but where is the problem then?

After the leak test.

the evaporator is okay.

We have two R22 condensers (Shell tube heat exchangers). One of them is okay. The second one has a leakage in a tube. R22 gets into water volume. Tomorrow we will try to weld that tube.

[RANGER1]

Andrey,
Have you checked relief valves for leakage as well?
Put something over outlet of valves like condom or surgical type rubber glove.

Normally reliefs are changed or retested every 5 years

High pressure switch set 10-15% below setting of valve.

Seems still short of refrigerant, but you are getting close.

Only you can repair leaks, as we can't see from here, this should be absolute highest priority & concentration on this is necessary or problems will never go away otherwise.
Have to repair condenser & be careful as not to allow water into refrigeration system.
Do you know what happened to original R22 charge, did it leak out somewhere?

[andrey7474]

Andrey,
Have you checked relief valves for leakage as well?
Put something over outlet of valves like condom or surgical type rubber glove.

Normally reliefs are changed or retested every 5 years

High pressure switch set 10-15% below setting of valve.

Seems still short of refrigerant, but you are getting close.

Only you can repair leaks, as we can't see from here, this should be absolute highest priority & concentration on this is necessary or problems will never go away otherwise.
Have to repair condenser & be careful as not to allow water into refrigeration system.
Do you know what happened to original R22 charge, did it leak out somewhere?

Hello, RANGER1.

Of course, I've checked all relief valves with a leak tester. Some of them had leakages through thread connections. Also, a few leakages were found on flanges connections. They have been tightened properly.

the high-pressure switch is set correctly.
Waiting for a welder to fix the condenser and after it, I will have to add R22 again. This overhaul cost a lot of money.

P.S.
R22 condenser on the photo. One of the tubes has a leakage.

[RANGER1]

Hello, RANGER1.

Of course, I've checked all relief valves with a leak tester. Some of them had leakages through thread connections. Also, a few leakages were found on flanges connections. They have been tightened properly.

the high-pressure switch is set correctly.
Waiting for a welder to fix the condenser and after it, I will have to add R22 again. This overhaul cost a lot of money.

If plant 12 years old should never have gone in on R22, against world trends.
Should have been ammonia, easy to find leaks

[andrey7474]

If plant 12 years old should never have gone in on R22, against world trends.
Should have been ammonia, easy to find leaks

In 2008, I only started working at this plant. I even didn't have any idea about R22 and ammonia Moreover, commissioning was made by a company that supplied to us this plant. Anyway, we hadn't had such kinds of problems before.

[andrey7474]

hi there.

I just wanted to say that we have solved the problem with leakages of R22, in the end. Two tubes were welded in an R22 condenser. We carried out the leak test. Everything is okay. Added R22 in the system. The refrigeration unit works well. The R22 levels in all vessels are stable.

There is just one thing I'm not satisfied with. We have a low superheat, low suction pressure. If I increase the R22 level in the evaporator, the suction pressure increases but superheat goes down.
I think there is a problem with the evaporator ( no heat transfer) but I'm not able to check it, unfortunately.

Thanks for helping.

Andrey.

[RANGER1]

hi there.

I just wanted to say that we have solved the problem with leakages of R22, in the end. Two tubes were welded in an R22 condenser. We carried out the leak test. Everything is okay. Added R22 in the system. The refrigeration unit works well. The R22 levels in all vessels are stable

There is just one thing I'm not satisfied with. We have a low superheat, low suction pressure. If I increase the R22 level in the evaporator, the suction pressure increases but superheat goes down.
I think there is a problem with the evaporator ( no heat transfer) but I'm not able to check it, unfortunately.

Thanks for helping.

Andrey.

Andrey, if evaporator level correct, expect zero or 1 to 2 deg C superheat if long suction line run.
Discharge temperature around 60 to 70 deg C
Expect ice build up on suction of compressor.
Oil temperature around 30 to 50 deg C depending on discharge pressure.

If compressor loading & doing work when level in increased (not knowing how you change, usually a sight glass or bullseye at correct operating level to verify) then evaporator working.
Oil skimmer system has to be working or else evaporator will have to much oil in it (oil logged).
If oil skimmer returning to much liquid to compressor has to be regulated of controlled.
This thing must be some way to see if working/performing?

[andrey7474]

Hello, RANGER1.

Respectively temperatures, you are right absolutely( as if you saw my log sheet )

Discharge temperature is 68°C
Oil temperature is 48°C
Superheat is about 1-3°C
The suction line is approx. 3-3.5 meters long.
Ice build-up on the suction side of the compressor (as usual)

Suction pressure is about 0.1-0.2 bar. Before, we had worked with suction pressure of 0.4-0.6 bar.
R22 evaporator level is 8-9 % I must say that this level is quite low level for us. We had worked with 18-22% of R22 in the evaporator before and superheat was about 5-7°C.

The oil level in the oil receiver is stable. I can see the level in a sight glass. The compressor works well. It is loaded on 100%. We installed a new ref.compressor.

As soon as I start increasing R22 level in the evaporator superheat is going to be 0°C.

R22 level in R22 receiver is stable as well- a bit low but stable. We still have a small shortage of R22 but I will fix it today.

that's all for now.

Andrey.

[andrey7474]

Hello, RANGER1.

You wrote "Oil skimmer system has to be working or else evaporator will have to much oil in it (oil logged).
If oil skimmer returning to much liquid to compressor has to be regulated of controlled.
This thing must be some way to see if working/performing?"

I have a drain valve on the bottom of the evaporator. I opened it and drain a little of R22 into a bucket. After R22 vaporizing, nothing left in the bucket - no traces of contaminations or oil. Is it good?

Before overhauling, I drained a blend of oil and refrigerant from there.https://youtu.be/z3hJXr_ehiU

The refrigeration unit works well, but I still have almost 0°C superheat, and low suction pressure.
I've increased the R22 level in the evaporator to 14%.

I really can't understand what's wrong with the system. Should I add more refrigerant?

[mbc]

Hi
Something we have to attention.
Density of R22 is heavy than oil
So oil stay on top of R22.

[andrey7474]

Hi
Something we have to attention.
Density of R22 is heavy than oil
So oil stay on top of R22.

Hi,mbc.

Even though the oil and refrigerant have different densities, I thought that R22 in low temperature and oil are miscible and create a mixture. Right?

Andrey.

[mbc]

Hi Andrey
What we see out of system when we drain oil mixture of oil and Refrigerant
In the system for example
A little liquid in crankcase we see fomming in carter.
But in flooded system oil ( oil with some Refrigerant) On the top of our refrigerant.
And this is a major problem in flooded system is working with the Frions gas's.

[RANGER1]

Andrey,
Sounds like still low on refrigerant, &/or you still have leaks.
There should be some kind of level indication to verify if at correct level.
Oil skimmer level, usually 3 return lines at evaporator working level returning oil.

You are reading 14%, where are you getting that, level probe readout?

Does manual give a % level it should be at?

Oil skimmer has to work all the time correctly, if level down in evaporator, oil skimmer probably won't be at correct level to work.

[andrey7474]

Hello, RANGER1.

You are right, I still have a shortage of R22 in the evaporator. As I wrote, the evaporator level is about 14% but it has to be about 22 -25%. I just don't have enough refrigerant at the time for adding. (Seems to me I've bought all refrigerant in our town for the last three weeks)

The level transmitter is installed in the evaporator which indicates the R22 level there. Based on the manual it has to be about 25%.

I can regulate all R22 levels and I see it works. So, I think, there is no R22 leak. The oil temperature is okay.

I will add more refrigerant as soon as possible.

Andrey.

[andrey7474]

Hi Andrey
What we see out of system when we drain oil mixture of oil and Refrigerant
In the system for example
A little liquid in crankcase we see fomming in carter.
But in flooded system oil ( oil with some Refrigerant) On the top of our refrigerant.
And this is a major problem in flooded system is working with the Frions gas's.

Hi, mbc.

thanks for replying but it's a bit hard for me to get it. Could you explain it more widely?

Thanks in advance.

Andrey

[mbc]

hi Andrey

one of the main difference between R (Frion ) and NH3 , we have to attention in our design and piping is a density

in NH3 system oil were in in bottom in Dx system and wet system and flooded systems

In R F gas we have to parts .
A : Dx system density oil of oil is heavy than gas of RF . So to return oil back we use horizontal gas flow evaporators
B : In wet or flooded system (R F) our R F liquid density is heavy than our oil .
So for return it we have to use and design reactor oil return system ,( we took some amounts of RF liquid from high level of liquid RF and then we warm it by inlet liquid to system (RF liquid boiled ) and then just we have oil later we took it and return it to our system

[andrey7474]

hi ,mbc.

Thanks for the explanation.

In other words, more liquid refrigerant in the evaporator( I mean, a sufficient amount of R22 for vaporizing) gives a better result for returning oil from there. Right? and if I have a shortage of R22 then the process is not going well.

Andrey.

[RANGER1]

Andrey,
This is one example of a lot of old good information on RE.
Just check search on many subjects.
Hard to find old R22 stuff it seems on internet.

http://www.refrigeration-engineer.com/forums/archive/index.php/t-6543.html

http://www.refrigeration-engineer.co...ed+evaporators

[andrey7474]

hello RANGER1.

Thanks for the links. I've read these threads and now, I'm a bit more confused about the type of our evaporator. I think it's a flooded evaporator.

I've found the scheme of our evaporator. It's a shell tube exchanger. The tubes side is a co2 side, shell side is R22 volume.

Please find the scheme in the attached file.



Andrey.

[RANGER1]

Andrey,
You have flooded evaporator.
Where the oil skimmer is located, I cannot quite work out.
Usually, as you may have read, there are normally 3 points to "skim" oil rich refrigerant.
One at level, one above normal level, one below normal level, each have a valve to regulate flow, goes through an oil rectifier back to suction of compressor in pure oil, R22 gas.
If refrigerant level to low, no oil skimming taking place, so oil concentration could build up over time.

Not sure what you have, if anything?

[andrey7474]

I can see in the scheme a designation N6- oil sump. This pipe has a drain valve from which I had drained the oil/R22 mixture before. This pipe is connected with another pipe where the R22 level transmitter installed. and the next pipe goes through an additional heat exchanger where two R22 flow meet ( from Evaporator and R22 receiver) . The oil from this heat exchanger goes to a suction pipe(there is a sight glass but it always freezing). all these pipes have shut-off valves, but they always are fully opened.

does it look like the oil skimmer?

Andrey.

[RANGER1]

I can see in the scheme a designation N6- oil sump. This pipe has a drain valve from which I had drained the oil/R22 mixture before. This pipe is connected with another pipe where the R22 level transmitter installed. and the next pipe goes through an additional heat exchanger where two R22 flow meet ( from Evaporator and R22 receiver) . The oil from this heat exchanger goes to a suction pipe(there is a sight glass but it always freezing). all these pipes have shut-off valves, but they always are fully opened.

does it look like the oil skimmer?

Andrey.

maybe a hand sketch to see what you have.

[andrey7474]

maybe a hand sketch to see what you have.

okay. I'll do it a bit later.

[andrey7474]

Hi there.

At the end of the day, the problems with low suction pressure and low superheat have been solved.

As it turned out, there was a mistaken calculation of superheat temperature in the program. I have found this fault looking at superheat temperature changing during stand by mode( stopped compressor). After correcting this part everything works well. I've installed an additional temperature gauge on a suction pipe to observe the suction temperature and compare it with the indication of the temperature transmitter.

Suction pressure 0.5-0.6 bar
Suction temperature -32-33°C
Superheat 5-6°C
R22 level in the evaporator 16-17%

However, I think I still have a problem with the oil return system. I can see a small decreasing the oil in the oil receiver. I'm going to increase the R22 level into the evaporator to 22-27%. I did that earlier and it helped to return the oil to the oil receiver.

I'll let you know what I'll get.

Best regards.

Andrey.

[andrey7474]

maybe a hand sketch to see what you have.

Hello RANGER1.

Please find below a hand sketch of a pipeline of the oil return system.

I hope it will be more clear.

Short decription

The liquid R22 from the receiver goes to the R22 evaporator and sub-cooled in the heat exchanger. The heat exchanger also acts as an oil return system from the R22 evaporator. Through valve, a small amount of R22 passing the heat exchanger, thus boiling out the oil contained in the R22. The oil flow can see in a sight glass before entering the refrigeration compressor suction pipe.

[mbc]

Hi
Something in drawing is not right
1)You took from bottom of evaporator
It should be between minimum and maximum of the out liquid level .
2)outlet should go on top of evaporator
3) should control inlet liquid.
4) Oil couldn't climb more than our level in evaporator, so is should drain for low level .
Also it can be vertical or horizontal. And can be small.

For climbing oil we can use ejector system or pressurize system.

[RANGER1]

Hello RANGER1.

Please find below a hand sketch of a pipeline of the oil return system.

I hope it will be more clear.

Short decription

The liquid R22 from the receiver goes to the R22 evaporator and sub-cooled in the heat exchanger. The heat exchanger also acts as an oil return system from the R22 evaporator. Through valve, a small amount of R22 passing the heat exchanger, thus boiling out the oil contained in the R22. The oil flow can see in a sight glass before entering the refrigeration compressor suction pipe.

Andrey,
All clear how it works, would have thought valve 3 would only be open a bit to control flow into heat exchanger, to return oil.
Should see activity in sight glass of some kind, but not liquid R22.
liquid level control valve , is it an on/off type of valve, or modulating, what is it brand/model.
Is valve 5 fully open?
Type of level transmitter brand/model

Nice if level control valve open a lot of the time, but maintaining level in evaporator, if not no oil return, evaporator has to much oil, level transmitter, if capacitance type will not work reliably, evaporator will not perform.
It is a balance to keep evaporator oil concentration low.

MBC is correct, as not conventional oil return but I question theory of oil concentration on top layer of refrigerant liquid level, as a lot of activity, boiling of refrigerant, new refrigerant added all the time to control liquid level.
The method Andrey has if working keeps concentration of oil down, as well as keeping control level column oil concentration down to work correctly.

In perfect world change compressor coalescer, make sure oil return system works

[andrey7474]

Hi RANGER1 and mbc.

RANGER1 ,you wrote "In perfect world change compressor coalescer, make sure oil return system works"

You are a wizard. Great job!)

I've just checked the solenoid oil return valve on a pipe from the oil separator to the compressor. It turned out, it is out of order. The solenoid coil worked but the valve itself didn't. The oil didn't go to the compressor through it.

I've fixed it and, Hallelujah, the oil has returned to the oil receiver immediately after starting of the compressor.
Now, I can see the correct oil level in a sight glass of the oil receiver.

Thank you for helping, RANGER1 and mbc.

I really appreciate your help, patience.

I've found out many new things thanks to you, guys.

Best regards.

Andrei.

[mbc]

Hi
Hope you solved the problem.
But it was different problem as you had .
Still oil will move to flooded evaporator and you should look for this case.