Trane CCUH oil problem

[wingman]

Hi guys,


I was called for a scheduled maintenance on a trane ECCUH250 unit.

I usualy start with checking out the compressors. I tested the oil for acid, all two circuits showed high amounts of acid in the oil so I changed the oil. I also replaced the filter dryer cores of both circuits.

A large amount of oil came out of the filter holders wich is not realy a good thing. I cleaned out the holders and the sift.

When I looked at the compressors (SZ185 danfoss) I noticed there were 2 oil heaters on the outside of the compressor. (one original and one they must have added additionaly) When the unit was working there was a lot of foam forming in the carter of the compressors (bad lubrification) and the compressors where ice cold (water drops forming on the outside)

So there is a huge oil return/lubrification problem with this unit. I was wondering if there were any other people here that have had a similar problem with this type of unit.

I might have a few solutions for this problem, but I want to know if they would suffice.

First I want to isolate the compressors with the acoustic isolation for those compressors available at danfoss, secondly I want to rinse the complete system so there is no more oil in the system especialy before the expantion valve and in the evaporator. Since oil in the filter could cause the expantion valve to clog and making temperatures lower in the carter.
Or are there any service bulletins from trane that are about the specific problem ? (I've asked but they ignored the request instead they have send me the user manual..... )

For those that wonder there are oil bends in the discharge line. The condensor unit is about 15 meters (about 15 yards) appart from the indoorunit. there is a height difference of about 2 meters (2 yards ..)
There is an oil bend about 4 meters away from the indoor machine where the discharge and liquid line go through the concrete ceiling and one right before the condensor unit.

Any help would be appreciated, as always

[El Padre]

Hi Wingman,

Did you check Superheat and subcooling and air or water flows? I take it that the crankcase heaters are working. When fully loaded does the problem eventually/temporarily disapear?

[wingman]

The crankcase heaters (thanks didn't realy know the correct translation) are all working perfectly. The problem does not disappear when the system is fully loaded.

Waterflow is allright, though I haven't checked out the SH and SC. But I assume I first need to get the oil back into the crankcase or atleast make sure it stays there because the oil will eventualy influence the suction pressure when it enters the expantion valve and evaporator. Next time that I am on site i'll check the SC and SH, that will be most likely next thurday for yet another oil and filter change since I tested the system again and the oil was plain acid again. If I recall correcly that was about 30 days ago.

[El Padre]

Sounds like you might have to replace the refrigerant as well and flush the system, if the charge is considerable perhaps you could send a sample of refrigerant for a lab test.

Cheers

[wingman]

Yes indeed I will have do that eventualy, a lab test of the refrigerant isn't going to be neccesary since I was plannig to recycle the gas anyway. The reason for doing so is something that has troubled me from the beginning when they first called me for some light maintenance of the condensor coil

Trane has allready changed out 4 compressors on both machines. All in their period of warranty. Reason for me to believe, that atleast one must have been a burn out or maybe two, due to the fact of acidic/bad lubrification. Problem here is I have absolutly no trace of documents concerning the trane tech repairs on the system. It would give me insight into this problem.


So first I need a solution for the oil return. Once that is resolved I will flush out the system and regas with new R407c and new oil.

[Tesla]

Hi Wingman
If you have acid in the oil it comes from one of two places. 1 a refrigerant leak allowing moisture into system,or2 a dirty system from previuos burnout - you should find sludge in system if 2. Then it sounds like there are other issues to address

[El Padre]

How many circuits and how many compressors per circuit? How about an oil seperator, is the oil seperator insulated?
Just trying to build up a picture of the system.

Cheers

[wingman]

The system has 2 circuits, each circuit has 2 compressors. There is no oil separator. The compressors aren't insulated. All four compressor have 2 crankcase heaters.

If you want I can take a few pictures from the group to help you visualize. I'll be onsite most likely next week.

[Lowrider]

Scrolls usually don't suffer as much from bad oil return. Unless they have a lot of starts/stops or when the piping has been made in the wrong way! A CCUH is a unit made from a factory build evaporator(s) and compressors with locally installed condensor and pipework between them. When the machine is lower than the condensor oil return can be an issue if the pipe work is not as it should be and therefor the oil doesn't return. Aspecially if the machine runs at low load all the time.

It's not unusual to find oil in the liquid filter-dryer if the system has just ran in part load for a short while or when the filter-dryer is very dirty.

So in order to tell if the reason for the compressor failures is due to bad construction of the pipe work or due to too many starts/stop one will have to inspect the machine and construction.

The reason the compressors stay wet would most likely be to too low or no superheat. So for me and the rest a complete report of the machine and a drawing with pipe sizes, oil traps and length and height difference of the system would be helpfull!

[wingman]

@ lowrider, thank you for joining

I want to make a few things straight, I've never had any complaints/problems with any of the trane machines I work on or not note worthy enough to mention. Once they run, and are maintained like the manual prescribes they seem to run forever. I have machines that are almost 30 years and still running 24/7 (ERAUB's)
Neither have I had any problems with any Trane techs in the past. Repairs were always done perfectly. Never left a mess in the machine rooms, unlike other companies I sometimes have to call for repairs when I am not able or do not have the neccesary tools/skills.

As for the aftersales here in Belgium I am a very happy tech that gets manuals when I ask them. Delivery times on spare parts are always between 1-2 days. So not even complaints there, I have much more problems with Daikin/mcquay machines and RCgroup.

Now on to the problem. I will sketch up the whole installation so you will have a good idea how the installation is build I will include pictures. etc.

Since this thread has caught your attention, I will visit the site tomorrow and post the results in the evening. I will also have a look at the parameters in the controller.

[Gary]

When the unit was working there was a lot of foam forming in the carter of the compressors (bad lubrification) and the compressors where ice cold (water drops forming on the outside)

Which indicates liquid refrigerant flooding back to the compressor.

I was called for a scheduled maintenance on a trane ECCUH250 unit.

I usualy start with checking out the compressors.

Here's a tip to make your life easier:

Always start an inspection by thoroughly checking for airflow problems, in both the evaporator and the condenser.

Then check for overcharge (high subcooling).

Then check for low superheat.

Then check for undercharge (low subcooling).

Then check for high superheat.

Then check the compressor.

Airflow problems will have an enormous effect on all of the other tests, so always start with airflow.

[lowcool]

definitely replace the refrigerant and flush the system well,leave your vac pump on overnight if possible then oil and refrigerant charge to manufacturers specs.sounds like every man and their dog has had a go at this system and not got it right,it could have a bum of a roosters of refrigerant and upsetting component operations.Best advice is to start at the beginning and see what evolves.

[wingman]

It took me a little while to post this, but I did not have a very good weekend


So here is the information I have gatherd.

The first picture shows the unit sideways show the discharge gas checkvalve.
http://www.refrigeration-engineer.co...&pictureid=999

The two other pictures are both showing the oiltraps.
http://www.refrigeration-engineer.co...&pictureid=997

http://www.refrigeration-engineer.co...&pictureid=998


This is a little schemtic I've made so you can picture yourself much better how the pipework is made. I am used to work with the metric system, but since most of you guys here work with the imperial system

http://www.refrigeration-engineer.co...229510&thumb=1

This is the measurement I have done on the system in 50% load, I wasn't able to get it to run on 100%
Since the building is nearly empty and there wasn't much demand.

http://www.refrigeration-engineer.co...pictureid=1000


I also have the unit settings I some would like that.

[Gary]

Is this what you are working on?

http://www.bvtpartners.ee/avalik/kat...H_kataloog.pdf

[Lowrider]

@ Gary: That's the one!

The non return valve may be fitted the wrong way, Oil could get trapped behind the plunger and prefent it from opening.

As you say the building was virtually empty. That could be part of the problem, lots of starts could cause the compressors to loose all their oil and because it doesn't go to full load, the oil stays in the traps and doesn't return to the compressors.

The previous burns could have been caused by the combination of very low load and the non return valve!

[Gary]

When the unit was working there was a lot of foam forming in the carter of the compressors (bad lubrification) and the compressors where ice cold (water drops forming on the outside)

This is the primary problem. Liquid refrigerant is flooding the compressor and flushing the oil out.

The very first thing I would check is the rotation of the water pump. If it is rotating in the wrong direction, this could be the cause of all of the problems.

We need to know the chiller entering and leaving water temperatures, as well as the subcooling and superheat.

[Gary]

I am not entirely sure what the temperature and pressure graph is showing us, but if I am reading it correctly the TXV is hunting badly. Yet another indication of insufficient water flow (low load).

[wingman]

Is this what you are working on?

http://www.bvtpartners.ee/avalik/kat...H_kataloog.pdf

Yes that is the one, except that the unit I am working on is fitted with a SMM module from trane.

[wingman]

@ Gary: That's the one!

The non return valve may be fitted the wrong way, Oil could get trapped behind the plunger and prefent it from opening.

The non return valves are fitted correctly it's something I have checked before.

As you say the building was virtually empty. That could be part of the problem, lots of starts could cause the compressors to loose all their oil and because it doesn't go to full load, the oil stays in the traps and doesn't return to the compressors.

The previous burns could have been caused by the combination of very low load and the non return valve!

Since I have almost no expierence with the SMM control, is there a way to set it to run on its own giving me a water temperature of 10°C and a dead zone of 5 degrees ?

[Lowrider]

The dead band setting is in a part that is password protected and I can't give that. You'll have to have Trane come and do that.

Anyway your on the right way, but keep in mind that the dead band works around the setpoint. So if you set the setpoint at 10 and the dead band at 5 then the chiller will start when the leaving water temperature is above 12.5 degrees and keep running until it gets below 7.5. As a rule of thumb we set the dead band as follows: twice the design delta T devided by the number of steps. In your case that would work out at 6, I think.

Futhermore to prevent the chiller from running with both compressors just because the temperature is high because of the increase in dead band, the add and remove mini-time and the restart inhibit time will also have to be adjusted. They are all in the password protected section.

Maybe if the engineer who visits the site is willing to give the password, but I get in trouble if word gets out that I gave it to you.

[wingman]

I have all the passwords from L80 SB 052 , Don't ask where I got it from

according to what I read - the default for this unit is 3°C.

If I calculted correctly, (formula on the SB) for this type of unit it should be 4°C. So I'll set it to atleast 5°C.

Next I will check out if I can delay the remote outputs with 10 minutes and see what that gives.

But the first thing I realy need to do is making sure that all the acidic oil is flushed out of the system, recharge with new oil and recharge with fresh gas.
That 'll keep me busy for a couple of days.

Then I can start to fine tune both machines.

Just a question, would insulation help aswell to keep those compressors warm ?

[Lowrider]

I don't know how bad the oil is,but if you put a burn out filter drier in the housing, get it to run as much as possible for a day, replace oil and filter-drier and keep that up until the oil stays clear and then remove the burn out filter drier and replace it for a normal filter-drier. That way you won't have to replace all the refridgeramt which will I think will cost less for the customer.

First you will have to correct all that's wrong here. By the looks of it, the piping is done correct. But I have my reservations about the non return valve, I've seen poblems with them with oil getting trapped, preventing them from opening at first and thus adding a lot of load to the compressor at start up.

Second, you have to get the chiller in full load and check if the dT across the evaporator is 6or 8, depending on the design. If it doesn't and you now for sure the exv and the charge are correct, then there is not enough water going through it! This must be corrected to prevent the machine from short cycling.

At second thought, 5 would be a nice value to use for the dead band,mixed up the unit size with a newer model which only has two compressors.

Then, since you already have the manual have a look at F101,F102, F105 and G106.

now that we covered the machine,how about the hydraulics, can you make a sketch or tell me how it's build? Maybe there's an error in there making the chiller do a lot of start/stops?

[wingman]

I don't know how bad the oil is,but if you put a burn out filter drier in the housing, get it to run as much as possible for a day, replace oil and filter-drier and keep that up until the oil stays clear and then remove the burn out filter drier and replace it for a normal filter-drier. That way you won't have to replace all the refridgeramt which will I think will cost less for the customer.

To give you an idea how bad the oil is. I used ETK's from virginia KMP, the first contact with the oil, the first time I was on site it turned yellow immediatly.
During the oil change I've taken a sample to see the color of the oil, even the color of the oil was yellow. It looked like someone had charged the system with frying oil. After a month it's acid again. But then again that could be normal if you take the amount of oil that was still in the system. I would prefer a complete change of refrigerant and oil with a flush, I suppose I better ask my customer what he would prefer. Most likely he wants me to decide what is best so no worries there for me (at least not financial )

First you will have to correct all that's wrong here. By the looks of it, the piping is done correct. But I have my reservations about the non return valve, I've seen poblems with them with oil getting trapped, preventing them from opening at first and thus adding a lot of load to the compressor at start up.

I've seen similar problems as you describe too, but I know for sure they are installed correctly. But thanks for stressing that, perhaps others might find this part of the thread handy

Second, you have to get the chiller in full load and check if the dT across the evaporator is 6or 8, depending on the design. If it doesn't and you now for sure the exv and the charge are correct, then there is not enough water going through it! This must be corrected to prevent the machine from short cycling.

True, it's something I haven't checked completly yet, since I was too busy with the oil return problem.

the dT over the evap in 50% load is about 1-2°c wich is still fairly low in my opinion. That was the reason why I checked the rotation of the primary pump. (wich is fine by the way. )

At second thought, 5 would be a nice value to use for the dead band,mixed up the unit size with a newer model which only has two compressors.

Then, since you already have the manual have a look at F101,F102, F105 and G106.

The F-values are now all the default values except for 105
F101 = 2min
F102 = 10min
F105 = 120
G106 I believe that is enabled, I am not sure about it, i'll check that later on this week.
[/quote]

now that we covered the machine,how about the hydraulics, can you make a sketch or tell me how it's build? Maybe there's an error in there making the chiller do a lot of start/stops?

Actualy its simple, two machines (2x ccuh) connected onto one primary pump. Goes over the reserve tank then into the collector. From the collector there are 2 lines, one that has another pump for the ventilation system and another circuit for the individual ventilation units at each office.
I'll sketch up something when I am on site.


I would allready like to thank you guys for the interest in this topic.

[Gary]

Does the water enter the bottom of the chiller barrel and exit the top?

[Magoo]

Back to the original post, that compressors are sweating heavily, oil foaming in sight glass, system saturated with oil, acidic oil after testing, four compressor changes.
The evaporator is flooding back, flushing oil out and destroying compressors. Possible TEV superheats, or water flow rates.
magoo

[Lowrider]

From what you desribe both chillers are fed by one pump? Please explain!