View Full Version : York YT chiller
10-25-2006, 11:52 PM
I came across a 550 ton York YT. chiller and I suspect It has a high boiling residue %.(excessive oil) I have sent the refrigerant sample in for analysis. Comparing it with the other identical machine in the room it is quite visable. The oil in the sump is low and and doesn't seem to be coming back. A total of 5 gal has been added and while running the level is below the glass. Had the machine running and took readings. Chiller carryover is occuring. A 5 deg. dis. superheat and 5 deg approach at 100% Level in refrigerant s/g was not present. The cooler gpm is nowhere near design and has been like that for years.(design=8 psid actual 25 psid) Attempted to achieve design but insufficient flow throughtout caused problems therefore had to switch both chilled water pumps to run. Machine seems to run under light load conditions at times. What may have caused the excess oil in the refrigerant and any suggestions how to correct it and prevent it from happening again.
10-26-2006, 06:07 PM
1) remove the oil
2) verify the charge is at factory specs.
3) insure the filters driers are replaced. ( all )
4) insure purge operation.
5) oil may have been added during low load operation/starup
oil was added to get the unit running and never removed once the unit was up and running.
6) correct the water flow ( it doesn't matter how long its been wrong its still wrong ) find out why it was changed and correct it.
*The oil level will change as the purge unit operates.
10-26-2006, 07:34 PM
The 5deg. Discharge S/H scares me most of all....
You are definitely pulling oil droplets by the gross into the 12k$ impeller and are eroding the wheel as they impact..
The X3 water flow is about 70% over design which is much better than being on the low side of flow..
Mainly verify that the Oil Return line from the eductor to the oil sump/gearcase is within 2-4deg.F of evaporator temp. Higher than that and it is indicative of either a restricted Drier core, plugged or restricted eductor, or an obstructed pick-up line going into the Evaporator...
I know of several YT's that were rebuilt to cure the "Oil Recovery" problems, only to find afterwards that it was nothing more than an obstructed oil recovery line going into the Evaporator.
Lastly....make certain that the oil recovery drier is fully insulated along with the entire line back to the compressor....A little insulation makes the system work many times better when pulling liquid back instead of it being vaporized due to lack of insulation...
10-26-2006, 09:54 PM
I am assuming that the oil sump heater is working sump temp 135-145. Have you tried manually loading the machine? does this help return oil? what kind of head are you running? 5 degree approach poor heat ex in the cooler, oil logged charge,( fouled tubes?) this can also contribute to your carryover. Check your chilled h20 pump (on a VFD?) make sure it's putting out the proper ft. of head. Get the flow through the barrel figured out then see whats happening. Worst case scenario- you could have worn bearings. Hope this helps.
[Edited by txhvac on 10-26-2006 at 09:58 PM]
10-26-2006, 10:18 PM
Those readings are when the machine is running at 100% The oil sump is at 140 and quickly drops down to 115 within 10 mins and then slowly begins to rise. no VFD installed. Must run two pumps to maintain sufficient flow for process plant. I should have results back from refrigerant analysis very soon expect high oil residue percentage. If results are high should I remove entire refrigerant charge and begin distilling process?
10-27-2006, 12:15 AM
What type of loop do you have?
Primary - secondary, constant flow or volume, variable - primary?
Two way or three way chilled water valves?
If you decide you have to distill the refirgerant you can do so by recovering vapor from a high point in the machine, as you remove the vapor & its condensed into a liquid as you store it in your storage tank or tanks, the oil should stay behind & pool in the bottom of the cooler, (evaporator)then you should be able to open the charging valve & drain the oil out.
You also mentione a change in oil level during purge drain cycle, there is a chek valve on the purge you may want to replace.
Remember, 1320 gpm will be about the middle of the curve, the chiller has a max & min flow.
The low DSH is a cause for concern, you need to address the problem soon.
10-27-2006, 10:14 AM
Change out the oil return drier, and be sure the gas line to the eductor is not plugged.
Then get ready to deal with the excess oil coming back.
11-01-2006, 11:06 PM
Received refrigerant sample Results: water content 40 ppm
Oil Residue 8.28 %. Dismantled educter piping, tee and replaced filter drier and no restriction or paint chip found. Ran machine and measured 2.5 deg. temp differnce than cooler ref. temp on eductor line back to compressor. Therefore eductor seems to be working. I have decided to have Eddy Current testing on both cooler and condenser due to the high moisture. How should I deal with the high oil residue situation and will that correct the carryover problem?
11-09-2006, 09:31 PM
Received refrigerant sample Results: water content 40 ppm
Oil Residue 8.28 %. Dismantled educter piping, tee and replaced filter drier and no restriction or paint chip found. Ran machine and measured 2.5 deg. temp differnce than cooler ref. temp on eductor line back to compressor. Therefore eductor seems to be working. I have decided to have Eddy Current testing on both cooler and condenser due to the high moisture. How should I deal with the high oil residue situation and will that correct the carryover problem? If the level in the oil sump keeps going down while the machine is running where is it going and why? Should I be installing an additional oil eductor system.
11-12-2006, 07:59 AM
You can replace the eductor, contrary to popular belief they do fail.
Being oil logged can give you carry over symptons.
If you suspect moisture I would quickly install & core holder with a dry eye & monitor it daily.
If it is wet, don't waste any time correcting the problem.
Let us know how the eddy current testing goes.
11-12-2006, 11:31 AM
You might have a leak in your oil cooler
that is located inside the purge chamber.
I have had to replace two of them so far.
Replacing foul gas check valves used to be
a standard maintenance task in the good old
days. If the foul gas line vibrates and you
cant settle down the vibes, you might want
to consider putting 2 check valves in series.
This has worked for me on a couple of T's.
11-12-2006, 03:20 PM
To get the oil out of the evaporator, try setting the CW to setpoint and raising the condenser water entering temp to 90 degrees. Run while observing and load the machine slowly. After 30 mins or so, the oil should begin to slowly return. After you get the oil back, make the needed repairs or adjustments. Hope this helps?
11-12-2006, 11:48 PM
I was talking to a guy the other day, that had the same problem you are having. He told me he replaced the eductor, even though it looked to be okay, and it did solve his problem. Make sure your pick up line is open (2 turns. 8.28 % oil is excessive, most manufacturers say I think around 2% or so. 40 ppm of water ain't good I agree w/ chiller mekanick install a clean up kit to dry your charge out, get your bundles eddy current tested. Once you get the oil coming back to the sump @ a proper rate, re-check your charge see what that does. Keep handling the issue one step @ a time. Hope this helps.
11-15-2006, 02:17 PM
Richard L hit the nail with the hammer, listen to the york guy and learn!
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