York YCAS chiller

[Miked1]

I have a York YCAS chiller with 2 compressors. One of the compressors had a stator burn out. The stator has been rewound and has been re-installed. We installed a suction line burn out kit with 3 drier cores. The system was evacuated and a new charge of refrigerant (R22) and oil was installed. The system runs at normal suction and discharge pressures but the discharge temperature and obviously the oil temperature just carries on climbing up to 120 Deg C.
The suction superheat is controlling at 6 Deg C.
The motor is cold almost up to the rotor housing where it suddenly gets extremely hot. The other compressor on this chiller runs at 50 Deg C discharge under full load conditions.
Has anyone out there experienced high discharge temps on DXS compressors? Could it be the internal relief valve that is bypassing discharge gas back into the inlet of the rotors????

[yorkman_gr]

Hi Mked1 the relief valve is one item you should check, also i am assuming that you have used the correct type of oil which is the type YORK L , and also i believe you have carried out a good vacuum, and you dont use this liquid type burn out cleaning stuff, also please check the discharge and oil temperature sensors which is both 50KΩ
And finally to be honest i believe that the second system is running to low on a discharge temperature , according to my experience you should be between 70-80 C on full load
best of luck

[Grizzly]

Hi Miked1
On ( Within) the DXS there is a discharge check valve, which if choked with burn out crud?

Would not work correctly and your discharge temp / Comp body temp would rise, I assume?
I don't know anyone who has not carried out a full comp exchange on a Motor burn out of a DXS!
So you are in new territory for me!
Good luck, High discharge temp and not pressure can be a result of Air in the system.
Let us know how you get on please.
Grizzly

[Magoo]

I agree with Grizzly, and internal check vav. probable cause of initial winding failure. Jammed up or failure. Either that or screw rotors are out of spec' generating internal heat reflected in discharge temperature.
What are the SST and SDT pressures?.

[RANGER1]

Oil filter needs checking/changing if not done already.
it may indicate wear, or is blocked causing HDT.

http://www.johnsoncontrols.com.au/co...407C_60_HZ.pdf

[Miked1]

These are the logs taken once the chilled water temperature was on set point. (7.5)
System 1.
SP=4.23 ST=9.4 SST=1.1 SSH=8.3
DP=18.7 DT=57.0 DST=50.7 DSH=6.3
OP=17.1 OT=40.3
SV=39 steps
EEV-76.2 SSH=8.3
91A 65%

Sys 2.
SP=4.24 ST=7.2 SST=1.5 SSH=5.7
DP=16.8 DT=107.1 DST=46.2 DSH=60.9
OP=15.4 OT=75.5
SV=41 steps
EEV=23.5 SSH=5.7
98A 70%

Chilled water in = 9.7
Chilled water out= 7.2

Pressures are BAR and Temps are Deg C.

Please let me have your thoughts!!!!!!

[AlexG]

Are you sure this is pure R22?

[RANGER1]

Check oil filter & oil charge for metal particles, as compressor could be shot.

Do these type of units have an oil cooler, is it working, as oil & discharge temperature out of control as you know.

Are you sure you have enough oil in it!

[Magoo]

Hi Miked1.
as per ranger1, start with an oil filter change, is oil pressure reading taken after oil filter, and the high oil temp entering, what is cooling the oil?
The chilled water temperature split is small at 70% load, what is design leaving temp.

[Miked1]

Hi AlexG, Ranger1 and Magoo
Well after evacuation for 12 hours and holding vacuum for a further 12 hours we charged with New R22 from a very reputable supplier.
I will change the oil filter and oil tomorrow and see if that makes a difference.
The oil cooler takes up the top 3 rows of the condenser coil. The oil pressure transducer is on the return oil line before it enters the oil filter housing. The control monitors difference between discharge pressure and oil pressure for High differential cut out and also monitors oil flow through compressor and cuts out on Low differential if the oil pressure is too low.
The chilled water temperature split is small because the client has more than design flow through the evaporator. The flow is however within the limits for this particular chiller. The design was originally 5 Deg split at the design water flow but they have increased the water flow as they have added an AHU to the system.

[Grizzly]

Hi Miked1
Just to throw a curve ball!
You have got all the oil line isolation valves open and the condenser fans are running correctly?
Only high discharge and oil temps can be due to poor air flow through the condenser?
Where "We" have all been assuming the comp was at fault!
Just a thought!
Grizzly

[Magoo]

Comparing discharge pressure, versus discharge temperatures, the problem compressor is not doing the business. Compression ratio is down, discharge temps high, would indicate slippage in the screws generating the heat. Hot oil and viscosity changes, lower oil pressure.
Time for a compressor replacement or total rebuild.
OK stupid question time..., is system economized.

[Miked1]

Hi Magoo
Yes the system does have an economizer installed.
Hi Grizzly
All valves are open on oil lines and all fans are running in right direction etc. I've even combed the fins that were a bit suspect to try and improve air flow.

I have ordered a new internal relief valve so will open the compressor when it arrives and will let you know what I found inside the comp.

Thanks for all the help so far.

[yorkman_gr]

Miked1 once are you gonna open the compressor to check or replace the relief valve, i am asking you to do a favor , after you finish with your relief valve , it is possible to take axial measurements from both screw male and female and you post or send iti by e-mail to me? because i cant post the numbers in an open forum, please take axial clearances measurements with inch or metric clock and i will tell you if your compressor is inside the margin
yorkman

[Miked1]

Hi yorkman
Will do so. It normally takes 2 to 3 weeks to get spares from JCI.

[GHAZ]

hi it could be the stator is not rewound properly, or the ends of the coils are over wrapped and is not getting the cooling, the internal pressure relief valve hardly ever goes , but since these high temperatures i would change it any way
the axial end clearance should be between 0.05mm to 0.10mm (roughly 2 to 3.5 thou)
the best way to check it is to hang the screw pack and measure it because checking in the body is too difficult

[Magoo]

interesting comment Ghaz.
seems the motor case is normal temp and rotor case is hot, being economized the system would rely on econo saturated vapor entering the partial port for added cooling effect which also effects discharge temp.
Perhaps look at economizer operation.

[Magoo]

interesting comment Ghaz.
seems the motor case is normal temp and rotor case is hot, being economized the system would rely on econo saturated vapor entering the partial port for added cooling effect which also effects discharge temp.
Perhaps look at economizer operation.

[srinitkr]

where is the that check valve can u show the picture

[Grizzly]

Hi.
I cannot extract the picture to post on here.
So I have emailed the relevant parts diagrams to you.
Item 40 page 23 and description is on page 25.
It's called a Button Check Valve and it comes in 4 different sizes, dependant upon your comp size!
Grizzly

[GHAZ]

Hi friend hope this helps, the brass bit is the PRV DSC_0159.jpg

[GHAZ]

im sorry about the big picture i couldnt make it small

[srinitkr]

hi friends i have same problem discharge pressure not build up but discharge temperature is high 120degree what was the problem

[nuwanchamara]

The brass bit is pressure relief valve .

[nuwanchamara]

Miked 1 ... Is your problem solved ?

[nuwanchamara]

Exactly rilef valve faulty.

[Miked1]

Replaced relief valve but made no difference. The axial floats are within tolerance at 3.5 thou. I have found that the TXV on the economiser is not working, have ordered new valve and will replace soonest. Will let you know what happens.

[RANGER1]

Replaced relief valve but made no difference. The axial floats are within tolerance at 3.5 thou. I have found that the TXV on the economiser is not working, have ordered new valve and will replace soonest. Will let you know what happens.

That will definitely improve performance & give a bit of cooling to compressor.

When you checked end float could you see rotors tips & their condition?

Also is there anything else in oil lines, like solenoids or oil cooler bypass valves?

[Miked1]

Thanks everybody for the help etc. The problem was the solenoid valve on the liquid line to the economizer. Changed the TXV but that also made no difference then discovered that even though the solenoid was energising the valve was staying closed. replaced the solenoid valve and now have normal discharge temperature again.

[Grizzly]

Thanks for the update Miked1.
We all live to Learn.
Thanks for bothering to update us all!
Grizzly