YCAS Compressor never takes more than 55 amp

[EHK]

Hello,

we have two chillers of York YCAS 0425EB50. Each has two compressors. On Chiller 1, System 1 compressor takes up to 90% load and system 2 compressor takes up to 50%.

on chiller 2, system 1 compressor takes up to 50 amp(49-50%) load and system 2 compressor takes around 73 amp(max).

we have tried to run only one compressor to see if it takes full load. It does not. I have checked the service mode settings, but it is programmed as 106 amp=100%. I changed the value to 120 amp=100%, yet there was no change in the amperage.

Our leaving temp set point is 6.7 deg c, even when the leaving temp is 14 or 15 deg c there is no increase in compressor load.

One thing that we have noticed that the difference between the leaving and return temp is always around 2deg c or 4-5 deg F. The maximum we observed was 6 deg F. Does the compressor loading depends on the temp diff between leaving temp and the set point or between leaving temp and return temp?

Could anybody please give me any idea why this is happening or what else we can check. Please let me know if you need any other information.


Best regards

[zw17]

Get your post count up and get a pro membership here. Then you will have access to the pro chiller forum and we can talk shop.

[milkyway]

Hello,

we have two chillers of York YCAS 0425EB50. Each has two compressors. On Chiller 1, System 1 compressor takes up to 90% load and system 2 compressor takes up to 50%.

on chiller 2, system 1 compressor takes up to 50 amp(49-50%) load and system 2 compressor takes around 73 amp(max).

we have tried to run only one compressor to see if it takes full load. It does not. I have checked the service mode settings, but it is programmed as 106 amp=100%. I changed the value to 120 amp=100%, yet there was no change in the amperage.

Our leaving temp set point is 6.7 deg c, even when the leaving temp is 14 or 15 deg c there is no increase in compressor load.

One thing that we have noticed that the difference between the leaving and return temp is always around 2deg c or 4-5 deg F. The maximum we observed was 6 deg F. Does the compressor loading depends on the temp diff between leaving temp and the set point or between leaving temp and return temp?

Could anybody please give me any idea why this is happening or what else we can check. Please let me know if you need any other information.


Best regards

something is keeping ur compressor from loading up , may be (limited).,
I would check superheat subcool discharge supereheat, liquid level., whatever may apply to your machine., it is possiable that the board may be acting funny., this is where the experience comes into play.,
GL

[Six]

Screw compressors with load and unload solenoids that use oil pressure and suction pressure to position the slide valve? If yes then there should be a way to install two toggle switches to manually load and unload that compressor. Also there should be a port to monitor oil pressure at the slidw valve.

Loading shoud increase amps and pressure. If you can manually run the slide valve up to FLA then you have a control issue. If it stops it could be the o-ring failing at higj pressure. I've changed a few slide vqlves in my time.

Also if your'e going to attempt this you have to know what your'e doing.

[EHK]

by mlkwal1 - "something is keeping ur compressor from loading up , may be (limited).,
I would check superheat subcool discharge supereheat, liquid level., whatever may apply to your machine., it is possiable that the board may be acting funny., this is where the experience comes into play.,
GL"

@mlkwal1, thank you very much for your suggestions. We have already checked those and the dilemma is everywhere it is suggested that we should check this values in full load. but, we can't go to full load. But, the values of superheat, liquid level and suction and discharge pressures at the current load seems to be in the range. I would say the board is ok.

by commtech77 - "Screw compressors with load and unload solenoids that use oil pressure and suction pressure to position the slide valve? If yes then there should be a way to install two toggle switches to manually load and unload that compressor. Also there should be a port to monitor oil pressure at the slidw valve.

Loading shoud increase amps and pressure. If you can manually run the slide valve up to FLA then you have a control issue. If it stops it could be the o-ring failing at higj pressure. I've changed a few slide vqlves in my time."

@commtech77, Thank you very much and I guess you are right. After checking other things, yesterday we suspected the slide valve solenoid. The microprocessor shows step 75 so I guess it is ok, but for some reason either the solenoid is faulty or it can't push the slide valve to the full load position. We are going to check the solenoid today.

What is the easiest way to find if the slide valve is mechanically stuck or not.

Thank you guys for all the help. Hope we could fix this real soon.

Best regards

[always looking]

Is this a really old YCAS that is blueish green in color or a newer that is beige? I'm guessing the 1st choice.

[KnewYork]

It's beige in the US. Not sure in other areas. That model number indicates that it is 380/415VAC, 3 phase, 50 Hertz. Refrigerant R-407C

Are the compressors DSX compressors?

[Bklyntek]

hi guys,just wanted to inform the O.P., YORK oversize their compressors. so if youre at step 75, then youre at full load already. anything below say step 40,it is completely un-loaded. so,you should be able to rely on oyure readings,as long as they within range.

[KnewYork]

hi guys,just wanted to inform the O.P., YORK oversize their compressors. so if youre at step 75, then youre at full load already. anything below say step 40,it is completely un-loaded. so,you should be able to rely on oyure readings,as long as they within range.

Not sure I understand what you are saying here. Please explain why the #1 compressor in chiller 2 will only load to 50% FLA. I know the OP has left out a few details, but judging from what I am reading it appears something isn't quite right with the compressors. If they are DSX compressors I would be more inclined to think there is either a solenoid problem or perhaps a spring problem. York published an entire bulletin on troubleshooting DSX compressors.

[Bklyntek]

Thanks York for your reply,it was my understanding, that York oversized their compressors.
For example, if a design spec. called for a 100 chiller. York's equivalent :100 ton is actually (2) 62.5 ton dxs compressors. I don't recall see them at nameplate FLA, but could verify full load step at:75 with 25%less than RLA. Excuse the caps setting, Im not yelling.

[EHK]

Please explain why the #1 compressor in chiller 2 will only load to 50% FLA. I know the OP has left out a few details, but judging from what I am reading it appears something isn't quite right with the compressors. If they are DSX compressors I would be more inclined to think there is either a solenoid problem or perhaps a spring problem. York published an entire bulletin on troubleshooting DSX compressors.

Actually I have found the problem. You are right KnewYork. Its a DSX compressor and problem is with the capacity control slide valve. We have two chillers so four compressors in total. Yesterday we pulled out the solenoid coil at full load (step 75). Only one compressor unloaded accordingly. Other three- no change. It seems now we have to replace three slide valve or more probably the spring(which I think is causing the problem).

I wish I knew about the york bulletin before. Now I have downloaded the bulletin to find out that it described the procedure to troubleshoot this problem in the very 1st step while we spent the whole week to figure this out.

Thanks everybody who has replied and helped me sort out the problem. Once we check the slide valves, I will let you know if it worked or not.


Best regards