PRV control for a centrifugal chiller

[hvacegy]

we have a centrifugal liquid york chiller with a variable speed drive and we take readings each 2 hours of operation and i am worried the our vane position is too small , for example the load of the chiller is at 56 % and 50 %and the vane position is at 20 % and 3 % respectively , my question here is shouldnot the vane position be open more before increasing the load on the chiller and consuming more power , thanks in advance


p.s i am a mechanical engineer and this is my first job at hvac so i am really willing to learn anything and everything about chillers from you guys or from any online source

[71CHOPS]

It depends on the software version how the vanes and drive react. it also is dependent on several operating parameters, including lift, tower water temp., chilled water temp., etc. etc.

it is not just a simple calculation based one or two inputs.


I used to have a YK that would never drop the speed drive output below 60hz unless the tower water temp. was in the 60's or less. factory kept telling me it was supposed to open the vanes to 100% then modulate the drive output regardless or tower temps, but it would never act the way they said it was supposed to act. machine was on a loop with low delta T syndrome, it used to do some whacky things that York could never seem to explain.

[ehsx]

50% & 56% is of rla or chiller rated capacity? Vane effect may be based on pressure ratio or similar calculation to prevent surge. You would need the controller program logic and compressor operating envelop for assessment.

[Chev5372]

If you could post a full log of chiller. Model number would help as well. Software changed over the years would allow looser control of PRV and speed. Verify sensors are correct and PRV is calibrated. The surge map may not let it run at other conditions.


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[HYP1278]

I assume your chiller is fairly new and is operating with the load control. The chiller will switch from VGD to VFD control.

[Dr Rotor]

Can you post a screen shot of the surge map?.

[ehsx]

Surge map or surge line is different for each compressor/gear/impeller combination. Mfg engineering or application would run the information to map the surge line.