York Centrifugal Chiller Capacity Limit

[Nuclrchiller]

Fouled tubes can affect the water pressure differential. It will increase the pressure drop. And if there is a pressure differential control, it will reduce the flow in order to bring that drop back to the control point. I'm not saying this is the problem, but being aware of the possibility can prevent you losing time chasing other possibilities. Having logs that show evaporator water flow pressures under the various conditions this chiller operates at, or a good baseline at full flow (with a consistent flow control valve status) would be a good help.

[lordsigma]

Fouled tubes can affect the water pressure differential. It will increase the pressure drop. And if there is a pressure differential control, it will reduce the flow in order to bring that drop back to the control point. I'm not saying this is the problem, but being aware of the possibility can prevent you losing time chasing other possibilities. Having logs that show evaporator water flow pressures under the various conditions this chiller operates at, or a good baseline at full flow (with a consistent flow control valve status) would be a good help.

Our valve only operates when there’s is insuffficient flow out in the building to satisfy the differential set point at the chiller - our pump speed is based on differential far out in the building. If that flow doesn’t meet the chiller’s DP set point on our BMS the controller opens the building bypass valve to add flow to the loop until we meet the requirement at the chiller. If the flow in the building by itself is equal to or greater than what we require at the chiller nothing happens - the sequence is fine with greater than set point flow at the chiller. Our mechanic is pretty sure all the tubes were cleaned this year - we are having JCI out next week. He is suspecting that we have air in the machine and that the purge unit may not be working properly as we have apparently had problems with that a number of years back and it had to be replaced.

[Nuclrchiller]

Our valve only operates when there’s is insuffficient flow out in the building to satisfy the differential set point at the chiller - our pump speed is based on differential far out in the building. If that flow doesn’t meet the chiller’s DP set point on our BMS the controller opens the building bypass valve to add flow to the loop until we meet the requirement at the chiller. If the flow in the building by itself is equal to or greater than what we require at the chiller nothing happens - the sequence is fine with greater than set point flow at the chiller. Our mechanic is pretty sure all the tubes were cleaned this year - we are having JCI out next week. He is suspecting that we have air in the machine and that the purge unit may not be working properly as we have apparently had problems with that a number of years back and it had to be replaced.

Yet, in post #20 you state the system maintains 7 psi across the chiller.

I'd like to help you, but the only thing in these forums that is more frustrating than a drip feed of info, is a drip feed of incorrect or misleading info. I wish you luck.

[lordsigma]

Yet, in post #20 you state the system maintains 7 psi across the chiller.

I'd like to help you, but the only thing in these forums that is more frustrating than a drip feed of info, is a drip feed of incorrect or misleading info. I wish you luck.

My apologies for not being clear. The system pumps maintain 10 psid at the far end of the building. The bypass valve maintains at least 7 psiD across the Chiller - more across the chiller is acceptable. As I said in an earlier post I do not claim to be an expert - my main point in posting was to see if there was a limit I could put in on the chiller controls (as controls is my area of expertise) as a band aid until we can get JCI and that question was answered - the question led to some discussion of the problem itself and I appreciate all the suggestions and have passed them on but as a disclaimer that I mentioned earlier - I am not an mechanic or chiller expert what I know I have learned from dealing with controls.

And by psi I mean PSID - differential pressure. Reading back it seems I was mixing PSI and differential pressure terminology. Our sensors are reading differential pressure and that is what we are controlling to.

[lordsigma]

Additionally I will heed your comment and in future postings on this forum I will try to provide more concise and complete info in my opening post.

[lordsigma]

We had JCI out to look at this. The tech found a very large amount of air in the chiller which seems to be what the main problem was. He altered the settings for the purge unit to disable high efficiency mode as it appears the purge was not effectively removing the air in this mode. With the air removed the machine is running MUCH better. Flow is still a question, but it appears the air was the main problem. We will be shutting the plant off in a couple more weeks for the winter and when they do our on-site staff is planning to clean all the strainers after they drain the cooling tower so that we are sure we have good flow next cooling season. Thanks for all the suggestions/thoughts/suggestions given on this topic, and I apologize if I was unclear at any point.

[Poodle Head Mikey]

I can tell you that I would have someone independent and trusted there for hands-on observation when JCI pulls the heads. <g>

PHM
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Our valve only operates when there’s is insuffficient flow out in the building to satisfy the differential set point at the chiller - our pump speed is based on differential far out in the building. If that flow doesn’t meet the chiller’s DP set point on our BMS the controller opens the building bypass valve to add flow to the loop until we meet the requirement at the chiller. If the flow in the building by itself is equal to or greater than what we require at the chiller nothing happens - the sequence is fine with greater than set point flow at the chiller. Our mechanic is pretty sure all the tubes were cleaned this year - we are having JCI out next week. He is suspecting that we have air in the machine and that the purge unit may not be working properly as we have apparently had problems with that a number of years back and it had to be replaced.

[BennyD]

I'd keep an eye on the purge count. Disabling the turbo pump option is only a bandaid. Either the purge hasn't pumped out in a long time (bad oil pump or solenoid) or the chiller has a leak. Either way, it needs to be repaired.