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  1. #14
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    The only thing you can do with BAS is to current limit the chiller. Or you could clean the tubes as JCN mentioned before and get more heat out of the refrigerant and into the tower water.

    you could change the high pressure limit to a much lower limit. This would force the Chiller to unload at a lower condenser pressure before the Chiller surges.

    All of these control panel setpoint changes are like giving aspirin to a guy with a tack in his foot. If you removed the tack, you could prevent the need for the aspirin.
    Don't step on my favorite part of the Constitution just to point out your favorite part.

    Political Correctness is forced on you because you have forgotten decency.

    Technically speaking, they are all heat pumps.

  2. #15
    Join Date
    Nov 2004
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    up in the hizzy
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    Quote Originally Posted by IndustrialTech View Post
    The purge units on YT models have always been a problem. Condenser is high compared to our YT I've never seen ours go over 20 psi ever and we're running a water temp set point of 75F

    Sent from my Pixel XL using Tapatalk
    I never had a problem with a York purge, I like them better than the earthwise.
    There is not better place for the working men than the union! 100% UA the only HVAC union!

  3. #16
    Join Date
    Mar 2010
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    Thread Starter
    Ended up dropping the condenser high pressure warning to serve as a limit. As a result getting more runtime and less activation of the surge protection unload mode though it is not perfect still surging . Limit was 28.8 PSI and I dropped it to 22. Any recommendations on a setting for that? Thankfully tomorrow should be the last day of this hot spell and the extreme dew points. After this season is over and they drain the tower going to recommend they check and clean any and all strainers on the tower loop and have JCI check/clean the tubes if needed next year and will also ask them to look into the problem to make sure there isn't a air or an issue with the purge unit. The difficulty is going to be recreating the problem for the chiller tech if we don't have a high dew point day. The problem is masked at lower dew points/cooler tower water.

  4. #17
    Join Date
    Jan 2013
    Location
    United Kingdom
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    You have taken logs I hope recording all the operating temps and pressures

  5. #18
    Join Date
    Mar 2010
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    Thread Starter
    Quote Originally Posted by raptyr View Post
    You have taken logs I hope recording all the operating temps and pressures
    Yes I have taken some screenshots since I know I won't be able to recreate this on a less humid day.

  6. #19
    Join Date
    Feb 2017
    Location
    New York
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    Looking at that screenshot, you have a massive evaporator approach. You need to check your flows. If they are good, you need to get a good chiller guy to check it out. May be low on charge, dirty tubes or all of the above. Remember, surge could be due to high condenser OR low evap pressure...
    -----Stop, step back, relax and have another go at it.-----

  7. #20
    Join Date
    Mar 2010
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    Thread Starter
    Quote Originally Posted by BennyD View Post
    Looking at that screenshot, you have a massive evaporator approach. You need to check your flows. If they are good, you need to get a good chiller guy to check it out. May be low on charge, dirty tubes or all of the above. Remember, surge could be due to high condenser OR low evap pressure...
    I spoke to our head HVAC mechanic today and he said JCI is supposed to be cleaning the condenser tubes yearly in our PM before annual startup and he said the strainers on the cooling tower loop were also cleaned earlier this cooling season. On the chilled water side we have a differential pressure transmitter that is showing normal (we have a bypass valve that maintains 7 psi across the chiller if necessary but when our rooftop ERU make up units have their chilled water coil valves open there is more than enough flow where the bypass is full closed (usually 10-11 PSI.)) I will check the actual PSI of each leg. We will be bringing JCI service in Asap. For now limiting the condenser prsssure is giving us more even cooling and less surges. It sounds like something that’s been getting worse progressively - we used to run with a 45 degree setpoint. Two years ago we started noticing these surge modes on super humid days so our mechanic lowered the setpoint to 48 which for a while worked fine in all conditions. Now the machine can barely hold 50 degrees on humid days without surging and that is with the warning limit I put in.

  8. #21
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
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    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.

  9. #22
    Join Date
    Mar 2010
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    Thread Starter
    Quote Originally Posted by Nuclrchiller View Post
    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.

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  11. #23
    Join Date
    Aug 2009
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    Prattville, Alabama
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    Quote Originally Posted by lordsigma View Post
    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.

  12. #24
    Join Date
    Mar 2010
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    Quote Originally Posted by Nuclrchiller View Post
    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.

  13. #25
    Join Date
    Mar 2010
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    Thread Starter
    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.

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