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  1. #1
    Join Date
    Oct 2007
    Location
    Arizona DUH
    Posts
    174

    Trane Chiller Information

    Can anyone tell me what the minumum pressure differential should be between the evaporator and condenser on a Trane CVHE 400 ton machine? A Trane salesman sent me an e-mail stating

    "For the varying of the condenser water flow, we just need to make sure that a 23 psid refrigerant pressure differential is maintained between the evaporator and condenser."

    I am starting up some chillers that our company made the primary chilled and condenser loop a varible flow system.

    Any help is appreciated.

  2. #2
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,036
    If it is an older CVHE (no refrigerant pump) it is 5 psid at steady state. If it is a newer CVHE (has refrigerant pump) it is 3 psid at steady state. I always asked my customers to please call me with any questions.... Same with any contractors- mechanical or controls. Or electrical, for that matter.

  3. #3
    Join Date
    Jan 2011
    Posts
    1,158
    Quote Originally Posted by Trane Salesman
    "For the varying of the condenser water flow, we just need to make sure that a 23 psid refrigerant pressure differential is maintained between the evaporator and condenser."
    That number seems sky high to me. If you are varying flow that would indicate to me that the chiller is equipped with a VSD. If so, then the goal is to get the condenser and evaporator pressures as close as possible (within reason since Tranes don't like cold condenser water). If you were trying to make 42*F CHW the corresponding pressure would be about 18" (or 9 PSIG) with 85*F condenser water the corresponding pressure would be about 1.5 PSIG. O.K., so we now have a 10.5 PSIG diferential between the condenser and evaporator pressure. How in heck can it get to 23 PSIG and still run?

    Either A. The salesman doesn't know chillers.
    B. He made a mistake and somehow the 23 had something to do with temperature.

    Why are you starting up a CVHE chiller rather than the local Trane office? Doesn't factory start-up come with the chiller?

    Shouldn't this thread be in the chiller forum?

  4. #4
    Join Date
    Oct 2007
    Location
    Arizona DUH
    Posts
    174
    2 of them do have VSD on the machine, the other 5 do not have them. I should have stated, I am starting up the machines (plant) after I put the variable pumping system in operation. Its been 5-6 years since I worked for Factory Trane so my qualifications for official startup have run out.......lol

    We have so many forums now I hardly look when I type, the old days on here were easy either technical or tools....lol

    I have no idea what the new equipment guy was saying when he said 23 PSID, thats what threw me for a loop.

  5. #5
    Join Date
    Sep 2010
    Location
    San Diego
    Posts
    66

    Condenser Water Temperature

    If you’re interested service bulletin CVHE-CSB-40 tower water temp and the myth that Trane chillers need warm water. To paraphrase the service bulletin, if you maintain a 5 PSID across the condenser and evaporator then the tower water can get as low as 55deg. The bulletin also says this logic can be applied to machines manufactured after 92.

  6. #6
    Join Date
    Oct 2007
    Location
    Arizona DUH
    Posts
    174
    Is that document out there publicly or a Trane only document?

  7. #7
    Join Date
    Sep 2010
    Location
    San Diego
    Posts
    66

    Condenser Water Temperatures

    Here is some newer documentation concerning condenser water temperature. The information you’re looking for is on page 7.
    Attached Images Attached Images

  8. #8
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
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    2,036
    Thanks, baspro, for sharing that. However, I believe that bulletin assumes that the chiller is supplied from the factory with the AdaptiView panel. If it is retrofitted onto an older chiller, a 3 psid between evap and cond will likely create problems - with motor cooling and oil temps. The refrigerant pump was added to allow the decrease from 5 psid to 3 psid, and was introduced with the CH530 and DynaView panel. If a chiller does not have the refrigerant pump, it would be best to go with the higher differential. There is another thread (maybe by same OP?) where Jayguy suggests actually set it up to control 1-2 psid higher than Trane says - I agree.

  9. #9
    Join Date
    Sep 2010
    Location
    San Diego
    Posts
    66

    Condenser Water temp

    You are correct, lower condenser water temps should be only used with refrigerant pumps. However, the lower condenser temps are not just limited to adaptive view units. Lower condenser temps can utilized on units with UCP2. Basically, units manufactured after 1992 can be subjected to cooler condenser temps.

  10. #10
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,036
    Baspro, if by "lower condenser temps" you mean below 75 F, I agree. But without a refrigerant pump I would be surprised to see to see an older Trane reliably control to setpoint with a 3 degree differential pressure between evap and cond. However, with that being said, if it has a UCP2 (which was before the refrigerant pump), I would be more agreeable to any attempt to do so. And that is simply because I have more faith in the later, improved controls to protect the chiller. And the customer would need to be made aware of the possibility of not tightly controlling chilled water temp, and of possible shutdowns on "High Bearing Temp" and High Oil Temp" due to decreased refrigerant flow to motor cooling and the oil cooler. This applies to CVHE/F. And Duplexes.

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