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  1. #1
    Join Date
    Feb 2010
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    Ontario, Canada
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    15

    Trane Chiller Condenser Fans

    I am working on a Trane outdoor chiller model #RTAA125. It's 36 degrees F outside, I have 3 fans running, one of which is the VSD and I have discharge pressure of 170 psi. I have ohm'd out the discharge temp sensor, and by the chart, it appears OK. Has anyone run into this problem as I feel my head pressure is too low. Thanks for any info.

  2. #2
    Join Date
    Oct 2004
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    Metro ATL
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    454
    What is the serial number of the unit? This will tell us what type of controls we are working with and can give you better information. The fan cycling logic on these machines leaves a lot to be desired.

  3. #3
    Join Date
    Aug 2006
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    2,583
    I've seen that on our RTAAs, with no problem, with all the sensors, electronic expansion valves and the way they separate the oil out, your not going to see a problem and the unit can run closer to the wire to save energy.
    BTW, are you doing process cooling or comfort cooling? They were runnning 25 F, for comfort cooling, made a few changes in the controls program, after I convinced them sky wasn't going to fall. Now run 62 F approach, 52 F extend, using O.A. for cooling.

  4. #4
    Join Date
    Feb 2010
    Location
    Ontario, Canada
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    Hi Jemawalton ,Thanks for your reply. The S# U98A07358 with a clear language display.

  5. #5
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    Feb 2010
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    Ontario, Canada
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    Thanks for the response Madhat. It is a process cooling Application with variable load.

  6. #6
    Join Date
    Aug 2006
    Posts
    2,583
    You have basically have the same Chiller as my new chiller. They had problems with head pressure on the earlier chillers, mostly after a failure restart, on a warm day, warm fluid. Reprogramming updates would take care of the problems.

    One thing you should do is have the chiller rewired so the Compressor and Evap. heaters are on a generator circuit. That way if you loose power for an extended time, you can be up and running, as soon as the power stabalizes.

    I made a sheet up that has the monthly and weekly log on it, it's Word so you can change it to what you have. I'll Email it to you if you are interested.

    The Chillers have a built in "set-up" feature that monitors the incoming verse the outgoing fluid, and analysis your load. The Chiller can "set-up" the leaving temperature, then set it back down when the load comes back. This is fully adjustable on response and degree of set-up. Could save you thousands of dollars in energy bills.
    Last edited by madhat; 02-09-2010 at 09:58 AM.

  7. #7
    Join Date
    Feb 2010
    Location
    Ontario, Canada
    Posts
    15
    Quote Originally Posted by madhat View Post
    You have basically have the same Chiller as my new chiller. They had problems with head pressure on the earlier chillers, mostly after a failure restart, on a warm day, warm fluid. Reprogramming updates would take care of the problems.

    One thing you should do is have the chiller rewired so the Compressor and Evap. heaters are on a generator circuit. That way if you loose power for an extended time, you can be up and running, as soon as the power stabalizes.

    I made a sheet up that has the monthly and weekly log on it, it's Word so you can change it to what you have. I'll Email it to you if you are interested.

    The Chillers have a built in "set-up" feature that monitors the incoming verse the outgoing fluid, and analysis your load. The Chiller can "set-up" the leaving temperature, then set it back down when the load comes back. This is fully adjustable on response and degree of set-up. Could save you thousands of dollars in energy bills.
    Madhat ,Thanks for the info

  8. #8
    Join Date
    Mar 2004
    Location
    ottawa canada
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    2,012
    170psi is not low .Ive seen them running at 120/125psi no problems . What was your suction psi?? If you have more than 70psi PD you will be Ok.
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  9. #9
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    Feb 2010
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    Quote Originally Posted by graham View Post
    170psi is not low .Ive seen them running at 120/125psi no problems . What was your suction psi?? If you have more than 70psi PD you will be Ok.
    Thanx Graham for the info. I will have to check the suction again but I believe it was around 52psi. The outdoor display has been freezing up (going blank)so I will have to get into the supervisors office to check on the remote display.Thanks again for the input.

  10. #10
    Join Date
    Dec 2005
    Location
    Vancouver BC
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    126
    Quote Originally Posted by graham View Post
    170psi is not low .Ive seen them running at 120/125psi no problems . What was your suction psi?? If you have more than 70psi PD you will be Ok.

    True, I went through this exercise with this chiller and a Carrier 30GT110610 with EXV's as well. I was surprised to see the low head figuring that everything would kick out but the VFD driven fans.The equipment runs fine and the factory says it's perfectly normal although getting an explaination of the fan control is another story since they seen to cycle differently under similar conditions.
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  11. #11
    Join Date
    Jul 2007
    Location
    The Hot South
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    1,297
    The fan staging logic maintains a 70 PSI differential between suction and discharge pressure. 170 PSI is not too low.

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