Page 1 of 3 123 LastLast
Results 1 to 13 of 34
  1. #1
    Join Date
    Jan 2004
    Posts
    164

    Confused Trane chiller RTAC low refrigerant temp trips

    Has anybody had problems with the new Trane RTAC chillers? We are having low evap temps on two machines (200) tones each and have had Trane out to help and we are still having issues. We have a computer room that has low load and they have 9 Crack units that are water cooled and to get enough load to keep the machines running at 28% I have put 5 units to cool at 70 and 4 units to heat to 74 and this is helping to get load up since the room is only about 10 tons of load at this time. They are suppost to load up the room up in the next 2 weeks so this is the best I can come up with to increase load for now. I have proven we have plenty of water flow and on a cold night (24 f ) we are going low because of the large coil and causing the evap to go out on low evap temp. I am concerned that the condenser pressure is dropping as it gives up heat and causing this issue so I had our controls guy trend the fla amps today to determine if this is the issue. If you guys have had issues with this I appricate any help you can offer as I am pulling my hair out on this. By the way Trane is no help and I will never reccomend them for replacement because of the lack of help on this issue.
    If you find it bad 3 different ways- ~its bad~

  2. #2
    Join Date
    Dec 2003
    Location
    45th Parallel
    Posts
    954
    Does the chiller control the start stop of the pump? If not, it needs to.

    Are you absolutely 110% positive you have correct water flow?
    Not just when you are there checking but at the time it trips.
    These units are pretty bulletproof if installed and controlled properly.
    Low flow WILL cause low evap refrig temps.

    Not trying to be a smart *** but how is trending FLA going to tell you if cond press is dropping and causing your trip? Maybe I am missing something.

  3. #3
    Join Date
    Jan 2004
    Posts
    164
    I have opened the bypass to ensure plenty of water flow because this is what i was thinking was causing the issu. I set it to 650 gpm manually to prove this was not the issuel. I put the vfd in hand mode and opened the bypass to prove this. I even looked up the min water flow and confirmed it to be 250 gpm. I trended the FLA to see if the chiller was shutting off to help identify if the condenser is subcooling the freon in cold ambiant temps because of the delay and after 10 min or so this might be causing a low head and a low suction issue. I am trying to fix this issue and trying to figure all the things I can think of to help me get this resolved. The condensor temp was really low on cold days and untill the unit ran for a while the temps did not come up to normal. Thats why I am leaning to low temp issues. I tried to get the engineer to sell them a cooler to allow for free cooling in the lower ambiant temps but they wont listen to a service teck as I don't have the schooling so here we are.
    If you find it bad 3 different ways- ~its bad~

  4. #4
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,011
    Never mind trending the RLA its the evap level and temp you should be trending , having said that how are you checking the water flow ?? 1 Gauge or 2 ?? and where are you checking delta P. The chiller has to conrol the CHW pump . Does the chiller control the pump ?
    Is the oil and refrigerant charge correct ?
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  5. #5
    Join Date
    Jun 2006
    Location
    Midwest
    Posts
    284
    Glycol present? If so which type and what percentage?
    I guess since I'm a Trane tech I can be of no help?
    It's All Good!!!

  6. #6
    Join Date
    Jan 2004
    Posts
    1,174
    Well, first off, what vintage is it. What version of Dynaview software are you running, do you have glycol and if so is the low trip set to that temp. Has anyone checked the evap oil return line for blockage, has it ever had oil added to it, has the float been checked, what is the EXV at when it trips. It may seem like a simple problem but there is a a certain way to troubleshoot low temp trips and anyone of the items above will cause them.
    Federal Reserve, stealing your kids futures since 1913

    UA290

  7. #7
    Join Date
    Dec 2006
    Location
    Massachusetts
    Posts
    29
    200 tons of cooling with a 10 ton load at this time?? that'll cause low evap temp

  8. #8
    Join Date
    Jan 2004
    Posts
    164

    Hmm

    Sorry I have been out of town. Unit still tripping every now and then. Seems to happen when its cold out. I am wondering if anyone has had issues with the units starting below 15 degrees OAT. I have also tried to load the room with half the units heating to 75 and half the units cooling to 70 to try to get more load in the space. I am at my witts end as I know there is not enough load to maintain the unit to run with at least 50%. I am not sure what to check as I have set the flow switches to make at 300 gpm and trip at 250 gpm just to make sure we have water flow. I thing there might be an issue with the head pressure controls but can not prove it at this time. What do you guys think I should trend to catch this issue. We can only trend what the Trane CH530 will let us. Any ideas would be appriciated. thx teckster
    If you find it bad 3 different ways- ~its bad~

  9. #9
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,011
    Not trying to be a dick but you really need to read the posts from the other guys and answer the questions they have put to you . The more info you give the more we can help you . How familiar/comfortable are you with the CH530 do you have a laptop with Techview on it . What version are you running what software version is on the chiller etc etc etc ????????????????
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  10. #10
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,254
    model number?

    Digit 17 - Condenser Temperature Range

    N - Standard ambient range
    25-115 deg F

    H - High ambient capability
    25-125 deg F

    L - Low ambient capability
    0-115 deg F

    W - Wide ambient capability
    0-125 deg F

    these numbers indicate the minimum starting ambient and the maximum running ambient.
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

  11. #11
    Join Date
    Apr 2009
    Location
    In the south
    Posts
    30
    Are there drives on the first fans of each circ. for head pressure control.

  12. #12
    Join Date
    Jan 2004
    Posts
    164

    Thumbs up

    Yes there is fan cycling for the first fans per circuit
    If you find it bad 3 different ways- ~its bad~

  13. #13
    Join Date
    Mar 2008
    Location
    NY NY
    Posts
    181
    I would agree with the members who question water flow rates. How are you validating gpm ? The control PID's established by Trane are factory tuned using the min. max flow rates. The loops are tuned with a expection that the connected load reflects the mim max values. You stated 200 tons with a mim of 250 gpm correct. If you provide the Delta t at the min flow we can work the numbers for you. You may also look at the min water content for this unit. Do you have the water content required ? Water content = the sum of all the piping and connected loads in us gallons fulid. You said all the crac units were not on line. Water content is as important as gpm when runnig chilled water on low evap loads.

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event