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Thread: Trane heater

  1. #1
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    Trane heater

    we recently installed electric pre-vacs on our chillers to keep our low pressure chiller at 0 psi to avoid sucking in air if there are minor leaks. this is the strange part; whenever we seem to run these heaters and then shut the heaters off to run the chiller, the oil return system doesn't seem to return the oil... the oil level is always low after use of the heaters.

    any ideas as to why?

  2. #2
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    Model number?
    Your poor planning does not constitute an emergency on my part!!!!

  3. #3
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    Quote Originally Posted by joey94 View Post
    ...the oil return system doesn't seem to return the oil... the oil level is always low after use of the heaters...
    1. what is the oil level when the chiller is off and the heaters are on?
    2. what temperature is the oil sump when the chiller is off and the heaters are on?

    most likely, the refirgerant is now condensing in the oil sump. this could be due to many factors, usually because the oil heater has failed or is failing. at start up, the extra refrigerant boils out of the oil sump and carries the oil with it.

    so you probably don't have an 'oil return' problem...you have an 'oil leaving' problem.

    model/serial number, age, refrigerant and the above would be most helpful.
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

  4. #4
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    Its a 10 year old 1900 ton, Trane cvhf1780. R-123. The oil sump temp maintains 140 when the chiller is off and at the top of the sight glass. I'm not having a problem with the oil sump heater, its working fine. we only have the problem with the oil level when we use the Prevac heater. If we leave the prevac off, then everything is fine.

  5. #5
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    at 1740 nominal tons, my guess is that you have around 3500 lbs of R123. at 0 psig (82.08F sat) you have about 290 gallons of liquid refrigerant and 9 gallons of oil...it does not take much refrigerant to saturate the oil. and the refrigerant has a better excuse than before to saturate the oil...the refrigerant is hotter!

    so, again, you may have 140F oil (keep in mind that the sensor is about 1/4 of the way up on the oil tank. so it is cooler at the top of the oil.

    before start up, the oil sump is at the same pressure as the rest of the chiller, 0 psig in theory. at start up, the vent line solenoid valve closes for about 90 seconds to prevent the oil sump from dropping the pressure too quickly...however, it still drops the pressure pretty quick. when this happens, the refrigerant is going to boil out of the oil sump and carry some oil with it...no big deal, that is why there are eductors on the chiller. if your vent line solenoid does not close, then you could very easily drop the oil sump pressure too quickly and the refrigerant boils out faster than it is supposed to...oil goes bye-bye!

    if you have cold oil or any reason for the oil to get more saturated than before (like say, i don't know, a pre-vac) then the problem grows worse than before. check your vent line solenoid for proper operation.

    i love pre-vacs. i sell them at every opportunity, however, some things need to be thought through all the way.
    my 1st time jumping out of a plane...http://youtu.be/Kv38G0MHsGo

  6. #6
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    Ditto Jayguy , vent line solenoid issue possibly .
    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 .

  7. #7
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    a vent line solenoid?? i dont remember it having one, but ill check tomorrow. if the sol is operating properly, then what? should i keep the prevac temperature below the oil sump temp?

  8. #8
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    [QUOTE=joey94;10450422]a vent line solenoid?? i dont remember it having one,

    If it doesnt BINGO ...Houston we have a problem .
    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 .

  9. #9
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    i know my YST's and YG's have them, didn't notice the tranes. we will see tomorrow.

  10. #10
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    [QUOTE=graham;10450492]
    Quote Originally Posted by joey94 View Post
    a vent line solenoid?? i dont remember it having one,

    If it doesnt BINGO ...Houston we have a problem .
    have a pair of CVHE710's, circa 1987 in my stable without oil sump vent line sillynoids, without oil problems.
    \m/
    original member of the racoon brotherhood

  11. #11
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    i just jinxed the machines, didn't i?
    \m/
    original member of the racoon brotherhood

  12. #12
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    do you have Pre-vacs on these chillers? that seems to be the root of the problem.

  13. #13
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    Quote Originally Posted by joey94 View Post
    do you have Pre-vacs on these chillers? that seems to be the root of the problem.
    used to have the prevac blankets. now have the mini water heaters, that aren't used. room is usually hot, machines when off are 2-3# positive.
    \m/
    original member of the racoon brotherhood

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