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  1. #1
    Join Date
    Apr 2007
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    Amarillo by mornin'
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    859

    Chilled water running through a non-running chiller

    Hey gents,
    I've got maybe a silly question, but I'm not exactly clear being I've heard a few different answers (I'm a controls guy so be easy on me!). I've got a mechanical guy telling me that 42° chilled water running through a standby York water cooled chiller, it will not do any harm to it, even for months on end.

    I don't have a model number handy, but if it helps I can get it tommorrow.

    Is he right or is he trying to get out of this mess?
    "It's not that I'm smart, it's that I stay with the problem longer”
    Albert Einstein

  2. #2
    Join Date
    Jan 2009
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    Not in Iran
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    1,107
    Not that this matters but is this in series?
    You can have either series or parellel setup,
    I don't see any harm with running chilled water through the machine evap
    ., now leaving the machine off for long periods of time is another story.
    no signature blast'em man blast'em
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  3. #3
    Join Date
    Apr 2007
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    Amarillo by mornin'
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    859
    No it's in parallel. During the winter the smaller chiller will run for months and this chiller will just sit there, this is the part we are worried about.
    "It's not that I'm smart, it's that I stay with the problem longer”
    Albert Einstein

  4. #4
    Join Date
    Mar 2007
    Posts
    3,124
    The main things I would be concerned with are:
    • If it's parallel, it's extremely wasteful to run water through a chiller that's not running. If it's series, it's also wasteful, but due to the added pressure drop from having to pump through a chiller that's not doing any work.
    • Premature rusting of the components due to the chiller barrel being cold all the time, eventually causing insulation failure and refrigerant leaks. Great way to shorten the chiller's life expectancy.
    • If it's a low-pressure machine, the purge will have to work a little harder to remove any air that accumulates while it's off.
    • If it has a D.P. or paddle mechanical flow-proving device, that device could get stuck in the closed position and fail to open when there is no flow. Seen it lots of times.
    "There is no greater inequality than the equal treatment of unequals."

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  5. #5
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
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    3,724
    Why not just valve off the idle chiller and force all the water thru the pony chiller?
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  6. #6
    Join Date
    Apr 2007
    Location
    Amarillo by mornin'
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    859
    Too much water flow and they are down to one pump, but they are wanting us to change the program to accommodate for this. So now it's our problem.

    I was just wanting to make sure before we go through and change programs it's not going to be a waste of time. Thanks for the replies so far.
    "It's not that I'm smart, it's that I stay with the problem longer”
    Albert Einstein

  7. #7
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
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    4,493
    if you have 55F water coming back to both chillers and 1 puts out 45F water while running and 1 puts out 55F because it is not running...what temperature water do you get going out to your building?


    hint: it is 50F

    now what would happen if you isolate the non-running chiller?
    "If you pull one more stunt like you just pulled with Tommy, you won't have to get on a plane because I will personally kick your ass from here to Korea!" - Best of the Best

  8. #8
    Join Date
    Jul 2007
    Location
    The Hot South
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    1,353
    It would be very hard for you to have 42F water running through a non running chiller piped in parallel unless you have absolutely no load in the building.

    As Jay said, if you have 52F entering both chillers and 42F leaving the running chiller, you still have 52F leaving the standby chiller mixing with the 42F from the running chiller and supplying the building with warmer water than you probably want.

  9. #9
    Join Date
    May 2010
    Location
    Michigan
    Posts
    37
    I am assuming from the OP that the idle chiller is completely off including its chilled water pump. If so, 42 degree chilled water from the running chiller is being pushed backwards through the idle chiller. The most likely cause for this is a check valve is not holding at the chilled water pump of the idle chiller. To remedy either get the check valve to hold or close a valve in the idle chiller's chilled water line. If you want to stop this with a control add an auto isolation valve in the idle chiller's chilled water line.

  10. #10
    Join Date
    Jan 2009
    Location
    Not in Iran
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    1,107

    wow good thread.,

    make sure you rotate the machines monthly.,
    weekly if possiable


    i be learning.,
    no signature blast'em man blast'em
    !!!KILL THE TERRORIST!!!

  11. #11
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,119
    If (primary) pumps are piped in parallel, with a common header to the chillers, then with only one pump running, each chiller would be getting only half its required flow, making this situation even worse still. Although, if this is the case, there should already be automatic isolation valves on the chillers.

  12. #12
    Join Date
    Mar 2004
    Location
    ottawa canada
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    2,100
    Im going to make a big assumption here and say that the one pump is big enough to supply all the water to both chillers ?
    Why not put a drive on the main pump and automatic valves on the chillers .
    When one chiller is on run the pump at a speed suitable for one chiller with the auto valves closed on the other chiller , both chillers on both valves open , speed up the pump to supply both chillers ...done ?? Again Im assuming both chillers are the same size piping is similar to both chillers as far as elbows etc for pressure drop etc .
    You could then rotate the valves and chillers to even out the wear and tear .
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  13. #13
    Join Date
    Mar 2003
    Posts
    7,326
    The way I read this, they have a pony chiller, but the pump associated with it has failed, causing them to use the larger pump on the smaller machine. Due to the larger pump being too much flow for the pony chiller, they are letting the flow go through both machines. This is causing the leaving chilled water to be mixed as noted. Since it is off peak cooling season, it is probably fine with respect to leaving water temp, they are just concerned about the flow through the larger machine doing damage to the machine.

    It most likely will be fine as far as real damage is concerned, but tube fouling will occur unnecessarily. Since the dewpoint is probably much higher right now than during peak cooling season, condensation shouldnt be too mcuh of an issue, especially since they are running return through it at say 50 degrees plus.

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