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  1. #1
    Join Date
    Oct 2008
    Location
    Canada
    Posts
    83

    Normally Open Normal?

    Took a look at a job today that one of our market accounts had done on their HVAC. They're using a chiller and multiple fan coil units, is it normal for guys to use normally open valves for the HW and CW lines at the air handler, also for the CW valve to be in the supply and the HW valve to be in the return? Am I nuts or should the CW coil be 2 row and the HW be 1 row, not vice versa? These things aren't working too well and they're looking for a reason...

  2. #2
    Join Date
    Jan 2005
    Posts
    605
    Not exactly sure what you are describing. Heating is definetly fail safe normally open, full heat so nothing will freeze.

  3. #3
    Join Date
    Oct 2008
    Location
    Canada
    Posts
    83
    fail safe sure, but the valves themselves are normally open, both of them CW and HW. CW valve is in the CW supply line and the HW valve is in the HW return line (lines to eah fan coil). My main question is about the coil though, should a 2/1 row - 4 pipe be 2 row cooling and 1 row heating?

  4. #4
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,724
    I guess the next question is are you transferring any load on your fan coils? Chiller temps and fan coil temps ?
    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.

  5. #5
    Join Date
    Jun 2010
    Location
    Miami
    Posts
    258
    I am seeing more guys go to normally open valves. I like normally closed but it doesn't get cold in Miami. The valves should both be on the return line IMHO. They should have circuit settings to limit GPM's.

    In Canada I could see the heating coil being bigger than the cooling coil. Needless to say in my area they are a lot smaller.

  6. #6
    Join Date
    Mar 2005
    Posts
    67
    Chilled water valves are and should be N/C fail safe, you never want to load the chiller just because you lost your air compressor control or a fan coil or AHU is down. Hot water valves are and should be N/O fail safe for freeze up's. Most of the time I see the control valve on the return side.

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