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Thread: Selection criteria for chilled water control valve in Air Handling unit

  1. #1
    Join Date
    May 2022
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    Selection criteria for chilled water control valve in Air Handling unit

    I want to know about how to choose Chilled water control valve for Air handling unit.
    I mean it is based on just the line size or else there are other selection parameters that need to be check.
    If any one having the selection guide then please do share.

    Also why it is always connected on the return side ?

  2. #2
    Join Date
    Dec 2004
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    Chicago area
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    Does not have to be on the return, more of just standard practice.

    But in the case of low pressure systems, or top of the system, the added pressure drop of the control valve at the oultet of the coil helps to maintain a full coil.

    Line size is not the correct way to select a control valve.

    If on/off only, then selection is simpler. Line sizing works, just need to account for the valve in the pump head.

    If modulating, you need to have enough pressure across the valve for modulation to be smooth.

    I typically use 5 or 6 psi pressure drop across the valve at design flow rate.

    Essentially the valve needs to have more pressure drop then the coil for modulation to work right.


    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Dec 2004
    Location
    Chicago area
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    If a valve already exists, then match the Cv value of that valve to the new one, or as close as possible


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