Results 1 to 7 of 7

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

  1. #1
    Join Date
    May 2022
    Posts
    5
    Post Likes

    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
    Location
    Chicago area
    Posts
    15,754
    Post Likes
    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
    Posts
    15,754
    Post Likes
    If a valve already exists, then match the Cv value of that valve to the new one, or as close as possible


    Sent from my iPhone using Tapatalk

  4. #4
    Join Date
    Jun 2022
    Posts
    3
    Post Likes
    Control valves are usually based on pipe size and the type of controls (JCI, Trane, Honeywell...).

    Connected on the return side to help keep the air entrained in the solution and to help prevent sediments from settling and clogging coil.

  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    40,292
    Post Likes
    Quote Originally Posted by btboys View Post
    Control valves are usually based on pipe size and the type of controls (JCI, Trane, Honeywell...).

    Connected on the return side to help keep the air entrained in the solution and to help prevent sediments from settling and clogging coil.
    No there not!

    CV ratings, flow ratings all play into sizing.

  6. #6
    Join Date
    Mar 2009
    Location
    Several Miles from Sane
    Posts
    2,337
    Post Likes
    Quote Originally Posted by btboys View Post
    Control valves are usually based on pipe size and the type of controls (JCI, Trane, Honeywell...).

    Connected on the return side to help keep the air entrained in the solution and to help prevent sediments from settling and clogging coil.
    I have to disagree as well.
    Brand has almost nothing to do with the selection. The selection should be based on Flow in GPM and expected (Since actual can only be know after the valve is installed and operating) Differential pressure.

    Look up the definition of the term "Cv". Is is basically the Flow in GPM at 1 PSI of Differential Pressure (Delta-P or DP). As the Delta-P increases the "Cv" decreases.
    I believe there is a section about this in the Honeywell Grey Manual but I could be wrong.
    If sense were so common everyone would have it !
    You cannot protect the Stupid from themselves !
    "Experience is the ability to recognize a mistake Before you make it again!" (Stolen Quote)

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    40,292
    Post Likes
    Quote Originally Posted by Cagey57 View Post
    I have to disagree as well.
    Brand has almost nothing to do with the selection. The selection should be based on Flow in GPM and expected (Since actual can only be know after the valve is installed and operating) Differential pressure.

    Look up the definition of the term "Cv". Is is basically the Flow in GPM at 1 PSI of Differential Pressure (Delta-P or DP). As the Delta-P increases the "Cv" decreases.
    I believe there is a section about this in the Honeywell Grey Manual but I could be wrong.
    Its in there also!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •