×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Three Way mixing valves

Three Way mixing valves

Three Way mixing valves

(OP)
Is better to use a diverting valve or mixing valve at the AHU on a chilled water system?

RE: Three Way mixing valves

It depends on weather the system is a constant flow or a variable flow system.
Three-way valves by their nature bypass supply chilled water into the return line, causing chilled water return temperatures lower than design. This exacerbates low delta -T problem. Therefor you want to  use a minimum of three-way valves in variable flow system. Two-position bypass valves across supply and return lines, strategically situated and controlled properly is preferred to ensure minimum flow.

RE: Three Way mixing valves

(OP)
The system will be constant. Thanks btw

RE: Three Way mixing valves

As I understand it, functionally there is no difference whether you use the mixing valve or diverting valve; however, I have seen more often than not, the mixing valve in these three-way valve applications (where the valve is in the return piping vs. the supply side of the coil where it would be a diverting valve).  I was told that this is because a mixing valve is typically less expensive than a diverting valve.

RE: Three Way mixing valves

We specify diverting valves on our projects. They have given us better cooling coil temperature control than mixing.

RE: Three Way mixing valves

stevenw:  I'd like to hear more about how exactly 3-way diverting valves give better cooling coil temperature control.

To reiterate the predominance of 3-way maixing valves, it's the reason you see two-way valves traditionally placed on the return side of coils (where the mixing valve would go as opposed to the diverting valve).

Ifc09:  Don't forget, when using the 3-way mixing valve,  you need a balance valve in the bypass line which matches the pressure drop of the coil so that a fluid "short circuit" won't occur.    

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources