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  1. #1
    Join Date
    Mar 2013
    Posts
    6

    WaterSide Economizer

    We have been having leaks appear on our econo coils. The units are mcquay swp air handlers with water cooled condensers and water side econo coils. This only happens in the free cooling seasons. The leaks are appearing in the clean out ends of the coils on the rubber o-rings. Coil rating are 400 psi. The piping to the unit also have motorized isolation valves on both the supply and return lines that are energized with the units cooling enable contacts. Our tech noticed that pressures on the lines running we're 175psi but when the isolation valves close the pressure in the lines as well as the coil slowly builds up to between 400-500 psi. My question is could the valves when close creat no room for expansion when the water sitting in the coils that was cold being warmed up by the return air of the air handler cause that much of a pressure increase. Or am I looking at this all wrong.

  2. #2
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    973
    what type of system do you have? closed loop/HX or open loop/tower fan.

    does the pressure only rise in the coil..What are the pressures in the loop when these valves close?

  3. #3
    Join Date
    Mar 2013
    Posts
    6
    The loop is a closed loop tower system with 40 percent glycol solution. The pressure in in the lines and coil that are after the isolation line have the issues. The system and lines before the isolation valves are around the 175 mark.

    Quote Originally Posted by dlove View Post
    what type of system do you have? closed loop/HX or open loop/tower fan.

    does the pressure only rise in the coil..What are the pressures in the loop when these valves close?

  4. #4
    Join Date
    Sep 2002
    Posts
    2,735
    Quote Originally Posted by LCJ View Post
    We have been having leaks appear on our econo coils. The units are mcquay swp air handlers with water cooled condensers and water side econo coils. This only happens in the free cooling seasons. The leaks are appearing in the clean out ends of the coils on the rubber o-rings. Coil rating are 400 psi. The piping to the unit also have motorized isolation valves on both the supply and return lines that are energized with the units cooling enable contacts. Our tech noticed that pressures on the lines running we're 175psi but when the isolation valves close the pressure in the lines as well as the coil slowly builds up to between 400-500 psi. My question is could the valves when close creat no room for expansion when the water sitting in the coils that was cold being warmed up by the return air of the air handler cause that much of a pressure increase. Or am I looking at this all wrong.
    Yes it can happen!

  5. #5
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    Sounds right. Can you delay one of the valves closing, do both lines need to close for proper cooling?

  6. #6
    Join Date
    Mar 2011
    Location
    East Coast FL
    Posts
    1,058
    Interesting. Serious water pressure. Is there a reason to close both lines and leave the coil with no room for expansion?

    Seen it done both ways - close the leaving - close the entering.

    In this case maybe just close the entering so the coil will equalize to the lower return water pressure?

  7. #7
    Join Date
    Sep 2002
    Posts
    2,735
    I see it done all the time,mostly in office buildings. The valves are closed only on water leak detection. That's the thing ,another valve should be used for control of temp.

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