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Thread: Water Hammer

  1. #1
    Join Date
    Apr 2011

    Water Hammer

    I am a heating and air conditioning contractor in the Philadelphia area. Been doing this stuff a long time, but I've run into something that I'm struggling with. I recently purchased a house with oil hot water baseboard heat. I added (2) radiant loops to the bathrooms when we renovated them this summer. They are off their own secondary loop with their own circ.
    I have (4) zones of heat not including the radiant, zoned with zone valves ( a mix of taco and honeywell 4 wire valves). A single Taco 007 circ pump (located on the return close to the boiler, pumping towards the expansion tank on the supply side).
    I'd never heard it hammer before the radiant loops went in, but now it happens almost every time another zone completes its call. It's bad too. The finned element sounds like it wants to jump out of the cabinet it's so violent. I figured it was being caused by the radiant circ somehow so I turned off the radiant, but that didn't stop it. It continues to happen, so now I'm assuming it is being caused by where the secondary loops for the radiant were tied in.
    Anyone have any experience with this? I'm stumped. Luckily it's in my own home, so I can just benefit from what I learn.

  2. #2
    Join Date
    Feb 2004
    New Mexico
    I'd probably start with the expansion tank.
    "What Fools these mortals be"....Puck

  3. #3
    Join Date
    Feb 2011
    Avon, Ohio
    I would check that the zone valves are in the right direction. I have seen Honeywell valves make a banging noise when they are in backwards.

  4. #4
    Join Date
    Nov 2011
    Long Island, NY
    You could change the 007 out for an ECM circ like the Alpha. I've used zone valves on the supply right after an Alpha with no hammering.

  5. #5
    Join Date
    Apr 2001
    Western PA
    Does it hammer when one zone ends and other zones are still calling, or does it hammer when the last zone ends?

  6. #6
    Join Date
    Mar 2008
    Fuquay Varina, N.C.
    Quote Originally Posted by hvacker View Post
    I'd probably start with the expansion tank.
    I have to agree here, I would check to see if the expansion tank has lost it's charge and become waterlogged, also because of the set up you have where the circulator is pumping towards the expansion tank check to see what your pressure builds up to, should be 12PSI but in that set up it could get up to 18PSI. if you have to replace the tank you may have to adjust the pressure.
    RSES Member.
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  7. #7
    Join Date
    May 2011

    water hammer

    i think i can help but there are somethings i'm curious about.where did you cut in the radiant loops-after the air scoop on the supply?where are the zone valves-supply or return?did you use a mixing valve on the radiant loops?did you make it so you can isolate the radiant loop from the system with ball valves?is the circulator on the supply or return on the radiant loop?what is pressure on the system?with all that being said i'm trying to keep it didn't have a problem til you added the radiant right,so maybe the problem may lie there.if you isolate the radiant loop then it's like it's not there right.
    if the banging still happens then it's a zone valve problem not an expansion tank problem.if the zone valves are installed directionally correct then take 1 of the springs off the honeywell zone valves.this slows the valve closure and may fix the problem.done this in the past on a few calls.

  8. #8
    Join Date
    Feb 2009
    Fox Lake IL
    sounds like your pump is still running when the zone valve is clossing making it bang.I had one unit that i had to put a flow reducer on (its a three way valve that slows the watter down. or your pump is to big and moving to much watter.

  9. #9
    Join Date
    Mar 2005
    Suppy NC
    remove the lower spring from the honeywell zone vzles
    if in a certan position they can hammer because of springing back and the ball bounces
    years ago you remove one spring and problem solved

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