Zoned system Water Hammer

Vertexmark

The company installed a new mod con boiler in place of an off peak electric tank system. The old system was not pressurized and  had 4 circulator zones. The  new system uses  a Wilo variable speed circulator pumping away from the tank with a short manifold to  4 Caleffi zone valves. The problem is that when two or more zones are operating and one shuts off a water hammer occurs in the zone where the valve is closing.

I was asked to solve the water hammer problem. I have lowered the speed of the Wilo to bring the temperature differential up to between 25 and 30 degrees depending on which zone is calling. This helped to make the hammer less.  I also added additional hangers to the system which changed the noise but did not eliminate the problem.

I put a temporary bypass from feed between the pump and zone valves to the return but it did not make a difference in the noise.  Wilo advertises that a bypass is not needed with a VS pump.  Any ideas would be helpful.

 

clammy

zone valve direction

I would double check and make the zone valves are installed going in the right direction and not installed backwards .peace and good luck clammy

Ironman

A Few Suggestions

First, Make sure the zone valves are closing against the flow, not with it. I've never installed Caleffi zone valves, they should have an arrow indicating the proper direction of flow. You may have to move them to the return which is the proper location when the pump is on the supply. They should not be close-coupled to the pump as they are now. I'd try checking something else first and leave this step as a last resort.



Check to make sure there are no lines trapped against framing members in such a manner that the pipes cannot freely expand when heated. Particularly where there's a change of direction such as above the boiler from vertical to horizontal.



A delta P circ should not have a pressure bypass valve and this may be part of your problem as both the pressure bypass and the Wilo are trying to compensate for a change in pressure at the same time. If you can manually close the bypass, I'd do that or else remove it.



And again, if none of this corrects the problem, consider moving the zone valves to the return.



As always, some pics would be helpful.

ChasMan

Hammer Bammer

If you are handy, it is possible to take a wind out of the return spring. It makes it close slower. They are fairly slow closing allready but not slow enough. Just be carefull not to let the whole valve fly apart and have an extra head around in case you muff it up. I busted one figuring it out.

meplumber

We ran across this problem.

There is a bypass available for the Caleffi manifolds.  We had the same problem.  Caleffi was great.  Contact me and I will pass along the specifics if you need it.