Water hammer in hydronic system

August Hasz

I have a water hammer problem in a 5 zone in-floor hydronic heating system. The downstairs zones are poured-in-slab and the upstairs zones are laid in gypcrete. I have one circ pump for all the zones with a pressure relief bypass valve at the "end" of the loop. The bypass is 3/4" on a 1-1/4" loop, but the pressure range is in-line with the pumping head range (OK?). Whenever one of the upstairs zones shuts off (and the pump is still running becuase another zone is calling) I get water hammer. The system pressure is 18psi, typical operating temp ranges from 94 to 126 and there is an adequately sized expansion tank. The vavles are a honeywell v8043e1061, which have two springs, so I will try dropping one of them when I get home tonight. The zone valves are on the supply leg of the zones. Is this really enough to cause the hammer? I read one message that said placing the valves on the return would cure the hammer... Can someone explain why this makes a big difference? Or propose a better solution?

Kal Row

dont mees with the springs in the ZV...

you’ll will just kill it, either go to their new 5000-8043 series, or a taco ZV (real slow) or put in a water hammer arrester

putting the ZV on the return is no good as you get single pipe gravity convection - and loose heat into zones even when the return ZV is off, UNLESS, you put a SPRING-CHECK in each zone supply to stop gravity displacement - like dan holohan says, "be the water", cooler and thus denser water, drops right through warmer water - even in one pipe


ps the reason for less hammer if zv is on the return, is that, there are a lot more bends between pump and the ZV to act as a spring and take up the water's inertia

August Hasz

ZV chioce

So is this a common problem with these honeywell valves? Also you mentioned a water hammer arrestor- how is this differnet from an expansion tank and where on the loop would you recommend locating it?

Kal Row

YES the old and fast 8043's caused hammer...

but they were reliable and easy to service

as for the arrestor, yes and expansion tanks can do the same, provided it's in that location, i suspect the pump or a checkvalve is between the ZV's and the exp tank

STEVE N

question

what size circ are you using? An over sized circ can do it as well. figure this divide btuh of boiler by 60 x 20 x8.3. 60 min in hr...20degree delta t and 8.3 weight of water. This gives you gpm required. Then go to the circ manufacturer and check. 1 1/4 will carry 14 gpm.

check this first. I never had much trouble with Honeywell valves... now Automag yes

steve

August Hasz

Circ pump size

The pump is sized correctly (100 MBH boiler, req'd flow per your calc is approx. 10 gpm). I am using a Grundfos UPS 15-58 superbrute. This pump has high head for a typical circ pump, and if anything is delivering less than 10 gpm. Also when I run it at the lower speeds the water hammer is definetly less- but still there. 1-1/4" pipe is fine, but anyway the small dia bypass could be causing this?

August Hasz

Follow up

karlo@pobox.com is correct, the expansion tank is upstream of the pump, then the zone valves off of the supply side. Does anyone think that moving this location would be enough to fix the problem?

Kal Row

nope: the exp tank is exactly where it's supposed to be...

where the exp tank connects is known as "the point of zero pressure change", and the pump is supposed to "pump away" from that point - so that the pumps differential increases pressure on the discharge side, rather than create a lowered pressure on the inlet, which would happen if the pump was pumping toward the point of zero pressure change – lower pressure anywhere is bad as air is more likely to get in

also an exp tank as a hammer arrestor is lousy, as there it usually contains simply to much water in it (with it's own inertia) to allow for rapid inertia absorption

I am afraid there is no cheap solution – I am assuming of course, that you have all boiler room piping hung/supported/clamped tightly with rubber isolation clamps – if not, then that, maybe, all you need – a good strut clamp below the ZV and on each side around the bend leading out of the boiler room usually does it – solid yet isolated boiler room pipe mounting is basic

I use 8043’s a lot with no complaints

clammy

pdb

May be you need to adjust the pressure diff.valve open more so as zones cycle off the pressure is by passed into your return piping ,there should be a thermal trap before tieing into the return i perfere them to chks most of the time .I've piped honeywells on the supply with a 3/4 by pass and never had any hamming noises when zv closed with taco 0010 and 5 or 6 zones .Sounds like by pass isn,t by passing enough good luck peace clammy

MrPaul

Water Hammer Problem Solved!

Yes, I had WH problem a new circulator that came with my new boiler. There was plenty of WH, so I chose to throttle the main circuits down, but that only relieved it a bit. So.... I put back the circulator from my old boiler and no problem now. I don't know the stats of my old circulator to compare the two units.

If I couldn't correct the problem, I was going to invent an electronic control system that would shut down the circulator when a zone valve closed. It would restart after the valve closes. Not an easy solution though.

kcopp

There is a simple solution....

A Delta P circulator. Either the Wilo Stratos or the Grundfos Alpha (15-55) will work. The problem is Hydraulic jump... very common w/ fast closing ZV and flat pump curve circulators. The circulator will match the pressure to the flow. as an added benefit you will save electricity to boot.

icesailor

Water Hammer/Wilo Stratos:

Wilo Stratos work nicely and as advertised. I put one in my own home with 6 zone valves, Taco 3/4" 571's They didn't make noises but are quieter since I installed the Stratos.

haventseenenough

haventseenenough

do you have a zone valve that is installed backwards?