Re: Hydronic system - pipes BANG when zone shuts down


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Posted by pillsbury on January 06, 1998 at 16:33:40:

In Reply to: Hydronic system - pipes BANG when zone shuts down posted by Dale Van Aken on January 04, 1998 at 10:45:25:


: I have a new hydronic system with 3 zones (h'well stats). Sometimes (not always - but in the middle of the night seems popular) when a zone satisfies, about 1 sec after I hear the circ stop, the pipes do this LOUD Bang-Bang-bang-bang thing - each bang a little less loud. The sound appears to be pipes flexing (sounds like copper hitting something). I have tried to isolate all combinations of zones and cannot duplicate this by myself (isn't this an engineering rule: "the defect never is visible when you're watching it"?). Anyway, I considered that the circ (Taco 011) might be running too long and trying to pump into a closed valve, but the circ is directly controlled by the zone valves with their outputs (N-switch?) in parallel. I don't see how the circ could run too long unless the timing in the zone valve is on the hairy edge, or inconsistent. Do zones valves fail in this manner? I've never had H'well ones before. Even if this is the case, can a circ like this create enough head to bang the pipes hard? I thought that they were able to run even against resistance. This is waking the kids and bothering the wife (which of course, is why I have to fix it!). I know there are soem real boiler pro's out there. Any ideas? Thanks.

if it were me i would start by looking at what the hi/low limit setting was on your aquastat
control. usually i will set them at hi (200) lo(180)
with diff.(20). you may find that your settings are to high causing the boiler to over heat the water at the tail end of a cycle thus boiling the water making steam, causing a banging sound. i've seen this many times id start with this before i tore apart a zone valve. also, if your limits are set at 200/180 try setting them at 190/170 ive also seen times where the control overides the limit a little and a lower setting had to be used because they are not always 100% accurate. also you should contact the person who put your system in because you will only make his job harder if you mess with it!!. but if you do decide to tackle it yourself i think your problem is with the limit settings. not the zone valve

pillsbury:


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