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HW baseboard bangs when shuts off

Hi, this is my first post. I have a hot water baseboard system that recently had the air bleeder valve and a zone valve replaced, ever since the zone valve was replaced I get the hammering noise in the pipes but only when the furnace shuts off after it has reached the tempature. I have spent time sitting in front of the boiler to try to see what is banging but it never happens when I'm watching it. it only does it once in a while but it bothers me knowing theres a problem. the system was bled twice by the oil contractor and I check the schrader valve on the air purge and it only hissed out a tiny bit of air once. any ideas?


Re: HW baseboard bangs when shuts off


This could be an air problem, but more likely it sounds like a loose connection on the zone valve.

Your unit is referred to as a boiler, never a furnace.

Could you post the model & make of the zone valve.

The installer who did the work should come back free of charge to check this out & correct the problem---why don't you call them now, while you're thinking of it.

Some models of zone valves will clatter or bang at the end of the heating cycle if the hold-down screws inside are loose.

It's always more effective to bleed air from the highest baseboards---upstairs in the living quarters (if you have bleed valves in those baseboards), since air in piping always migrates to the highest point in the system.

Re: HW baseboard bangs when shuts off

thank you for the reply, the zone valve cover says it is a honywell. I can not find any bleeders on the system other than the air purge at the boiler.

thank you

jim hankinson
Re: HW baseboard bangs when shuts off

Was the complete zone valve replaced or just the power head? If the valve is installed backwards it will most definitely bang on closing.

Blue RidgeParkway
Re: HW baseboard bangs when shuts off
comsec1 wrote:

I had posted about a problem with my hot water base board banging(water hammer) when the zone shut off. the problem was the new honeywell zone valve that the oil company service put in.
after 3 house calls for the same problem their lead tech was sent and removed a spring on the valve that assists closing the valve. he said they have received many complaints of this and honeywell said they had changed this spring to a heavier spring. spring is not needed and now I can sleep. hope this helps others if needed and thanks to the people who replied

It was nice to hear that you resolved this problem. I'm quoting your follow-up post which you placed on another string for the benefit of those that actively participated in your original topic string (here).

This is a direct link to your follow-up (new topic string): http://advice.thisoldhouse.com/showthread.php?t=10318

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