Steam boiler water hammer

Al Brown

We replaced a residential steam boiler this fall and have been driven crazy ever since. The boiler hammers durring a heating cycle. We added two automatic zone valves to the system but didn't change anything else. The opening of the zone valves has been slowed with relays to approx 10 minutes. The boiler operates at 8oz with a 4 oz differential. It makes great dry steam and the noise(s) are not from or near the boiler itself. It does not flood or run short on water. Of course the homeowner is blaming us for the problems. We think we have narrowed it down to noise from two different risers that go under the 2nd floor. Any suggestions?

Dana

Post a drawing of the near boiler piping with the location of the zone valves, pipe sizes, etc. Some of the guys on this site will definately be able to help you with more info.

[Deleted User]

The noise

is probably from the condensation that forms at the valves when they are closed. Steam & water don't mix well in confined spaces. If you must use zone valves, the condensation must have a way to drain from the pipe before the valves open.

That is normally done thru a radiator trap back to the return. If you are maintaining pressure at all times, you might want to re-wire so that the aux switches on the valves turn the burner on only when heat is required. For more info on valves and steam, get Dan's book -"The Lost Art of Steam Heating."

Happy steaming.

steve_6

zone valves

Set those zone valves to the manual open position and leave it that way for a while and see if that doesn't help. Keep us posted!!!

Steamhead

I'll bet

those zone valves have turned the A dimension into a B dimension, causing water to back up into the mains. Then when steam hits the water- BANG! Lock them open as Steve suggested, I'll bet the noise goes away.

Best way to zone steam is with TRVs.

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