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New water hammer on old boiler
Hoping someone can help. I have a Weil-MClain SGO-4 that we installed 20 years ago. It is running a single pipe steam system with in-wall convectors. It has run well and QUIETLY for the past 20 years until this heating season.
The whole system, but in particular one radiator, is banging like crazy whenever the heat comes up. It is both violent and persistent. As far as I can tell it does this until the air vent closes in the farthest radiator and then it quiets for the remainder of that heat cycle.
I changed some air vents and the main line vents thinking that could be the problem but no dice. I have noticed the sight glass water dips lower than normal when making steam than it had before but returns to normal height after the boiler shuts off.
A few recent changes; 1) the burner had some ignition problem causing soot and fouling and my service company came and cleaned the combustion chamber and performed annual maintenance. 2) in October I had the hot water coil that sits inside the boiler replaced due to corrosion.
It seems like a high pressure problem but my boiler's steam pressure gauge is broken/frozen so I am replacing that today to diagnose if my pressuretrol is malfunctioning or clogged. The switch in the pressuretrol definitely cuts the burner when tripped but I am not sure what pressure it is tripping at.
The only other thing I can come up with in my research is skimming but I am afraid of breaking something when removing the 1 1/2" cast iron plug that's been in place for 20 years.
Am I on the right track? Any other suggestions? What is overfiring?