One pipe residential steam

Rrothowski

Why does it bang at the end of the heating cycle? It bangs once in the vicinity of the radiator at the end of the heating cycle.

Jamie Hall

Depends on what's banging, and what kind of bang. Usually at the end of a cycle -- the boiler has just turned off -- it will be a contraction noise as pipes and the radiators cool.

ethicalpaul

I'm trying to think of an issue that would cause a water hammer interaction between steam and cooler water at the end of a heating cycle and I'm not coming up with one...but maybe?

I would think if any kind of time has passed since the end of firing (like more than a couple minutes) then it is probably physical contraction of pipes like @Jamie Hall said

KC_Jones

Where is the bang? In the vicinity of a radiator, or at the boiler?

I've watched on with a Hartford loop at the wrong height that would make a fairly loud bang at the end of every cycle.

Besides that, I'd tend to agree with @ethicalpaul that it most likely is expansion noise.

DanHolohan

Could be a clogged wet return. 

Rrothowski

Thank you All,  you all are true Master Professionals. 

Hap_Hazzard

Check your water level when the banging happens. If the level drops below the Hartford loop you can get some water hammer. This can happen if your wet return is clogged or your boiler is throwing too much water into the system. Either condition should be addressed.

PhilKulkarni

All my Sunrad recessed radiators make a clicking sound as they heat up; my free standing Burnhams don’t. The largest Sunrad however, makes a loud thud just before the vent closes, and makes the same loud thuds 3 mins after the boiler shuts off. This is followed by 2 thuds about the same amplitude 5-6 mins later. The plaster wall just above the vent on this rad frequently cracks and using a paper tape instead of fiberglass has minimized the width of the crack but not eliminated it after fixing it 3X.

Pipes stay quiet.

I have increased the pitch of this rad but it has made no difference. I have downsized the vent, but that raises the temp of my upper floors since the stat is located on the same floor as the said vent and the boiler runs longer. Any suggestions?

neilc

this may be expansion contraction,
see if you can slip some cuts of plastic milk jug where3 the fin tube rests on mounts, or against cover ribs or what nots, also check for rubbing where pipes come thru walls or floors, more plastic strips there

BobC

The Sunrad in my bathroom talks to me while heating up, i think it's caused by being set into a tiled wall. The tile is set right up against the cast iron so it has no room to move, it's going to be an expensive job if that rad ever has to be pulled out. The noise is not ay all obtrusive so I've let it be for the last 4 decades.

Bob