air hammering in a main branch

john_216

I recently had a new Weil McClain boiler installed. Everything works fine. The heat comes up really fast and all the radiators get hot very quickly. The only problem is that one of the two mains hammers like no tomorrow at the end a cycle. The boiler shuts down and the hammering begins. All radiators are shimmed to drain, all supply valves are open all the way and new air valves have been installed in the area of the hammering. Any ideas?

nicholas bonham-carter

noisy mains

is this a 1-pipe or 2-pipe system? is the hammering coming from the dry return?

have you looked at the area which misbehaves for low spots, which can trap water? what sort of main [not rad] vents are installed, and could they be hoffman 76-vacuum models? what sort of pressure is the system getting up to, verified by an accurate low-pressure gauge?

are the supply pipes insulated?--nbc

john_216

air hammering in main branch

It's a one pipe system. Supply pipes are insulated. There is a visible low spot on the main in question. I not sure what the definatioin of a dry return is but I can't tell where exactly the noise is coming from either steam main or return. I have Gorton # 1's at the boiler retrurns. The Honeywell pressure troll is set at 1 psi.

john_216

air hammering in main branch

It's a one pipe system. Supply pipes are insulated. There is a visible low spot on the main in question. I not sure what the definatioin of a dry return is but I can't tell where exactly the noise is coming from either steam main or return. I have Gorton # 1's at the boiler retrurns. The Honeywell pressure troll is set at 1 psi.

Steamhead

Fix the low spot

and the hammering should go away.

john_216

air hammering in a main branch

Thanks. I've never corrected a low spot. Would I disconnect the rads on that end and jack up the pipe and strap it to a joist?

Jamie Hall

You may not have to

jack up the radiators, but you may well have to put in some new hangars -- which don't have to fancy, so long as they work.  What you need to make sure of is that the low spot really is fixed, and the only way to do that is with a really good level.  Don't even try to do it by eye.