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air hammering in a main branch

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john_216
john_216 Member Posts: 12
in Strictly Steam
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?

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  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    edited February 2012
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    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
    john_216 Member Posts: 12
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    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
    john_216 Member Posts: 12
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    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
    Steamhead Member Posts: 16,835
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    Fix the low spot

    and the hammering should go away.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • john_216
    john_216 Member Posts: 12
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    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
    Jamie Hall Member Posts: 23,286
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    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.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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