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Dunham system with new boiler, banging in pipes

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paul_81
paul_81 Member Posts: 27
I installed a Weil McLain LGB 7 in a system that has a Dunham 640 in the basement above the boiler. There are also Dunham valves and steam traps on most of the radiators. I am getting intermittent banging in a few of the radiators. Most of the steam traps in the building are ancient.

As the boiler starts to steam, the 640 is purging tons of air. Towards the end of the cycle the 640 air noise is pulsating.

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  • paul_81
    paul_81 Member Posts: 27
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    some pictures...may help
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
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    Pressure? Traps working OK? Are there crossover traps? Are they OK? If not, fix those problems first. Then go and look for places where water might be caught.

    Also I hate to ask, but... did you match the old water line when you installed the new boiler? If not, you could have some real -- and hard to fix -- problems with wet returns.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • paul_81
    paul_81 Member Posts: 27
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    I have the pressure as low as the control will go - it cuts off at about 2 psi

    I found 1 crossover trap that seems to be working - it is at the end of a main and connects to a pipe that runs back to the 640

    water line is not matched, can you tell me more about that
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,544
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    If the new boiler water line does not match the water line of the old boiler height wise you cold have issues. Can you post some pictures of a radiator, cross over trap and some pictures of the boiler and the piping around it, not too close stand back so we can see
  • paul_81
    paul_81 Member Posts: 27
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    There are two pictures a few posts back. Here's a few more:
  • paul_81
    paul_81 Member Posts: 27
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    return piping
  • EzzyT
    EzzyT Member Posts: 1,295
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    What size is the header you plumbed on that boiler?
    A boiler that size the header should be at least 6” and the 2nd supply tapping should’ve been used too.
    You need to add at least a swing joint on that header.
    Pressure on that system needs to operate at a maximum of 8oz not 2 pounds.
    Cross over traps, radiator traps and f&t traps need to be looked at too.

    E-Travis Mechanical LLC
    Etravismechanical@gmail.com
    201-887-8856
  • MilanD
    MilanD Member Posts: 1,160
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    Is the banging new with the new boiler or has it banged the same with the old one too? Where are these radiators in relationship to the boiler: closer, midway, end of main? Does the main turn 90 right before or after the rad riser takeoff? As ezzyT said re header and takeoff, your steam quality conditions and speeds may have changed with the new boiler depending on the boiler riser and header set up, thus all the questions above to try to diagnose what changed to cause this banging. 
  • paul_81
    paul_81 Member Posts: 27
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    The banging is at two radiators- one on the second floor and one on the third floor, towards the end of the main

    I read through many posts here, consulted with the Lost Art of Steam Heating, and the Weil Mclain manual to determine that a single supply tapping of 4" is sufficient.

    It looks like I should get a vaporstat, set to 8 oz, get a 1-3 psi gauge instead of 30 psi and check the traps on the far away radiators
  • MilanD
    MilanD Member Posts: 1,160
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    That sounds like a good plan. Also see that the rads are pitched properly, in this case towards the trap. You didn't say if the banging was there with the old radiator too (or I missed that info). May have nothing to do with the new boiler, but again, lowering the pressure may help. I'm also assuming the boiler was properly sized. You may also explore installing hi-low on that boiler if needed for even heat distribution, esp if people are regulating heat at individual rads. Lo-hi-lo comes standard with its gas train, all you need is another vaporstat.
  • tumbz
    tumbz Member Posts: 94
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    paul_81 said:

    The banging is at two radiators- one on the second floor and one on the third floor, towards the end of the main

    I read through many posts here, consulted with the Lost Art of Steam Heating, and the Weil Mclain manual to determine that a single supply tapping of 4" is sufficient.

    It looks like I should get a vaporstat, set to 8 oz, get a 1-3 psi gauge instead of 30 psi and check the traps on the far away radiators

    i had banging also for years that woke me up every night. i finally fixed it. I made sure all the valves are working and opened all the way. I changed all my air vents to vent rites #1 adjustable so i can balance the system. I went to every radiator and pitched it correctly, and raised it and the pipes as high as i could get it. I switched to a vapor stat at 8 cut in and 14 cut out with a 1-3 PSI gauge.

    My system now runs at about 4-6 ounces, depending on which air vents i opened or closed and banging is all gone.

    I love this forum....
    MilanD