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Could Bad Main Return Vents Cause Water Hammer?

Hey guys we installed a new boiler and the near boiler is correct, all the radiators valves are open and the main is pitch correctly. The boiler was still knocking . I changed 1/3 main return vents and was still knocking. Came back today and the other 2 main return Vents that was hidden . Changed them both and boiler stopped knocking.... Can someone please explain why changing the main return vent will cause water hammer 

Comments

  • ethicalpaul
    ethicalpaul Member Posts: 4,176
    The pressure might have risen to a point that could cause water level problems.

    did you skim it?

    can we see the correct near boiler piping? It’s such a rare treat.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    EdTheHeaterMan
  • pedmec
    pedmec Member Posts: 711
    The vent might not have opened back up after the pressure dropped and formed a vacuum. this could have cause flashing of the condensate because its at its saturation point already. flashing of the condensate and rapid contraction of the steam is one cause of water hammer.
  • ChrisJ
    ChrisJ Member Posts: 13,863
    pedmec said:
    The vent might not have opened back up after the pressure dropped and formed a vacuum. this could have cause flashing of the condensate because its at its saturation point already. flashing of the condensate and rapid contraction of the steam is one cause of water hammer.
    Certainly doesn't sound realistic to me.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • pedmec
    pedmec Member Posts: 711
    @ChrisJ Then you don't know what a flash tank is do you?
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    I'm going to assume that the near boiler piping is correct, but... is this single pipe steam? if so, one possible problem has to do with how the high level steam main extensions (often called dry returns, though they aren't) are connected at the boiler.

    Can you clarify?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ChrisJ
    ChrisJ Member Posts: 13,863
    pedmec said:
    @ChrisJ Then you don't know what a flash tank is do you?
    Isn't that the show with the 4 rich people that listen to ideas?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,097
    I think it unlikely that bad main vents would cause knocking. There is probably more to this story.
    ethicalpaul
  • Dairon421
    Dairon421 Member Posts: 78
    The pressure might have risen to a point that could cause water level problems.

    did you skim it?

    can we see the correct near boiler piping? It’s such a rare treat.
    The pressure might have risen to a point that could cause water level problems.

    did you skim it?

    can we see the correct near boiler piping? It’s such a rare treat.
    I'm going to assume that the near boiler piping is correct, but... is this single pipe steam? if so, one possible problem has to do with how the high level steam main extensions (often called dry returns, though they aren't) are connected at the boiler. Can you clarify?
    One pipe 
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    Near boiler should be OK. That's something! I notice, however, an insulated pipe behind the boiler. What is that pipe?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,913
    edited October 2022
    Is the flue connector (smoke pipe from boiler to the chimney crock) properly sloped at least 1/4" per foot going up from boiler to chimney? It looks like the pitch is the wrong way... But it may just be the camera angleOtherwise, The near boiler steam piping looks good. Nice Work!
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • ethicalpaul
    ethicalpaul Member Posts: 4,176
    Is it a single main with three vents on it, or are there multiple mains splitting off that one riser?

    it seems kind of big to just have one riser, but it’s hard to tell from looking
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • Dairon421
    Dairon421 Member Posts: 78
    Near boiler should be OK. That's something! I notice, however, an insulated pipe behind the boiler. What is that pipe?
    That the return piping 
  • Dairon421
    Dairon421 Member Posts: 78
    Dairon421 said:
    Near boiler should be OK. That's something! I notice, however, an insulated pipe behind the boiler. What is that pipe?
    That the return piping 
    That may be the problem. I saw the water line surging 
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    So I expect that's the problem with the hammer. It is much too close to the water line. Either raise it at least 28 inches or drop it to the floor.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pedmec
    pedmec Member Posts: 711
    i think the OP asked the question why changing the air vents stopped the system from banging?
  • Jamie Hall
    Jamie Hall Member Posts: 20,416
    pedmec said:

    i think the OP asked the question why changing the air vents stopped the system from banging?

    So he did -- and my guess, and it's just a guess, is that changing the venting changed the internal pressures just enough so that that pipe is just barely solidly wet, which would make the difference.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ethicalpaul
  • Dairon421
    Dairon421 Member Posts: 78
    Yeah I found the problem. The problem was my Hartford loop tee wasn't low enough Below the water line. I thought it was supposed to be 2" below but the boiler I'm installing said 6" below water line. What was happening was steam was pushing back to my return and causing water hammer because the tee wasn't low enough 
  • ethicalpaul
    ethicalpaul Member Posts: 4,176
    6" below is odd but yeah it shouldn't hurt anything. Especially since the Hartford loop doesn't protect you to speak of anyway.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG