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Only Bangs when thermostats satisfied.

qtown
qtown Member Posts: 9
I have a 20 year old Burnham Hot water Boiler that's worked perfectly. Converted gravity system, original piping and column radiators, with a Taco110 circulator. I have 2 HTX 60 expansion tanks installed. This is the 3rd straight heating season I've been putting up with this problem. The thermostat calls, pump goes on , house is heated, thermostat is satisfied, pump shuts off. Any where from 3-5 minutes after this sequence I get loud banging from the pipes inside the walls.

It is always the same banging, like someone is banging on them with a hammer. and it is not from the radiators. Boiler temperature usually stays at 140, Boiler pressure at 20psi when circulator is running, slightly less when it's not. Can't bleed any air out of the radiators. And it doesnt' matter if I turn the pump on for just a few minutes and turn it off before the boiler water gets a chance to heat up, so I don't think it's expansion. This problem is driving me crazy. Any ideas anyone?

Comments

  • RobbieDo
    RobbieDo Member Posts: 131
    Need more info

    What type of zone valves do you have, or is a pump running the zones? Why would you try and bleed air out of the radiators, there should be boiler drains where the boiler is. Are you pumping away from the expansion tanks? How many floorsmis the house?
    Rob
  • qtown
    qtown Member Posts: 9
    qtown

    No Zone valves, 1 zone with a 110 circ, on return. Been like this for 20 years with no problem until recently.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Is the banging

    on the return piping side or the supply side? Or can you even tell. It sounds like water hammer due to some restriction in the system perhaps or piping which slowly expands due to heat on the run cycle but then when pipes cool down and the pipe contracts it falls back into its original position. You will have to track down the exact location and then perhaps open a wall to find the cause. Sorry but that is all I can see to do. I am assuming you do not have any flow checks on the system if you do that could be causing the problem. Have you checked the flow control valve to make sure it is working correctly? I again assume you may have one if in the past you got domestic hot water from the boiler.
  • RobbieDo
    RobbieDo Member Posts: 131
    Bang

    You said it doesn't matter if the boiler is cold, you start the pump then shut it off and the bang still happens? Is there flow controls in the line?
    Rob
  • qtown
    qtown Member Posts: 9
    thanks for the input

    No flow control valves, there is a separate hot water heater . Down by the boiler there seems to be more of a vibration on the supply piping than the return. If I could pinpoint the location I'd gladly open the wall. 
  • RobbieDo
    RobbieDo Member Posts: 131
    Pump

    Which side is the pump on, supply or return? Are you pumping through the boiler or out of the boiler? Are any of the valves partially open? Do you have pics of the system? That might help as we don't have much info to go on.
    Rob
  • qtown
    qtown Member Posts: 9
    PUMP

    Is on the return. There are ball valves before and after the pump, and they are both wide open 
  • RobbieDo
    RobbieDo Member Posts: 131
    Pics

    Well, with the lack of info and you said nothing has changed. It is going to be difficult for us to help with your issue. Your boiler temps of 140 are very low for a non-condensing boiler, there is an issue there too.
    Rob
  • Big Ed_4
    Big Ed_4 Member Posts: 1,775
    What Has Changed

    What was changed on the system at the time the problem started ?
    I have enough experience to know , that I dont know it all
  • Gordy
    Gordy Member Posts: 9,514
    Expansion tank pressure?

    Are they set to the proper psi when isolated from the system?
  • qtown
    qtown Member Posts: 9
    HTX60

    Heating contractor added an additional HTX 60 in line with the existing. I am told the boiler pressure on the gauge at 20psi is slightly higher than it should be.

    Adding the Expansion tank did nothing to alleviate the problem.
  • qtown
    qtown Member Posts: 9
    expansion tank pressure

    I'm afraid I don't understand how to answer that. 
  • Gordy
    Gordy Member Posts: 9,514
    checking tank pressure

     There is a schrader valve on each tank check with a tire pressure gauge. The tank should be isolated from the system when doing so. It should check out between 12-15psi unless you have a really tall house of more than 3 stories.
  • qtown
    qtown Member Posts: 9
    been shoveling roofs

    Priorities! Expansion tanks read just under 15psi
This discussion has been closed.