Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Noisy boiler problem still persists

About 5 years ago we had the boiler at our building replaced. This building has 35 units and 4 commercial spaces, the replacement boiler is a Weil-McLain Model #1088 series 1B W/A power flame burner model # cr2-go-20b dual-fired which we run on gas.

There is a strange very loud noise coming from inside sounds like towards the bottom of the boiler about 1-2 minutes after the initial start-up. Also i noticed it is even louder when it is colder outside. After about 1-2 minutes of these loud intermittent clanging or knocking sounds they stop and the boiler runs ok.

I asked a boiler installer about this and he said due to the fact that we have a tankless coil on the boiler (this supplies heat to the one basement apartment) We would need to install a "blanket" on the boiler, cost around $2500. The technician who i spoke with at Weil-McLain also indicates that this may be required. I have no idea what we should do. If anyone has had this experience and can offer us some sound advice, it would be appreciated. I have enclosed some pictures. Thank you.

Update on noise from boiler: I posted this about a month ago and installed a couple of new air vents on the return lines and it helped somewhat, but it has not completely solved this problem. So I am now reposting this in hope that i can get some further answers that would help me with this problem. I also posted pictures of the boiler and piping.


  • JStarJStar Posts: 2,668Member

    Can you describe the sound?
  • DaveB55DaveB55 Posts: 21Member
    Noisy boiler problem still persists

    The noise sounds like a big bass drum that is coming through an amplifier. And it sounds as though it may be near the front close to the gas burner. It is definately louder when the temperature drops outside, like it did this week. My previous posts about the new air vents helping to lower this sound may now have been only minimally effective at best., so I am still searching for solutions. Thanks
  • ttekushan_3ttekushan_3 Posts: 917Member
    edited January 2013
    May be combustion related

    Where's the barometric damper? I can't see one in the pictures.

    I'll assume that the boiler doesn't need to be boiling yet for this phenomenon to occur.

    All power burner boilers require a draft regulater for any meaningful adjustments to the fuel air mixture to occur. [when venting into a chimney as it appears from the pictures to be doing.] How the burner could be set up properly without one under these circumstances is beyond me.

    It is probable that the initiation of chimney draft after a few minutes begins allows gas to go unignited further down the combustion chamber but without complete flame failure. It will ignite with a "boom" until the combustion chamber heats up.

    I have only seen this once, and the sound you describe is perfect. It is not a hammer, but a big single hit to a bass drum. And the one instance I experienced this involved a boiler outlet breaching improperly installed without a draft regulator, and yes, it was worse the colder the temperatures were. A big barometric damper solved the problem and allowed for the proper calibration of the power burner.

    [edit: when I experienced this, the flame amplifier voltage dropped but not enough to shut down the burner. But flame lockouts were common until the damper was installed]

    You may need a draft regulator and a proper calibration of the burner with a combustion analyzer, preferably by someone trained to use it.
  • ttekushan_3ttekushan_3 Posts: 917Member
    Please see

    Page 5 of this manual.

    From your pictures, the breech is going straight into a chimney. The chimney will develop negative draft. Therefore you need an arrangement like those on the right side of the page under "balanced draft" installation.

    The only time it is acceptable to go without a draft regulator is if the chimney is under POSITIVE pressure, i.e., forced draft. This would require the specified chimney liner or stub vent. All of this is in addition to any breecher damper adjustments.

    This might send you in a new direction to solve the problem.
  • DaveB55DaveB55 Posts: 21Member
    Boiler noise persists update

    I have a friend who listened to the sound and he said it sounds more like a car engine 'knocking' noise than a drum, and he may be correct , but there may be two sounds going on and I am going to have him come here again and listen with him before I determine the accurate sound.

    To answer your question , the water in the boiler is not boiling yet when this noise starts. Also, I am conducting an experiment today. I shut off the two hot and cold water valves which run the tankless/ baseboard heating unit for that basement apartment to check if that affects this noise at all.

    Your comments about the barometric damper are also under consideration. I see a hinged lever at the back of the boiler at the base of the flue piping, (you may be able to see it if you can enlarge the picture) but I do not know what type of damper it has?

    Anyway, thanks for all your valuable suggestions and I am still on the case and will continue with communication until I solve this problem. Thanks
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!