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Terrible racket for 2 minutes when my Weil-McLain Ultra 105 starts cold

mcieslakmcieslak Member Posts: 4
I have a 10-year old Weil-McLain Ultra 105 boiler that, under certain conditions, has been making a terrible racket for about 2 minutes when it starts cold. Here are the details.

I turn up a thermostat in any one of our three zones and the boiler goes through the normal cycle, displaying 1, then 2, then 3 on the panel. Almost exactly 20 seconds after the 3 appears a terrible racket comes from the boiler, around the back of the blower. It is a type of low-pitched “metallic howl” and is accompanied by a very large vibration of the jacket. (The first time this noise came I was upstairs and thought the neighbor started his lawn mower.) The noise lasts for 1 minute 58 seconds then stops. This seems to only happen if the water temperature displayed on the panel is cool, like about 66. If the water temperature is high, say from the boiler still hot from having supplied heat to another zone, the noise seems to be absent.

After further investigation, I find two things happen while this noise is taking place. First, the exhaust pipe blows air outside at a very high velocity, much higher than normal. Second, I took off the jacket and inspected the air silencer, discovering that air was pulsating out from the holes at the top of the air silencer.

I realize the heating session is over but I would like to get this diagnosed well before I need the boiler again. I’m working with my local dealer but unfortunately it did not act up the last time he was at the house. I told him I would keep records to help him diagnose the issue.


  • DocfletcherDocfletcher Member Posts: 476
    Get a video of it making the noise.
  • kcoppkcopp Member Posts: 3,607
    Need more info... LP or Natural gas?
    When was it last serviced/ combustion test done?
    Does your hot water come off the system?
  • mcieslakmcieslak Member Posts: 4
    The boiler is natural gas, running just for heat. The last service before the noise issue was 18 months ago. The description of the work indicated the ignitor was cleaned, the pumps oiled and a general check was performed. No mention of a combustion test. In 2010 the control board and inducer motor were replaced under warranty after error code E29 was showing.

    A video of the unit firing up can be seen at boiler noise begins at 38 seconds.mp4?dl=0
    As the title indicates, the noise begins at 38 seconds.
  • Tom_133Tom_133 Member Posts: 719
    It sounds like you need a proper clean and tune, the air to gas mix ratio is pretty far out. When the unit fires (I believe it does so at around 50%) it then ramps up based on water coming in and going out, your boiler is not getting the proper ratio. Whoever does the cleaning will need a combustion analyzer. Also, make sure there is not grass or debris anywhere near the termination. By chance is the big black plastic piece still connected in the unit? It's the same piece that the silver gas line is sometimes is connected to.
    Montpelier Vt
  • kcoppkcopp Member Posts: 3,607
    edited May 2016
    Its starving for gas. Needs to be set up w/ a combustion tool. The reason it does that when cold is it wants to ramp up the firing rate to high.
  • mcieslakmcieslak Member Posts: 4
    Thank you, Tom and kcopp, for your ideas. I passed them, as well as the link to this conversation, to my dealer.

    Tom, the only big plastic piece I see is the air silencer and its adapter where it connects to the blower. Everything else under the jacket is metal. Also no obstruction of the exhaust, except a screen to keep the chipmunks out. But this screen has been on for 10 years.

    I forgot to mention that this situation developed rather quickly over the last month. Before then there were no problems. Does this suggest anything? Again, thanks.
  • Tom_133Tom_133 Member Posts: 719

    The air silencer is what I am referring to. If that comes off sometimes the boilers get loud at high fire. If yours is in place than its all good. The thing about it just starting to happen is as the heat exchanger gets dirtier it can start to throw combustion off, causing your noise. A thorough cleaning is necessary, taking off the heat exchanger front plate and cleaning the pins and base. I would also make sure the water quality is correct in the system, the PH needs to be as directed by the manufacturer. Those aluminum heat exchangers won't put up with much.
    Montpelier Vt
  • TomSTomS Member Posts: 53
    I notice the temperature gauge does not move. Defective or no fire?
  • mcieslakmcieslak Member Posts: 4

    I need to do another run to check out the dial gauge, as I never noticed that before. The digital gauge does work and it went to 126 during a test a few days ago.

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