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Munchin 80M Boiler Noise At Startup

We have a Munchkin 80M boiler in our home. It is about 11 years old. For about the last 3 winters it has been making a vibrating noise when it first kicks on. The colder the outside air temperature, the louder and longer the noise lasts. It's usually under 30 seconds but it can go for close to a minute and can literally shake the whole house. Once the vibration stops, it purrs like a kitten. No more problems until the next time it kicks on. Any ideas on what this could be? It wakes us up several times during the night. Thanks for any help!

Comments

  • HomerJSmith
    HomerJSmith Member Posts: 1,370
    Look thru the sight glass. The flame should be orange and not blue. Is there a change in the combustion while this is happening? The Munchkins had a blower disintegration problem brought on by gas reversion. The big problem was concentric venting allowing exhaust back into the air intake. Does this vibration happen with the cabinet cover off? The colder the air the more dense and heavy it is. A second consideration is that you are having flashing in the HX. Maybe your pump is not circulating water soon enough or with sufficient flow.

    The Munchkin need to be installed in a primary/secondary system. Just to satisfy the requirements of the HX, a Taco 007or Grundfos UPS 15-58 on sp 2 is needed. Taco pumps do clog up.

    Munckins do need a yearly cleaning of the electodes and a HX cleaning of about 3-4 years. This maintenance is extremely important. When ever a heavy maintenance is done a combustion analysis with a recently calibrated meter should be done, also.

    The lack of a fault code indicates to me that the boiler is probably functioning properly and that you may have a pump problem.
    tomandbicka
  • HomerJSmith
    HomerJSmith Member Posts: 1,370
    Another possibility is that it is not the boiler at all, but a swing check on the boiler piping that is rattling until the flow evens out.
    Is there an Indirect W/H connected to this boiler?
    tomandbicka
  • HomerJSmith
    HomerJSmith Member Posts: 1,370
    With the cabinet cover off, is the aluminum, gas valve, metal blower and boiler face plate pristine and shinny or pitted, encrusted and degraded? If degraded you have gas reversion and a more serious problem.
    tomandbicka
  • HomerJSmith
    HomerJSmith Member Posts: 1,370
    If you don't have a 3/8" hole in the exhaust flue within about 2 feet where it leaves the boiler, you have never had a combustion analysis done. You need professional help. It should be someone who has the latest rev3 software on his computer the means to connect to the boiler controller and a recently calibrated CO analyzer. The new software can be installed, stored fault codes reviewed and cleared. New software changes the post purge from 25 sec to 100 sec.
    tomandbicka
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,290
    When was the last time you had the boiler serviced?? It probably just needs servicing, by someone with combustion test equipment
    tomandbicka
  • rbeck
    rbeck Member Posts: 56
    If the unit has been serviced maybe it is just an O2 adjustment. Noise is a common problem with harmonics.
  • tomandbicka
    tomandbicka Member Posts: 2
    Thanks for all the great comments! We have had the flame adjusted a couple times but that didn't seem to help. I did pull the cover back a few inches to let in some room air, so we'll see if that makes a difference. When I removed the cover everything looks really good. We'll see how removing the cover affects the noise. If it doesn't help, we'll move onto something else. Thanks again, folks!