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Issue with Muchkin 80M boiler

thehustlathehustla Posts: 3Member
edited October 2018 in Heating Hell
Currently having an issue with my Muchkin 80m boiler.
The boiler is getting a F09 error.
After a few resets, the boiler finally comes on and does something very strange. I replaced the combustion blower about 2 years ago. Seems like the issue might be the draft inducer again, swirl plate, or gas valve?
Here's a of what it is doing video:


  • DZoroDZoro Posts: 1,015Member
    Could be the board and or the inducer. Has the system been cleaned? If not I would start there...
  • kjbhvacrkjbhvacr Posts: 2Member
    replace the inducer motor again.
  • edited October 2018
    Here's a thread that might help:

    Sounds like a gas mix problem. Check your incoming and manifold gas pressures with a manometer and then gas analyze your exhaust to make sure your gas mix is correct.
    Often wrong, never in doubt.

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  • ZmanZman Posts: 5,519Member
    edited October 2018
    kjbhvacr said:

    replace the inducer motor again.

    As Alan suggested, starting with combustion analysis is a good plan.
    If it does turn out to be a bad motor (again), don't just change it, find the route cause of the problem. Cross contamination of combustion air with exhaust is a likely cause.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • DZoroDZoro Posts: 1,015Member
    Zman and Alan are correct. Along with a good cleaning, combustion analysis should be done again. Double check the gas pressures, venting exhaust and intake should be at least 18" apart, 12" above snow levels, away from inside corners. Have the tech leave his combustion report inside the boiler when he is finished.
  • HomerJSmithHomerJSmith Posts: 801Member
    edited October 2018
    I'm late to the party. Here's your problem. The flame rectification is intermittent.

    The fix, as John Siegenthaler sez, is, drum roll please, do a through cleaning of the heat exchanger if it hasn't been done in more than 3 yrs. While you're at it replace the burner tube gasket after cleaning its mating surfaces. Tighten the 4 screws holding the burner tube to the front boiler plate, tightly. The problem is the 4 screws are not tight and the grounding thru the flame is intermittent. The flame rectification goes from the rectification probe thru the flame to the burner tube thu the 4 screws to the front boiler plate to ground. Lastly, do a combustion analysis with a recently calibrated meter on the boiler. Waalaa!
  • HomerJSmithHomerJSmith Posts: 801Member
    edited October 2018
    There was another problem with the 80M and that was the gas valve was too close to the back of the cabinet. There is a brass vent on the rear of the gas valve and that vent touched the cabinet back. The fix was to drill a 3/8" hole thru the cabinet back where the brass vent is located. This allowed the vent to do its job. Just drill thru the inside wall of the cabinet, you don't have to go thru the outside wall.
  • The gas valve on a Munchkin isn't anywhere near the back of the cabinet.
    Often wrong, never in doubt.

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  • HomerJSmithHomerJSmith Posts: 801Member
    edited October 2018
    Alan, of course it is. Look at the video. The brass vent is about 1 1/4" long and projects out of the rear of the gas valve toward the rear cabinet wall. Honeywell gas valves only.

    thehustla, I don't see a swirl plate on that boiler. This appears to be an R1 version or earlier.

    You need to check your system out as to combustion, venting, condensate drain, and system flow. I haven't heard that growling from a Munchkin before. I think off hand that sound is a combustion issue. I wouldn't run the boiler like that.

    Look into the sight glass while the boiler is going and see if the flame is more orange colored than blue. and look for any water in the combustion chamber. There may be a water line on the back refractory.

    It doesn't sound like flashing in the heat exchanger, but what do I know.

    Perhaps, the burner tube is so loose that it's rattling.
  • thehustlathehustla Posts: 3Member
    All - I replaced the inducer and that took care of both problems.

    When I replaced the inducer about 3 years ago, it was a used inducer so it could've been old or close to end of life.

    This time, I didn't cheap out and bought it new.

    Everything is working perfectly now.

    Thanks to everyone for the inputs!

  • tim smithtim smith Posts: 2,299Member
    edited October 2018
    I would still pull face plate and completely clean combustion chamber, flush out with water, make sure condensate trap is clear. ( don’t use any metal for cleaning inside) have new burner gasket and target wall on hand. Flush out burner tube while apart. Clean burner mounting flange and mounting nuts with fine sand paper or steel wool to improve ground path for flame signal. Check burner plate gasket for condition prior to reassembly. Do not be completely surprised if heat exchanger doesn’t start spraying during or after cleaning coffee grounds from combustion chamber. Make sure to clean between heat ex tubes with your unwanted plastic credit card or the like. Check and clean/adjust or replace igniter while apart. After assembly, check Venturi and swirl plate, check all wire connections. After all visual inspects, fire off check for any flue gas leaks and do combustion analysis. ABOVE SHOULD ONLY BE DONE BY QUALIFIED SERVICE TECH.
  • Good advice.

    I've had a few Munchkins with failed heat exchangers. Has anyone ever replaced one? I hear they have them available, but imagine it's not an easy job.
    Often wrong, never in doubt.

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  • Intplm.Intplm. Posts: 1,047Member
    Check to see if any debris has dislodged and got caught in the path of fuel supplying the gas valve. Pipe dope , teflon tape? Something in the pipe that falls in and out of the path of the gas valve. The screen in the valve partially or intermittently plugged?
    Had it happen to me. Because it didn't happen all the time, I'm bald now from pulling my hair out.
  • HomerJSmithHomerJSmith Posts: 801Member
    edited October 2018
    The heat exchangers are not available from HTP. They told me so when I asked them for a 140M that I thought had a leaking heat X.

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