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Repeated f09 and f10 error codes on older munchkin boiler

lukenurnlukenurn Member Posts: 7
edited December 2019 in THE MAIN WALL
*Updated* see edit at bottom--- Hi, I have a munchkin boiler 80m from 2004. Ran great when I purchased home last year in harsh Wisconsin winter. No errors. It had not been tuned up in Maybe 3-5 years, so I opened burner door a few months ago to find inside in bad shape with half inch of soot on bottom that ruined much of burner door, ceramic parts, gaskets, etc. so purchased new parts as follows: spark electrode, flame rectification probe, burner door assembly, burner gasket, ceramic target wall, and new condensate pump. Also cleaned inside thoroughly with mild approved solution and flushed condensate with water until it was crystal clear.

Put everything back together and after a week or so of running on and off occasionally during fall it began with F09 error codes. I would reset and it would run fine for a day then another F09. Became more frequent (2-3 times in 24 hour period) for a week or so then just went away and ran just fine with no error codes.

2 months of running error code free then we began getting f10 error codes. Same thing. Runs fine , have to reset 1-3 times every 24 hours. Did this for a week or so and then I went down and adjusted output temp from 165 (with 20 degree range to 145) up 5-10 degrees. Suddenly it ran fine for 3-4 days then began doing f10 just like before. We have to reset it and it works fine for a while kicking on and off and 6-12 hours later it goes F10 again.

I’ve watched the flame when it lights and it looks great and steady. All blue except Every second or two there is a faint flick of orange. Haven’t been able to watch it the moment the code goes off to see what is going on as it is after hours and I would have to be really lucky or put a camera on it.

I am not a heating professional, however I suspect they might have sent me a bad sensor as it was running fine with no errors before I worked on it.

Any help/tips would be greatly appreciated. Thanks!

EDIT: GOT LUCKY - checked it moments before it began malfunctioning and took a video of the behavior. When the thermostat called for heat, it began this cycle of lighting for 10-15 seconds, then would suddenly go out with a click and change in sound of the blower, then re-cycle until F10 error code. I quickly reset it and grabbed my phone and recorded video. Same malfunction was happening until video time (~1:40) when it stayed lit after a handful of failed attempts. *turn sound up

uploaded to google drive (I apologize for long link) >


  • DZoroDZoro Member Posts: 1,032
    Something is off, that system should never have soot. Really need to have combustion testing, and gas pressure testing on it for starters. Once those numbers are known then further analysis can be done.
  • clammyclammy Member Posts: 2,455
    If it has a fresh air inlet piped I would check it for any obstruction and also the exhaust ,also has this u it been serviced ,they usually require to be dis assembled and cleaned including flushing of the condensate trap and cleaning of the heat exchanger . Did u check for any signs of leakage where the burner mounts to the door there is a gasket there ? And has the swirl plate been checked for damage ? While you had the burner plate off did you check your flame sensor and it’s distance from your mesh burner ,did you use compressor air of nitrogen to blow any debrie off the mesh burner and did the mesh burner look to be in good shape ? Did you replace or clean the flame sensor . Was the burner plate mounting area on the boiler clean of any debrie it need to be mounted to a clean surface to ensure a good ground between the surfaces .i would chk gas inlet pressure while cycling between hi and low fire I ve seen gas meter stick and lock out burner on flame failure last but not least combustion testing these types of burner need to be set up and re check every few years ,I recently had to clean my own munchkin and had to do a little adjust to my gas valve aside from preventive replacement of the original swirl plate due to becoming brittle due to age and exposure to heat over time better then it breaking and damaging the blower . Mine is about the same age and even though she running great 2 error codes since installed bout 04 I know her replacement is coming and I de rather do at convince then an emergency . If issues continue then I would suggest you get some one in there with the right tools required to properly trouble shoot and check and set the combustion up properly peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • lukenurnlukenurn Member Posts: 7
    EDIT: GOT LUCKY - checked it moments before it began malfunctioning and took a video of the behavior. When the thermostat called for heat, it began this cycle of lighting for 10-15 seconds, then would suddenly go out with a click and change in sound of the blower, then re-cycle until F10 error code. I quickly reset it and grabbed my phone and recorded video. Same malfunction was happening until video time (~1:40) when it stayed lit after a handful of failed attempts. *turn sound up

    uploaded to google drive (I apologize for long link) >
  • HomerJSmithHomerJSmith Member Posts: 844
    edited December 2019
    If you have a blue flame with flickers of orange, your combustion is not set correctly. The flame should be mostly orange. You need some one with a recently calibrated CO meter and check the combustion. That is probably a Honeywell gas valve.

    The Honeywell gas valve has a 1" brass nipple about the diameter of a pencil facing the rear of the cabinet. That brass nipple must not touch the cabinet. If it is touching the cabinet, drill a 1/2" hole where it touches thru the inside wall, only, of the cabinet, so the vent hole on that nipple is unobstructed.

    I can see from your video that the combustion is off. Check the incoming gas pressure (supply). It should be 7" Water/Column for nat gas and 11" W/C for propane. HTP says that an F09 is caused by insufficient or too high supply gas pressure.

    Make sure all the grounds are well anchored. On the control module, pull and re-seat the plugs one at a time.

    I hope that you tightened the four screws holding the burner tube to the front burner front wall cover, tightly, as a loose burner tube can cause F09 errors.

    Oh, by the way, please tell me you have concentric venting, gasp!

  • lukenurnlukenurn Member Posts: 7
    edited December 2019
    Thanks all for your help. Had a company come out to look at the system. They replaced the flame sensor and everything runs smoothly now- other company must have sent me a faulty one.

    I have two separate vent outlets and they both go to the same place outside the home, so I think it’s okay.

    Regarding combustion and orange flickering, they said a little orange is acceptable with a unit this old, and they probably wouldn’t be able to adjust the combustion effectively because you calibrate it when it’s new and after you use it for a while it loses balance due to soot, dirt, or other things and will never be able to be back to 100% clean burning.

    Does this sound right? Everything I see and read says it needs to be adjusted. They didn’t think it would do much.

  • HomerJSmithHomerJSmith Member Posts: 844
    edited December 2019
    Give a freaking break, they told you what? Of course, I wouldn't do a combustion analysis without cleaning the HX first. I do this analysis after every cleaning. Many times the combustion need tweaking to bring it into the combustion curve recommended by HTP. Once in a blue moon, I have to adjust the off-set. When was your last cleaning?

    These guys probably don't even have a meter and they're telling you nonsense.

    If you got mostly blue flame, it ain't right.

    I don't know if anyone told you, you can check the rectifying current with the display console. When I'm finished cleaning the boiler my rectifying current is 4.2 micro-amps. It don't get no better.

    Press S4/Reset key for 3 sec. d1 will blink alternately up--press S4 for the next value till you get to d7. That's the flame ionization current of the rectification probe. Press S3 to exit the programing.
  • lukenurnlukenurn Member Posts: 7
    Thanks Homer and everyone. Started getting F09 again. I took another video of the boiler Having trouble staying on this time with the d7 up so we can see behavior. I will post soon.
  • lukenurnlukenurn Member Posts: 7

    Is it supposed to be so up and down?? Notice these times too:
    4:10 sudden drop
    4:35 blower kicks up a notch and it jumps to 4.0, eventually reaches 4.1
  • HomerJSmithHomerJSmith Member Posts: 844
    edited December 2019
    I watched your movie. I still think your combustion is off. I would check the incoming gas pressure for 7" W/C. Nat Gas. You are losing your rectification current, which is indicated by the restarts. It could be the board, but I would not replace the board ( it's expensive) without fixing the combustion first. I would also check the molex plugs and the grounding (green wires) on the ground bar and at the connection at the power source. I have had problems with the molex plug's sockets. You can try wiggling the rectifier probe wire at the molex plug and at the flame sensor.

    The flame should be a tight blue at the burner tube and long orange feathered tips. The reason you do a combustion analysis is because the BTU's in a cubic foot of gas varies across the country and the oxygen content of the air varies on altitude. The setting at the manufacturer may not be optimal for your region. Also, the setting on a modulating gas valve can change over time (usage).
  • lukenurnlukenurn Member Posts: 7
    I think the issue is fixed, though I’m hesitant to say that confidently until I ride it out for a few weeks. It was indeed a grounding issue that I only discovered after digging through other forum threads discussing flame ionization current troubleshooting- never would have guessed what was actually wrong!

    The burner screws holding down the burner tube were too loose- these are the only items grounding the burner tube to anything, which I guess affects the ionization current readings. Since I replaced the burner door during my DIY tune-up, I had to thread the screws into the aluminum holes and I just didn’t drive them far enough to be super flush and tight. I also took a green scrub pad and shined the burner tube screw surface, screws, and any other metal touch points that, if dirty, might disturb the grounding quality. Once reassembling, it fired right up with a 3+ ionization current that quickly and steadily arose to 4.1 without any drops. L

    I recall leaving a tiny bit of slack in some of the screws to prevent damage during constant heating and cooling, but must have been too generous.

    Thread with answer is here... very insightful read!

    I’ll still look into getting combustion checked.

    Thanks everyone for the insight and assistance! Learned a lot through this and hopefully issue is solved.
  • HomerJSmithHomerJSmith Member Posts: 844
    Case Closed! I think I mentioned the burner tube screws, eariler. That is a common F09 error code which isn't in HTP error code summary.
  • lukenurnlukenurn Member Posts: 7
    You did, and I completely overlooked it! I appreciate everything. Looking forward to surviving this Wisconsin winter with a toasty home now!
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