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f09 fault on a Munchkin80

Guy_6 Member Posts: 450
Flow Gradient Limit is something that I saw on nearly every boiler that I worked on and it is nothing. Essentially it appears when the supply and return delta is higher than the control expects. On a cold start, that is nearly every cycle. This has nothing to do with the F09.

The F09 could stem from low gas pressure, lean gas mixture, or condensate issues as listed above. Check the flame current with the software. It should never fall below 1.0 at any point. 2.0 to 4.0+ is the normal range.

If it is falling below, the usual cause is the gas/air mixture. Check the CO or CO2 levels out the vent.

Keep HTP in the loop with this- they want to help.


  • peter dawson_2
    peter dawson_2 Member Posts: 1
    Munchkin fails with F09

    I contunue to have problems with my Munchkin boiler I have acces to the HTP925serv software and it is reporting F09 No ignition with the blocking Flow Gradient limit. Any ideas
  • Jim D_3
    Jim D_3 Member Posts: 1

    clean flame sensor
  • hr
    hr Member Posts: 6,106
    What's the flame signal read?

    the digital readout and/ or that software will tell you.

    How long has it been installed? Was it set up with a combustion analyzer? What were the hi and low fire readings? I like to record them in the owners manual or on the boiler jacket itself.

    hot rod

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  • Larry F
    Larry F Member Posts: 25
    Check Condensate

    Have you checked to be sure the condensate drain is clear? We had a 140M intermittantly tripping on flame failure recently. Condensate was draining but not at the rate the Munchie was producing it during longer firing cycles.

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