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Knight 80 Lockout

J Matthers_2
J Matthers_2 Member Posts: 140
I have a Knight 80 that is locking out on me after initial burn. The boiler was cleaned and serviced a month ago. It locks out after an initial successful burn. When reset, it will purge, light and then shutdown. If I turn it off and leave it for 6 hours it fires right up on initial burn but then will lockout on a re-start. Any ideas? I am thinking flame sensor and have ordered a new one (cleaned but never replaced).

Comments

  • Ironman
    Ironman Member Posts: 6,702
    Is this a KBN floor model or WHN wall hung?

    If it's the KBN, was the cleaning done as prescribed in the service manual. Most times it's not. If the heat exchanger, burner and drain are not properly cleaned, you'll get the kind of symptoms you're describing.

    I doubt if it's your flame rod, but it's possible.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • J Matthers_2
    J Matthers_2 Member Posts: 140
    Floor Model. Yes, cleaning done as prescribed in service manual though it may be the condensate drain is still partially blocked and there is some backup. that would explain the restart after a time laps. I always get lots of "coffee grounds" on each cleanout and perhaps some were missed. Will do another cleanout and see if that helps.
  • Ironman
    Ironman Member Posts: 6,702
    Use an old credit card to get between the coils of the heat exchanger.A brass bristle wire brush and CLR work well on fouled areas. Flush with lots of water. A gentle spray from a hose nozzle or garden sprayer. The CLR will help clean the drain.

    Make sure both flue pipes are clear of obstruction.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • J Matthers_2
    J Matthers_2 Member Posts: 140
    thank, turns out there is a pin hole leak in the HEX. Noticed a slight drop in system pressure so had a feeling that may have been the problem. Fortunatly this just supplys backup for the GEO. New unit on the way.
  • Don_197
    Don_197 Member Posts: 184
    you never mentioned what the lockout was?? Was it "auto reset hi limit" or what did the lockout say?? A pin hole on the HX won't cause a lockout........more likely the condensate switch or the outlet temp going too high........and the hi limit is opening
  • J Matthers_2
    J Matthers_2 Member Posts: 140
    No Flame Ing - which was strange since there was ignition each startup cycle and then shutdown - and only after a re-start after a runtime. last runtime was almost 24 hr with cold snap. I am assuming the leak opened up with a hot coil and closed as it cooled? It was positioned perfectly to hit the flame sensor so a wet sensor perhaps causing a read error?