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2002 Dunkirk gas boiler often won't turn on automatically.

hmaxwell Member Posts: 2
Hello, first time here, having trouble with my gas boiler; will not turn on automatically or with increasing thermometer on wall; this appears to happen when esp windy and cold out, but has gotten progressively more unpredictable this season. It does seem to work well when temps greater than 40, but unsure if its the water heater causing it to turn on. I am able to turn the red boiler power safety switch on and off 3 times and it fires up in 20 seconds. Sometimes this will work enough to heat house (I have 2 zones attached to it at this time, unsure that makes a difference) other times it only stays on for less than 5 min.
Recently has someone look at it and he is not 100% sure but thinks it could be the roll out sensor. He did check the venting and all seem to be in order. Will order and replace that, but was looking for some input as to what else it could be from this forum. Thank you all in advance for and help. I want to be well informed if and when I have to call him or someone else back. Merry Christmas to all.



  • Jamie Hall
    Jamie Hall Member Posts: 18,935
    Have you tried a different thermostat?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 9,761
    Can you hear it trying to start? Spark....tick...tick..tick?
    Flame roll out sensors are at the front of the burner and some are a one time fuse. Or a manual reset button.

    There would be a blocked flue sensor on the back of the draft hood that might also be manual reset.

    My best guess is a dirty flame sensor, intermittent starting and not staying on when it does light.
  • Ironman
    Ironman Member Posts: 6,868
    What's the actual model number of the boiler? Can you post some pics of the boiler and it's near piping? There are several models and some are quite different, so we need a model number.

    I doubt that it's the flame roll out since most of those are manual reset. There would also be evidence from flame rollout of the flames burning or staining the plate above the burners.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • hmaxwell
    hmaxwell Member Posts: 2
    the thermostat (not thermometer, lol,,,I've been a nurse for too long) was checked by the person who came by yesterday and mentioned replacing the sensor. Jaime Hall, thanks so for replying,,,

    I have not noticed any ticking noises while down there checking it out, JUGHNE, will check out the sensor more closely, thanks for replying so quickly.

    I will get pictures asap, Ironman, thanks for quick reply,,,,

    I'm sorry I don't know how to individually reply to your comments,,,I'm a wreck with technology.

    JUGHNE Member Posts: 9,761
    You mentioned a 2002 boiler. That would most likely have spark ignition for the pilot light. Then there is a flame sensor rod that must recognize the fire being on.
    The flame sensor in mounted up on the burners at the pilot light.

    It is often the cause of your symptoms. If a burner person did anything at all, cleaning the flame sensor would be the first possible easy remedy. Then go from there if that doesn't fix it.