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HB Smith Cast iron residential boiler tripping out on rollout switch

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kappy24
kappy24 Member Posts: 2
in Gas Heating
I have a natural gas smith cast iron boiler (GB-100) that is tripping out on a rollout switch located above the burners. I’ve brushed cleaned the heat exchanger, cleaned the burners, removed the flue piping and inspected the chimney to make sure it’s drafting and there are no blockages, replaced the pilot assembly and thermocouple. I’ve even replaced the rollout switch rated for 350° and the boiler will run but will not satisfy and trips out due to excessive heat by the manual reset rollout switch. Asking for help on what to do next to get this customers boiler working again, Thank you. 

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,523
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    Either you putting too much gas into it, the boiler or flue pipe is plugged with soot or the chimney is not drafting.

    Look up inside the chimney for blockages, the tile in the chimney may have broken down.

    But a draft gauge on the boiler flue and see what you getting for draft. That boiler has a built in draft hood I think.
  • kappy24
    kappy24 Member Posts: 2
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    I made sure the chimney was drafting and the flue pipe was completely clear. The gas pressure is spot on 3.5” w.c. The boiler does have a draft damper but I can watch the damper open up all the way and hit the end switch starting the  ignition sequence. I suppose I can get up on the roof and look down the chimney just to be sure from the top down.

    would turning the gas pressure down or trying to adjust the combustion air on the burners fix this issue? 
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,523
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    @kappy24

    You can probably safely lower the gas pressure to 3" wc but you need to use a combustion analyzer.

    If the fire is rolling out you have to find out why.

    If you pour water into a funnel and it overflows what do you do? Pour faster or slow the pouring down? Same thing

    What is your draft reading? You have to use a draft gauge and an analyzer

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