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Controls for Combustion Air


I did an audit on a large church building and they have 3 steam boilers in a fairly small boiler room. They were told by their insurance company that in order to have enough combustion air in the boiler room they have to a fan forced duct blowing outside air into the room. The boiler do not operate all at once and the maintenance person is wondering if there is a control system that could adjust the air intake as one boiler fires and another, etc so that there is not all this cold air being blown into the building 24/7.




  • Charlie from wmass
    Charlie from wmass Member Posts: 4,253
    edited January 2010

    use individually sized fan-in-a-cans. one for each boiler Fields make them.

    Unless you have power burners, gas or oil, they may have boots available for fresh air intake
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • BobbyG
    BobbyG Member Posts: 79

    least expensive option probably.


    I think Exhausto probably has a variable speed version.
  • seabee570
    seabee570 Member Posts: 89

    the combustion air supply must be sized properly to handle all 3 boilers as if they were firing all at once. alot of places just have an louvered opening to supply the air.if they need a fan,the fan should be interlocked with the boilers so that if the fan does not run,the boilers do not run.lots of ways to do this.if you had just outside louvers with a motorized damper,you would have end switches on the dampers,so that the end switch would close when the damper motor drives the damper open,and trips the end switch,sending power to the boilers.if you had a fan,you could have a current sensing relay,sensing current of the fan,and then sending power to the boilers.
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