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  1. #1
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    May 2009
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    Poorly ventilated boiler room

    have a 16 section hot water boiler operating in a boiler room that has poor ventilation

    so bad that boiler has trouble bringing up heat of the water when burner is firing. when the boiler room door is opened , air flow dramatically improves and boiler heating improves.

    is there any harm being done to boiler by depriving the burner of good ventilation.

    seems that it might be stressful along with inefficient performance

    there is a window with an exhaust fan but its left off most of time.

    any suggestions

  2. #2
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    Insufficient combustion air can lead to sooting of the sections and production of CO.

  3. #3
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    More air. Code will dictate the minimum opening size based on burner rating.

    Hows about removing the window and installing a louvered grill in its place?

    What does the door lead to? If outdoors, cut door louvers into it if allowed by code.

    Got a roof over the boiler? Install a louvered make up air assy there(away from stack termination).

  4. #4
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    The NFPA 31 (oil) and NFPA 54 (LP NG) are very specific as to the size and arrangement of the combustion air if it is brought into the boiler room from an interior space or the outside. Each application is different.

    Find a competent contractor in your area and have them analyze the situation. Adequate Combustion Air is one of the three keys to proper combustion.

  5. #5
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    the ASME standards require 1 sq inch of opening per 5,000 btu's which is interesting

    so how would this change if there was an intake fan?? only operating when burners are firing?

  6. #6
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    A pressurized boiler room would be a bad situation for a boiler with atmospheric burners. Maybe as bad as what you have going on now, couldn't say for sure.

  7. #7
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    Quote Originally Posted by btuhack View Post
    A pressurized boiler room would be a bad situation for a boiler with atmospheric burners. Maybe as bad as what you have going on now, couldn't say for sure.
    Not sure what you are saying. Are you saying a positive pressure in a room with natural draft appliances is bad?

  8. #8
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    Could be, am i wrong?

    Why Yes I am. Upon further consideration, i retract my earlier, poorly thought out posting.

    Oh the shame and humiliation, what must the neighbors be thinking?

  9. #9
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    LOL thought maybe I was going to learn something new!

  10. #10
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    Yeah, sorry for the tease.
    I'd rather have my post called out, then mislead a member/guest.

    Turned my brain on and 2 seconds later, I knew why my post blew.

    Typical B- /C+ student back in school. "It's not that he's not dumb, he just doesn't always apply himself".

  11. #11
    Join Date
    May 2009
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    this is all very nice

    what does installation of a fan in a window do to overall picture (ie. less of a need for a certain size air outlet opening)

    if there are two large boilers and an opening in wall that only satisfies one boiler, would a fan to pull air be the solution

    how are most basement level boiler rooms ventilated??

  12. #12
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    Actually fan powered combustion air is the only way you can be sure you will always have enough combustion air.

    For passive make up air to work there has to be a negative pressure inside to cause air to move into the building! Is negative pressure relative to outside good in a room with atmospheric burners? NO!! Different wind conditions can and do cause downdrafts and venting problems when setting up combustion air per code.

    Attached is an image clipped from an ASHRAE report.
    Attached Images Attached Images  

  13. #13
    Gib's Son's Avatar
    Gib's Son is offline ARP Committee/Professional Member*
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    Quote Originally Posted by zeppy View Post
    this is all very nice

    what does installation of a fan in a window do to overall picture (ie. less of a need for a certain size air outlet opening)

    if there are two large boilers and an opening in wall that only satisfies one boiler, would a fan to pull air be the solution

    how are most basement level boiler rooms ventilated??
    Boiler room design has changed over the years. It could be that the fan was installed to push air into the room. If it is exhausting, and the boiler is not sealed combustion, that's bad. It used to be that you had to have two ducts, one high, and one low in space. Code has changed and now only requires one high. How you get your combustion air, I.E., freely communicating with exterior space, getting from confined space....and other scenarios.....changes the required amount of free area (size) of the duct per total btu input in room.

    The combustion air openings need to be sized for all the gas appliances in the space. That means water heaters in the same room, unit heaters etc.

    If the burners are not getting combustion air directly ducted to them than the next best thing, IMO, is a powered fan. Not a propeller, mind you. A fan that can be easily balanced to the burners air flow. Interlock fan, or fans, with burner controls such that in case of supply fan failure, burners do not come on.
    If a nation expects to be ignorant and free, in a state of civilization, it expects what will never be. (Thomas Jefferson 1816)

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