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  1. #1
    Join Date
    Oct 2007
    Location
    St Louis, MO
    Posts
    21

    Ventilation Rqmt in Mechanical Room

    Hello pros,
    Appreciate any advice you offer. We are remodeling a basement in our 10 year old home by adding a bedroom to an open space that includes a furnace and water heater on one end. The furnace is a HE gas Trane unit with intake and combustion air vented outside, that was added last year by the previous owners. The 80k BTU gas water heater has an electric blower on top, but I believe the combustion air comes from the room. This new downsized mechanical room is about 9' x 11.5' with a 9' ceiling. There was conditioned air delivered into the room before the remodel started, but that has now been sealed.

    Today our contractor said he needed to add an air passage vent from one of the adjacent living spaces to the mechanical room. Do we really need to do this? Can adding a replacement conditioned air vent meet this need?
    Brian

  2. #2
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,914
    No, you need the properly sized pass thru grills (ceiling and floor) to communicate to a large enough space to provide combustion air.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    An 80,000 BTU gas fired appliance needs a free air volume of 4,000 cubic foot. So yes, you need to have combustion air added to that room.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Oct 2007
    Location
    St Louis, MO
    Posts
    21
    I was afraid that would be the answer. We'll make it work. Thanks for the help!
    Brian

  5. #5
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,729
    Kick the low efficiency pig to the curb. Install a 98% efficient sealed combustion on demand water heater and you can leave the room alone.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  6. #6
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Make sure they follow IFGC section 304 and IMC section 702.3,---702.3.1 and 702.3.2

    also IFGC section 303
    Last edited by second opinion; 09-14-2011 at 09:32 AM. Reason: left out 303

  7. #7
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by tedkidd View Post
    Kick the low efficiency pig to the curb. Install a 98% efficient sealed combustion on demand water heater and you can leave the room alone.
    +1. If the hot water heater is the original builder grade unit, it's worth replacing. I'd get a HE unit as mentioned above. One AO Smith unit has enough output capacity that it can provide almost continous hot water almost like a on demand system. I plan to install one of those in the next few years to get my flue out of my chimney... or rather to stop using my 86 y/o brick probably unlined chimney as a flue.

  8. #8
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Quote Originally Posted by BC Eagle View Post
    Hello pros,
    Appreciate any advice you offer. We are remodeling a basement in our 10 year old home by adding a bedroom to an open space that includes a furnace and water heater on one end. The furnace is a HE gas Trane unit with intake and combustion air vented outside, that was added last year by the previous owners. The 80k BTU gas water heater has an electric blower on top, but I believe the combustion air comes from the room. This new downsized mechanical room is about 9' x 11.5' with a 9' ceiling. There was conditioned air delivered into the room before the remodel started, but that has now been sealed.

    Today our contractor said he needed to add an air passage vent from one of the adjacent living spaces to the mechanical room. Do we really need to do this? Can adding a replacement conditioned air vent meet this need?
    Brian
    omg yes! its the only sure way to do it. cutting a hole in a wall doesnt mean air will go into that room.

  9. #9
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    Quote Originally Posted by beshvac View Post
    No, you need the properly sized pass thru grills (ceiling and floor) to communicate to a large enough space to provide combustion air.


    are you suggesting taking ventilation air from inside the structure/living ares?



    Quote Originally Posted by beenthere View Post
    An 80,000 BTU gas fired appliance needs a free air volume of 4,000 cubic foot. So yes, you need to have combustion air added to that room.
    even a 90+ 2-pipe?
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  10. #10
    Join Date
    Oct 2011
    Location
    NJ
    Posts
    149
    Isn't it true that transfer air can be through openings or mechanically induced through a fan? The problem I see with the A/C vent is that there is no guarantee that the unit will be running to bring in air when the gas water heater is firing.

    Couldn't a dedicated supply fan be used to blow air into the room, either a constantly running or interlocked with the water heater, as an option?

  11. #11
    Join Date
    Dec 2009
    Location
    Bristol NH
    Posts
    229
    You are not allowed ato put a non sealed combustion gas water heater in a bedroom, I would think you shouldn't take combustion air from that room through grilles either. Better call the code enforcement officer or fire chief on thar one first

  12. #12
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,671
    Quote Originally Posted by boilerman856 View Post
    You are not allowed ato put a non sealed combustion gas water heater in a bedroom, I would think you shouldn't take combustion air from that room through grilles either. Better call the code enforcement officer or fire chief on thar one first
    Boilerman856,

    Read and follow AOP forum rules.

    You should apply for Professional Membership.

  13. #13
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    Hello Smitty

    Quote Originally Posted by jpsmith1cm View Post
    Boilerman856,

    Read and follow AOP forum rules.

    You should apply for Professional Membership.
    Although there is a good reason to have and follow rules, even if they are newly instituted, I would like to point out that what boilerman said, in no uncertain terms, is what secondopinion referenced in his post.
    Clearly boilerman has been very forthright and correct in warning the OP with his remarks and is right in doing so in a potentially dangerous situation.

    So I think if your post could have begun with a thank you, agreed with him and then invite him to apply. The OP might have gotten the idea that boilerman's concerns were not valid.
    NO GAS APPLIANCES IN SLEEPING AREAS ALLOWED
    We would like to see the occupants wake up in the morning
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

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