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  1. #1
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    combustion air intake for condensing furnace

    Building an 1800 SF break room / restroom inside a conditioned warehouse which is over 500,000 SF with roof +/- 40' AFF. Plans call for 120K BTU condensing gas furnace / 5 ton AC split system.
    Question: Is it an acceptable practice to not provide combustion air intake from the outside?
    Would this violate 2009 IFGC and IMC?

    TIA

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  3. #2
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    That would be a combination of mfg's instruction and the local jurisdiction's taste in installs.

    Personally, I'd go with sealed combustion and a pipe the combustion air. Much more reliable and less warehouse dirt gets inhaled by the furnace, FWIW...

    Use a concentric vent termination. Least susceptible to wind and snow.

  4. #3
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    Mecahnical code says 50 sqft free space per 1000 btu. I'd still go 2 pipe to the outside if possible. Ask the General Contractor or Architect. The sizing sounds a little large through unless, there is relatively little insulation. But you probably have a stamped PE print or specification you are working from. Not really your problem if it turns out bad

  5. #4
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    and who sized this?

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  7. #5
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    and who sized this?
    PE sized it. There are a lot of warehouse workers that will be using the new break room.

  8. #6
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    Quote Originally Posted by pecmsg View Post
    and who sized this?

  9. #7
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    Quote Originally Posted by johng1054 View Post
    Building an 1800 SF break room / restroom inside a conditioned warehouse which is over 500,000 SF with roof +/- 40' AFF. Plans call for 120K BTU condensing gas furnace / 5 ton AC split system.
    Question: Is it an acceptable practice to not provide combustion air intake from the outside?
    Would this violate 2009 IFGC and IMC?

    TIA
    I'm Flat Out Amazed that Your "Architect" , ... Even submitted a System like this for what You have stated, & You are left to ask about "Combustion Air".

    I'm hoping that the "Blue Prints" are Free, as well as who-ever has the "Deep pockets" for this project, has placed truck-loads o Cash in escrow for Your Future & Immense Utility Bills.

  10. #8
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    Quote Originally Posted by johng1054 View Post
    Building an 1800 SF break room / restroom inside a conditioned warehouse which is over 500,000 SF with roof +/- 40' AFF. Plans call for 120K BTU condensing gas furnace / 5 ton AC split system.
    Question: Is it an acceptable practice to not provide combustion air intake from the outside?
    Would this violate 2009 IFGC and IMC?

    TIA
    1800 sq ft inside a "conditioned" warehouse needs very little heat if the warehouse is kept at 70, or even 65°F. The snack/vending machines along with the refrigerator/refrigerators will provide a large amount of the heat the area will need. So the furnace can be small. 5 tons of A/C sounds like it might be enough.

    Combustion air would be better to come from the outside, but code does permit it to come from inside as long as free air and non combustible vapor conditions are met.
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  11. #9
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    Why not use a 5 ton heat pump and air handler? Even if it gets really cold where you're located, the condenser could (in most cases) be located in the warehouse.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  12. #10
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    Quote Originally Posted by johng1054 View Post
    PE sized it. There are a lot of warehouse workers that will be using the new break room.
    You could fill that room with workers and it is still oversized!

    Hang the PE's degree in the ************

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