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  1. #14
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    Mar 2018
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    Quote Originally Posted by firecontrol View Post
    Is this really about what is right or wrong? The furnace is able to be vented either with or without according to the install instructions and the inspector. What the difference is is the customer sounds as if they now want the unit direct vented. I'd do what the customer wants (charge him for the material and time) and smilingly say "I appreciate the job and your contacting me to take care of your concern.".
    Now a drywaller has planted a seed in the client's head. Probably fear also if you don't do it. Ya better do it.
    Hey can you cut combustion air in from the attic into the little furnace room?

  2. #15
    Join Date
    Aug 2009
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    Beatrice, NE
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    It always bothers me to think a furnace could suck gasoline fumes into the heat exchanger. I just don't see that or exhaust fumes as being beneficial to the life of the furnace. Depending on the house 20' of pipe, a concentric vent terminal, and a rubber boot and it's done.

  3. #16
    Join Date
    Mar 2013
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    Billington Heights, NY
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    Quote Originally Posted by theoldscroll View Post
    Hey can you cut combustion air in from the attic into the little furnace room?
    What attic have you seen that doesnt need some ventilation? I'd pull from an attic if i knew there was adequate retrun air to the attic available.

    Quote Originally Posted by BNME8EZ View Post
    It always bothers me to think a furnace could suck gasoline fumes into the heat exchanger. I just don't see that or exhaust fumes as being beneficial to the life of the furnace. Depending on the house 20' of pipe, a concentric vent terminal, and a rubber boot and it's done.
    Eh, IMO VOCs being burned are the least of the worries. How many blower compartments have you seen are fully sealed from external gases?

  4. #17
    Join Date
    Jan 2015
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    Iowa
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    My first comment would probably be: Then why isn't the drywall guy doing HVAC instead of drywall?

    Second comment, what do you intend to do in the garage that you did not tell me about that makes you believe something better or different is needed.

    Third comment would probably be: what does he mean by "dirty air" as that is not a typical HVAC term.

    Typically for a condensing furnace in a garage I will use a two pipe vent system whenever posible, just because. Because all the original owner is doing is washing their car in the winter, Because the next owner made the garage a paint booth, Because the next owner has made it their work out gym, Because the last owner has decided to open a beauty shop in the garage. While the furnace meets the OEM instructions and the building code requirements when it was installed, does not mean the homeowner(s) can't change how the garage area is used and subject the furnace to a worse environment. To me a two pipe system offers the best chance at the longest service life. In general for any furnace, as long as the cold air return and burners (combustion air) are 18" off the floor I don't worry about it unless the owner wants something special.

    For garages my recommendation is typically an 80%, forced air, hang it from the ceiling, single pipe, double wall vent out a side wall. Something just to raise the temps enough to let the ice melt off the car in the winter.

  5. #18
    Join Date
    Mar 2013
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    Billington Heights, NY
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    Quote Originally Posted by Answer-Man View Post
    My first comment would probably be: Then why isn't the drywall guy doing HVAC instead of drywall?
    These are my thoughts -

    Maybe the contractor guy DOES know a bit about hvac but is happier doing his drywall trade. So, refer the potential problems to a specific other professional trade.

    Maybe the contractor knows only enough to be dangerous. But, to not make oneself sound stupid, refer it to another trades person.

    Maybe the drywall contractor sees a potential problem and doesnt want to be involved. Point finger at someone else.

    There ARE contractors that do care about working in conjunction with other trades, rather than against them.

  6. Likes BNME8EZ liked this post
  7. #19
    Join Date
    Jun 2012
    Location
    Northern NV
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    ....and mebee the drywall guy has had to buy a furnace caked with drywall dust!

  8. #20
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
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    Quote Originally Posted by Juan Madera View Post
    ....and mebee the drywall guy has had to buy a furnace caked with drywall dust!
    Maybe, but it would more likely be from a packed blower/exchanger and not combustion air.

  9. #21
    Join Date
    Aug 2002
    Location
    Avon Lake, Ohio
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    All this talk about furnaces in garages, but what about water heaters? If anything is going to be affected by fumes and dirty air it would be a burner that sits closer to the floor. Gas fumes are supposedly heavier than air. If the air is corrosive then everything in the garage should be rusted.

    When a furnace is in the garage I would be more concerned about how much fumes are being sucked into the return duct?
    captain CO

  10. #22
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
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    Isn't it,for each CuFt of gas burned there is needed up to +/- 15 to 20 CuFt of air required to support the flame and draft.

  11. #23
    Join Date
    Jul 2007
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    Virginia
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    Quote Originally Posted by TechmanTerry View Post
    Isn't it,for each CuFt of gas burned there is needed up to +/- 15 to 20 CuFt of air required to support the flame and draft.
    1000 btus of fuel needs 10.5 cu.ft. of air for perfect combustion (0% O2).

    If your furnace is tuned to have 6% O2, you need 10.5 cu.ft. for the fuel + 4.5 cu.ft. (added O2) = 15 cu.ft. of air.

    Induced draft and condensing equipment have no additional dilution air.

    Drafthood equipment needs 15 cu.ft. for fuel and 15 cu.ft. for the Drafthood = 30 cu.ft.

    Equipment that has a Barometric installed instead of a Drafthood needs 15 cu.ft. for fuel and 5 cu.ft. for the Barometric = 20 cu.ft.
    Instead of learning the tricks of the trade, learn the trade.

  12. Likes Jim Davis liked this post
  13. #24
    Join Date
    Jan 2015
    Location
    Iowa
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    The Mechanical (and Plumbing) code requires:

    Any heating or cooling equipment that are installed in garages which can generate a glow, spark or flame (in the appliance) capable of inginting flammable vapors, the pilots, burners, heating element and switches must be mounted no less than 18" above the floor level. (UMC 308.0)

    Air Supply for a gas burning appliance has two requirement: 1 Sq/inch opening for every 1000 btu capacity and/or 50 cu/ft for every 1000 cu/ft capacity (UMC 701.1, 703.4.1 and Table 7-1)

    mebee the drywall guy has had to buy a furnace caked with drywall dust!
    In new contruction , or any location that heavy dust or debris can be drawn in a heating or AC system can be a huge problem. Drywall dust get's into the return air stream as well as in the combuston air. I have had one that was so bad that the drywaller had to pay for new furnace. It is my practice to install extra filter media over cold air returns, floor registers (supply side) and combustion air make up inside the house. The one that had to be replaced the drywaller removed the filters because they became so fouled with drywall dust the furnace would not run. Instead of replacing the filters he took them off and continued to work until the furnace would no longer run

    In places I really think it will be a problem, typically the winter I try to work out a deal with the owner to install a temporary furnace or AC system. When the drywall work in the finishing stages, the real (new) equipment is installed. Easy access to clean the duct out too.

  14. #25
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    Jan 2015
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    Iowa
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    My first comment would probably be: Then why isn't the drywall guy doing HVAC instead of drywall?

    Second comment, what do you intend to do in the garage that you did not tell me about that makes you believe something better or different is needed.

    Third comment would probably be: what does he mean by "dirty air" as that is not a typical HVAC term.
    Please do not take my comments wrong. The comments are not stated in a condesending, ridiculing manner and all are said at the same time. Maybe I could be looking for some addition help? Yes I believe HVAC-Marc is correct in the potential characterization of some.

    I don't judge a book by it's cover, (me I have a medical degree, but work in HVAC & Plumbing). Kind of like the first time you see/hear Jim Neighbers (Gomer Pyle) or Susan Boyles sing, their ability is drasticly different than appearance and mannerism. I have run across some very skilled and knowledgable people in the least likely places in my work life. In the course of any year I work with many many different people from all the trades (union, non-union, project manager, senior managers, and even engineers) and we figure out how we are going to get our individual things completed. Some are sharp, expert and knowledgable of many things. Others let's just say they are not the sharpest knife in the drawer.

    But I have also learned cutomers don't always tell you what their intentions are. Customers/home owners rarely know the codes or get permits. Many times I have seen them make the original installations non-code compliant when they build stuff. You can't anticipate what your customer and any other future owners do after you have completed your work, You do the best to cover as many possibilities for the money that was approved. As I said in a garage, a condensing furnace, two pipe as much as possible and everything a minimum of 18" off the floor.

    Have good afternoon

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