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  1. #14
    Join Date
    Jun 2001
    Louisville, KY
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    Page 22:

    Step 9—Direct Venting
    The 58MVP furnaces require a dedicated (one 58MVP furnace
    only) direct-vent system. In a direct-vent system, all air for
    combustion is taken directly from outdoor atmosphere, and all flue
    gases are discharged to outdoor atmosphere.
    What's the question?

  2. #15
    Join Date
    Apr 2004
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    Originally posted by wayner211
    It can be done and it does not lower the efficiency. I know this for a fact and I'm sorry but I can't tell you where I work.
    So who pays for the air coming in through the envelope of the house that will only be heated then be used for combustion and sent back outside?

    When I say efficiency, I mean efficiency. AFUE would not be affected but the cost of heating the home would be greater with a single pipe system (unless its in an attic or crawl space).

    Now there is an instruction manual. It either says direct vent only or it allows for 2 pipes. My understanding is two pipe (direct vent) is the only acceptable practice on this furnace.

  3. #16
    Join Date
    Jun 2005
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    It is a better system 2 pipe...... we can argue all day if it reduces the actual furnace efficeny by using a single pipe install--but by bringing in the outside air via sealed combustion makes the sytem more efficent.

  4. #17
    Join Date
    Apr 2002
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    The manual will show approved venting methods for the furnace. If this is a condensing furnace and it only approves direct air from the outside ducted directly to the unit, then it shall be installed that way.

    From an energy standpoint, you make better use of your fuel with the combustion air ducted directly to the furnace from the outside.

    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

  5. #18
    Join Date
    Oct 2005
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    Thread Starter
    Thanks everyone for your input. It is appreciated. I don't know of anywhere else where we can find this much HVAC knowledge given so generously. Hopefully I will be able to repay somehow, someday.

    The decision on installing this furnace using combustion air from inside the house was based almost entirely on the fact that the furnace being replaced was set up that way. I believe too many variables were not considered, or at least if they were, they were not communicated to me.

    I will ask the installer to change the combustion air setup to outside air.


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