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chimmney sizing

Steve-O
Steve-O Member Posts: 21
in THE MAIN WALL
I recently was called on a job where the homeowner wanted to move his gas fired hot water heater from one location to another. Why because of renovations. So now I have two opotions , one scrap the heater that he has and put a direct vent gas hot water heater in.Or try and utilize another chimmney being used for a gas furnace.The furnace has an out put of 140000btu with a 8" flue. The chimmney is 11"x11" with a height of 30'. The hwh has output of 40000btu .Is this chimmney to big or to small for both of these units. Would they both work effectivlyin the same chimmny?An A.O. Smith engineer told me this could be done but only guarantees this if i put a draft inducer on hwh flue pipe. Is this realy needed?Is there any charts to go by to figure this out for myself?Any help would be great thanks...

Comments

  • Frank_5
    Frank_5 Member Posts: 49
    chimney

    The horrizontal run of any appliance cannot be more than 50% of the verticle height of the chimney.
    Sizing goes this way.... Diameter squared X 5 =BTU in K's
    So if the 11x11 was rounded off, 11*x5=605,000 BTU....no problem with putting both units into that chimney. However, you should always install the W.H. flue above the house heating flue. Why??? 'cause it's in some book somewhere that sez so, AND the dead men always did it that way.
  • Gary Fereday
    Gary Fereday Member Posts: 427
    It depends

    On what the furnace is. Is it a high efficiency one or just a normal asperated gas furnace. Some high eff. ones requier special chimneys. Other than that All should be ok. Is the chimney lined or just brick with no vertified clay liner. Is it all indoors surrounded by warm in house air at all times? If lined and in a warm area ok. if not~~~~. Your gas utility people should have a chimney pamphlet for you to see as to what is required in your area.
  • Alan R. Mercurio
    Alan R. Mercurio Member Posts: 588


    Hi Steve, The charts you're looking for can be found at the following web site http://www.protechinfo.com/

    You can also find the information you're looking for in NFPA-211

    If I can be of any further help to you please don't hesitate to E-mail me.

    Your friend in the industry,
    Alan R. Mercurio
    www.oiltechtalk.com
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