Results 1 to 12 of 12
  1. #1

    Gas Furnace Vent Pipe Question..

    Hi. I have a 4" furnace flue and a 3" hot water heater going into a 5" B Vent to the roof. Is the 5" B Vent big enough to handle both? Or does it have to be 6"?

    I am in Illinois. Thx ; )

  2. #2
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,567
    There is more to venting than just sizing.

    When it comes to venting a combustion appliance, the consequences of an error can be death.

    Best to have a professional evaluate the venting rather than taking the advice of guys on the internet. Even pictures can be misleading.

  3. #3
    Join Date
    Sep 2010
    Location
    Florida
    Posts
    88
    You need to know the BTU's of each appliance, how many elbows and the length of the pipes.

  4. #4
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    3" natural draft and 4 inch induced? Good night

    A 3 and a 4 together have the same area (19 and change) as a 5" but sounds like you have bigger problems

  5. #5
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Quote Originally Posted by captain123 View Post
    You need to know the BTU's of each appliance, how many elbows and the length of the pipes.
    Just check draft, it'll tell u if it works or not

  6. #6
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    Venting combinations are determined by venting tables published by GAMA(gas appliance mfg. association) and the National Fuel Code. As mentioned before if not done correctly can be hazardous or deadly to life and property. By just checking draft as mentioned is not the only determining factor that a vent system is performing correctly. Seek professional help.

  7. #7
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Quote Originally Posted by acwizard View Post
    Venting combinations are determined by venting tables published by GAMA(gas appliance mfg. association) and the National Fuel Code. As mentioned before if not done correctly can be hazardous or deadly to life and property. By just checking draft as mentioned is not the only determining factor that a vent system is performing correctly. Seek professional help.
    No, draft is the only measure if they work or not. Gama is crap and they admit " nO safety factors were included" in their tables

  8. #8
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,567

  9. #9
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Yessir will do!

  10. #10
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    Quote Originally Posted by Gross View Post
    No, draft is the only measure if they work or not. Gama is crap and they admit " nO safety factors were included" in their tables
    I am not here to debate that yes draft is important along with stack temperature.The average homeowner is not going to have the means to determine if the draft is correct. I would never make a statement that GAMA is crap since they are a very large organization that comprises over 90% of all gas appliance manufacturers in the USA. My point is that these tables are what each mfg has based their venting requirements in their installation manuals to comply with safe venting. One must always be cautious when using common venting with a natural draft appliance and an induced draft appliance. It is very easy to see draft when both are fired and not to draft properly when one or the other is off.Consult a professional always.

  11. #11
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,567
    Quote Originally Posted by acwizard View Post
    I am not here to debate that yes draft is important along with stack temperature.The average homeowner is not going to have the means to determine if the draft is correct. I would never make a statement that GAMA is crap since they are a very large organization that comprises over 90% of all gas appliance manufacturers in the USA. My point is that these tables are what each mfg has based their venting requirements in their installation manuals to comply with safe venting. One must always be cautious when using common venting with a natural draft appliance and an induced draft appliance. It is very easy to see draft when both are fired and not to draft properly when one or the other is off.Consult a professional always.
    acwizard,

    You should apply for Professional Membership.

  12. #12
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,350
    A HO cannot determine the venting needs of gas appliances.

    GAMA tables are the requirement of avoidance of legal jeopardy. The disclaimer about safety is also a legal requirement.

    This is not a question that is subject to discussion in the AOP, other than to state that a local Pro must get involved.

    Capiche?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event