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  1. #1
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    Commercial Boiler Venting Questions

    I am new to the boiler venting design world and was hoping that someone could shed some light on some questions I have as I am trying to learn the best practices. Looking for info more on the CAT II, III, and IV side of venting.

    1) What are some of the biggest mistakes and challenges with boiler venting?
    2) What are common design practices?
    3) How is boiler vent duct size determined?
    4) For forced air boilers, are these on/off or how do they operate?
    5) Dedicated run per boiler vs. common venting.

    Thank you.

  2. #2
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    Feb 2016
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    Go to the manufacturer for the info you want. There are too many boiler designs for us to give you the answers you need. The most common problem I saw was not providing the correct room pressure which caused the boiler to flame out.
    No man can be both ignorant and free.
    Thomas Jefferson

  3. #3
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    Mar 2015
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    Medford, N.Y.
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    Start w/ RSES,SAM# 630-131,"Gas Heating Venting Tables",
    Then try the "National Fuel Gas Code Handbook",
    Then try Hart&Cooley "Gas Vent & Chimney Systems"
    Then try Field Controls Co. "Engineering Manual"
    Then try Carrier Applied Heating, "Ventilation & Combustion Air" Form # GTH7-101
    For starters. You are fooling w/ peoples lives here.

    All a Good Read!

  4. #4
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    Mar 2015
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    Quote Originally Posted by WAYNE3298 View Post
    Go to the manufacturer for the info you want. There are too many boiler designs for us to give you the answers you need. The most common problem I saw was not providing the correct room pressure which caused the boiler to flame out.
    X2 on that.

    Check each and every Mfrg IOM for "THEIR" requirements which should match all the reading material I gave you.

  5. #5
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    Mar 2015
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    [QUOTE=WAYNE3298;25782074]Go to the manufacturer for the info you want. There are too many boiler designs for us to give you the answers you need. The most common problem I saw was not providing the correct room pressure which caused the boiler to flame out

    Twitchy finger.

  6. #6
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    Feb 2016
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    Louisburg Kansas
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    Terry I haven't done boiler design in years. The ones I worked on were steam coal fired. They were big boilers with ID & FD fans. You gave some good references. I would add Babcock and Wilcock to that list. They have a good book with general discussion on boilers. The smallest ones I worked on were 250,000 Pounds per hour.
    Doing water balance the only boilers with work to do on are water.
    No man can be both ignorant and free.
    Thomas Jefferson

  7. #7
    Join Date
    May 2018
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    VA/DC
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    Quote Originally Posted by boilerductguy View Post
    I am new to the boiler venting design world and was hoping that someone could shed some light on some questions I have as I am trying to learn the best practices. Looking for info more on the CAT II, III, and IV side of venting.

    1) What are some of the biggest mistakes and challenges with boiler venting?
    2) What are common design practices?
    3) How is boiler vent duct size determined?
    4) For forced air boilers, are these on/off or how do they operate?
    5) Dedicated run per boiler vs. common venting.

    Thank you.
    It varies a lot with what boiler you are installing. We could be here all night talking about the multitude of options.

    When in doubt read the install manual. It will answer most every question you have. and if you follow it you should not have any issues.

  8. #8
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    May 2018
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    [QUOTE=TechmanTerry;25782083]
    Quote Originally Posted by WAYNE3298 View Post
    Go to the manufacturer for the info you want. There are too many boiler designs for us to give you the answers you need. The most common problem I saw was not providing the correct room pressure which caused the boiler to flame out

    Twitchy finger.
    they never calculate make up air. 500k boiler. " but there is space under the door"

  9. #9
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    Jul 2009
    Location
    Columbia, MD
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    Common venting mistakes;

    Vent too big

    Vent too small

    Improper common venting

    No barometric damper

    Negative pressure in the room causing the flue pipe to become a intake pipe


    A draft gauge and combustion analyzer are your friend.


    Sent from my iPhone using Tapatalk

  10. #10
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    Mar 2015
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    Medford, N.Y.
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    Just a Jaw Flapper here Bros. Just between you and me,ok now.? Just how many CubicFeet of unhindered air is required to "PROPERLY" burn just 1 CF of Natural Gas?????. OK, ok, "UP TO" how many CF of breathable air with a piece of crap 1970 Res Furnace.

    Just between you and me and "them", just how many CUFT of "air" is required to burn just 1 gallon of #2 Fuel Oil?????? Of course, PROPERLY,of course!

  11. #11
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    Quote Originally Posted by TechmanTerry View Post
    Just a Jaw Flapper here Bros. Just between you and me,ok now.? Just how many CubicFeet of unhindered air is required to "PROPERLY" burn just 1 CF of Natural Gas?????. OK, ok, "UP TO" how many CF of breathable air with a piece of crap 1970 Res Furnace.

    Just between you and me and "them", just how many CUFT of "air" is required to burn just 1 gallon of #2 Fuel Oil?????? Of course, PROPERLY,of course!
    Not a lot


    Sent from my iPhone using Tapatalk

  12. #12
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    Mar 2015
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    Medford, N.Y.
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    No offence , ok,but thats like saying "I got normal P/T's" on a regular degree day",,,

  13. #13
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    Jul 2009
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    Old 1970 furnace - .5cfm per CF
    Oil #2 - 24cfm per gallon


    Sent from my iPhone using Tapatalk

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