Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.


Alexander Member Posts: 2
If I have a burner of a certain size that pumps out X amount of BTU,s or burns X liters of oil per hour, what is the caculation required to figure out the size of the flue that is required? Thanks


  • Brad White_185
    Brad White_185 Member Posts: 265
    It depends,

    If the combustion is atmospheric, the induced air volume increases the total effluent volume. Forced draft is somewhat less, condensing probably the least of all.

    The total volume is a function of the fuel input (as you know), plus the net combustion air (for theoretically perfect or stoichiometric combustion), plus excess air plus any dilution from the barometric control device...

    All of the input values are represented in identical terms in the end, volume, even if they are initially in weight or mass. Temperature also affect the volume of course.

    I would suggest that if this is for your use in sizing a stack or chimney you fall back on the manufacturer's recommendations. These too presuppose a certain height (usually but not always 30 feet); the draft inherent in a certain height may affect the size if it were borderline. A taller stack might be a size smaller than a short one for example.
  • Alexander
    Alexander Member Posts: 2

    Hi Brad,

    I have a heating exam in 2 days and sort of need a general formula to take with me to the exam.
This discussion has been closed.