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Boiler flue sizing??
area of a flue pipe:
A = 3.1416 X radius squared
or A = .7854 X diameter squared
Circumference of a circle is:
C = 3.1416 X diameter
An example is 4" flue area is 12.56" (A = 3.1416 X 2 (radius of a 4" circle) squared)
A = 3.1416 X radius squared
or A = .7854 X diameter squared
Circumference of a circle is:
C = 3.1416 X diameter
An example is 4" flue area is 12.56" (A = 3.1416 X 2 (radius of a 4" circle) squared)
0
Comments

flue
What was that old smoke pipe sizing formula from school?
Was it D2+1/2d or something like that. Does anyone remember how it goes.
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formulae
d squared x 5 = maximum btu for that size pipe0 
a 6" flue would be:
6 squared or 36 X 5 = 180 BTU's ???0 
GREAT FORMULA,FRANK0 
The area of the flue
in inches determines btu as per the American Gas Association rules of 4500 to 6500 BTU's per square inch. It is then determined by the manufacturer which btu per square inch they will use.
On newer high efficiency equipment those rules do not pertain.0
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