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Technical Training Department ©2003
Ashland City, Tennessee
SBN TANK TYPE COMMERCIAL GAS WATER HEATER
SERVICE HANDBOOK
1. The vent pipe should ALWAYS
be the same size as the outlet of
the draft diverter or factory
supplied vent reducer.
• Model SBN 120 are
supplied with a 6” to 5”
reducer.
• Models SBD 250, 251
and 275 are supplied
with a 8” to 6” reducer.
When vents are combined, the area of the com-
bined vent should be equal to area of the largewst
single vent, plus 50% of area of all others joining.
EXAMPLE: To combine two 6” vents with
an 8” vent, the area of a
combined vent should be
one half area of two 6 inch
vents (14 + 14) plus area of 8 inch vent (50)
or 78 sq. inches. Referring to char, 78
sq. inches require 10” diameter vent.
Vent Size
A
rea in
Square Inches Vent Size
A
rea in
Square Inches
5" 20 10" 79
6" 28 12" 113
7" 38 14" 154
8" 50 16" 201
9" 64 18" 254
NINE RULES FOR
GOOD VENTS
2. The diameter of a vent pipe
should NEVER be reduced, no
matter what the circumstances.