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Technical Training Department ©2003
Ashland City, Tennessee
SBN TANK TYPE COMMERCIAL GAS WATER HEATER
SERVICE HANDBOOK
GENERAL QUESTIONS AND ANSWERS
Q: What is the effect of the draft inducer?
A: The draft inducer has several effects:
• minimizes the excess air through the heater—this often reduces the required
vent size
• reduces draft through the heater when it is off
• replaces the draft hood of comparable products
• does not pressurize the vent—common “B” vent materials and the familiar fuel
gas codes for venting Category I, fan-assisted, products still apply. Do not
combine vent with products that do create a positive pressure vent (Category III
or IV).
Q: What is the significance of low NOx (nitrogen oxide)? (SBN Models)
A: Currently, only Southern California and Texas have adopted rules to reduce the NOx
emissions under Rules 1121 and 1146.2, but more of California and Texas are expected
to implement this requirement in 2001. Ground-level ozone from man-made pollution is
a major ingredient in smog. NOx is a contributor to this ground-level ozone formation.
The boilers and water heaters affected by Rule 1121 and 1146.2 release about 14 tons
of NOx emissions into the air each day. By comparison, approximately the same quantity
of NOx is emitted by 288,000 typical passenger vehicles daily. It is estimated that a full
implementation of this emissions rule will reduce NOx by about 11 tons daily.
These emission requirements are expected to be implemented by other cities and
states soon. The rules apply to natural gas water heaters and boilers.
SBN
Induced
Draft
Model Vent
BTR
Atmospheric
Mocels
Vent Dia.
(
inches
)
120 5 120 5
154-390 6 154-275 6
305-390 8