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Introduction

The Bradford White DEFENDER Safety System™

The Bradford White DEFENDER Safety SystemTMwas designed to resist the ignition of flammable
vapors that can occur outside of the water heater. Use and installation are nearly identical to
previous versions of atmospherically f ired and vented water heaters. A number of exclusive
design features are incorporated in the system that will require additional knowledge on the part
of the qualified service provider. The following information will instruct service professionals on
the function, proper diagnosis and repair of water heaters employing the Bradford White
DEFENDER Safety System .

How the Safety System Works™

During normal operation, air for combustion is drawn into the water heater through the
openings in the jacket. This air travels down and around the combustion chamber and enters
through holes in the very bottom of the corrosion-resistant combustion chamber. The air then
travels up through the oriented flame arrestor plate louvers, where the velocity of the air is
increased and its direction altered. The air then mixes in a normal manner with supplied gas
and is efficiently combusted, producing very low NOx emissions. In the unlikely event trace
amounts of flammable vapors are present in the air flowing into the combustion chamber, the
vapors are harmlessly ignited by the burner / pilot flame. If flammable vapors are in sufficient
quantity to prevent normal combustion, the burner / pilot flame is shut down. Should the
flammable vapors continue to burn, the flame arrestor plate prevents the flames from traveling
backwards and igniting vapors outside of the combustion chamber. The calibrated,
multipurpose thermal switch recognizes this and shuts down the pilot and main burner. This
switch also deactivates the burner and pilot in the unlikely event of restricted airflow caused by
severe lint, dust or oil accumulation on the arrestor plate. If accumulation occurs, the
ScreenLok flame arrestor can be easily cleaned and when the inner door is properly secured
the unit can then be placed in operation. A cleaning procedure is included in this service
manual.