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INTRODUCTION
The Bradford White DEFENDER Safety System
®
The Bradford White DEFENDER Safety System
®
was 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 fired 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 opening 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 the supplied gas and is efficiently combusted,
producing very low NOx emissions.
In the case where 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 the burner, 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.