Bradford White TW4-75S-76B-3X - Manual (Page 4)

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Introduction
The new Bradford White TTW1, TTW2 & TW4 water heaters are designed to provide reliable
performance with enhanced standard features. New design features include reliable spark to pilot
ignition system, enhanced diagnostics, simplified servicing, significantly quiet operation and additional
vent lengths and Bradford White Defender Safety System®.
Spark to Pilot Ignition System - employing the spark to pilot ignition system promotes reliable and
consistent pilot and main burner ignitions to provide hot water on demand.
Integrated Immersion Thermostat/Gas Control Valve with LED - was developed for ease of
troubleshooting by providing simple diagnostic codes to pinpoint an installation or component
performance issue.
New Powerful Blower - will eliminate problems with difficult venting situations.
Quieter and Cooler Blower Operation - blower noise is significantly reduced for both interior and
exterior environments. Cooler operation increases blower life by reducing bearing wear and noise.
Rugged Wiring Connections - receptacle type connections promote error free wiring.
Increased Vent Lengths - increased venting performance is achieved while maintaining Energy Factor
& FHSR performance.
The TTW1, TTW2 & TW4 water heaters use a combustion system where flue gases are combined with
dilution air to reduce the flue gas temperature in the blower. The diluted flue gases are evacuated to the
exterior through low temperature vent materials. The gas control maintains water temperature, ignition
sequence and regulates gas flow. A safety circuit consisting of a pressure switch and blower
temperature switch verifies proper conditions exist for safe and reliable operation. If a situation outside
of normal operating parameters exists, the gas control diagnostic LED will flash a code to positively
identify an operational issue.
This service manual is designed to facilitate problem diagnosis and enhance service efficiency. To
further promote quicker service times the new gas valve can be removed and replaced without draining
the water heater. A special tool is required and will be provided with each gas valve kit shipped from
our Service Parts department.
Please read the service manual completely before attempting service on this new series of power vent
models.
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 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. If flammable vapors are in
sufficient quantity to main burner. Should be flammable vapors continue to burn, the flame arrestor
plate prevents the flames from traveling backwards and igniting vapors outside of the combustion
chamber.
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