Bradford White UDH-75T-50FR-3N - Manual (Page 3)

The new Bradford White UDS and UDH water heaters are designed to
provide reliable performance with enhanced standard features. Design
features include reliable standing pilot ignition system, enhanced
diagnostics, simplified servicing, certified FVIR technology and Ultra
Low NOx emissions.
The UDS and UDH water heaters use a combustion system where
combustion air is drawn from the outside of the building. The gas control
maintains water temperature and maintains gas flow. If a situation outside
of normal operating parameters exists, the gas control diagnostic LED wll
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
gas valve can be removed and replaced without draining the water heater.
Please read the service manual completely before attempting service on
this new series of direct vent water heaters.
How the Safety System Works
During normal operation, air for the combustion chamber is drawn into
the water heater through the vent pipe from outside your building. The air
travels into the closed combustion chamber. The air then mixes in a
normal manner with supplied gas and is efficiently combusted, producing
Ultra Low NOx emissions.
In the unlikely event trace amounts of flammable vapors are present in the
area surrounding the water heater, the sealed combustion system prevents
the flammable vapors from reaching the ignition source.
INTRODUCTION
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