Service Manual

4
4
Introduction
The Bradford White Ultra Low NOx Atmospheric Vent Water Heater is designed to deliver hot water
at up to 82% thermal efficiency in a quiet running unit with a top exhaust vent connection that allows
for installation in existing locations. While this unit is vented atmospherically, there is no damper
required to maintain heat loss during off cycle. Several technologically advanced design features are
incorporated that will require additional knowledge on the part of the qualified service provider. The
information in this manual will instruct service and maintenance professionals on the function, proper
diagnosis, and repair of The Bradford White Ultra Low NOx Atmospheric Vent Water Heater.
This water heater uses an Ultra Low NOx premix power burner located at the top of the water heater
to direct a turbulent flame down into the water backed combustion chamber. This turbulence causes a
thorough mixing of gas and air for optimum combustion. The combustion gases then travel through a
two pass flue system keeping the gases moving at a high velocity. The combination of high
turbulence and velocity results in an optimum transfer of heat from the flue gases into the water.
Burner operation is controlled using an electronic ignition module. The module monitors the status of
the electronic thermostat, blocked vent limit switch, flame sensor to control output voltage to blower
motor, spark rod, and gas valve. The module contains programming which determines the sequence
of operation and timings for purge periods, trial for ignition, flame sensing, and lockout. The module
will also provide diagnostic information to help in determining the cause of system lockouts.
The contents in this manual are detailed informational tools to assist in the proper diagnosis of the
water heater’s operational faults. Please read this service manual completely and record as much
information regarding the Ultra Low NOx Atmospheric Vent Water Heater operation and installation
specifics related to any concerns.
How to Use This Manual
It is intended for this manual to be used by qualified service personnel for the primary purpose of
troubleshooting analysis and repair of the water heater. Understanding the sequence of operation
section of this manual will contribute greatly to troubleshooting this product.
An Installation Checklist is shown towards the end of this manual. Compare the installation against
the installation checklist to confirm all requirements are met. A Service Report is shown towards the
end of this manual. Completing this form will assist in the troubleshooting efforts. Should you need to
call for Technical Support, please provide the information shown on this form to the support
technician to help ensure accurate troubleshooting. Troubleshooting begins with System Observation
to determine failure mode as indicated by the error code on the system display. Troubleshooting
continues with Failure Modes and Probable Cause directing the service provider to a series of test
procedures to determine root cause of failure. Component replacement procedures directly follow the
test procedures for a given component. In some difficult to diagnose conditions, it may be necessary
to isolate the heater from the vent system to determine root cause.
Contact Technical Support immediately if diagnosis is not determined using the methods described in
this service manual.