Introduction; Qualifications; Service Warning; Service Reminder - A.O. Smith SERIES 120 Service Handbook

INTRODUCTION

This Service Manual is designed to be an aid in servicing and troubleshooting A. O. Smith
Master-Fit models BTR 500 Series 120/121 commercial water heaters. The instructions
and illustrations contained in this service manual will provide you with troubleshooting
procedures to verify proper operation and to diagnose and repair common service
problems.
This Service Manual does not replace or supersede the instruction manual that came with
the water heater. Always refer to the instruction manual that came with the water heater for
complete installation instructions. If the instruction manual is not available, copies can be
obtained from the manufacturer's web site or by calling the toll free phone number shown
on the back cover of this service manual.

QUALIFICATIONS

Servicing the products referenced in this manual requires the ability (in the field involved)
equivalent to that of a Qualified Service Agent as defined by the American National Standards
Institute (ANSI) below. Installation skills such as plumbing, air supply, venting, gas supply,
electrical supply are required in addition to diagnostic and electrical testing skills.
ANSI Z223.1 2006 Sec. 3.3.83: "Qualified Agency" - "Any individual, firm, corporation or
company that either in person or through a representative is engaged in and is responsible
for (a) the installation, testing or replacement of gas piping or (b) the connection,
installation, testing, repair or servicing of appliances and equipment; that is experienced in
such work; that is familiar with all precautions required; and that has complied with all the
requirements of the authority having jurisdiction."

SERVICE WARNING

If you are not qualified (as defined by ANSI above) and licensed or certified as required by
the authority having jurisdiction to perform a given task, do not attempt to perform any of
the procedures described in this manual. If you do not understand the instructions given in
this manual, do not attempt to perform any procedures outlined in this manual.

SERVICE REMINDER

When performing any troubleshooting step outlined in this service manual, always consider
the wiring and connectors between components. Perform a close visual inspection of all
wiring and connectors to and from a given component before replacement. Ensure wires
were stripped before being crimped in a wire connector, ensure wires are crimped tightly in
their connectors, ensure connection pins in sockets and plugs are not damaged or worn,
ensure plugs and sockets are mating properly and providing good contact.
Failure to perform this critical step or failing to perform this step thoroughly often results in
needless down time, unnecessary parts replacement, and customer dissatisfaction.
Servicing should only be performed by a Qualifi ed Service Agent
INTRODUCTION
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