Troubleshooting; Installation Checklist; Water Heater Location; Venting - A.O. Smith 300 Series Instruction Manual

INSTALLATION CHECKLIST

The list below represents some of the most critical installation
requirements that, when overlooked, often result in operational
problems, down time and needless parts replacement. This is not
a complete list. Before performing any troubleshooting procedures
use the list below to check for installation errors. Costs to correct
installation errors are not covered under the limited warranty. Ensure
all installation requirements and instructions in this manual have
been maintained and followed.

WATER HEATER LOCATION

Ensure proper clearances to combustibles are maintained and
1.
there is sufficient room to service the water heater.
Ensure the area is free of corrosive elements and flammable
2.
materials.

VENTING

Ensure the intake air and/or vent (exhaust) piping is the correct
3.
size for the installed length.
Ensure the maximum equivalent feet of pipe has not been
4.
exceeded for the intake air and/or vent pipe.
Ensure the maximum number of elbows has not been exceeded
5.
in the intake air and/or vent pipe.
Ensure all exterior clearances for the intake air, vent and
6.
concentric terminations are maintained. These clearances and
those cited by local and national codes must be maintained.
If venting direct vent, ensure the screen located in air intake at
7.
the water heater was removed.

GAS SUPPLY AND PIPING

Ensure the supply gas line to each water heater meets the
8.
minimum supply gas line size requirements.

CONDENSATE DRAIN

Ensure the condensate drain is properly connected to the exhaust
9.
elbow on the water heater and draining freely to a suitable floor
drain.

ELECTRICAL CONNECTIONS

10. Ensure the water heater is properly grounded. Flame sensing
requires an adequate earth ground. If the water heater is not
properly grounded it will cause Ignition Failure.
11. Ensure the power supply connections to the water heater are
polarity correct.

TROUBLESHOOTING

TROUBLESHOOTING

SEQUENCE OF OPERATION

Read Sequence Of Operation (page 57) before attempting to correct
any operational problems. See Features and Components (page 10)
for the location of various water heater components described in
this section.
When the control system is first powered, during boot up, it will
1.
display water heater model information during initialization. After
a few moments the control system LCD Touch Display which is
part of the UIM (user interface module) will display the default
screen known as the "Desktop" screen.
If the control system determines that the actual water temperature
2.
inside the tank is below the programmed Operating Set Point
minus the Differential setting, a heating cycle is activated.
The control system then performs selected diagnostic system
3.
checks. This includes confirming the blocked exhaust, blocked
intake and ECO (energy cut out) switch contacts are closed.
If all diagnostic checks are successfully passed, the control
4.
system energizes the Combustion Blower for pre-purge.
The control system energizes the Spark Ignition Transformer..
5.
After a few seconds, the control system energizes the 24V Gas
6.
Control Valve allowing gas to flow to the Main Burner.
The control system monitors the flame sensor to confirm a flame
7.
is present at the Main Burner. If a flame is not verified during the
ignition trial period the control system will try for ignition up to
two more times. If flame can not be verified after three trials for
ignition, the control system will lock out and display the "Ignition
Failure" Fault message.
If a flame is verified, the control system will de-energize the
8.
Spark Ignition Transformer and enter the heating mode where
it will continue heating the water until the Operating Set Point is
reached. At this point, the control system will de-energize the
24-volt gas valve and enter the post-purge cycle (approximately
60 seconds).
The Combustion Blower will run for the duration of the postpurge
9.
cycle to purge the water heater of all combustion gases. When
the post-purge cycle is complete, the blower is de-energized and
will coast to a stop.
10. The control system now enters the standby mode while continuing
to monitor the internal storage tank water temperature and the
state of other system devices. If the tank temperature drops below
the Operating Set Point minus the Differential setting, the control
will automatically return to Step 2 and repeat the operating cycle.
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