Features And Components; The Eliminator (Self Cleaning System); High Limit Switch; Electronic Ignition Control - AO Smith BTR120 Manuel D'instructions

THE ELIMINATOR (SELF-CLEANING SYSTEM)
These units include The Eliminator (Self-Cleaning System) installed
in the front water inlet, See Figure 1. The Eliminator inlet tube can
only be used in the front water inlet connection. Do not install the
Eliminator inlet tube in either the top or back inlet water connection.
The Eliminator must be oriented correctly for proper function. There
is a marked range on pipe nipple portion of the Eliminator, that
must be aligned with top of inlet spud. A label above the jacket hole
has an arrow that will point to marked portion of pipe nipple if the
orientation is correct. If the arrow does not point within the marked
range on pipe nipple, adjust the pipe nipple to correct. A pipe union
is supplied with the Eliminator to reduce probability of misaligning
the Eliminator accidentally while tightening the connection to inlet
water supply line. Improper orientation of the Eliminator can cause
poor performance of heater and can significantly reduce outlet water
temperatures during heavy draws.
Note: The Eliminator may have 1, 3 or 7 cross tubes.
FIGURE 1.

HIGH LIMIT SWITCH

The digital thermostat (Figure 2) contains the high limit (energy
cutout) switch. The high limit switch interrupts main burner gas flow
should the water temperature reach 203°F (95°C).
In the event of high limit switch operation, the water heater cannot be
restarted unless the water temperature is reduced to approximately
120°F (49°C). The high limit reset button on the front of the control
then needs to be depressed.
Continued manual resetting of high limit control, preceded by higher
than usual water temperature is evidence of high limit switch operation.
The following is a possible reason for high limit switch operation:
• A malfunction in the thermostatic controls would allow the gas
control valve to remain open causing water temperature to
exceed the thermostat setting. The water temperature would
continue to rise until high limit switch operation.
Contact your dealer or service agent if continued high limit switch
operation occurs.
DIGITAL THERMOSTAT
FIGURE 2.

ELECTRONIC IGNITION CONTROL

Each heater is equipped with a Honeywell ignition module. The
solid state ignition control ignites the pilot burner gas by creating a
spark at the pilot assembly. See Figure 3. Pilot gas is ignited and

FEATURES AND COMPONENTS

burns during each running cycle. The main burner and pilot gases
are cut off during the OFF cycle. Pilot gas ignition is proven by the
pilot sensor. Main burner ignition will not occur if the pilot sensor
does not first sense pilot ignition.
IGNITION MODULE

AUTOMATIC FLUE DAMPER

All units are equipped with an automatic flue damper that reduces
heat loss during the OFF cycles. The automatic flue damper
drive assembly is a field replaceable part and may be obtained
by contacting A. O. Smith Corporation at 500 Tennessee Waltz
Parkway, Ashland City, TN 37015, 1-800-433-2545. In Canada,
contact A.O. Smith Enterprises LTD., P.O. Box, 310 - 768 Erie
Street, Stratford, Ontario, Canada N5A 6T3, 1-800-265-8520.
Each automatic flue damper drive assembly is equipped with a
"Service Switch", as shown in Figure 4
The "Service Switch" has 2 positions: AUTOMATIC OPERATION
and HOLD OPEN DAMPER. For normal operation the switch
should be in the AUTOMATIC OPERATION position.
If there is a problem with the damper the "Service Switch" can be
placed in the HOLD OPEN DAMPER position. When the switch
is placed in the HOLD OPEN DAMPER position the damper disc
will rotate to the open position and the heater may be used until
vent assembly is repaired or replaced. DO NOT turn the damper
disc manually; damage will occur to the drive assembly if operated
manually. Refer to TESTING DAMPER OPERATION section of
this manual for additional information.

UNCRATING

The heater is shipped with the flue damper already installed. The
wiring conduit runs from the thermostat to the damper drive cover.
Before turning unit on, check to make sure the wiring conduit is
securely plugged into damper drive.
7
FIGURE 3.
FLUE DAMPER
FIGURE 4.