A.O. Smith 300 Series, Инструкция по эксплуатации

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12
CONTROLS AND SWITCHES
This model is provided with two pressure switches. These switches
are essential to the safe and proper operation of the unit. The
switches are wired in series. The controller is set up to shut the
unit down whenever there is a failure of either of the switches. It is
important to understand the purpose of both switches.
Figure 5. 50 Gallon Unit
Figure 6. 75 Gallon Unit
BLOCKED OUTLET SWITCH
The Blocked Exhaust Switch is set up to shut the unit off when a
build-up of positive pressure in the exhaust vent pipe occurs. This
switch is a positive pressure switch that requires an increase in
pressure to change the electrical contacts from normally closed to
open. When this switch prevents the unit from igniting, most likely the
exhaust is blocked by some means. Check to see if the condensate
is allowed to flow freely from the exhaust elbow and for obstructions
in the exhaust venting and exhaust vent terminal. Also verify that
the vent length does not exceed the maximum allowed as shown
in the Vent Section of this manual.
BLOCKED INTAKE SWITCH
The Blocked Intake Switch is set up to shut the unit off when a build-
up of negative pressure in the intake air pipe occurs. This switch
is a negative pressure switch that requires an increase in negative
pressure to change the electrical contacts from normally closed to
open. The switch is connected to the pressure tap on the PVC pipe
connected to the inlet of the blower. When this switch prevents
the unit from igniting, most likely the intake is blocked. Verify that
the screen on the intake air connection (conventional vent), the
intake air pipe and termination (direct vent installations) are free of
obstructions that may prevent air from entering the unit. Ensure the
screen on intake air connection has been removed on direct vent
installations. See Figure 18 (page 25). Also verify the intake air pipe
length does not exceed the maximum allowed as shown in the Vent
Section of this manual.
WATER HEATING ENABLE/DISABLE SWITCH
Important: The Enable/Disable switch listed in this manual is
NOT
an “on/off” switch and does not disconnect 120
volt power to the CCB and other heater components.
Water Heater’s Enable/Disable Switch. When in the “Disabled”
position the switch removes electrical power from the gas valve so
that water heating is disabled. The display, CCB, and other electrical
components will still be energized and the display will read “Water
Heating Disabled”.
SPARK IGNITER
The Spark Igniter is a device that ignites the main burner by spark.
When high voltage is applied to the igniter, spark is generated to
ignite the main burner.
CONFIGURATION KEY
The configuration key is located inside the control box. It provides
for the ability of the heater to retain information collected over its
lifetime, even if the control board is replaced because of failure.
The configuration key should stay with the heater.
POWERED ANODE ROD
Some of the models covered in this manual are equipped with
a powered (non-sacrificial) anode rod. Protective current is
fed by the control system to the titanium electrode at the end
of the anode rod. This current flows through the water to the
conductive surfaces inside the storage tank which diminishes
the corrosive effect of water when it comes in contact with steel.
Note: To see if a powered anode rod is installed, check the Heater
Status menu of the UIM (user interface module). Refer to
Features and Components (page 10) to locate the UIM. If the
water heater is equipped with a powered anode rod, this
menu will display the Anode Current, Anode Tank Voltage,
and Anode Drive Voltage statuses. See Heater Status Menu
(page 45)
for more information.