Controls And Switches - A.O. Smith 100 Series Installation And Operating Manual

CONTROLS AND SWITCHES

CONTROL MODULE
This heater includes a control module with a user interface and a
LCD display (see Figure 5). There are three primary functions of the
control: turn the appliance on/off, set/control water temperature,
setting operating/vacation mode. To turn heater on: hold the
OFF) button depressed for 5 seconds. To change desired setpoint
temperature use the (Plus) or
setpoint by depressing (Lock/Unlock). To enable Vacation mode
press and simultaneously for 5 seconds. For more information
on this control module. See Control System Operation (page 40).
ON/OFF ON/OFF LOCK
LOCK/ SERVICE RADIATOR
UNLOCK (NOT IN
Figure 5. User Interface Screen
PRESSURE SWITCHES
This model is provided with two pressure switches. These switches
are essential to the safe and proper operation of the unit. Each switch
provides feedback to the control to ensure the control will detect
which switch has been activated and indicate the appropriate error
code (blocked vent outlet or blocked air intake).
OUTLET AIR PRESSURE SWITCH (OAPS)
The Outlet Air Pressure Switch is set up to shut the unit off when a
build-up of positive pressure in the exhaust vent pipe occurs. This
(Minus) buttons, then lock in
FLAME ON CELSIUS
FAHRENHEIT WARNING
USE)
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 condensate trap 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
(ON/
Planning the Vent System (page 14).
INTAKE AIR PRESSURE SWITCH (IAPS)
The Intake Air Pressure 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
PLUS
closed to open. The switch is connected to the pressure tap on the
rubber blower adapter connected to the inlet of the blower. When
this switch prevents the unit from igniting, most likely the intake is
blocked. Verify that the intake air pipe, and the intake air termination
are free of obstructions that may prevent air from entering the unit.
Also verify the intake air pipe length does not exceed the maximum
allowed in Planning the Vent System (page 14).
HOT SURFACE IGNITER (HSI)
MINUS
This heater is provided with a Hot Surface Igniter. It can automatically
ignite the burner when a "call for heat" is received. On a "call for heat"
the Hot Surface Ignitor will heat up for 12 seconds and will ignite the
gas/air mixture when the gas valve opens. The ignitor then turns off.
FLAME SENSOR
This heater includes a flame sensor to detect the flame current and
continue to monitor the flame current during the burner operation to
ensure the burner operates only in a safe condition.
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