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I-UNIT COMPONENTS
Unit components are shown in FIGURE 1. The gas valve,
combustion air inducer and burners can be accessed by
removing the access panel. Electrical components are in
the control box (FIGURE 2) found in the blower section.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic
electronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
A- Control Box
1. Control Transformer (T1)
A transformer located in the control box provides power
to the low voltage section of the unit. Transformers on all
models are rated 40VA with a 120V primary and a 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch is wired in series with line voltage.
When the inner blower access panel is removed the unit
will shut down.
®
SureLight
Integrated
Control
Interlock Switch
Circuit Breaker
FIGURE 2
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box.
The switch provides overcurrent protection to the trans-
former (T1). The breaker is rated 3A at 32V. If the current
exceeds this limit the breaker will trip and all unit opera-
tion will shutdown. The breaker can be manually reset by
pressing the button on the face. See FIGURE 3.
discharge
can
affect
Transformer
CIRCUIT BREAKER CB8
PRESS TO RESET
Shock hazard.
Disconnect power before servicing. Integrated
control is not field repairable. If control is
inoperable,
simply
Can cause injury or death. Unsafe operation will
result if repair is attempted.
4. Integrated Control (A92)
103699 and 107048
Units are equipped with the SureLight
grated control. The system consists of a ignition / blower
control (FIGURE 4 and FIGURE 5) with control pin desig-
nations in TABLE 1, TABLE 2 and ignitor. The control and
ignitor work in combination to ensure furnace ignition and
ignitor durability.
The control provides gas ignition, safety checks and in-
door blower control with two-stage gas heating. The fur-
nace combustion air inducer, gas valve and indoor blower
are controlled in response to various system inputs such
as thermostat signal, pressure and limit switch signal and
flame signal. The control features a seven-segment LED
display, indicating furnace status and error codes. The
LED flashes in single digits. For example using table 4
under LIMIT CODE, an "E" followed by "2" followed by "5"
followed by "0", the limit switch circuit is open. The control
also has two unpowered (dry) 1/4" contacts for a humid-
ifier and a 120 volt accessory terminal. Both rated at (1)
one amp each.
Electronic Ignition
At the beginning of the heat cycle the integrated control
monitors the first stage and second stage combustion air
inducer pressure switch. The control will not begin the
heating cycle if the first stage pressure switch is closed
(bypassed). Likewise the integrated control will not be-
gin the second stage heating cycle if the second stage
pressure switch is closed, and will remain in first stage
heat. However, if the second stage pressure switch closes
during the first stage heat pre-purge, the control will allow
second stage heat. Once the first stage pressure switch
is determined to be open, the combustion air inducer is
energized on low (first stage) heat speed. When the differ-
ential in the pressure switch is great enough, the pressure
switch closes and a 15-second pre-purge begins.
Page 5
FIGURE 3
WARNING
replace
entire
two-stage, inte-
®
control.
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