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I-UNIT COMPONENTS
SLP99DFV unit components are shown in FIGURE 1. The
gas valve, combustion air inducer and burners can be
accessed by removing the access panel. Electrical com-
ponents are in the control box (FIGURE 2) found in the
blower compartment.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can aect
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. Interlock Switch (S51)
An interlock switch rated 14A at 125VAC is wired in series
with line voltage. When the inner blower access panel is
removed the unit will shut down.
CONTROL BOX
SURELIGHT®
INTEGRATED
CONTROL
TRANSFORMER
CIRCUIT
BREAKER
DOOR
INTERLOCK
SWITCH
FIGURE 2
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transformer
(T1). The breaker is rated 3A at 32V. If the current exceeds
this limit the breaker will trip and all unit operation will shut
down. The breaker can be manually reset by pressing the
button on the face. See FIGURE 3.
CIRCUIT BREAKER CB8
PRESS TO RESET
FIGURE 3
WARNING
Shock hazard.
Disconnect power before servicing.
Integrated control is not eld repairable. If control is
inoperable, simply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
4. Integrated Control (A92)
SLP99DFV units are equipped with the Lennox SureLight
®
variable-capacity integrated control. This control can be
used with a communicating thermostat as part of a com-
municating system. The control can also operate with a
conventional single or two-stage thermostat. The system
consists of an ignition / blower control (FIGURE 4 and
FIGURE 5) with control pin designations in TABLE 1, TA-
BLE 2 and ignitor. The control provides gas ignition, safety
checks and indoor blower control with variable capacity
rate gas heating. The furnace combustion air inducer, gas
valve and indoor blower are controlled in response to vari-
ous system inputs such as thermostat signal, pressure and
limit switch signal and ame signal. The control features a
seven-segment LEDdisplay, indicating furnace status (in-
cluding indoor blower) and error codes. The LED ashes
in single digits. For example using table 14 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 120 volt accessory terminals (used for a humidier
and electronic air cleaner) rated at (1) one amp each.
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