I Unit Components - Lennox SLP99DF070XV36B Unit Information

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 components are in
the control box (figure 2) found in the blower compartment.
CAUTION
Electrostatic discharge can affect elec­
tronic components. Take precautions to
neutralize electrostatic charge by touch­
ing 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 mod­
els are rated 40VA with a 120V primary and a 24V secon­
dary.
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 re­
moved the unit will shut down.
CONTROL BOX SLP99DFV
SURELIGHT®
INTEGRATED
CONTROL
DOOR
INTERLOCK
SWITCH
FIGURE 2
TRANSFORMER
CIRCUIT
BREAKER
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 shut down. The breaker can be manually reset by
pressing the button on the face. See figure 3.
CIRCUIT BREAKER CB8
PRESS TO RESET
Shock hazard.
Disconnect power before servicing.
Integrated control is not field repairable. If control
is inoperable, simply replace entire control.
Can cause injury or death. Unsafe operation will re­
sult 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 commu­
nicating system. The control can also operate with a con­
ventional single or two-stage thermostat. The system con­
sists of an ignition / blower control (figures 4 and 5) with
control pin designations in tables 1, 2 and ignitor. The con­
trol 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 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 (including indoor blower)
and error codes. The LED flashes in single digits. For exam­
ple 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 humidifier and electronic air cleaner) rated at (1)
one amp each.
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FIGURE 3
WARNING
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