Page 14
I−UNIT COMPONENTS
SLP98UHV 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.
SLP98UHV units are factory−equipped with a bottom return air
panel in place. The panel is designed to be field removed as
required for bottom air return. Markings are provided for side
return air and may be cut out in the field.
CAUTION
Electrostatic discharge can affect electronic com-
ponents. Take precautions during furnace instal-
lation and service to protect the furnace’s elec-
tronic controls. Precautions will help to avoid con-
trol exposure to electrostatic discharge by putting
the furnace, the control and the technician at the
same electrostatic potential. Neutralize electro-
static charge by touching hand and all tools on an
unpainted unit surface, such as the gas valve or
blower deck, before performing any service pro-
cedure.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
A−Control Box 1
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.
FIGURE 2
CONTROL BOX SLP98UHV
SURELIGHT®
INTEGRATED
CONTROL
TRANSFORMER
CIRCUIT
BREAKER
INTERLOCK
SWITCH
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.
FIGURE 3
CIRCUIT BREAKER CB8
PRESS TO RESET
WARNING
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)
SLP98UHV units are equipped with the Lennox SureLight
®
variable−capacity integrated control. This control can be
used with the icomfort Touch
thermostat as part of a com-
municating comfort system. The control can also operate
with a conventional single or two−stage thermostat. The
system consists of an ignition / blower control (figures 4 and
5) with control pin designations in tables 1 and 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 blow-
er 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.
