I Unit Components - Lennox SL280UHNX Series Unit Information

I-UNIT COMPONENTS
SL280UHV(X) 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 section.
SL280UHV(X) 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.
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)
An interlock switch rated 14A at 125VAC is wired in series
with line voltage. When the indoor blower access panel is
removed the unit will shut down.
CONTROL BOX
Transformer
Door Interlock Switch
Circuit Breaker
Tw-Stage Variable Speed
FIGURE 2
discharge can
Ignition Control
Blower Drive
(some units)
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.
CIRCUIT BREAKER CB8
PRESS TO RESET
affect
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
result if repair is attempted.
4. Integrated Control (A92)
Units are equipped with a communicating enabled Sure-
Light two-stage, variable speed integrated control. This
®
control is used with a communicating thermostat as part
of a communicating comfort system. The control can also
operate with a non-communicating conventional single or
two-stage thermostat. The system consists of a ignition
/ blower control (FIGURE 4 103130-XX and FIGURE 5
107045-XX) with control pin designations in TABLE 1, TA-
BLE 2, TABLE 3 and ignitor (FIGURE 15). The control and
ignitor work in combination to ensure furnace ignition and
ignitor durability. The control provides gas ignition, safety
checks and indoor blower control with two-stage gas heat-
ing. The furnace combustion air inducer, gas valve and in-
door 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-seg-
ment LED display, indicating furnace status (including in-
door blower) and error codes. The LED flashes in single
digits. For example using 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" con-
tacts for a humidifier and a 120 volt accessory terminal.
Both rated at (1) one amp each. See "Ignition Control Di-
agnostic Modes" on page 22, "Ignition Control 103130-
XX Diagnostic Codes" on page 23 and "Ignition Control
107045-XX Diagnostic Codes" on page 29.
Page 17
FIGURE 3
WARNING