I Unit Components - Lennox EL280UHX Series Unit Information

I-UNIT COMPONENTS
EL280UHE(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.
EL280UHE(X) units are factory equippeWiring Diagram
With Integrated Control 107048d 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)
A door interlock switch is wired in series with line voltage.
When the inner blower access panel is removed the unit
will shut down.
CONTROL BOX
Transformer
Circuit Breaker
FIGURE 2
discharge can affect
Interlock Switch
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SureLight Integrated Control
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
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)
103699 and 107048
Units are equipped with the SureLight
grated control. The system consists of a ignition / blow-
er control (FIGURE 4 and FIGURE 6) with control pin
designations in TABLE 1 and TABLE 2 and ignitor. The
control and ignitor work in combination to ensure furnace
ignition and ignitor durability. The control provides gas ig-
nition, safety checks and indoor blower control with two-
stage gas heating. The furnace combustion air inducer,
gas valve and indoor blower are controlled in response
to various system inputs such as thermostat signal, pres-
sure 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 humidifier and a 120 volt accesso-
ry 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.
Page 8
FIGURE 3
WARNING
two-stage, inte-
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