I Unit Components - Lennox EL296UHE Series Unit Information

I-UNIT COMPONENTS
EL296UHE unit components are shown in figure 1. The
gas valve, combustion air inducer and burners can be ac-
cessed by removing the access panel. Electrical compo-
nents are in the control box (figure 2) found in the blower
section.
EL296UHE units are factory equipped with a bottom re-
turn 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
®
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)
Units are equipped with the SureLight® two-stage, inte-
grated control. The system consists of a ignition / blower
control (figures 4 and 5) with control pin designations in ta-
bles 1 and 2 and ignitor (figure 14). 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 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 and error codes.
The LED flashes in single digits. For example using ta-
ble 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 accessory terminal. Both rated
at (1) one amp each.
Electronic Ignition
At the beginning of the heat cycle the integrated con-
trol monitors the first stage and second stage combus-
tion air inducer pressure switch. The control will not be-
gin the heating cycle if the first stage pressure switch is
closed(bypassed). Likewise the integrated control will not
begin 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. When the differ-
ential in the pressure switch is great enough, the pressure
switch closes and a 15-second pre-purge begins.
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FIGURE 3
WARNING