I Unit Components - Lennox EL180UHNE Series Unit Information

I-UNIT COMPONENTS
EL180UHNE unit components are shown in figure 1.The
gas valve, combustion air inducer and burners can be ac­
cessed by removing the upper access panel. Electrical
components are in the control box (figure 2) found in the
blower section.
CAUTION
Electrostatic discharge can affect elec­
tronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
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 sec­
ondary.
2. Door Interlock Switch (S51)
A door interlock switch is wired in series with line voltage.
When the blower door is removed the unit will shut down.
NOTE - The door interlock switch is a safety switch. Do not
by-pass or jumper switch.
CONTROL BOX EL180UHNE
TRANSFORMER
(T1)
CIRCUIT
BREAKER
(CB8)
FIGURE 2
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transformer
(T1). The breaker is rated at 3A at 32V. If the current ex­
ceeds this limit the breaker will trip and all unit operation will
shutdown. The breaker can be manually reset by pressing
the button on the face.
DOOR INTERLOCK
SWITCH (S51)
INTEGRATED IGNITION
CONTROL
(A92)
4. Integrated Control (A92)
Shock hazard.
Disconnect power before servicing. Control is not
field repairable. If control is inoperable, simply re­
place entire control.
Can cause injury or death. Unsafe operation will re­
sult if repair is attempted.
The hot surface ignition control system consisting of an in­
tegrated control (figure 3 with control terminal designa­
tions in tables 1, 2 and 3), sensor and ignitor (figure 6). The
integrated control and ignitor work in combination to en­
sure furnace ignition and ignitor durability. The integrated
control, controls all major furnace operations. The inte­
grated control also features a RED LED for troubleshoot­
ing and two accessory terminals rated at (1) one amp. See
table 4 for troubleshooting diagnostic codes. The nitride
ignitor is made from a non-porous, high strength propri­
etary ceramic material that provides long life and trouble
free maintenance.
Electronic Ignition (Figure 4)
On a call for heat the integrated control monitors the com­
bustion air inducer pressure switch. The control will not be­
gin the heating cycle if the pressure switch is closed (by-
passed). Once the pressure switch is determined to be
open, the combustion air inducer is energized. When the
differential in the pressure switch is great enough, the pres­
sure switch closes and a 15-second pre-purge begins. If
the pressure switch is not proven within 2-1/2 minutes, the
integrated control goes into Watchguard-Pressure Switch
mode for a 5-minute re-set period.
After the 15-second pre-purge period, the ignitor warms up
for 20 seconds during which the gas valve opens at 19 sec­
onds for a 4-second trial for ignition. The ignitor remains
energized for the first 3 seconds during the 4 second trial. If
ignition is not proved during the 4-second period, the inte­
grated control will try four more times with an inter purge
and warm-up time between trials of 35 seconds. After a to­
tal of five trials for ignition (including the initial trial), the inte­
grated control goes into Watchguard-Flame Failure mode.
After a 60-minute reset period, the integrated control will
begin the ignition sequence again.
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