Lennox ML193UH045P36B Unit Information page 10

4. Integrated Ignition Control 103085 (A92)
WARNING
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 6 with control terminal designations
in tables 4 and 5), flame sensor and ignitor (figure 10). 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 troubleshooting
and two accessory terminals rated at (1) one amp. See
table 6 for troubleshooting diagnostic codes. The 120 volt
ignitor is made from a high strength, silicon nitirde material
that provides long life and trouble free maintenance.
Electronic Ignition (Figure 7)
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 after which the gas valve opens for a 4-sec­
ond trial for ignition. The ignitor remains energized during
for the first 3 seconds of trial for ignition. If ignition is not
proved during the trial for ignition, the integrated control will
try four more times with an inter purge and warm-up time
between trials of 30 seconds. After a total of five trials for
ignition (including the initial trial), the integrated control
goes into Watchguard-Flame Failure mode. After a
60-minute reset period, the integrated control will begin the
ignition sequence again.
TABLE 4
4-Pin Terminal Designation
PIN #
1 Combustion Air Inducer Line
2 Ignitor Line
3 Combustion Air Inducer Neutral
4 Ignitor Neutral
FUNCTION
12-Pin Terminal Designations
PIN #
1 High Limit Output
2 Sensor
3 24V Line
4 Not Used
5 Rollout Switch Out
6 24V Neutral
7 High Limit Input
8 Ground
9 Gas Valve Common
10 Pressure Switch In
11 Rollout Switch In
12 Gas Valve Out
DIAGNOSTIC CODES
LED Status
LED Off
LED On
1 Flash
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes
7 Flashes
8 Flashes
9 Flashes
Note - This control is equipped with a push button switch for
diagnostic code recall. The control stores the last 5 fault
codes in non-volatile memory. The most recent fault code
is flashed first, the oldest fault code is flashed last. There is
a 2 second pause between codes. When the push button
switch is pressed for less than 5 seconds, the control will
flash the stored fault codes when the switch is released.
The fault code history may be cleared by pressing the push
button switch for more than 5 seconds.
Page 10
TABLE 5
FUNCTION
TABLE 6
DESCRIPTION
No power to control or control harware
fault detected.
Normal operation.
Flame present with gas vavle
de-energized.
Pressure switch closed with combustion
air inducer de-energized.
Pressure switch open with combus­
tion air inducer energized.
Primary limit switch open.
Rollout switch open.
Pressure switch cycle lockout.
Lockout, burners fail to light.
Lockout, buners lost flame too many
times.
Line voltage polarity incorrect.