I-Unit Components - Lennox ML193DFE Series Unit Information

I-UNIT COMPONENTS

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.
ML193DFE unit components are shown in FIGURE 1.The
combustion air inducer, gas valve and burners can be ac-
cessed by removing the burner access panel. The blower
and control box can be accessed by removing the blower
access door.
A-Control Box Components (FIGURE 2)
Unit transformer (T1) and integrated ignition control (A92)
are located in the control box. In addition, a door interlock
switch (S51) is located in the control box.
Control Box
Door Interlock
Switch (S51)
Circuit Breaker (CB8)
FIGURE 2
1. Transformer (T1)
A transformer located in the control box provides power
to the low voltage section of the unit. The transformers on
all models are rated at 40VA with a 120V primary and 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located
on the control box. The switch is wired in series with line
voltage. When the blower door is removed the unit will
shut down.
discharge can affect
Integrated Igition
Control (A92)
Transformer (T1)
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transform-
er (T1). The breaker is rated at 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.
4. Integrated Ignition Control (A92)
103217-03 & 107163-01
Shock hazard.
Disconnect power before servicing. 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.
The hot surface ignition control system consisting of an
integrated control (FIGURE 3 or FIGURE 5 with control
terminal designations in TABLE 1, TABLE 2 and TABLE
3), sensor and ignitor (FIGURE 7). The integrated control
and ignitor work in combination to ensure furnace ignition
and ignitor durability. The integrated control, controls all
major furnace operations. The integrated control also fea-
tures a RED LED for troubleshooting and two accessory
terminals rated at (1) one amp. The nitride ignitor is made
from a non-porous, high strength proprietary ceramic ma-
terial that provides long life and trouble free maintenance.
4-Pin Terminal Designation
PIN #
1
2
3
4
12-Pin Terminal Designations
PIN #
1
2
3
4
5
6
7
8
9
10
11
12
Page 6
WARNING
TABLE 1
FUNCTION
Combustion Air Inducer Line
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
FUNCTION
High Limit Output
IFC 103217-03 Not Used
IFC 107163-01 Flame Sense
24V Line
Not Used
Rollout Switch Out
24V Neutral
High Limit Input
Ground
Gas Valve Common
Pressure Switch In
Rollout Switch In
Gas Valve Out