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I-UNIT COMPONENTS
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions to neutralize
electrostatic charge by touching your hand
and tools to metal prior to handling the
control.
ML193UHE unit components are shown in FIGURE 1.
The combustion air inducer, gas valve and burners can
be accessed 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
Integrated Control
Door Interlock
Switch
Transformer
Circuit Breaker
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 volt
-
age. When the blower door is removed the unit will shut
down.
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
WARNING
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, TABLE 3,
sensor and ignitor (FIGURE 6). 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 features
a RED LED for troubleshooting and two accessory termi
-
nals rated at (1) one amp. The nitride ignitor is made from
a non-porous, high strength proprietary ceramic material
that provides long life and trouble free maintenance.
TABLE 1
4-Pin Terminal Designation
PIN #
FUNCTION
1
Combustion Air Inducer Line
2
Ignitor Line
3
Combustion Air Inducer Neutral
4
Ignitor Neutral
TABLE 2
12-Pin Terminal Designations
PIN #
FUNCTION
1
High Limit Output
2
IFC 103217-03 Not Used
IFC 107163-01 Flame Sense
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
