Unit Components; Make-Up Box; Control Box Components; Surelight Ignition System - Lennox G43UF SERIES Unit Information

I−UNIT COMPONENTS
G43UF unit components are shown in figure 1. The com-
bustion air inducer, gas valve and burners can be accessed
by removing the burner access panel. The blower and con-
trol box can be accessed by removing the blower access
door. G43UF units are designed for bottom and side re-
turn air.
A−Make-Up Box (Figure 2)
A field make-up box is provided for line voltage wiring. Line
voltage wiring to unit is routed from the make up box. The
hot" wire is connected to the door switch and then from the
switch to the integrated ignition control. The make−up box
may be installed inside or outside the unit and on the unit left or
right side (right side shown figure 2).
INTERIOR MAKE−UP BOX INSTALLATION
MAKE−UP
BOX
FIGURE 2
B−Control Box Components (Figure 3)
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.
DOOR INTERLOCK
SWITCH (S51)
INTEGRATED IGNITION
CONTROL BOARD
(A92)
FIGURE 3
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. SureLight
G43UF−1 Units
Shock hazard.
Disconnect power before servicing. Control is
not field repairable. If control is inoperable, sim-
ply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
Right Side
Electrostatic discharge can affect electronic
components. Take precautions during furnace
installation and service to protect the furnace's
electronic controls. Precautions will help to avoid
control exposure to electrostatic discharge by
putting the furnace, the control and the techni-
cian at the same electrostatic potential. Neutral-
ize electrostatic charge by touching hand and all
tools on an unpainted unit surface, such as the
gas valve or blower deck, before performing any
service procedure.
The SureLight ignition system consists of ignition control
board 32M88 (figure 6 with control terminal designations
in table 3), ignitor (figure 9) and sensor (figure 10). Control
board 32M88 and ignitor work in combination to ensure
furnace ignition and ignitor durability. The control board
controls all major furnace operations. The control board
also features two green LED lights (DS1 and DS2) for
troubleshooting and two accessory terminals rated at (1)
one amp. Tables 1 and 2 show jack plug terminal designa-
TRANSFORMER
tions. See table 4 for troubleshooting diagnostic codes.
(T1)
The SureLight ignitor is made of durable silicon−nitride. Ig-
nitor longevity is also enhanced by voltage ramping by the
control board. The control board finds the lowest ignitor
temperature which will successfully light the burner, thus
increasing the life of the ignitor.
Page 9
®
Control 32M88 (A92)
WARNING
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION