Electronic Ignition; Fan Time Control - Lennox G43UF SERIES Unit Information

TABLE 1
SureLight BOARD J156 (J2) TERMINAL
DESIGNATIONS
PIN #
1 Combustion Air Inducer Line
2
Combustion Air Inducer Neutral
3
4
TABLE 2
SureLight BOARD J58 (J1) TERMINAL
DESIGNATIONS
PIN #
1
2
3
4
5
6
7
8
9
10
11
12
TABLE 3
TERMINAL DESIGNATIONS
COOL−H 120V HOT
HEAT−H
EAC−H
HUM−H
XFMR−H
LINE−H
LINE−N 120V NEUT
HUM−N
EAC−N
XFMR−N
CIR−N
PARK
(FLAME SENSE)
Electronic Ignition (See Figure 5)
On a call for heat the SureLight
combustion air inducer prove switch. The control will not
begin the heating cycle if the prove switch is closed (by−
passed). Once the prove switch is determined to be open,
the combustion air inducer is energized. When the differen-
tial in the prove switch is great enough, the prove switch
closes and a 15−second pre−purge begins. If the prove
switch is not proven within 2−1/2 minutes, the control goes
into Watchguard−Pressure Switch mode for a 5−minute re−
set period.
FUNCTION
Ignitor Line
Ignitor Neutral
FUNCTION
High Limit Output
Not Used
24V Line
Not Used
Rollout Switch In
24V Neutral
High Limit Input
Ground
Gas Valve In
Pressure Switch Out
Rollout Switch Out
Gas Valve Out
Blower Cooling Speed (120VAC)
Blower Heating Speed−(120VAC)
Electronic Air Cleaner (120VAC)
Humidifier (120VAC)
Transformer (120VAC)
Input (120VAC)
Input (Neutral)
Humidifier (Neutral)
Electronic Air Cleaner (Neutral)
Transformer (Neutral)
Blower (Neutral)
Alternate Blower Speeds (dead)
Flame Sensor
®
control board monitors the
After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds during which the gas valve opens
at 19 seconds for a 4−second trial for ignition. The ignitor
stays energized during the 4 second trial until flame is
sensed. If ignition is not proved during the 4−second period,
the control will try four more times with an inter purge and
warm−up time between trials of 35 seconds. After a total of
five trials for ignition (including the initial trial), the control
goes into Watchguard−Flame Failure mode. After a 60−min-
ute reset period, the control will begin the ignition sequence
again.
The SureLight control board has an added feature that pro-
longs the life of the ignitor. After a successful ignition, the
SureLight control utilizes less power to energize the ignitor
on successive calls for heat. The control continues to ramp
down the voltage to the ignitor until it finds the lowest
amount of power that will provide a successful ignition. This
amount of power is used for 255 cycles. On the 256th call
for heat, the control will again ramp down until the lowest
power is determined and the cycle begins again. Each time
120V is removed and then re−applied, the control re−starts
the learning process.

Fan Time Control

The fan on time of 45 seconds is not adjustable. Fan off
time (time that the blower operates after the heat demand
has been satisfied) can be adjusted by setting the dip
switches located on the control board. The unit is shipped
with a factory fan off setting of 90 seconds. For customized
comfort, monitor the supply air temperature once the heat
demand is satisfied. Note the supply air temperature at the
instant the blower is de−energized. Adjust the fan−off delay
to achieve a supply air temperature between 90° − 110° at
the instant the blower is de−energized. (Longer delay times
allow for lower air temperature, shorter delay times allow
for higher air temperature). See figure 4.
FAN-OFF TIME ADJUSTMENT
60sec.
OFF ON OFF
(Black square indicates switch position)
To adjust fan−off timing, flip dip switch to desired setting.
Page 10
120sec.
90sec. 180sec.
ON
OFF ON OFF
FIGURE 4
ON