Lennox 80MGF Series Manual page 15

TABLE 7
SureLight BOARD J156 (J2) TERMINAL
DESIGNATIONS
PIN #
1
2
3
4 Combustion Air Blower Line Voltage
5
6 Combustion Air Blower Neutral
TABLE 8
SureLight BOARD J58 (J1) TERMINAL
DESIGNATIONS
PIN #
1
2 Gas Valve Common
3 Roll Out Switch Out
4
5 Pressure Switch In
6 Pressure Switch and Primary Limit Out
7
8 Roll Out Switch In
9
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
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.
FUNCTION
Ignitor
Not Used
Ignitor Neutral
Not Used
FUNCTION
Primary Limit In
Gas Valve 24V
Not Used
Ground
a−Electronic Ignition
On a call for heat the SureLight control monitors the com-
bustion air blower 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 blower is energized. When the
differential in the pressure switch is great enough, the
pressure switch closes and a 15−second pre−purge be-
gins. If the pressure switch is not proven within 2−1/2 min-
utes, the control goes into Watchguard−Pressure Switch
mode for a 5−minute re−set period.
After the 15−second pre−purge period, the SureLight igni-
tor warms up for 20 seconds after which the gas valve
opens for a 4−second trial for ignition. 80MGF units with
board 63K89, 24L85 or 56L83: the ignitor stays energized
for the first second of the 4−second trial. Units with board
97L48: ignitor stays energized for the full 4−second trial for
ignition. If ignition is not proved during the 4−second peri-
od, the control will try four more times with an inter purge
and warm−up time between trials of 35 seconds. After a to-
tal of five trials for ignition (including the initial trial), the
control goes into Watchguard−Flame Failure mode. After a
60−minute reset period, the control will begin the ignition
sequence again.
The SureLight control board has an added feature that
prolongs the life of the ignitor. After a successful ignition,
the SureLight control utilizes less power to energize the ig-
nitor 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 low-
est power is determined and the cycle begins again.
b−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 flipping the dip
switches located on the SureLight integrated control. The
unit is shipped with a factory fan off setting of 90 seconds.
Fan off time will affect comfort and is adjustable to satisfy
individual applications. See figure 10.
FAN-OFF TIME ADJUSTMENT
60sec.
To adjust fan−off timing, flip dip switch to desired setting.
Page 15
90sec. 120sec.
FIGURE 10
180sec.