Lennox SL280DF060NV36B Instruction Manual page 7

Once the first stage prove switch is determined to be open,
the combustion air inducer is energized on low (first stage)
heat speed. When the differential in the prove switch is
great enough, the prove switch closes and a 15-second
pre-purge begins.
NOTE - During abnormal conditions such as low supply
voltage or low outdoor temperatures and the low fire pres­
sure switch does not close, the combustion air inducer will
switch to high fire. After a 15 second pre-purge the high fire
pressure switch will close and the unit will begin operation
on high fire. After 10 to 20 seconds of high fire operation the
unit will switch to low fire.
After the 15-second pre-purge period, the SureLight ignitor
warms up for 20 seconds after which the gas valve opens
for a 4-second trial for ignition. The ignitor energizes during
the 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 sec­
onds. After a total of five trials for ignition (including the ini­
tial trial), the control goes into Watchguard-Flame Failure
mode. After a 60-minute reset period, the control will begin
the ignition sequence again.
Two Stage Operation / Thermostat Selection DIP
Switch
The control can be utilized in two modes: SINGLE-STAGE
thermostat or TWO-STAGE thermostat. The thermostat
selection is made using a DIP switch and must be posi­
tioned for the particular application. DIP switch 1, labeled
T"STAT HEAT STAGE is factory-set in the OFF position for
use with a two-stage thermostat. Move the DIP switch to
ON for use with a single stage thermostat.
While in the single-stage thermostat mode, the burners will
always fire on first-stage heat. The combustion air inducer
will operate on low speed and indoor blower will operate on
low heat speed. The unit will switch to second stage heat
after a "recognition period". DIP switch 2, labeled SECOND
STAGE DELAY, is factory set in the OFF position for a 7
minute recognition period. The switch can be moved to the
ON position for a 12 minute recognition period, after which
time the unit will switch to second­stage heat.
While in the two-stage thermostat mode (two DIP switch
setting) the burners will fire on first-stage heat. The com­
bustion air inducer will operate on low speed and indoor
blower will operate on low heat speed. The unit will switch
to second-stage heat on call from the indoor thermostat. If
there is a simultaneous call for first and second stage heat,
the unit will fire an first stage heat and switch to second
stage heat after 30 seconds of operation. See Sequence of
Operation flow charts in the back of this manual for more
detail.
®
SureLight Control 5 Pin Terminal Designation
PIN #
1
2
3
4
5
®
SureLight Control 12 Pin Terminal Designation
PIN #
1
2
3
4
5
6
7
8
9
10
11
12
®
SureLight Control 6 Pin Terminal Designation
PIN #
1
2
3
4
5
6
Page 7
TABLE 1
Function
Ignitor
Combustion Air Inducer High Speed
Combustion Air Inducer Low Speed
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
Function
Gas Valve High Fire
Second Stage Prove Switch
Rollout In
Ground
24V Hot
Primary Limit In
Gas Valve Low Stage
Gas Valve Common
24V Neutral
Ground
Rollout Switch Out
1st Stage Prove Switch
TABLE 3
Function
Data Input From Motor
Common
Not Used
Data Output To Motor
5 Volt Bias Supply
Not Used