Lennox EL280DF070E36A - Page 6

Page 6
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. The ignitor remains
energized 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 be
tween trials of 35 seconds. After a total of five trials for igni
tion (including the initial trial), the control goes into Watch
guard-Flame Failure mode. After a 60-minute reset period,
the control will begin the ignition sequence again.
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 speed. After the low & high pressure switch
close, the unit will proceed with a 15 sec pre-purge, fol
lowed by a 20 sec ignitor warm up, then ignition on high-
fire. After 10 to 20 seconds of high fire operation the unit will
switch to low fire.
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 second-stage heat.
While in the two-stage thermostat mode, the burners will
fire on first-stage heat. The combustion air inducer will op
erate 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 on first
stage heat and switch to second stage heat after 30 sec
onds of operation. See Sequence of Operation flow charts
in the back of this manual for more detail.
TABLE 1
SureLight
®
Control 5 Pin Terminal Designation
PIN # Function
1 Ignitor
2 Combustion Air Inducer High Speed
3 Combustion Air Inducer Low Speed
4 Combustion Air Inducer Neutral
5 Ignitor Neutral
TABLE 2
SureLight
®
Control 12 Pin Terminal Designation
PIN # Function
1 Gas Valve Second Stage
2 Second Stage pressure Switch
3 Rollout Switch In
4 Ground
5 24V Hot
6 Primary Limit In
7 Gas Valve First Stage
8 Gas Valve Common
9 24V Neutral
10 Ground
11 Primary Limit Out
12 First Stage pressure Switch