Lennox EL297DFV Series Unit Information page 10

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 op-
eration 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 ig-
nitor 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
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-minute reset
period, thecontrol 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 oper-
ate on low speed and indoor blower will operate on low
heat speed. The unit will switch to second stage heat af-
ter 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, the burners will 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 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 oper-
ation. 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 10
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 Second Stage
Second Stage Prove Switch
Rollout Switch In
Ground
24V Hot
Primary Limit In
Gas Valve First Stage
Gas Valve Common
24V Neutral
Ground
Rollout Switch Out
First Stage Prove Switch
TABLE 3
Function
Data Input From Motor
Common
Not Used
Data Output To Motor
5 Volt Bias Supply
Not Used