Lennox EL297UH045XV36B Unit Information page 27

When the differential in the prove switch is great enough,
the prove switch closes and a 15-second pre-purge be-
gins.
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
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, 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 in-
ducer 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, la-
beled 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
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 simultane-
ous 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
Pin #
1
2
3
4
ig-
®
5
SureLight
®
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
SureLight
Pin #
1
2
3
4
5
6
Page 27
TABLE 1
Control 5 Pin Terminal Designation
®
Function
Ignitor
Combustion Air Inducer High
Speed
Combustion Air Inducer Low
Speed
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
Control 12 Pin Terminal Designation
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
Control 6 Pin Terminal Designation
®
Function
Data Input From Motor
Common
Not Used
Data Output To Motor
5 Volt Bias Supply
Not Used