Lennox EL280UHE Series Unit Information page 9

After the 15-second pre-purge period, the SureLight
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.
®
igni­
SureLight
PIN #
1
2
3
4
5
®
SureLight
PIN #
1
2
3
4
5
6
7
8
9
10
11
12
Page 9
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 pressure Switch
Rollout Switch In
Ground
24V Hot
Primary Limit In
Gas Valve First Stage
Gas Valve Common
24V Neutral
Ground
Primary Limit Out
First Stage pressure Switch