Page 9
When the dierential in the pressure switch is great
enough, the pressure switch closes and a 15-second pre-
purge begins .
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 ame 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 ve 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.
NOTE - During abnormal conditions such as low supply
voltage or low outdoor temperatures and the low re 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-
re. After 10 to 20 seconds of high re operation the unit
will switch to low re.
Two Stage Operation / Thermostat Selection DIP
Switch
The control can be utilized in two modes: SINGLE-STAGE
thermostat or TWO-STAGE thermostat. The thermo-
stat selection is made using a DIP switch and must be
positioned 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 re on rst-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 “recog-
nition 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 re on rst-
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 rst
and second stage heat, the unit will re on rst stage heat
and switch to second stage heat after 30 seconds of oper-
ation. See Sequence of Operation ow 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 Pressure Switch Second Stage
3 Rolout Switch
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 Pressure Switch First Stage
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