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Sequence of Operation G32−5, −6
Sequence depends on type thermostat used. Units are
applicable for single stage or two stage thermostats.
Both type thermostats are described below. Thermo
stat jumper E20 dictates which mode unit will operate
in. See flow chart for more sequence detail.
SureLight Control Self Check
When there is a call for heat, the SureLight integrated con
trol runs a self check. The control checks for S10 primary
limit, S21 secondary limit (s) and S47 rollout switch nor
mally closed contacts. The control also checks for S102
high heat and S128 low heat prove switch (G32−75 only)
normally open contacts. Once self check is complete and
all safety switches are operational, heat call can continue.
Two−Stage Thermostat, Two Stage Heat. Jumper E20
set at TWO".
4− SureLight control energizes combustion air inducer B6
on low heat speed. Combustion air inducer runs until
S102 prove switch contacts close (switch must close
within 2 1/2 minutes or control goes into Watchguard
Pressure Switch mode.
G32−75 ONLY−SureLight control energizes combus
tion air inducer B6 on low heat speed. Combustion air
inducer runs until S128 prove switch contacts close
(switch must close within 2 1/2 minutes or control goes
into Watchguard Pressure Switch mode. Prove switch
S102 may also close). A 15 second pre−purge follows
once S128 closes.
5− SureLight control begins 20 second ignitor warm up
period.
6− Gas valve opens on first stage for a 4 second trial for
ignition. Ignitor stays energized during the trial or until
flame sensed.
7− Flame is sensed, gas valve remains on first stage heat,
ignitor de−energizes.
8− After 45 second delay, indoor blower B3 is energized
on low heat speed.
The furnace will stay in this mode until first stage de
mand is satisfied OR a second stage heat demand is
initiated.
9− Second stage heat demand initiated. A 30 second sec
ond stage recognition period begins.
10− The combustion air inducer ramps up to high heat
speed.
G23−75 ONLY−S102 prove switch closes.
11− Gas valve energizes second stage heat.
12− B3 indoor blower ramps up to high heat speed.
Single−Stage Thermostat, Two Stage Heat. Jumper
E20 set at SINGLE"
1− SureLight control energizes combustion air inducer B6
on low heat speed. Combustion air inducer runs until
S102 prove switch contacts close (switch must close
within 2 1/2 minutes or control goes into Watchguard
Pressure Switch mode.
G32−75 ONLY−SureLight control energizes combus
tion air inducer B6 on low heat speed. Combustion air
inducer runs until S128 prove switch contacts close
(switch must close within 2 1/2 minutes or control goes
into Watchguard Pressure Switch mode. Prove switch
S102 may also close). A 15 second pre−purge follows
once S128 closes.
2− SureLight control begins 20 second ignitor warm up
period.
3− Gas valve opens on first stage for a 4 second trial for
ignition. Ignitor stays energized during the trial or until
flame sensed.
4− Flame is sensed, gas valve remains on first stage heat,
ignitor de−energizes.
5− After 45 second delay, indoor blower B3 is energized
on low heat speed.
6− A 10 minute (factory set) or 15 minute (field set) second
stage heat delay period begins.
7− The combustion air inducer ramps up to high heat
speed.
G32−75 ONLY−S102 prove switch closes.
8− Gas valve energizes second stage heat.
9− B3 indoor blower ramps up to high heat speed.
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