E−Surelight Board 100870 - Lennox G61MPV Service Manual

E−SureLight Board 100870
Sequence depends on type thermostat used.
G61MPV units are applicable for single stage or two
stage thermostats. Both type thermostats are de-
scribed below. Thermostat dip switch selection dic-
tates 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 normally open
contacts. Once self check is complete and all safety
switches are operational, heat call can continue.
Two−Stage Thermostat, Two Stage Heat. Dip Switch
set at TWO".
10− SureLight control energizes combustion air inducer B6
on low heat speed. Combustion air inducer runs until
S128 low heat prove switch contacts close (switch
must close within 2 1/2 minutes or control goes into
Watchguard Pressure Switch mode. High heat prove
switch S102 may also close). A 15 second pre−purge
follows once S128 closes.
11− SureLight control begins 20 second ignitor warm up
period.
12− Gas valve opens on first stage for a 4 second trial for
ignition. Ignitor stays energized during the trial or until
flame sensed.
13− Flame is sensed, gas valve remains on first stage heat,
ignitor de−energizes.
14− 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.
15− Second stage heat demand initiated. A 30 second sec-
ond stage recognition period begins.
16− The combustion air inducer ramps up to high heat
speed.
17− S102 high heat prove switch closes and the gas valve
energizes second stage heat.
18− B3 indoor blower ramps up to high heat speed.
Single−Stage Thermostat, Two Stage Heat. Dip
Switch set at SINGLE"
1− SureLight control energizes combustion air inducer B6
on low heat speed. Combustion air inducer runs until
S128 low heat prove switch contacts close (switch
must close within 2 1/2 minutes or control goes into
Watchguard Pressure Switch mode. High heat 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− After the delay the combustion air inducer ramps up to
high heat speed.
8− S102 high heat prove switch closes and the gas valve
energizes second stage heat.
9− B3 indoor blower ramps up to high heat speed.
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