Lennox KGA Series Service Literature page 23

Rollout switch open / Prove switch open or
3 Flashes
4 Flashes Primary High Limit switch open.
5 Flashes Flame sensed but gas valve not open.
6 Flashes On Board Microprocessors Disagree
TABLE 5
P2 TERMINAL DESIGNATIONS
Pin #
1 R 24 Volts to thermostat
2 W1 Heat Demand
3
4
5
6 BL OUT Indoor Blower Relay
7 W2 Second Stage Heat
TABLE 6
J1 TERMINAL DESIGNATIONS
Pin #
1
2 Rollout Switch / Prove Switch Out
3 Gas Valve Common
4
5 Rollout Switch / Prove Switch In
6
IGNITION CONTROL A3
FLAME
Line voltage
FIGURE 15
closed.
Function
Y Cool Demand
C Common
G Indoor Blower
Function
Limit Switch Out
Gas Valve Out
Limit Switch In
LED
CAI Line
IGNITION CONTROL A3
S18 COMBUSTION
AIR PROVING SWITCH
Flame rectification sensing is used on all KGA units.
Loss of flame during a heating cycle is indicated by an ab­
sence of flame signal (0 microamps). If this happens, the con­
trol will immediately restart the ignition sequence and then lock
out if ignition is not gained after the third trial. See System
Service Checks section for flame current measurement.
The control shuts off gas flow immediately in the event of a
power failure. Upon restoration of gas and power, the control
will restart the ignition sequence and continue until flame is
established or system locks out.
Operation
On a heating demand, the ignition control checks for a
closed limit switch and open combustion air prove
switch. Once this check is complete and conditions are
correct, the ignition control then allows 30 seconds for
the combustion air inducer to vent exhaust gases from
the burners. When the combustion air inducer is purging
the exhaust gases, the combustion air prove switch
closes proving that the combustion air inducer is operat­
ing before allowing the ignition control to energize.
When the combustion air prove switch is closed and the
delay is over, the ignition control activates the gas valve,
the spark electrode and the flame sensing electrode.
Once the gas valve is energized, the non-adjustable
40-second indoor blower delay period begins. Sparking
stops immediately after flame is sensed or at the end of
the 8-second trial for ignition.
The control then proceeds to "steady state" mode where
all inputs are monitored to ensure the limit switch, rollout
switch and prove switch are closed as well as flame is
present. When the heat call is satisfied and the gas valve
is de-energized, a combustion air inducer post purge pe­
riod of 5 seconds begins along with a 120-second blower
off delay.
Page 23
A3 IGNITION
CONTROL
FIGURE 16