Early Model G24M Furnace Control (A3); .Krnace Control A3 Limit Response During Operation - Lennox G24M SERIES Unit Information

SPARK OUTPUT
LINE VOLTAGE
TERMINAL
CONNECTIONS
See Table 6 for
Terminal
Functions
DIAGNOSTIC
LED

.Krnace Control A3 Limit Response During Operation

Combustion
Condition
Air
Blower
Loss of Flame
Sensed Before
End of 45 se-
cond Blower
On
On Delay
(3 or Fewer
Trials
for Ignition)
Loss of Flame
Sensed After
45 second
Blower On On
Delay (3 or
Fewer Trials
for Ignition)
Loss of Flame
Sensed (More
Off
Than 3 Trials
for Ignition)
Flame Sensed
Without
On
Demand
Primary or
Secondary On
Limit Open
Rollout Switch
On
Open
Combustion
Air Prove On
Switch Open

EARLY MODEL G24M FURNACE CONTROL (A3)

TABLE 5
Response
Supply
Gas
Air
Valve
Blower
On
(Spark
Starts On
Within 0.8
seconds)
Off Then
On With
Spark On
After Pre-
Purge
Off Off
Off On
Off On
Off On
Off On
FIGURE 9
When flame is sensed, the indoor blower starts after a
45 second delay. Gas valve remains open and blower
continues to run until demand stops, flame sensor
senses loss of flame, a limit opens or the prove switch
Diagnostic
opens. If any of these events occur during a thermo-
LED
stat demand, the gas valve closes and the diagnostic
LED registers the error condition (table 5).
Blower Control and Timings
Fast Flash
Electrical Shock Hazard.
This control contains field adjustable switches
and also contains line voltage. Make sure power
is disconnected before making any field adjust-
Fast Flash
ments or performing any service procedure.
NOTE—If fan “off” time is set too low, residual heat
in heat exchanger may cause primary limit S10 to
2 Flashes
trip resulting in frequent cycling of blower. If this
occurs, adjust blower to longer time setting.
Fan “ON” timing (time that the burners operate before
5 Flashes
the supply air blower starts) is fixed at 45 seconds and
cannot be adjusted.
4 Flashes
Fan “OFF” timings (time that the blower operates after
a heating or cooling demand has been satisfied) are de-
4 Flashes
termined by the arrangement of switches on the fur-
nace control board. See figure 9. To adjust fan “off ”
3 Flashes
timings, gently reposition the switches to a new timing
Page 12
24VAC VOLT
TERMINAL
CONNECTIONS
PLUG P20
FAN-OFF TIMING
SWITCHES
THERMOSTAT
CONNECTIONS
DANGER