Lennox 80MGF Series Manual page 10

SPARK OUTPUT
LINE VOLTAGE
TERMINAL
CONNECTIONS
See Table 2 for
Terminal Func-
tions
DIAGNOSTIC
LED
TABLE 1
Furnace Control A3 Limit Response During Operation
Combustion
Condition
Air
Blower
Loss of Flame
Sensed Before
End of 45 sec-
ond 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 Sec-
ondary Limit
On
Open
Rollout Switch
On
Open
Combustion Air
Prove Switch
On
Open
RAM CONTROL (A3)
Response
Supply
Gas Diagnostic
Air
Valve LED
Blower
On
(Spark
Starts On Fast Flash
Within 0.8
seconds)
Off Then
On With
Spark On Fast Flash
After Pre-
Purge
Off Off 2 Flashes
Off On 5 Flashes
Off On 4 Flashes
Off On 4 Flashes
Off On 3 Flashes
FIGURE 5
When flame is sensed, the indoor blower starts after a 45
second delay. Gas valve remains open and blower contin-
ues to run until demand stops, flame sensor senses loss of
flame, a limit opens or the prove switch opens. If any of
these events occur during a thermostat demand, the gas
valve closes and the diagnostic LED registers the error
condition (table 1).
Blower Control and Timings
Electrical Shock Hazard.
This control contains field adjustable switches
and also contains line voltage. Make sure power
is disconnected before making any field adjust-
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 trip re-
sulting in frequent cycling of blower. If this occurs, ad-
just blower to longer time setting.
Fan ON" timing (time that the burners operate before the
supply air blower starts) is fixed at 45 seconds and cannot
be adjusted.
Page 10
24VAC VOLT
TERMINAL
CONNECTIONS
See Table 2 for
Terminal Func-
tions
FAN-OFF TIMING
SWITCHES
THERMOSTAT
CONNECTIONS
DANGER