Lennox KGC Series Unit Information page 52

First Stage Heat:
1 - The thermostat initiates W1 heating demand.
2 - 24VAC is routed from TB1 to ignition control A3
through P2. A3 proves N.C. primary limit S10 and
N.C. rollout switch S47.
3 - Combustion air inducer blower B6 is energized.
4 - After the combustion air inducer B6 has reached
full speed, the combustion air proving switch S18
contacts close.
5 - After a 30 second delay, A3 energizes the ignitor
and LO terminal (low fire) of gas valve GV1.
Second Stage Heat:
6 - With first stage heat operating, an additional heating
demand from the thermostat initiates W2.
7 - A second stage heating demand is received by TB1.
The second stage heat signal passes from TB1 to
A3.
8 - A3 energizes HI terminal (high fire) of gas valve
GV1.
GAS HEAT SEQUENCE OF OPERATION
End of Second Stage Heat:
End of First Stage Heat:
Optional Low Ambient Kit:(ETL/CSA -50° C Low
Ambient Kit)
Page 52
9 - Heating demand is satisfied. Terminal W2 (high fire)
is de-energized.
10 - Terminal HI of GV1 is de-energized by A3 control
module.
11 - Heating demand is satisfied. Terminal W1 (low fire)
is de-energized.
12 - Ignition A3 is de-energized in turn de-energizing
terminal LO of GV1.
13 - Line voltage is routed through the N.C. low ambient
kit thermostats S60 and S61. K125 relay is energized
closing N.O. K125-1 contacts and energizing the
low ambient kit heater HR6.