Sequence Of Operation; Start-Up / Standby; Heat Mode; Recovery From Lockout - LG GEN2 Series Installation And Operation Manual

Sequence of Operation

Start-Up / Standby

Prior to start-up, verify that all field-installed sensors
have been installed. This includes a room temperature
sensor (optional) and a discharge air temperature sensor
(standard).

Heat Mode

When the unit or furnace controller calls for heat:
1. The ignition control will check that the pressure
switch for the combustion blower is open.
2. The combustion blower will energize and the
15 second pre-purge begins.
3. The gas valve is energized and the igniter will spark
for up to 10 seconds. If a flame is not sensed during
the trial for ignition, two additional tries will be
attempted before going into lockout for one hour.
4. When a flame is sensed, sparking stops immediately.
The gas valve and combustion blower remain
energized.
5. Ignition
4:1 Electronic Modulation - The burner will light at
100% fire and remain there for 10 seconds. The main
burner gas valve will then modulate from 100% down
to a minimum of 25%, as needed. The combustion
blower will change between high and low speed
to maintain acceptable combustion airflow. If the
high speed pressure switch does not pull in when
required, the furnace will lock out.

Performance Data

Input
Model
(BTU/hr)
50 50,000
75 75,000
100 100,000
125 125,000
150 150,000
175 175,000
200 200,000
225 225,000
250 250,000
275 275,000 10185
300 300,000 11111
325 325,000 12037
350 350,000 12963
400 400,000 14815
20°F 30°F 40°F
1852 1235 926
2778 1852 1389
3704 2469 1852
4630 3086 2315
5556 3704 2778
6481 4321 3241
7407 4938 3704
8333 5556 4167
9259 6173 4630
6790 5093
7407 5556
8025 6019
8642 6481
9877 7407
High Turndown Electronic Modulation - The
furnace controller will ignite the necessary
manifold(s) at 100% for 10 seconds. The main burner
gas valves will then modulate from 100% down to
a minimum of 25% as needed. The combustion
blower will change between high and low speed to
maintain acceptable combustion airflow. If less heat
is needed, a manifold section will be turned off. Each
time a manifold section is initialized, the manifold
section will ignite at 100%.
6. The ignition control constantly monitors the call for
heat, the pressure switch and the burner flame to
assure proper operation.
7. When the unit or furnace controls are satisfied,
the main gas valve is then de-energized and the
combustion blower shuts off following a 30 second
post-purge period.

Recovery from Lockout

If the furnace goes into lockout, the ignition control will
automatically reset after one hour if the thermostat is still
calling for heat. If needed, a manual reset can be
accomplished by either shutting off the power or turning
off the call for heat (turn off the thermostat) for a period
of five seconds.
Supply Air Temperature Rise
50°F 60°F 70°F
CFM
741 617 529
1111 926 794
1481 1235 1058
1852 1543 1323
2222 1852 1587
2593 2160 1852
2963 2469 2116
3333 2778 2381
3704 3086 2646
4074 3395 2910
4444 3704 3175
4815 4012 3439
5185 4321 3704
5926 4938 4233
80°F 90°F 100°F
463 412 370
694 617 556
926 823 741
1157 1029 926
1389 1235 1111
1620 1440 1296
1852 1646 1481
2083 1852 1667
2315 2058 1852
2546 2263 2037
2778 2469 2222
3009 2675 2407
3241 2881 2593
3704 3292 2963