Lennox G24M3/4-100 User Manual

Page 26
FANOFF TIME ADJUSTMENT
To adjust fan-off timing, flip dip switch to desired setting.
60sec. 90sec. 120sec. 180sec.
FIGURE 25
Temperature Rise
Check the temperature rise and, if necessary, adjust the
blower speed to maintain the temperature rise within the
range shown on the unit rating plate.
Thermostat Heat Anticipation
Set the thermostat heat anticipation:
0.50 amps White Rodgers gas valves
0.70 amps Honeywell gas valves
Electrical
1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace (furnace
operating).
3 - Check ampdraw on the blower motor.
Motor Nameplate__________Actual__________
Blower Speeds
NOTE - CFM readings are taken external to unit with a dry
evaporator coil and without accessories.
1 - Turn off electrical power to furnace.
2 - Remove unit access panel.
3 - Disconnect existing speed tap at control board speed
terminal.
NOTE - TERMINATION OF ANY UNUSED MOTOR
LEADS MUST BE INSULATED.
4 - Refer to blower speed selection chart on unit wiring dia
gram for desired heating or cooling speed.
5 - Connect selected speed tap at control board speed
terminal.
6 - Resecure unit access panel.
7 - Turn on electrical power to furnace.
Electronic Ignition
The SureLight integrated control has an added feature of
an internal watchguard control. The feature serves as an au
tomatic reset device for ignition controls lockedout because
the burner has failed to light. This type of nuisance lockout is
usually attributed to low gas line pressure. After one hour of
continuous thermostat demand for heat, the watchguard will
break and remake thermostat demand to the furnace and
automatically reset the control to relight the furnace.
Flue And Chimney
1 - Check flue pipe, chimney and all connections for tight
ness and to make sure there is no blockage.
2 - Check unit for proper draft.
3 - Is pressure switch closed? Obstructed flue will cause
unit to shut off at pressure switch. Check flue and out
let for blockages.
4 - Reset manual flame rollout switches on burner box
cover.
Burner Flame Adjustment
The G24M burner flame is not adjustable; however, the
flame should be inspected at the beginning of each heating
season. If necessary, clean the burners. The burner flame
should be blue when burning natural gas, and blue/yellow
when burning propane gas. See figure 26.
Burner Flame
BURNER
FLAME
HEAT
EXCHANGER
TUBE
VEST
PANEL
FLAME APPEARS BLUE IF
BURNING NAT. GAS; BLUE/
YELLOW FOR PROPANE.
FIGURE 26
Turbulator
G24M(X) series units include a ceramic fiber turbulator in
each heat exchanger inlet. The turbulators lower nitrogen
oxide emissions. Prior to unit startup, inspect the turbula
tors for shipping damage. The turbulators are fragile; they
should be removed only if it is necessary to replace them.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse?
5 - Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shutoff valve open?
8 - Is the internal manual shutoff valve open?
9 - Is the unit ignition system in lock out? If the unit locks
out again, call the service technician to inspect the unit
for blockages.

Lennox G24M3/4-100 Specifications

General

Brand	Lennox
Model	G24M3/4-100
Category	Furnace
Language	English