Lennox G24M SERIES Unit Information

Page 13
position. Fig u r e 10 show s th e va r i ous fan of f tim i ngs
and how switches should be positioned. Unit is shipped
with a factory fan off setting of 180 seconds. Fan off
time will affect comfo rt and efficiency and is adjustable
to satisfy individual applicatio ns. The fan off timing is
initiat ed after a heating or cooling demand but not after a
blower demand (that is, when indoor therm ostat switch
is changed from ON to AUTO and heating/cooling de-
mand is not present, the blower stops immediate ly).
TABLE 6
FURNACE CONTROL A3 TERMINAL DESIGNATIONS
Terminal Type Function
24VAC HOT 1/4 Spade 24VAC In From Transformer
GND 1/4 Spade To Cabinet Ground
Y Screw Strip Cooling Demand
G Screw Strip Blower Demand
R Screw Strip 24VAC to Thermostat
W Screw Strip Heating Demand
C Screw Strip 24VAC Common
120VAC HOT 1/4 Spade Line Voltage In
120VAC RTN 1/4 Spade Line Voltage Neutral
120VAC TX 1/4 Spade Line Voltage Out To Transformer
CMB J20/P20 Pin 1
Switched 120VAC to
Combustion Air Blower
CMB RTN J20/P20 Pin 2
120VAC Common
Combustion Air Blower
ACB HEAT 1/4 Spade
Switched 120VAC to
Blower Heating Tap
ACB LOW 1/4 Spade
120VAC Output to Supply Air
Blower for Continuous Opera-
tion During No Demand
ACB COOL 1/4 Spade
Switched 120VAC to Blower
Cooling Tap
VLV HOT J20/P20 Pin 13 24VAC to Gas Valve
VLV RTN J20/P20 Pin 9
24VAC Common From
Gas Valve
PSW IN
J20/P20
Pin 10
24VAC In From Pressure Switch
Switch Open: Prohibits Ignition
Switch Closed: Allows Ignition
HIL IN
J20/P20
Pin 11
24VAC In From Limits
Limit Open: Closes Gas Valve
Limits Closed: Allows Ignition
HIL OUT
J20/P20
Pin 14
24VAC to Limit Train
and Pressure Switch
RO OUT J20/P20 Pin 7 24VAC Out To Rollout Switches
RO IN J20/P20 Pin 15 24VAC In From Rollout Switches
SPARK
ELECTRODE
Male Spark
Plug Type
High V oltage Out To
Spark Electrode
FS J20/P20 Pin 12 Flame Microamp Sensing
FIGURE 10
FAN-OFF TIME ADJU STMENT SWITCHES
LOCATED ON FURNACE CONTROL (A3)
Fan-Off Timings
Switch
12
Timing
Seconds
Off
OnOff
Off
OffOn
On On
120
90
180
240
Diagnostic LED
The furnace control is equipped with a diagnostic LED
used for troubleshooting the unit and the control. LED
functions are shown in table 7.
TABLE 7
Furnace Control A3 Diagnostic LED
LED State Meaning Remedy
Steady On Control Failure Replace Control
Slow Flash
Normal Operation
and No Call For Heat
----
Fast Flash
Normal Operation
with Call For Heat
----
Two
Flashes
Control Lockout
Faile d to Sense or Sustain
Flame. Check Gas V a lv e ,
Burners , Spark Electrode
and Wire, Flame Sensor.
Repla ce Control If All OK.
Three
Flashes
Pressure Switch Open
Failed to Prove Combus-
tion Blower Operation or
Blocked Vent. Repair or
Replace as Necessary.
Four
Flashes
Open Limit
Check Primary Limit,
Rollout Switches and Sec-
ondary Limits. Find source
of Overtemperature. If all
OK, Reset or Replace Lim-
its as Necessary .
Five
Flashes
Flame Sensed and Gas
Valve Not Energized.
Check Gas Valve. If OK,
Check Flame Sensor.
B--Blower Motors and Capacitors
All G24M units use direct drive blower motors. All mo-
tors used are 120V permanent split capacitor motors to
ensure maximum efficiency. See table8 for ratings.
TABLE 8
G24M BLOWER RATI NGS 120V 1PH
BLOWER MOTOR HP
G24MQ2
G24MQ3
G24MQ3/4
CAP
1/2
1/3
1/4 5MFD 370V
5MFD 370V
7.5MFD 370V
G24MQ5/6
G24MQ4
G24MQ4/5
1/2 7.5MFD 370V
3/4 40MFD 370V
3/4 40MFD 370V
FIGURE 11
SUPPLY AIR BLOWER
AND SECONDARY LIMITS
Front
Bottom
Right
Left
Top
Back
BLOWER
MOTOR
To Remove Blower From Unit: Remove Bolts and
Wiring Jackplugs. Then Slide Out Front of Unit.
MOTOR
CAPACITOR
SECONDARY
LIMITS (S21)

Lennox G24M SERIES Specifications

General

Brand	Lennox
Model	G24M SERIES
Category	Furnace
Language	English