Lennox G50UH Series User Manual

Page 35
G50UH Series
Repair Parts List
The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model
number listed on the CSA International nameplate −− Example: G50UH(X)−24A−045−8. All service must be performed by a
licensed professional installer (or equivalent), service agency, or gas supplier.
Cabinet Parts
Upper access panel
Blower panel
Top cap
Control Panel Parts
Transformer
SureLight
®
ignition board
Door interlock switch
Circuit breaker
Blower Parts
Blower wheel
Motor
Motor mounting frame
Motor capacitor
Blower housing cutoff plate
Heating Parts
Flame Sensor
Heat exchanger assembly
Gas manifold
Combustion air inducer
Gas valve
Main burner cluster
Main burner orifices
Pressure switch
Ignitor
Primary limit control
Flame rollout switch
Secondary limit (not used on 24A−45−1)
Ignition Control Board Diagnostic Codes
DIAGNOSTIC CODES
Make sure to Identify LED’S Correctly.
Refer to Installation Instructions for control board layout.
DS1
(Red or Green)
DS2
(Green)
DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
SLOW FLASH
Power on −− Normal operation.
Also signaled during cooling and continuous fan.
SIMULTANEOUS
FAST FLASH
SIMULTANEOUS
FAST FLASH
Normal operation −− Signaled when heating demand initiated at thermostat.
SLOW FLASH ON
Primary or secondary limit switch open. Limit must close within 3 minutes or unit
goes into 1−hour Watchguard.
OFF SLOW FLASH
Pressure switch open;
OR: Blocked inlet/exhaust vent;
OR: Condensate line blocked;
OR: Pressure switch closed prior to activation of combustion air inducer.
ALTERNATING
SLOW FLASH
ALTERNATING
SLOW FLASH
Watchguard −− Burners failed to ignite, limit open longer than 3 minutes, or flame
sense lost 5 times in one heating cycle.
SLOW FLASH OFF Flame sensed without gas valve energized.
ON SLOW FLASH Rollout switch open.
ON ON
Circ it board fail re or control ired incorrectl Check 24 olt and 115 olt
ON OFF
Circuit board failure or control wired incorrectly. Check 24−volt and 115−volt
connections to board.
OFF ON
connections
to
board
.
FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral. Improper main ground.
SLOW FLASH FAST FLASH Low flame signal. Check flame sensor.
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
The following conditions are sensed during the ignitor warm−up period only:
1) Improper main ground;
2) Broken ignitor; OR: Open ignitor circuit;
3) Line voltage below 75 volts.
NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Drop out flame sense current = 0.15 − 0.24 microAmps.

Lennox G50UH Series Specifications

General

Brand	Lennox
Model	G50UH Series
Category	Furnace
Language	English