INSTALLATION INSTRUCTIONS
 2000 Lennox Industries Inc.
Dallas, Texas, USA
INSTALLATION
INSTRUCTIONS
G23(X) SERIES UNITS
GAS UNITS
503,884M 
1/2000
Supersedes 5/99
Table of Contents
Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Parts Arrangement 3. . . . . . . . . . . . . . . . . . . . . . . . . . . 
Requirements 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
General 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Combustion, Dilution, & Ventilation Air 5. . . . . . . . . . 
Installation - Setting Equipment 7. . . . . . . . . . . . . . . . 
Return Air Opening Guidelines 7. . . . . . . . . . . . . . . . . 
Filters & Optional Filter Assembly 8. . . . . . . . . . . . . . 
Duct System 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Venting 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Gas Piping 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Electrical 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Unit Start-Up 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Gas Pressure Adjustment 22. . . . . . . . . . . . . . . . . . . . 
High Altitude Information 23. . . . . . . . . . . . . . . . . . . . . 
Other Unit Adjustments 23. . . . . . . . . . . . . . . . . . . . . . 
Service 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
Repair Parts List 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . 
SureLight Troubleshooting 27. . . . . . . . . . . . . . . . . . . . 
Start-Up & Performance Check List 31. . . . . . . . . . . . 
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
WHAT TO DO IF YOU SMELL GAS:
Do not store or use gasoline or other
flammable vapors and liquids in the vi
cinity of this or any other appliance.
Installation and service must be per
formed by a qualified installer, ser
vice agency or the gas supplier.
 Do not try to light any appliance.
 Do not touch any electrical switch; do not use 
any phone in your building.
 Immediately call your gas supplier from a 
neighbor's phone. Follow the gas supplier's 
instructions.
 If you cannot reach your gas supplier, call the 
fire department.
 Extinguish any open flames.
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury, or death.
WARNING
Litho USA