Page 1
03/10
*2P0310*
506497−01
*P506497-01*
E 2010 Lennox Industries Inc.
Dallas, Texas, USA
UPFLOW
INSTALLATION
INSTRUCTIONS
G43UF
MERIT SERIES GAS FURNACE
UPFLOW AIR DISCHARGE
506497−01
03/2010
Supersedes 505,064M
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This a safety alert symbol and should never be ignored.
When you see this symbol on labels or in manuals, be alert
to the potential for personal injury or death.
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a licensed professional installer (or
equivalent), service agency or the gas supplier.
Table of Contents
Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shipping and Packing List 4. . . . . . . . . . . . . . . . . . . . . . .
Safety Information 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Use of Furnace as Constrction Heater 5. . . . . . . . . . . .
General 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution & Ventilation Air 6. . . . . . . . . . . . .
Installation − Setting Equipment 8. . . . . . . . . . . . . . . . . .
Filters 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Duct System 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pipe & Fittings Specifications 12. . . . . . . . . . . . . . . . . . .
Vent Piping Guidelines 14. . . . . . . . . . . . . . . . . . . . . . . . .
Joint Cementing Procedure 15. . . . . . . . . . . . . . . . . . . . .
Venting Practices 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Piping 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Start−Up 33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Pressure Adjustment 35. . . . . . . . . . . . . . . . . . . . . .
High Altitude Information 36. . . . . . . . . . . . . . . . . . . . . . .
Testing for Venting and Combustion Air 37. . . . . . . . . .
Other Unit Adjustments 38. . . . . . . . . . . . . . . . . . . . . . . .
Blower Performance Data 39. . . . . . . . . . . . . . . . . . . . . .
Service 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Planned Service 43. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Control Board Diagnostic Codes 43. . . . . . . . .
Troubleshooting 44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List 47. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Vent Pipe Sizing Worksheet 48. . . . . . . . . . . . . . . . . . . .
Start−Up & Performance Check List 49. . . . . . . . . . . . . .
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