Lennox 80MGF3/4-100 - User Manual

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Corp. 9801−L2

80MGF

Service Literature

Revised 08−2004

80MGF SERIES UNITS

80MGF series units are mid−efficiency gas furnaces

manufactured with tubular heat exchangers formed of alu-

minized or stainless steel. 80MGF units are available in

heating capacities of 45,000 to 140,000 Btuh and cooling

applications up to 5 tons. Refer to Engineering Handbook

for proper sizing.

Units are factory equipped for use with natural gas. A kit is

available for conversion to LPG operation. All 80MGF units

built proir to September 98 use electronic (direct spark) igni-

tion. 80MGF−11 model units are equipped with the Lennox

SureLight ignition system. The 80MGFX unit meets the

California Nitrogen Oxides (NO

) Standards and California

Seasonal Efficiency requirements. All units use a redun-

dant gas valve to assure safety shut−off as required by

A.G.A. or C.G.A.

The heat exchanger, burners and manifold assembly can

easily be removed for inspection and service by simply dis-

connecting gas, unplugging wiring harness and spark wires

and removing four screws holding the heat exchanger in

place. Then the heat exchanger slides out of the cabinet.

All specifications in this manual are subject to change.

Procedures outlined in this manual are presented as a rec-

ommendation only and do not supersede or replace local

or state codes. In the absence of local or state codes, the

guidelines and procedures outlined in this manual (except

where noted) are recommended only and do not constitute

code.

Units may be installed in upflow, downflow or horizontal

position. The heat exchanger is designed for upright or

horizontal use only. When the unit is installed in the down-

flow position, the heat exchanger is field removed and re-

installed so it is upright when the cabinet is inverted. No

field conversion is required when the unit is installed in the

horizontal position.

TABLE OF CONTENTS

Introduction 1. . . . . . . . . . . . . . . . . . . . . . . .

Specifications 2. . . . . . . . . . . . . . . . . . . . . .

Blower Data 5. . . . . . . . . . . . . . . . . . . . . . .

Parts Identification 7. . . . . . . . . . . . . . . . . .

I Unit Components 9. . . . . . . . . . . . . . . . . .

II Installation 19. . . . . . . . . . . . . . . . . . . . . . .

III Start Up 19. . . . . . . . . . . . . . . . . . . . . . . . .

Preliminary Seasonal Checks 20 . . . . .

Heating Start Up 20. . . . . . . . . . . . . . . .

IV Heating System Service Checks 20. . .

V Typical Operating Characteristics 22. . .

VI Maintenance 24. . . . . . . . . . . . . . . . . . . .

VII Wiring and Sequence of Operation 26.

VIII SureLight Control Troubleshooting 40.

Main Page

Brand	Lennox
Model	80MGF3/4-100
Category	Furnace
Language	English

Brand

Lennox

Model

80MGF3/4-100

Lennox 80MGF3/4-100 - User Manual

Table of Contents

Summary

80 MGF PARTS IDENTIFICATION and ORIENTATION

I-UNIT COMPONENTS

A-Blower Door Components

4- EGC Control (A3)

Blower Operation; Fan Off Timings

Troubleshooting

6- SureLight Ignition System A3 (-11 models)

III-START-UP

IV-HEATING SYSTEM SERVICE CHECKS

C-Testing Gas Piping

V-TYPICAL OPERATING CHARACTERISTICS

A-Blower Operation and Adjustment

B-Temperature Rise

VI-MAINTENANCE

Filters

A-Cleaning Heat Exchanger and Burners

VII-WIRING AND SEQUENCE OF OPERATION

80 MGF WITH RAM CONTROL

80 MGF TROUBLESHOOTING SEQUENCE

80 MGF TROUBLESHOOTING SEQUENCE - COOLING

80 MGF TROUBLESHOOTING SEQUENCE - FAN ONLY

SURELIGHT CONTROL HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE

ABNORMAL HEATING MODE

SURELIGHT CONTROL COOLING SEQUENCE OF OPERATION

NORMAL COOLING MODE

ABNORMAL COOLING MODE

SURELIGHT CONTROL CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION