Lennox 80UHG3-75 User Manual

Page 1
 1999 Lennox Industries Inc.
Litho U.S.A.
Corp. 9728−L12
80UHG
Service Literature
Revised 01−2002
80UHG series units are mid−efficiency gas furnaces used
for upflow or horizontal applications only, manufactured
with tubular heat exchangers formed of aluminized steel.
80UHG units are available in heating capacities of 45,000
to 120,000 Btuh and cooling applications up to 5 tons. Refer
to Engineering Handbook for proper sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. 80UHG−1 model
units use electronic (direct spark) ignition. 80UHG−2 and −3
model units are equipped with the Lennox SureLight silicon
nitride ignition system. The 80UHGX unit meets the Califor
nia Nitrogen Oxides (NO
x
) Standards and California Sea
sonal Efficiency requirements. All units use a redundant gas
valve to assure safety shut−off as required by A.G.A. or
C.G.A. Units may be installed in upflow or horizontal posi
tion.
All specifications in this manual are subject to change. Pro
cedures outlined in this manual are presented as a recom
mendation 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.
TABLE OF CONTENTS
Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Data 3−4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Altitude 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification 5−6. . . . . . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components 6−15. . . . . . . . . . . . . . . . . . . . . . . . . . .
II Installation 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Start Up 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks 16−17. . . . . . . . . . .
V Typical Operating Characteristics 18. . . . . . . . . . . . . .
VI Maintenance 19−20. . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation 21−28. . . . . . . . .
VIII SureLight Troubleshooting Guide 29−34. . . . . . . . . .

Lennox 80UHG3-75 Specifications

General

Model	80UHG3-75
Type	Gas Furnace
Heating Capacity	75, 000 BTU/hr
AFUE Rating	80%
Blower Type	Multi-speed
Stages	Single-stage
Fuel Type	Natural Gas
Blower Motor Type	PSC
Ignition Type	Hot Surface Ignition
Vent Diameter	4 inches

Summary

Unit Specifications

Blower Performance Data

80UHG Blower Performance

Air volume data for various blower speeds and static pressures for specific 80UHG models.

Filter Air Resistance

Table showing air resistance in inches of water gauge for various airflow rates.

High Altitude Derate

Information on manifold pressure settings for installations at different altitudes and fuels.

80UHG Parts Identification

Heating Components

Diagram and identification of key heating components within the furnace unit.

Burner Assembly Identification

Detailed view and identification of the burner assembly components.

Unit Components Overview

General identification of major unit components and their locations.

Furnace Control (80UHG-2, -3 Models)

Description of the SureLight ignition system for 80UHG-2 and -3 models.

SureLight Ignition Sequence

Visual representation of the SureLight control ignition sequence for heating.

SureLight Integrated Control Board

Diagram and explanation of the SureLight control board terminals and functions.

Furnace Control (80UHG-1 Model)

Description of the integrated ignition/blower control for 80UHG-1 models.

Thermostat and Control Connections

Information on thermostat wiring and control board connections.

Combustion Air Inducer

Description of the combustion air inducer motor and its function.

Flame Rollout Switches

Details on the flame rollout safety switches and their function.

Primary Limit Control

Description of the primary limit control (S10) and its operation.

Secondary Limit Controls

Description of the secondary limit controls (S21) and their operation.

Spark Electrode and Flame Sensor

Details on the spark electrode and flame sensor for 80UHG-1 models.

Gas Valve Information

Description of the gas valve, its types, and safety features.

Combustion Air Blower Prove Switch

Explanation of the combustion air blower prove switch (S18) function.

Installation and Start-Up Procedures

Placement and Installation

Guidelines for proper unit placement and installation according to codes.

Start-Up Procedures

Steps for unit start-up, including preliminary checks and heating start-up.

Turning Off Gas To Unit

Procedure for safely turning off the gas supply to the furnace.

Safety or Emergency Shutdown

Instructions for immediate safety or emergency shutdown of the unit.

Extended Period Shutdown

Procedure for safely shutting down the unit for extended periods.

Heating System Service Checks

A.G.A./C.G.A. Certification

Information on unit certification standards for gas appliances.

Gas Piping

Requirements and considerations for gas supply piping installation.

Testing Gas Piping

Procedure for testing gas piping for leaks and pressure integrity.

Testing Gas Supply Pressure

Procedure for checking and verifying gas supply pressure.

Check Manifold Pressure

Procedure for checking and verifying manifold gas pressure.

Proper Gas Flow

Method for checking and adjusting gas flow rate for optimal unit operation.

Flame Signal Measurement

Procedure for measuring the flame signal for ignition control diagnostics.

Typical Operating Characteristics

Blower Operation and Adjustment

General information on blower operation and thermostat control.

Temperature Rise Measurement

Procedure for measuring and adjusting the unit's temperature rise.

External Static Pressure

Procedure for measuring external static pressure using a manometer.

Blower Speed Taps (Leadless Motors)

Instructions for selecting blower speed taps on leadless motor models.

Blower Speed Taps (Leaded Motors)

Instructions for selecting blower speed taps on leaded motor models.

Unit Maintenance

Filter Maintenance

Guidelines for checking, cleaning, or replacing air filters.

Heat Exchanger and Burner Cleaning

Procedure for cleaning furnace burners and inspecting the heat exchanger.

Supply Air Blower Maintenance

Instructions for checking and cleaning the supply air blower.

Flue and Chimney Inspection

Procedure for checking flue pipe, chimney, and connections for blockages.

Electrical System Checks

Checks for wiring connections, voltage, and blower motor amp-draw.

Wiring and Sequence of Operation

80UHG-1 Model Wiring Diagram

Wiring diagram for the 80UHG-1 model with SureLight control.

80UHG-1 Heating Sequence

Flowchart detailing the normal and abnormal heating operation sequence.

80UHG-1 Cooling Sequence

Flowchart detailing the cooling operation sequence.

80UHG-1 Continuous Fan Sequence

Flowchart detailing the continuous fan operation sequence.

80UHG-2 Model Heating Sequence

Description of the heating sequence for 80UHG-2 models with SureLight control.

General Heating Sequence of Operation

Flowchart for normal and abnormal heating sequences.

Continued Heating Sequence

Continuation of the heating sequence flowchart.

Cooling Sequence of Operation

Flowchart for normal and abnormal cooling sequences.

Continuous Heat Speed Fan Sequence

Flowchart for continuous heat speed fan operation.

Troubleshooting SureLight Control

SureLight Troubleshooting Guide

Guide to diagnose and resolve common unit operational issues using diagnostic codes.