Lennox LGC Series

© 1999 Lennox Industries Inc.
Litho U.S.A.
Page 1
Corp. 9913−L7
LGA/LGC
LCA/LCC
Service Literature
21 / 30 TON
74 / 105 kW
Revised 01−2009
LGA/LGC/LCA/LCC SERIES
The LGA /LGC/ LCA/LCC 21, 25 and 30 ton (74, 88, 105 kW)
units are configured to order units (CTO) with a wide selection
of factory installed options. The LGA/LGC248H/360H gas/
electric packaged rooftop units are available in 260,000 Btuh,
360,000 Btuh and 480,000 Btuh (76.2 kW, 105.5 and 137.7
kW) heating inputs. Gas heat sections are designed with Len-
nox’ aluminized steel tube heat exchangers. The LCA/
LCC248H/360H cooling packaged rooftop units are
equipped with the same cooling sections as the LGA/
LGC248H/360H units.
LCA/LGA248, LCC/LGC300H and LCC/LGC360H units
may contain a supply air blower equipped with a variable
frequency drive A96 (VFD) which varies supply air CFM. As
duct static increases, the supply air volume will decrease.
As duct static decreases, the supply air volume will in-
crease.
Optional electric heat is factory−or field−installed in LCA /LCC
units. Electric heat operates in single or multiple stages de-
pending on the kW input size. 30kW through 120kW heat
sections are available for the LCA/LCC248H/360H. LGA/
LGC and LCA/LCC units have identical refrigerant circuits
with 21, 25 and 30 ton (74, 88 and 105kW) cooling capaci-
ties. LGA/LCA360H units utilize three compressors, while
the LGA/LCA300H and LGA/LCA248H units utilize four
compressors.
Units are also designed for R−410A refrigerant. See unit
nameplate for refrigerant type and charge. Operating pres-
sures and pressure switch settings are significantly higher
than units charged with R−22. Service equipment for
R−410A units must be rated for R−410A refrigerant.
The LGA and LCA units are designed to accept any of sev-
eral different energy management thermostat control sys-
tems with minimum field wiring. Factory or field provided
control options connect to the unit with jack plugs. When
"plugged in" the controls become an integral part of the unit
wiring.
Information contained in this manual is intended for use by
qulified service technicians only. All specifications are sub-
ject to change. Procedures outlined in this manual are pre-
sented as a recommendation only and do not supersede or
replace local or state codes.
If the unit must be lifted for service, rig unit by attaching four
cables to the holes located in the unit base rail (two holes at
each corner). Refer to the installation instructions for the prop-
er rigging technique.
LGA360
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 qualified installer or service
agency.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon-
nect switch(es). Unit may have multiple
power supplies.

Lennox LGC Series Specifications

General

Brand	Lennox
Model	LGC Series
Category	Air Conditioner
Language	English

Summary

Specifications

Cooling Performance

Details cooling capacity, airflow, and efficiency ratings for various models.

Gas Heat, High Altitude, and Electrical Data

Gas Heat Specifications

Input/output capacities, thermal efficiency, and gas supply requirements.

Electric Heat Capacities

Electrical Data

Optional Electric Heat Accessories

Electric Heat Control Modules and Fuse Blocks

Part numbers for electric heat control modules and fuse blocks based on unit model and kW.

Terminal Block and Unit Fuse Block Details

Control Box Components

Control Box Layout Diagram

Illustrates the location of control modules, transformers, relays, and terminal blocks within the control box.

Unit Components - General

Control Box Component Details

Descriptions of disconnect switches, transformers, terminal strips, and other control box parts.

Compressors and Crankcase Heaters

Cooling Components

Compressors and Protection Devices

Details on compressors, crankcase heaters, high/low pressure switches, and ambient switches.

Blower Operation and Adjustment

Blower Operation and Access

Instructions on initiating blower operation, accessing the blower assembly, and determining CFM.

Pulley Alignment and Belt Tension

Procedures for ensuring proper pulley alignment and belt tension for optimal blower performance.

Heat Exchanger and Burner Assembly

Heat Exchanger and Burner Details

Gas Heat Components

Control Box Components for Gas Heat

Ignition and Flame Sensing

Gas Valves and Spark Electrodes

Optional Electric Heat Components

Electric Heat Control and Protection

Details on electric heat relays, transformers, high temperature limits, and fuses.

Heating Elements and Vestibule

Electric Heat Section Fuse Ratings

Placement, Startup, and Charging

Preliminary Checks and Cooling Start-Up

Procedures for unit installation checks and initiating cooling operation.

Refrigerant Charge Verification

Methods for checking refrigerant charge using approach temperature and pressure readings.

Heating Start Up

Placing Unit In Operation and Safety

Steps for starting the unit and safety procedures for emergency shutdown.

Systems Service Checks

Heating System Service Checks

Procedures for checking gas piping, supply pressure, and manifold pressure.

Cooling System Service Checks

Control Systems and Sensors

Thermostat Systems and Smoke Detectors

Wiring Diagrams and Operation Sequence

Wiring Diagrams Overview

Introduction to the wiring diagrams and sequence of operation sections.

Sequence of Operation

Power, Blower, and Economizer Operation

Describes the initial power-up, blower, and economizer sequences.

Cooling and Heating Sequences

Detailed step-by-step operation for first and second stage cooling and heating.