Lennox LGC300H2 - User Manual

© 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 LGC300H2 Specifications

General

Brand	Lennox
Model	LGC300H2
Category	Air Conditioner
Language	English

Summary

LGA;LCA Specifications

Cooling Performance

Details unit cooling capacity, airflow, power consumption, and efficiency ratings.

Gas Heat Specifications

Gas Heating Performance

Details gas heat input, output, efficiency, and gas pressure requirements.

Electric Heat Capacities

Electrical Data

Optional Electric Heat Accessories

Electric Heat Control Module and Fuse Blocks

LTB2 Electric Heat Terminal Block

Control Box

Control Box Components

Unit Components

Electrostatic Discharge Precautions

Safety guidelines to prevent damage from static discharge.

Control Box Components Overview

Cooling Components

Compressors

Information on compressor types, stages, and electrical specifications.

High Pressure Switches

Explains the role and settings of high-pressure safety switches.

Low Ambient Switches

Describes the function of low-ambient switches for cold weather operation.

Gas Heat Components

Control Box Components for Gas Heat

Identifies control box components specific to gas heating systems.

Burner Ignition Control

Details the function and operation of burner ignition controls.

Optional Electric Heat Components

Control Box Components for Electric Heat

Lists control box components relevant to electric heat systems.

Electric Heat Contactors

Primary High Temperature Limits

Details primary high-limit safety controls for electric heat.

Redundant High Temperature Limit

Describes the redundant high-limit safety control for electric heat.

Terminal Strip and Heating Elements

Placement and Installation

Preliminary Checks

Startup, Operation, and Charging

Cooling Start-Up

Step-by-step guide for initiating cooling operation.

R410 A Refrigerant and Charge Check

R410 A Refrigerant Considerations

Important information and precautions regarding R410A refrigerant.

Refrigerant Charge and Check

Procedures for verifying and adjusting refrigerant charge.

Heating Start Up

Heating Start Up Procedures

Safety and operational steps for initiating heating.

Systems Service Checks

Heating System Service Checks

Procedures for servicing and troubleshooting heating systems.

Gas Piping

Gas Supply Pressure Testing

Steps for testing and verifying gas supply pressure.

Manifold Pressure Check

Procedure for checking and adjusting gas manifold pressure.

Wiring Diagrams and Operation Sequence

Wiring Diagrams and Operation Sequence Introduction

Introduction to wiring diagrams and operational sequences for unit systems.

Sequence of Operation

Power and Blower Operation

Economizer Operation

First Stage Cooling

Detailed sequence for first stage cooling activation.

Second Stage Cooling

Detailed sequence for second stage cooling activation.

Sequence of Operation (Continued)

First Stage Heat

Detailed sequence for first stage heating activation.

Second Stage Heat

Detailed sequence for second stage heating activation.

Sequence of Operation (Heating)

Heating Elements

First Stage Heat Sequence

Detailed sequence for first stage electric heat activation.

Second Stage Heat Sequence

Thermostat Operation Sequence

Thermostat Operation Sequence

Economizer Wiring Diagram and Operation

Economizer Wiring Diagram and Operation