Lennox LGA Series 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 LGA Series Specifications

General

Refrigerant	R-410A
Cooling Capacity (BTU/h)	18, 000 - 60, 000
Heating Capacity (BTU/h)	18, 000 - 60, 000
Series	LGA
Warranty	10-Year Limited Warranty on compressor, 5-Year Limited Warranty on covered components

Summary

LGA/LGC/LCA/LCC Series Overview

LGA/LCA Specifications

Cooling Performance

Details cooling specifications and performance data.

Indoor Blower and Drive Selection

Information on indoor blower and drive selection.

LGA/LCA Specifications - Continued

Compressor Type (no.)

Details compressor types and quantity.

Electrical characteristics

Lists electrical characteristics of the units.

LGC/LCC Specifications

Cooling Performance

Details cooling specifications and performance data.

3 Compressor Model Specifications

Gas Heating Performance

Details gas heating input and output specifications.

Gas Heat Specifications

HIGH ALTITUDE

Derating information for units at higher altitudes.

ELECTRIC HEAT CAPACITIES

Lists electric heat capacities by kW and voltage.

Electrical and Electric Heat Data (LGA/LCA)

Compressors

Electrical data for compressors.

Minimum Circuit Ampacity

Minimum circuit ampacity requirements.

Electrical and Electric Heat Data (LGA/LCA) - Continued

Disconnect

Electric heat control kit disconnect options.

Terminal Block

Electric heat terminal block options.

Electrical and Electric Heat Data (LGA/LCA) - Continued

Indoor Blower Motor

Electrical data for the indoor blower motor.

Electrical and Electric Heat Data (LGA/LCA) - Continued

Disconnect

Electric heat control kit disconnect options.

Electrical and Electric Heat Data (LGC/LCC)

Compressors

Electrical data for compressors.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Terminal Block

Electric heat terminal block options.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Indoor Blower Motor

Electrical data for the indoor blower motor.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Disconnect

Electric heat control kit disconnect options.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Compressors

Electrical data for compressors.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Terminal Block

Electric heat terminal block options.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Indoor Blower Motor

Electrical data for the indoor blower motor.

Electrical and Electric Heat Data (LGC/LCC) - Continued

Disconnect

Electric heat control kit disconnect options.

Options and Accessories

COOLING SYSTEM

Options related to the cooling system.

HEATING SYSTEM

Options for the heating system.

Options and Accessories - Continued

ELECTRIC HEAT ACCESSORIES/OPTIONS

Accessories and options for electric heat.

ECONOMIZER

Details on economizer options and controls.

Options and Accessories - Continued

ROOF CURBS - CLIPLOCK 1000

Roof curb options for unit mounting.

Optional Electric Heat Accessories

ELECTRIC HEAT CONTROL MODULE AND UNIT FUSE BLOCKS

Details control modules and fuse blocks for electric heat.

Blower Data - Base Unit

TOTAL STATIC PRESSURE

Static pressure data for blower operation.

Blower Data - Continued

CAV FACTORY INSTALLED DRIVE KIT SPECIFICATIONS

Specifications for CAV factory installed drive kits.

Blower Data - Continued

Gas Heat Exchanger

Blower data related to gas heat exchangers.

Ceiling Diffuser Air Resistance

CEILING DIFFUSER AIR THROW DATA

Air throw data for ceiling diffusers.

Power Exhaust Fans - 50% High Static

HIGH STATIC POWER EXHAUST FANS WITH CONSTANT AIR VOLUME - DRIVE KIT SPECIFICATIONS

Drive kit specs for high static power exhaust fans.

LGA/LGC Parts Arrangement

LCA/LCC Parts Arrangement

Control Box Components

I- UNIT COMPONENTS

ELECTROSTATIC DISCHARGE (ESD)

Precautions and procedures for ESD.

A-Control Box Components

Details control box components.

Integrated Modular Control Boards

19-Main Control Module A55 (all units)

Describes the main control module A55 functions.

360H Plumbing Components

COMPRESSOR DETAIL

Detailed view of compressor plumbing.

Plumbing Components (248H, 300H, 360H)

COMPRESSOR DETAIL

Detailed view of compressor plumbing.

Cooling Components

1-Compressors B1, B2, B13, B20

Details compressor types and protection.

3-High Pressure Switches S4, S7, S28, S96

Description of high pressure switches.

Low Pressure Switches

5-Low Pressure Switches S87, S88, S98, S97

Details low pressure switches.

Determining Unit CFM

4- Constant Air Volume (CAV) Supply Air Blowers

Adjusting CFM for CAV blowers.

5- Variable Air Volume (VAV) Supply Air Blowers

Adjusting CFM for VAV blowers.

Blower Belt Adjustment

PULLEY ALIGNMENT

Procedure for pulley alignment.

Gas Heat Components (LGA Units)

1-Control Box Components

Details control box components for gas heat.

Burner Ignition Control A3 and A12

Describes burner ignition controls.

Heat Exchanger

2-Heat Exchanger (Figures 15 and 16)

Description of heat exchanger styles.

High Temperature Limits

4-Primary High Temperature Limits S10 & S99

Details primary high temp limits for gas heat.

Flame Rollout Limits

6-Flame Rollout Limits S47 and S69

Describes flame rollout limits and their function.

Gas Valves

10-Gas Valves GV1 and GV3

Details operation of two-stage gas valves.

Optional Electric Heat Components

3-High Temperature Limits S15 and S107 (Primary)

Primary high temp limits for electric heat sections.

4-High Temperature Limit S63 (Redundant)

Redundant high temp limit for electric heat.

Electric Heat Section Parts Arrangement

Electric Heat Vestibule Parts Arrangement

Placement and Installation

A-Preliminary Checks

Pre-startup checks for unit installation.

R410A Refrigerant

C-Refrigerant Charge and Check

Procedure for checking refrigerant charge.

Heating Start Up

E-Heating Start Up

Procedures for starting the heating system.

Placing Unit In Operation

Gas Valve Operation for White Rodgers 36C Series Valve

Operation of White Rodgers gas valves.

System Service Checks

1-Gas Piping

Guidelines for gas piping installation.

3-Testing Gas Supply Pressure

Procedure for testing gas supply pressure.

Gas Flow Checks

5-Proper Gas Flow

Procedures for checking gas flow to burners.

Maintenance

A-Filters

Information on filter inspection and replacement.

D-Evaporator Coil

Instructions for inspecting and cleaning evaporator coils.

Electrical Checks

F-Electrical

Steps for checking electrical connections and voltage.

Accessories - Transitions and Dampers

B-Transitions

Optional supply/return transitions.

D-LAOAD(M) 30/36Outdoor Air Dampers

Details on outdoor air dampers.

Economizer Modes

1-"TMP” MODE (SENSIBLE TEMPERATURE)

Economizer mode based on sensible temperature.

2-“ODE” MODE (OUTDOOR ENTHALPY)

Economizer mode based on outdoor enthalpy.

Control Systems

1- Electro-mechanical thermostat (13F06)

Description of electro-mechanical thermostats.

O-Supply Air VFD

Information on supply air VFD operation.

Supply Air VFD and Duct Static

Excessive Duct Static

Handling issues with excessive duct static pressure.

Wiring Diagrams and Operation Sequence

COMBINATION UNIT-ROOFTOP GAS HEAT

Wiring diagram for gas heat units.

Wiring Diagrams and Operation Sequence - Continued

HEATING SECTION-A2

Wiring diagram for heating section A2.

Electric Heat Wiring Diagram (A6)

HEATING SECTION-A6

Wiring diagram for electric heat section A6.

Sequence of Operation

FIRST STAGE COOLING

Operation sequence for first stage cooling.

SECOND STAGE COOLING

Operation sequence for second stage cooling.

Electric Heat Wiring Diagram (A7)

HEATING SECTION-A7

Wiring diagram for electric heat section A7.

Sequence of Operation - Heating

FIRST STAGE HEAT:

Steps for first stage heating operation.

SECOND STAGE HEAT:

Steps for second stage heating operation.

Electric Heat Wiring Diagram (A6) - Continued

HEATING SECTION-A6

Wiring diagram for electric heat section A6.

Sequence of Operation - Electric Heat

FIRST STAGE HEAT:

Steps for first stage electric heat.

SECOND STAGE HEAT:

Steps for second stage electric heat.

Electric Heat Wiring Diagram (A6) - Continued

HEATING SECTION-A6

Wiring diagram for electric heat section A6.

Thermostat Wiring and Operation

OPERATION:

Describes the operation of the thermostat system.

L Series Economizer

SEQUENCE OF OPERATION

Describes economizer operation modes.