Lennox LDT240

100083
LDT SERIES
Service Literature
13 to 20 ton
LDT156 through 240
The LDT156, 180 and 240 units are configure to order units
(CTO) with a wide selection of factory installed options.
The LDT156 is available in 169,000 to 360,000 Btuh. The
LDT180/240 is available in 169,000 to 480,000 Btuh..
Gas heat sections are designed with stainless steel tube
heat exchangers with stainless steel as an option.
Cooling capacities range from 13 to 20 tons. The LDT 156,
180 & 240 utilize two compressors and six condenser fans.
Multi-Stage Air Volume MSAV
®
blower option is available.
The VFD-driven blower will operate at lower speeds when
demand is low and increase to higher speeds when
demand is high.
All LDT units are designed to accept any of several different
energy management thermostat control systems with
minimum field wiring. Factory- or field-provided control
options connect to the unit through Smartwiret
connectors. When "plugged in" the controls become an
integral part of the unit wiring.
The CORE Control System is designed to accelerate
equipment install and service. Standard with all Enlight
rooftop units, control system integrates key technologies
that lower installation costs, drive system efficiency, and
protect your investments.
The CORE Unit Controller is a microprocessor-based
controller that provides flexible control of all unit functions.
Information contained in this manual is intended for use by
qualified service technicians only. All specifications are
subject to change. Procedures outlined in this manual are
presented 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
proper rigging technique.
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
To prevent serious injury or death:
1-Lock-out/tag out before performing maintenance.
2- If system power is required (e.g., smoke detector
maintenance, disable power to blower, remove fan
belt where applicable, and ensure all controllers and
thermostats are Set to the “OFF” position before per
forming maintenance.
3- Always keep hands, hair, clothing, jewelery, tools,
etc.,c away from moving parts.
Table of Contents
Options / Accessories Page 2.....................
Specifications Page 6............................
Gas Heat Specifications / High Altitude Page 7......
Blower Data Page 8.............................
Electrical Data Page 11...........................
Unit Parts Arrangement Page 13...................
I-Unit Components Page 13.......................
II-Placement and Installation Page 31...............
III-Charging Page 31..............................
IV Start Up - Operation Page 32....................
V-System Service Checks Page 34.................
VI-Maintenance Page 36.........................
VII-Accessories Page 37..........................
VIII-Staged Blower Page 42.......................
IX-Wiring and Operation Sequence Page 45.........

Lennox LDT240 Specifications

General

Refrigerant	R-410A
Phase	1
Sound Level	As low as 51 dBA
HSPF	Up to 11
Operating Voltage	208-230V

Summary

Unit Overview and Safety Information

General Safety Precautions

Outlines essential safety warnings for installation and maintenance to prevent injury or death.

Unit Specifications

General Unit Data

Provides key data like tonnage, model, efficiency, blower type, and refrigerant details.

Cooling and Heating Performance

Details cooling and heating capacities, airflow, power usage, and thermal efficiency.

Gas Heating Specifications

Details gas heat input, output, temperature rise, efficiency, and gas supply requirements.

Electrical Specifications

13 Ton Electrical Data

Details electrical ratings for compressors, fans, and blower for 13-ton units.

15 Ton Electrical Data

Details electrical ratings for compressors, fans, and blower for 15-ton units.

20 Ton Electrical Data

Details electrical ratings for compressors, fans, and blower for 20-ton units.

Cooling System Components and Operation

Compressor Protection and Controls

Details compressors, heaters, high/low pressure switches, and safety controls.

Blower System Operation and Adjustment

Three Phase Compressor Voltage Phasing

Details ensuring correct three-phase compressor and blower rotation.

Gas Heat System Operation

Burner Ignition Control (UTEC)

Details the UTEC ignition control, its functions, LED codes, and lockout procedures.

Gas Burner and Safety Controls

Describes burner assembly, orifice, limits, and air prove switches.

Gas Valve Operation and Spark Ignition

Explains gas valve operation, regulation, and spark electrodes for ignition.

System Charging and Installation

Flame Sensor Operation

Details the function of flame sensors in monitoring ignition and flame status.

Refrigerant Charge Verification

Provides procedures and tables for checking refrigerant charge.

Startup Checks and Cooling Startup

Lists preliminary checks and procedures for initiating cooling operation.

Furnace Operation and Safety Shutdown

Pre-Lighting Safety Procedures

Provides warnings and procedures for safely lighting the appliance.

Ignition System and Gas Valve Operation

Explains automatic ignition, gas valve operation, and startup sequence.

Emergency Shutdown Procedures

Details how to safely shut down the unit in case of emergency or for servicing.

System Service Checks and Adjustments

Gas Piping and Supply Pressure Checks

Guides on inspecting gas piping, testing supply pressure, and checking for leaks.

Manifold Pressure Adjustment

Spark Electrode and Flame Sensing

Multi-Staged Blower Operation

Blower Speed and CFM Configuration

Manual VFD Bypass Procedure

Wiring Diagrams and Operation Sequences

Gas Heat Wiring Diagram

Gas Heat and Heat Pump Operation Sequence

Thermostat Wiring and Control Connections

Economizer Control Wiring

Economizer and Cooling Operation Sequence