Lennox LHT078H

2022
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 mainte
nance), disable power to blower, remove fan belt where
applicable, and ensure all controllers and thermostats are
set to the “OFF” position before
performing maintenance.
3- Always keep hands, hair, clothing, jewelry, tools, etc.,
away from moving part
s.
Table Of Contents
Dimensions Page 2.................................
Parts Arrangements Page 4.........................
Shipping and Packing List Page 5....................
General Page 5....................................
Safety Page 5.....................................
Unit Support Page 6................................
Duct Connection Page 7............................
Rigging Unit For Lifting Page 7.......................
Condensate Drains Page 7..........................
Gas Piping Page 9.................................
Pressure Test Gas Piping Page 10.....................
High Altitude Derate Page 11.........................
Download Mobile Service App Page 11.................
Electrical Connections - Power Supply Page 12.........
Electrical Connections - Control Wiring Page 12.........
Blower Operation and Adjustments Page 14............
Direct Drive Start-Up Page 16.........................
Cooling Start-Up Page 19............................
Prognostic & Diagnostic Sensors Page 21..............
INSTALLATION
INSTRUCTIONS
LHT/LDT078H
LHT/LDT092H
LHT/LDT102H
LHT/LDT122H
LHT/LDT150H
(6.5 Ton)
(7.5 Ton)
(8.5 Ton)
(10 Ton)
(12.5 Ton)
PACKAGED UNITS
508320-01
10/2022
WARNING
Improper installation, adjustment, alteration, ser
vice or maintenance can cause property damage,
personal injury or loss of life. Installation and ser
vice must be performed by a licensed professional
HVAC installer or equivalent, service agency, or the
gas supplier
Gas Heat Start-Up Page 24...........................
Heating Operation and Adjustments Page 26............
Electric Heat Start-Up Page 26........................
Cooling Operation Page 27...........................
Service Page 28....................................
Field-Installed Accessories Page 35...................
Unit Controller Parameter Settings Page 35.............
Use this QR code to download the mobile service app. Follow the prompts
to pair the app with the unit control system and configure the unit. Refer to the
“Download Mobile App” section in this manual and the Setup Guide provided
with this unit. The QR code is also available in the unit control area.
The app can be downloaded from the appropriate iOS or Android store.
Look for the following icon.
Attention!

Lennox LHT078H Specifications

General

Brand	Lennox
Model	LHT078H
Category	Air Conditioner
Language	English

Summary

Unit Dimensions

LHTLDT078, 092, 102 H Dimensions

Shows external dimensions and views for specific LHT/LDT models.

LHTLDT122, 150 H Dimensions

Shows external dimensions and views for specific LHT/LDT models.

Parts Arrangement

Installation Safety and Support

General Safety Warnings

Covers electrical shock, explosion, and roof damage hazards during installation.

Unit Support and Mounting

Instructions for proper unit support, including downflow applications and mounting frames.

Duct and Condensate Connections

Duct Connection

Requirements for connecting ductwork to the unit, including insulation and weatherproofing.

Condensate Drain Connections

Procedures for connecting condensate drains, including side and bottom configurations.

Gas Piping Installation and Testing

Connecting Gas Piping

Guidelines for connecting gas supply piping, including pressure requirements.

Pressure Test Gas Piping

Procedures for safely testing gas piping connections for leaks.

Electrical Connections

Power Supply Wiring

Steps for connecting the main power supply wiring to the unit.

Control Wiring

Routing and connecting thermostat and zone sensor control wiring.

Blower Operation and Calibration

Blower Operation Basics

Explains variable speed blower operation and controller settings.

Direct Drive Blower Calibration

Procedures for calibrating and starting the direct drive blower assembly.

Cooling Operation and Refrigerant

Cooling Start-Up Procedure

Steps for initiating full load cooling operation and checking the system.

Refrigerant Charge and Check

Methods for checking and verifying refrigerant charge using various techniques.

Diagnostic Sensors

Explains the function and location of thermistors used for system monitoring.

Heating Operation and Start-Up

Gas Unit Heating Start-Up

Steps for safely initiating gas heating operation and lighting the burner.

Electric Heat Start-Up

Procedures for starting up the electric heat option in LHT units.

Unit Service and Maintenance

Filter and Coil Maintenance

Instructions for checking and replacing air filters and cleaning coils.

Burner, Inducer, and UVC Maintenance

Procedures for cleaning burners, inducer, and maintaining UVC light system.

Unit Controller Settings

Factory Blower Settings

Lists default blower speed settings and adjustment procedures via mobile app.

Configuration ID Setup

Explains how to set configuration IDs for various unit options and features.

Start-Up Report