LENNOX CORE CONTROL SYSTEM (UNIT CONTROLLER) APPLICATION GUIDE - Issue 485115 3/2024

Oct 17, 2026

LENNOX® CORE CONTROL SYSTEM unit controller application guide detailing installation and service safety requirements, including electric shock hazard warnings and lock-out/tag-out procedures. The guide explains unit controller description, M4 unit controller layout and connections, communication interfaces (USB flash drive, S-BUS, MODBUS), local interface indicators, and LED status code interpretation. It also covers W4 communication module features, available accessories, firmware update preparation via USB, and CORE Service App unit operations such as pairing, alarms, data trending, reporting, and settings.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages145

Reading Time6 h 5 min

AccessFree to download

Abbreviations and Terms

Unit Controller Description

M4 Unit Controller Layout and Connections

Lennox CORE Service App

CORE Unit Controller-Connections, Inputs / Outputs, Jumpers, and LEDs Locations

Thermostat Common Isolation-TSTAT_COM Jumper

Humidistat Common Isolation-HMD_COM Jumper

W4 Control-USB Flash Drive Interface Usage

S-BUS (Smartwire™) (J304)

MODBUS Connections

CORE Unit Controller LED Indicators

Local Interface-Push Buttons and Heart Beat

Local Interface-Four Character Seven-Segment LED-Status Codes

W4 Communication Module-Connections, Buttons, and LEDs

Buttons and LED Indicators

Pairing Button and LED

Reset Button and Heart Beat LED

Cloud / IP Button and LED Indicators

BLE Wireless Gateway

CORE Service App

Cloud Firmware Updates

Available Accessories

LCS-5030 Wireless Sensor (21L07)

Wireless Repeater (21L09)

Wireless Smart IAQ Sensor (25B37)

Updating M4 Firmware

Confirming Current M4 Unit Controller Firmware Version

Preparing USB Flash Drive

Files Needed for Update

Creating Folder

Updating Firmware

CORE Service App-Unit Operations

CORE Service App Menu Selection Overview

Pairing CORE Service App to CORE Unit Controller

System Overview-Room Sensor Mode

Active Alarms

CORE Service App General Menu + User Preference

CORE Service App RTU Menu

Setup

Install Menu Navigation

Network Integration

Test and Balance

Data

Alarm History

Data Trending

Factory

Runtimes

System Data / Sensor Data / Output

Service

Component Test

Report

Advanced Control

Settings

RTU Options

Install

Main Controller Operations

LENNOX® CORE CONTROL SYSTEM (UNIT CONTROLLER) APPLICATION GUIDE 485115 3/2024 Supersedes 2/2024 | WARNING | | | --- | --- | | | Electric Shock Hazard. Can cause injury or death. Unit must be properly grounded in accordance with national and local codes.
Line voltage is present at all components when unit is not in operation on units with single-pole contactors. Disconnect all remote electric power supplies before opening access panel. Unit may have multiple power supplies. | | WARNING | | --- | | Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a licensed professional HVAC installer or equivalent, service agency, or the gas supplier. | | 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 performing maintenance.
3. Always keep hands, hair, clothing, jewelry and tools away from moving parts. | Table of Contents 1. Abbreviations and Terms................................................ 5 2. Unit Controller Description............................................. 6 2.1. M4 Unit Controller Layout and Connections .........................6 2.1.1. CORE Unit Controller Overview ............................ 7 2.1.2. Lennox® CORE Service App ................................. 8 2.2. Lennox CORE Unit Controller-Connections, Inputs / Outputs, Jumpers, and LEDs Locations................................8 2.2.1. Thermostat Common Isolation-TSTAT_COM Jumper .................................................................. 8 2.2.2. Humidistat Common Isolation-HMD_COM Jumper .................................................................. 8 2.2.3. W4 Control-USB Flash Drive Interface Usage ... 8 2.2.4. S-BUS (Smartwire™) (J304) ................................. 8 2.2.5. MODBUS Connections ......................................... 8 2.2.6. CORE Unit Controller LED Indicators ................... 9 2.2.7. Local Interface-Push Buttons and Heart Beat..... 9 2.2.8. Local Interface-Four Character Seven-Segment LED-Status Codes .............................................. 9 3. W4 Communication Module-Connections, Buttons, and LEDs ........................................................................ 10 3.1. Buttons and LED Indicators................................................. 10 3.1.1. Pairing Button and LED ....................................... 10 3.1.2. Reset Button and Heart Beat LED ...................... 10 3.1.3. Cloud / IP Button and LED Indicators ................. 10 3.2. BLE Wireless Gateway ....................................................... 10 3.3. CORE Service App.............................................................. 10 3.4. Cloud Firmware Updates..................................................... 11 4. Available Accessories................................................... 11 4.1. LCS-5030 Wireless Sensor (21L07) ................................... 11 4.2. Wireless Repeater (21L09) ................................................ 11 4.3. Wireless Smart IAQ Sensor (25B37) ................................... 11 5. Updating M4 Firmware .................................................. 11 5.1. Confirming Current M4 Unit Controller Firmware Version... 11 5.2. Preparing USB Flash Drive ................................................. 11 5.3. Files Needed for Update ..................................................... 11 5.4. Creating Folder.................................................................... 11 5.5. Updating Firmware .............................................................. 12 6. CORE Service App-Unit Operations .......

FAQs

What safety precautions does the guide require before servicing the unit controller?

The guide requires proper grounding, disconnecting remote power supplies before opening the access panel, and using lock-out/tag-out before maintenance. If system power is needed (e.g., smoke detector maintenance), it instructs disabling power to the blower and setting all controllers and thermostats to the “OFF” position before working.

Which communication interfaces are described for the CORE unit controller?

The guide covers USB flash drive interface usage, S-BUS (Smartwire™) (J304), and MODBUS connections. It also describes local interfaces such as push buttons and heart beat, plus LED indicators and seven-segment LED status codes.

How does the document guide firmware updating for the M4 unit controller?

It explains confirming the current M4 firmware version, preparing a USB flash drive, listing files needed for the update, creating the required folder, and then performing the firmware update.

Oct 17, 2026

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