MILLENNIUM® 25-40 TON SINGLE PACKAGE COMMERCIAL ROOFTOP UNIT EQUIPPED WITH SIMPLICITY® CONTROLS - Technical Application and Programming Guide

Oct 22, 2026

Technical application and programming guide for the Millennium® 25-40 Ton Single Package Commercial Rooftop Unit equipped with Simplicity® Controls. The manual describes how Simplicity® controls operate as a digital system, consolidating monitoring and control functions previously handled by discrete relays and interlocking hardware. It covers recommended installation and technical aids, a structured table of contents, digital communications, programming options, operating modes and parameters (including metric operation), sequence of operation for heating and cooling, sensor and VAV operation, scheduling, and troubleshooting with status and failure-mode guidance.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages44

Reading Time1 h 51 min

AccessFree to download

THE MILLENNIUM® SIMPLICITY® CONTROL

INTRODUCTION AND OVERVIEW

DIGITAL LINGO

ANALOG TO DIGITAL CONVERTER

COMMUNICATIONS BUS

OPTIONAL Simplicity® LINC TRANSLATOR

COMPONENT DESCRIPTION

SIMPLICITY® PROGRAMMING OPTIONS

INITIAL STARTUP OPTIONS

METRIC OPERATION (ENGLISH)

SETTABLE SYSTEM PARAMETERS

MILLENNIUM® SEQUENCE OF OPERATION

TROUBLESHOOTING A MILLENNIUM® SIMPLICITY® CONTROL

351579-YTS-C-0111 TECHNICAL APPLICATION AND PROGRAMMING GUIDE MILLENNIUM® SINGLE PACKAGE ROOFTOP UNITS 25, 30 & 40 TON EQUIPPED WITH SIMPLICITY® ELITE CONTROLS MILLENNIUM® 25-40 TON SINGLE PACKAGE COMMERCIAL ROOFTOP UNIT EQUIPPED WITH SIMPLICITY® CONTROLS This manual includes application, programming and service procedures for the Millennium® 25-40 Ton Single Package Commercial Rooftop Unit equipped with Simplicity® Controls. These procedures are the same for all 25-40 Ton Millennium® Rooftop units in this series except as noted. This manual covers Simplicity® controls only, for unit installation information please refer to the following. RECOMMENDED TECHNICAL AND INSTALLATION AIDS Millennium® 25-40 Ton Single Package Installation and Operation Manual-524158 Millennium® 25-40 Ton Technical Guide-246837 ISO 9001 Certified Quality Management System TABLE OF CONTENTS MILLENNIUM® 25-40 TON SINGLE PACKAGE COMMERCIAL ROOFTOP UNIT EQUIPPED WITH SIMPLICITY® CONTROLS .................... 1 RECOMMENDED TECHNICAL AND INSTALLATION AIDS ........................ 1 THE MILLENNIUM® SIMPLICITY® CONTROL .... 3 INTRODUCTION AND OVERVIEW ................. 3 DIGITAL LINGO ................................ 4 ANALOG TO DIGITAL CONVERTER ............... 4 COMMUNICATIONS BUS ........................ 5 OPTIONAL Simplicity® LINC TRANSLATOR.......... 5 COMPONENT DESCRIPTION..................... 5 SIMPLICITY® PROGRAMMING OPTIONS ....... 11 INTERACTING THROUGH THE MILLENNIUM® SIMPLICITY® ................................ 11 INITIAL STARTUP OPTIONS .................... 11 METRIC OPERATION (ENGLISH) ................ 11 SETTABLE SYSTEM PARAMETERS ........... 11 MILLENNIUM® SEQUENCE OF OPERATION .... 18 OVERVIEW .................................. 18 RUN SEQUENCE.............................. 18 UNIT CONTROLS SEQUENCE ................... 18 VARIABLE AIR VOLUME UNIT (VFD & IGV) ........ 20 OCCUPIED / UNOCCUPIED / MORNING WARM-UP . 21 UNIT CONTROLS ............................. 21 HEAD PRESSURE CONTROL ................... 26 SEQUENCE OF OPERATION-FOR HEAD PRESSURE CONTROL................................... 26 INTELLI-START ............................... 27 DEVICES AND RULES ......................... 27 COMFORT VENTILATION MODE ................. 28 HYDRONIC HEAT ............................. 29 COOLING LOCKOUT ON OAT ................... 29 WATER COIL FREEZE STAT (FSI) ................ 29 CV OPERATION .............................. 29 THERMOSTAT OPERATION FOR COOLING WITH Y1, Y2, Y3 AND Y4 INPUTS ........................ 30 OPERATION FOR HEATING WITH W1, W2, AND W3 INPUTS ..................................... 30 SENSOR OPERATION ......................... 30 TYPES OF SPACE SENSORS ................... 31 VAV OPERATION ............................. 32 SUPPLY DUCT PRESSURE CONTROL ALGORITHM. 34 MORNING WARM UP / VAV OCCUPIED HEATING CONTROL ALGORITHM ....................... 34 CONTROLLING EXCESSIVE SAT (SUPPLY AIR TEMPERATURE) .............................. 35 SAT SETPOINTS USED DURING COOLING WITH ECONOMIZER OPERATION .....................36 DEMAND VENTILATION .........................39 EXHAUST OPERATION .........................40 SCHEDULING OPERATION ......................41 COMPRESSOR STATUS MONITORING ............41 TROUBLESHOOTING A MILLENNIUM® SIMPLICITY® CONTROL .................... 43 STATUS LED CHART ...........................43 FAILURE MODES AND DEFAULT OPERATION ......43 SENSOR FAILURES AND DEFAULT OPERATION ....43 SYSTEM ERRORS .............................44 LIST OF FIGURES Fig. \# Pg. \# 1 SIMPLICITY® CONTROLLER ................... 3 2 SIMPLICITY® CONTROLS PUSH BUTTONS ...... 3 3 ANALOG TO DIGITAL CONVERTER ............. 4 4 VFD CONTROL WIRING ....................... 8 5 SEQUENCE OF SETTING THE SET POINTS ..... 14 6 COMFORT VENTILATION ECONOMIZER CONTROL .................................. 28 7 SAT CONTROL BAN

FAQs

What does the Simplicity® control system do on the Millennium® 25-40 ton rooftop unit?

It performs control and monitoring functions that were previously handled by separate discrete relays, controls, and interlocking hardware, reducing manufacturing, service, and maintenance costs.

Which topics are covered by the manual besides the control overview?

The manual covers programming options, startup and settable parameters, sequences of operation for different operating modes, and device/sensor and VAV operation, plus troubleshooting and failure modes.

How does the manual approach troubleshooting of a Simplicity® control system?

It provides troubleshooting guidance including a status LED chart, failure modes and default operation, sensor failure handling, system errors, and related reference tables.

Oct 22, 2026

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