Lochinvar 1.5 - Manual (Page 2)

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Introduction
The information contained in this manual provides general guidelines for the implementation of ModBus communication with
the Lochinvar Crest boiler.
All ModBus networks are implemented utilizing a master-slave arrangement where all Crest boilers are slaves and the master is
a building automation system capable of communicating over a RS-485 serial connection.
Contents
1. INTRODUCTION
Defi nitions .................................................................... 2
Minimum System Requirements .................................. 2
2. CONFIGURATION
Addressing
................................................................... 3
Timing Specifi cations ................................................... 4
Parity ............................................................................ 4
Data Transmission Mode ............................................. 4
ModBus Board Diagnostics ......................................... 4
Internal Faults ......................................................... 4
ModBus Function Set ............................................. 5
ModBus Exception Codes ........................................... 6
3. MEMORY MAP
Primary Data Tables .................................................... . 7
Crest Boiler Memory Map ............................................ 7-8
Input Registers ....................................................... . 8
Holding Registers ................................................... . 8
Confi guration Bits ........................................................ . 8
4. WIRING REQUIREMENTS
Physical Wiring ............................................................ . 9
Typical Boiler System Wiring .................................. 12-13
5. UNIT OPERATION
Unit Operation with ModBus Communications ...... 14-17
6. TROUBLESHOOTING ........................................... 18-21
7. DIAGRAMS
Ladder
Diagram ............................................................ 22
Wiring Diagram ............................................................ 23
Revision Notes ................................................... Back Cover
Abbreviation or Acronym Meaning
ASCII American Standard Code for Information Interchange
BAS Building Automation System
Baud (Baud Rate) Number of data bits transmitted per second (bps)
EMS Energy Management System
FDX Full-Duplex
HDX Half-Duplex
Hex Hexadecimal Number (0 - 9, A - F)
I/O Box Input/Output (I/O)
LSB Least Signifi cant Byte
ModBus® A serial, half-duplex data transmission protocol developed by AEG Modicon
MSB Most Signifi cant Byte
RS232
A standard for serial, full-duplex (FDX) transmission of data based on the
RS232 Standard
RS485 A standard for serial transmission of data based on the RS-485 Standard
RTU Remote Terminal Unit
Defi nitions
Minimum System Requirements
• BAS system or computer with a serial or USB port with a converter to RS-485.
Shielded twisted pair communication cable.