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Perform steps in the order given. Failure to comply could result in severe personal injury, death, or substantial property damage. WARNING Save this manual for future reference. MODBUS COMMUNICATION INSTRUCTIONS Crest Models: 1.5 - 3.5 Contents Contents 1. INTRODUCTION 3. MEMORY MAP 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 Primary Data Tables ..................................................... 7 Crest Boiler Memory Map ............................................7-8 Input Registers ........................................................ 8 Holding Registers .................................................... 8 Configuration 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 1 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. Definitions 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 Minimum System Requirements • BAS system or computer with a serial or USB port with a converter to RS-485. Shielded twisted pair communication cable. ModBus Instructions ModBus Instructions 2 Configuration The ModBus communication board is equipped with a set of ten dip switches that are used to set the board confi guration (address, baud rate, and parity settings). The first eight are used to set the address of each board. The ninth is used to set the baud rate. The tenth is used to set the parity. Figure 2-1_ModBus Communication Board Addressing The ModBus addressing space is comprised of 256 different addresss. • 0 is reserved for broadcast messages from the master device • 1 - 247 are free to use for each unique device • 248 - 255 are reserved To set the ModBus address the dip switches can be set in either the 0 position or the 1 position. For switches set to the 1 position their value will be added together to determine the address. For each switch set to the 1 position it has the following value: Dip switch 1 = 1 Dip switch 2 = 2 Dip switch 3 = 4 Dip switch 4 = 8 Dip switch 5 = 16 Dip switch 6 = 32 Dip switch 7 = 64 Dip switch 8 = 128 Any dip switch set to 0 has a value equal to 0. DIP SWITCHES LED’S Example: To set the address of the ModBus board to 50, dip switches 2, 5, and 6 have to be set to the 1 position. The address is determined by adding the values of all the dip switches together. Address = Value of Dip switch 1 + Value of Dip switch 2 + Value of Dip switch 3 + Value of Dip switch 4 + Value of Dip switch 5 + Value of Dip switch 6 + Value of Dip switch 7 + Value of Dip switch 8 In this example: Address = 0 + 2 + 0 + 0 + 16 + 32 + 0 + 0 = 50 ModBus Instructions ModBus Instructions 2 Configuration Timing Specifications The baud rate for the ModBus board is selectable with Dip switch #9. 1 = 19200 bps 0 = 9600 bps Each message is started by at least 3.5 character times of silence. The maximum delay between frames is 1.5 character t...