Specifications

6.1.8 BASIC Cascade Controller 158
6.1.9 Pump Staging with Lead Pump Alternation 159
6.1.10 System Status and Operation 159
6.1.11 Fixed Variable Speed Pump Wiring
Diagram 160
6.1.12 Lead Pump Alternation Wiring Diagram 160
6.1.13 Cascade Controller Wiring Diagram 161
6.1.14 Start/Stop Conditions 161
7 Installation and Set-up
162
7.1 Installation and Set-up
162
7.1.1 Network Connection 162
7.1.2 Hardware Setup 162
7.1.3 Parameter Settings for Modbus Communication 163
7.1.4 EMC Precautions 163
7.2 FC Protocol Overview
163
7.3 Network Configuration
164
7.4 FC Protocol Message Framing Structure
164
7.4.1 Content of a Character (byte) 164
7.4.2 Telegram Structure 164
7.4.3 Length (LGE) 165
7.4.4 Address (ADR) 165
7.4.5 Data Control Byte (BCC) 165
7.4.6 The Data Field 165
7.4.7 The PKE Field 166
7.4.8 Parameter Number (PNU) 167
7.4.9 Index (IND) 167
7.4.10 Parameter Value (PWE) 167
7.4.11 Data Types Supported by the Frequency Converter 168
7.4.12 Conversion 168
7.4.13 Process Words (PCD) 168
7.5 Examples
168
7.5.1 Writing a Parameter Value 168
7.5.2 Reading a Parameter Value 169
7.6 Modbus RTU Overview
169
7.6.1 Assumptions 169
7.6.2 Prerequisite Knowledge 169
7.6.3 Modbus RTU Overview 169
7.6.4 Frequency Converter with Modbus RTU 170
7.7 Modbus RTU Network Configuration
170
7.8 Modbus RTU Message Framing Structure
170
Contents VLT® HVAC Drive FC 102 Design Guide
MG16C102 - Rev. 2013-08-20 5