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Operating and Maintenance Instructions
Appendix G – Example of Modbus Relay Operation
Initial Configuration Steps
•
BMS Network has slave addresses 1 and 2 available e.g. not taken by any other device
•
Both MDCs have successfully addressed all their respective fans
•
Both MDCs have changed their operating mode to "Monitor & Control" (the control mode is not important)
o See H8 – Operation Mode - Monitor & Control
o This step is purely taken to set all fans to "Modbus" speed control opposed to their factory settings
of "Analogue 0-10V" speed control
•
MDC1 Modbus Slave address is kept at its factory setting value of "1"
•
MDC2 Modbus Slave address has been changed to "2"
o See H18 – Advanced Settings – BMS Settings
•
Both MDCs have changed their operating mode to "Modbus Relay"
o See H10 – Operation Mode - Modbus Relay
Example of setting the speed of Fan 4 (at Fan Array 1) to 100%:
•
Modbus master writes value "65535" to holding hegister 801(hex) of device at Modbus slave address 1
Example of reading the Motor Status Register of Fan 3 (at Fan Array 2):
•
Modbus master reads input register 40B of device at Modbus slave address 2
210-OMI14229-Iss2
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Operation & Maintenance Instructions
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