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Operating and Maintenance Instructions
Appendix C – Remote Monitoring & Control
By connecting the MDC to a RS485 Modbus master device (e.g. BMS) it is possible to remotely monitor and/or
control the fan array or individual fans within an array.
C.1 Remote Monitoring
The remote monitoring of individual fan parameters is achieved by reading Modbus registers from either the MDC
or directly from the fans. The MDC has dedicated holding registers for each fan in the array, which hold the same
values as those displayed on the LCD. An advantage of using those dedicated registers is that, for example, the
fan speed is available from a single register opposed to reading two registers straight from the fan to obtain the fan
speed.
The monitoring of fan array parameters, such as total power consumption, group alarms, etc is achieved by reading
the MDC Input Registers Addresses 1 thru 6. See Appendix D – Modbus Input Registers
IMPORTANT: Do not attempt to read more than 6 Modbus registers at a time
C.2 Remote Fan Array Control
Remote fan array speed control is achieved via Modbus by changing the value of certain MDC Holding Registers
such as speed or target pressure/volume. The most common Holding Registers used for remote control are:
•
HREG Address 2: Enable/Disable 0-10V Control
o Enable/disable local fan array 0-10V speed control (local potentiometer connected to the MDC)
•
HREG Address 4: Set Speed Register
o Changes the speed of the fan array
•
HREG Address 6: RPM Limit All Fans
o Broadcasts a new RPM limit value to all fans within the fan array
•
HREG Address 16: Target Pressure
o Sets a new target pressure setpoint
•
HREG Address 27: Target Volume
o Sets a new target volume setpoint
See
Appendix E – Modbus Holding
NOTE: Remote fan array control is only available during "Monitor & Control" or "Constant
IMPORTANT: Do not attempt to write more than 6 Modbus registers at a time
C.3 Remote Single Fan Speed Control
To remotely control the speed of a single fan in the array, the MDC must be either set to "Modbus Relay" mode
(see Appendix G – Example of Modbus Relay Operation) or set to "Monitor Only" operating mode and then
have each fan's "Set Value Source" register set to "RS485" via Modbus.
IMPORTANT: During Modbus Relay mode operation, it is possible to read/write more than 6 Modbus
210-OMI14229-Iss2
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Registers
for a full list of registers.
Volume/Pressure" operating modes
registers at a time
Operation & Maintenance Instructions
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