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Operating and Maintenance Instructions
5.3.3 Monitor mode: pressure sensor connection – differential pressure or volume measurement
Figure 10 - Typical wiring diagram for Monitor operating mode – using external sensor monitoring
Note: On the diagram above, the MDC must be powered using an external 24VDC supply to provide
power to the DS85 sensor. Alternatively, the DS85 sensor can be powered externally in case it is desired to
supply the MDC with a voltage below +24VDC. However, GND connections must be shared between the
DS85 external supply and the MDC's supply.
5.4 Monitor & Control mode
5.4.1 General
In "Monitor & Control" operating mode, the fans will no longer respond to a separate speed signal, such as a 0-10V
analogue input signal connected to the Analogue input terminal at the fan. In this mode, the fan speed is entirely
controlled by the MDC via Modbus. The MDC can receive an analogue input signal to set the speed to all fans
within the array, or the fan speeds are set by a Modbus master writing to the MDC's Holding Register 4, or locally
by using the MDC's keypad.
In "Monitor & Control" operating mode three control options are available:
0-10V Input control
The MDC is configured to respond to a 0-10VDC input voltage from an external source. This can be from either a
BMS or from a 10kΩ potentiometer using a +10VDC supply.
MODBUS Control
The MDC is configured to receive Modbus commands from a BMS or an application controller to set speed of the
fan array using the MDC's Holding Register 4. The MDC will relay the new set point to the fan array whilst
retaining the monitoring and alarm functionality.
Keypad – Manual operation
It is possible to control the fans by setting the speed using the keypad. If this option is chosen, a new submenu
called "Set Speed" will become available inside the Main Menu, where it is possible to set the speed of all fans
using the keypad. See H11 – Keypad Control.
5.4.1.2 Measuring the fan performance using a pressure sensor
When "Monitor & Control" operating mode is selected it is also possible to connect a DS85 differential pressure
sensor to the 0-10V input terminal on the controller and use this to display the current pressure in the fan array or
to calculate the total volume flow. If that is the case, the MDC's 0-10V Input control mode will become unavailable
as it will be used to read output voltage from the sensor.
210-OMI14229-Iss2
© ebm-papst UK Ltd 2018
Operation & Maintenance Instructions
Chelmsford Business Park Chelmsford Essex CM2 5EZ
Telephone: +44(0)1245468555 Fax: +44(0)1245466336
e-mail
sales@uk.ebmpapst.com
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