XM0

Category

• Compact controller for volume flow rate
• Control of a constant or variable volume flow rate setpoint
• Electronic controller for the connection of a reference variable and tapping of an actual value for integration into a Modbus-based building management system
• The actual value relates to the nominal volume flow rate so that commissioning and subsequent adjustment are simplified

Application

• Dynamic transducer for clean air in ventilation and air conditioning systems
• Modbus commands (Modbus operating mode)
• External switching contacts/wiring (with analogue interface)

Supply voltage

• 24 V AC/DC

Actuator

• Integrated; slow-running (running time 100 s for 90°)

Installation orientation

• Either direction

Interface/signalling

• Modbus RTU (RS-485) or alternative analogue signals (0 – 10V or 2 – 10V DC) can be used
• Interface type preset in the factory on the basis of the order code

Connection

• Terminals with cover by rubber cap, therefore no additional terminal box required
• Double terminal for supply voltage for easy further wiring of up to 3 controllers

Interface information

• Modbus: among other things, volume flow setpoint and actual value signal, damper position, override control
• Alternative: Volume flow setpoint and actual value signal as analogue signal

Special functions

• Clearly visible external indicator light for signalling the functions: Set, not set, and power failure
• Display for actual values, parameterisation and for test functions
• Activation q_vmin, q_vmax, closed, open by: Modbus (with Modbus control), external switch contacts (with analogue control)

Parameter setting

• Parameters specific to VAV terminal unit set at the factory
• Operating values: q_vmin, q_vmax and interface type set in the factory
• Subsequent adjustment via display and control element directly on the device or with optional tools: adjustment device, PC software (wired in each case), in Modbus mode as well as via Modbus register access

Factory condition

• Electronic controller factory set on control unit
• Factory setting of parameters
• Functional test under air; certified with sticker

Product details

Modbus operation (operating mode M in the order code)

A smooth exchange of data in the Modbus RTU network (network by others) requires that the communication parameters and the user address for the Modbus interface are set.
The interface offers standardised Modbus register access to the available data points by means of the ReadHoldingRegister (3) and WriteSingleRegister (6) functions.

Setpoint value setting

• In operating mode M, the setpoint is only specified by specifying the volume flow setpoint [%] in Modbus register 0
• The percentage value refers to the volume flow rate range specified by q_vmin - q_vmax defined volume flow rate range
• Volume flow rate range q_vmin - q_vmax set at the factory according to the order code details
• Subsequent adjustment of q_vmin or q_vmax possible in the setting menu on the display, with setting device or via Modbus interface

Note:

Cyclic writing to registers with storage in the EEPROM is not permitted.
This applies in particular to the basic setting parameters for the working range q_vmin (register 105) , q_vmax (Register 106)
and the definition of the interface type (register 122) as well as all other registers from number 100.

Actual value as feedback for monitoring or tracking control

• In Modbus register 7, the current actual volume flow can be called up in the set volumetric flow unit (register 201)
• In addition to the actual volume flow rate, further information can be read out via other Modbus registers;
  Overview see register list
• For diagnostic purposes, the actual volume flow rate can be tapped at terminal U in Modbus mode
• The volume flow rate range 0 – q_vnom always corresponds to the signal voltage range of 2 - 10V DC

Override control

For special operating situations, the volume flow controller can be set to a special operating state (override control). The following modes are possible: control q_vmin, control q_vmax, control damper in open position (OPEN) or control damper closed (CLOSED).

Override control via the Modbus

Specifications are made via Modbus register 1.

Override control through bus failure monitoring

If Modbus communication fails for a specified period of time, a predefined operating state q_vmin, q_vmax, OPEN or CLOSED can be activated.

• The override control to be activated in case of bus failure is defined via register 108
• The determination after which bus failure time the override control is activated is made via register 109
• Any Modbus communication resets the bus failure monitoring timeout

Override controls for diagnosis

Activation via the diagnostic menu on the controller display or via the service tools (setting device, PC software).

Prioritisation of different default options

Specifications for override controls via service tools are prioritised over Modbus specifications.

• Highest priority: Defaults coming from a service tool (service connector), e.g. adjustment device or PC software, for test purposes
• Lowest priority: Defaults coming from Modbus 1 or the diagnosis menu on the controller

Note:
Cyclic writing to registers with storage in the EEPROM is not permitted. This applies in particular to the basic setting parameters for the working range q_vmin (register 105 or 120), q_vmax (register 106 or 121), the definition of the interface type (register 122) and all other registers from number 100.
See also notes on writeability at the end of the Modbus register description.

Analogue operation 0 - 10V DC or 2 - 10V DC (order code, operating mode V, F)

The analogue interface can be set for the signal voltage range 0 - 10V DC or 2 - 10V DC.
The assignment of volume flow setpoint or actual value to voltage signals is shown in the characteristic diagrams.

• The set signal voltage range applies to both setpoint value and actual value signals.
• The signal voltage range is set in the factory according to the order code
• Signal voltage range can be adjusted on site in the setting menu on the display or with the setting device

Setpoint value setting

• In operating mode V (variable operation), the setpoint is only specified with an analogue signal at terminal Y
  
  • Setpoint specifications via Modbus register 0 are rejected
• Selected signal voltage range 0 - 10V or 2 - 10V DC is adjusted to the set volume flow rate range q_vmin – q_vmax assigned to
• Volume flow rate range q_vmin – q_vmax set at the factory according to the order code details
• Subsequent adjustment of q_vmin or q_vmax possible in the setting menu on the display or with the setting device
• In operating mode F (fixed value operation), no analogue signal is required at terminal Y
• The value given by q_vmin is controlled through the fixed volume flow rate
• Volume flow q_vmin set at the factory according to the order code details
• Subsequent adjustment of q_vmin possible in the setting menu on the display or with the setting device

Actual value as feedback for monitoring or tracking control

• The actual volume flow rate measured by the controller can be captured as a voltage signal at terminal U
• The selected signal voltage range 0 – 10 V DC or 2 – 10 V DC is mapped to the volume flow rate range 0 – q_vnom shown
• In analogue mode (operating mode V, F), there is the parallel option of querying operating data via the Modbus interface

Override control

For special operating situations, the volume flow controller can be set to a special operating state (override control). The following modes are possible: control q_vmin, control q_vmax, control damper in open position (OPEN) or control damper closed (CLOSED).

Override controls via signal input Y
With suitable wiring at signal input Y, the override controls can be activated according to the wiring diagrams by wiring with external switching contacts/relays (see wiring examples). OPEN and CLOSE are only available if the controller is supplied with alternating current (AC).

Override control CLOSE using signal input Y

• With signal voltage range 0 - 10 V DC and q_vmin = 0: CLOSE is activated when command signal Y < 0.3 V DC
• With signal voltage range 0 - 10 V DC and q_vmin > 0: No shut-off possible
• With signal voltage range 2 - 10 V DC and q_vmin = 0: CLOSE is activated when command signal Y < 2.3 V DC
• With signal voltage range 2 - 10 V DC and q_vmin > 0: CLOSE is activated when command signal Y < 0.8 V DC
  Between 0.9 V and 2 V, q_vmin regulated.

Override controls in analogue mode via Modbus interface

If the Modbus interface is also connected in analogue mode, override control can also be specified via Modbus register 1.

Override control for diagnosis
Activation via the diagnostic menu on the controller display or the service tools (setting device, PC software).

Prioritisation of different default options
Various override options are prioritised by the controller as follows:

• Highest priority: Defaults coming from a service tool (service connector), e.g. adjustment device or PC software, for test purposes
• Medium priority: Specifications via Modbus register 1 or the diagnostics menu on the controller
• Lowest priority: Specifications via wiring at the Y-signal input of the controlle