XM0

VAV terminal units control the volume flow in a closed loop, i.e. measurement – comparison – correction.
For volume flow rate measurement the effective pressure is measured first. This is done with a differential pressure sensor. The integral differential pressure transducer transforms the effective pressure into a voltage signal. The actual volume flow rate is available as a voltage signal. The factory setting is such that 10 V DC always corresponds to the nominal flow rate (q_vnom).
The volume flow rate setpoint value comes from a higher-level controller (e.g. room temperature controller, air quality controller, central BMS). Variable volume flow control results in a value between q_vmin and q_vmax. It is possible to override the room temperature control, e.g. by a complete shut-off of the duct.
The controller compares the differential pressure setpoint value to the actual value and controls the actuator accordingly if there is a difference.

Compact controller for VAV terminal units

TR0VM-024T-05I-DD15-MB

Interface configuration of the control component

Depending on the setting, the Modbus communication interface or the analogue interface for the setpoint value specification of volume flows are available here. The so-called interface mode is preset at the factory according to the order key and can be adjusted on site by setting via the menu navigation or the Modbus registers.

Typical interface configuration

By special configuration of the Modbus register Interface-Mode, mixed operations of Modbus operation and analogue operation can be configured. See the description of the interface mode in Modbus register 122.

Supplementary use of the Modbus interface in analogue mode

In analogue mode, only the setpoints at the analogue input are evaluated by the controller. A setpoint specification via the Modbus interface (register 0) is not possible. Any write attempts are acknowledged with an error response. Regardless of the selected interface configuration, however, the other Modbus registers can be used. In this way, the operating values of the actual volume flow rate and damper position can be read out from a higher-level management and control equipment (MCE), with local control using an analogue signal via a connected Modbus. Central override controls can also be triggered.

Communication interface Modbus RTU (operating mode M)

* Factory setting: Modbus address 1

R = register readable

R,W = register readable and writeable

RAM = register value volatile

EEPROM = register value not volatile, but permanently stored (maximum 1 million write operations)

Note:

All registers from register number 100 with storage in the EEPROM are not designed for cyclical write access, e.g. by the building management system. Cyclic write operations are only permitted on registers with storage in RAM.

Detailed information on register 122 (communication interface setpoint/actual value - interface mode)

Detailed information on register 568 (Modbus communication parameters)

** Factory setting: Modbus communication parameters

Commissioning
After installation, wiring and connection of the supply voltage

• When using the Modbus interface: Set Modbus communication parameters via the integrated menu, then the air terminal unit is ready for operation
• Setpoint value default setting via Modbus register
• When using the analogue interface: air terminal unit is immediately ready for use
• Remove terminal cover of the control component only for wiring

Observe volume flow control ranges

• TVE: 4 - 100 % of q_vnom
• TVE-Q: 10 - 100 % of q_vnom
• In particular, do not set values below the minimum volume flow of the control unit

Range of display functions

Display functions

• Actual volume flow rate (unit optionally m³/h, l/s, cfm)
• 3-character display with place value indication
• Status and error display for various operating states, including display of activated override control and diagnosis function

Parameter settings

• Adjustment option for the unit of the volume flow rate display m³/h, l/s, cfm
• Adjustment option for the operating range q_vmin, q_vmax
• Selection of the interface configuration Modbus or analogue, including signal voltage range 0 - 10 V or 2 - 10 V DC. For the variant with RJ12 connection socket, only the interface configuration Modbus is suitable
• Setting option for Modbus communication settings (address, baud rate, stop bits, parity)

Diagnostic functions

• Activation of a test run
• Activation of override controls Open, Closed, q_vmin, q_vmax, motor stop (observe prioritisation)
• Display of the voltage value on the analogue input

Use and description of the display

Table 1: Description of the menu items

Description of status LEDs and error messages

LED flashing signal	Status	Display
	no power supply connected
	Service tool plugged in. On-site network connection deactivated. Forced controls from the service tool have priority
	Undervoltage detected. Supply voltage outside the tolerance range. Control function not guaranteed
	TROX service technicians provide information. Incomplete parameterisation was detected during power-on/reset *
	Drive overload detected (block) *
	Synchronisation drive after Power Up *
	Test mode enabled *
	Overpressure sensor (Overpressure) *
	Setpoint or forced control position not yet reached (display changes between e.g. Hi = high and actual value) *
	Forced control position reached (display changes between e.g. Hi = High and actual value) *
	Offset: Is signalled as long as the drive does not rotate to readjust the setpoint value *

Notes:

1. The signal spans 2 seconds. 1 = LED is illuminated, 0 = LED is not illuminated
2. For service tool plugged in (display: Pc) and undervoltage detected (display: Lou), no special flashing signal appears on the LED button. Instead, one of the operating states marked with an asterisk (*) is displayed.