XD0

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 volume flow rate actual value 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

Compact controller 227V-024-15-DS3

Product details

Analogue interface 0 – 10 V or 2 – 10 V DC (operating mode V, F)

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

• 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
• The signal voltage range can be adjusted with an adjustment device (by others)

Setpoint value default setting

Operating mode V (variable operation)

• The setpoint comes from an analogue signal on terminal Y
• The selected signal voltage range 0 – 10V or 2 – 10V DC is mapped to the volume flow rate range qvmin – qvmax
• Volume flow rate range qvmin – qvmax is set in the factory according to the order code
• Subsequent adjustment of qvmin or qvmax is possible with an adjustment device

Operating mode F (constant value mode)

• No analogue signal required at terminal Y
• The set flow rate constant value qvmin is used
• Volume flow rate qvmin is set in the factory according to the order code
• Subsequent adjustment of qvmin is possible with an adjustment 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 – qvnom

Override control

For special operating situations, the volume flow controller can be put in a special operating mode (override control). The following modes are possible: control qvmin, control qvmax, damper blade in the OPEN position or damper blade CLOSED.

Override control via signal input Y

With appropriate wiring on the signal input Y, the override controls can be activated according to the connection diagrams via wiring with external switch contacts/relays. OPEN and CLOSE are only available if the controller is supplied with alternating current (AC).

Override control CLOSE using control signal on Y

• With signal voltage range 0 – 10 V DC: CLOSE is activated if qvmin = 0 and the control signal on Y < 0.5 V DC
• With signal voltage range 2 – 10V DC: CLOSE is activated if the control signal is Y < 0.8V (*1) DC (*1) 0.8 V = factory setting

Override control for diagnosis

• For test purposes, override control can also be activated with the service tools (adjustment device, PC software)

Priority of the various setting options

• High priority: Default value setting using the service connector (adjustment device, PC software) for test purposes
• Low priority: Default value setting using the Y signal input on the controller

Commissioning

• On-site adjusting is not required
• As the volume flow rates are factory set, the terminal units have to be installed at the specified locations
• After successful installation and wiring, the controller is ready for use
• Comply with the volume flow rate control ranges of the VAV terminal units, do not set a volume flow rate which is below the minimum flow rate