Functional description

VAV terminal units control the volume flow in a closed loop, i.e. measurement – comparison – control.

The volume flow rate is determined by measuring the differential pressure (effective pressure). For this purpose the VAV terminal unit is fitted with a differential pressure sensor.

The integral differental pressure transducer transforms the effective pressure into a voltage signal. The volume flow rate actual value is hence available as a voltage signal. The factory setting is such that 10 V DC always corresponds to the nominal volume flow rate (V_nom).

The volume flow rate setpoint value comes from a higher-level controller (e.g. room temperature controller, air quality controller, central BMS) or from switch contacts. Variable volume flow control results in a value between V_min and V_max. It is possible to override the room temperature control, e.g. by a complete shut-off of the duct.

The controller compares the volume flow rate setpoint value to the actual value and controls the integral actuator accordingly.

The volume flow rate parameters V_min and V_max are factory set on potentiometers. Voltage ranges are factory stored in the controller. Changes on the customer's site can easily be carried out using an adjustment device or a notebook with service tool.

Volume flow control

• The volume flow controller works independent of the duct pressure
• Differential pressure fluctuations do not result in permanent volume flow rate changes
• To prevent the control from becoming unstable, a dead band is allowed within which the damper blade does not move.
• The factory set volume flow rate parameters can be altered by the customer

Application

• Electronic volume flow controller VRD3 as Universal controller
• Variable air or constant air volume flow control
• The flow rate is measured using the dynamic measurement principle
• Voltage range for the actual and setpoint value signals 0 – 10 V DC or 2 – 10 V DC
• Separate inputs for override controls enable the centralised switching of groups of controllers

Construction

Volume flow controller VRD3 with

• B13: Actuator NM24A-V for TVR, TVJ, TZ-Silenzio, TA-Silenzio TVZ, TVA
• B11: Actuator SM24A-V for TVT
• B1B: Spring return actuator NF24A-V for TVR, TVJ, TVT, TZ-Silenzio, TA-Silenzio TVZ, TVA
• B27: Actuator NM24A-V for TVM

Signal voltage range

• 0: 0 – 10 V DC
• 2: 2 – 10 V DC with shut-off function (< 0.1 V DC)

Operating modes

E: Single and M: Master

• V_min: Minimum volume flow rate
• V_max: Maximum volume flow rate

S: Slave operation

• V_min: 0 %
• V_max: Volume flow rate ratio to the master controller

F: Constant value

• V_min: constant volume flow rate
• V_max: 100 %

Parameters are factory set. The customer defines the required operating mode and the volume flow rates in the order code at the time of ordering. The jumper for input w is factory set to VRD3.

Commissioning

• On-site adjusting is not required
• When installing the VAV terminal units it is important to assign each room the correct unit based on the ordered volume flow rates
• After successful installation and wiring the controller is ready for use
• The volume flow rate parameters V_min and V_max can be adjusted at a later stage using a potentiometer or an adjustment device

Volume flow controller VRD3

Actuators NM24A-V and NM24A-V-ST

Actuators SM24A-V and SM24A-V-ST

Spring return actuators NF24A-V and NF24A-V-ST

Application

• Electronic volume flow controller GUAC-D3 as Universal controller
• Variable air or constant air volume flow control
• The flow rate is measured using the dynamic measurement principle
• Voltage range for the actual and setpoint value signals 0 – 10 V DC or 2 – 10 V DC

Construction

XC3: Volume flow controller GUAC-D3 with spring return actuator 361C-024-20-V/ST07 for TVR, TVJ, TVT, TZ-Silenzio, TA-Silenzio, TVZ, TVA

Signal voltage range

• 0: 0 – 10 V DC
• 2: 2 – 10 V DC with shut-off function (< 0.8 V DC)

Operating modes

E: Single and M: Master

• V_min: Minimum volume flow rate
• V_max: Maximum volume flow rate

S: Slave operation

• V_min: 0 %
• V_max: Volume flow rate ratio to the master controller

F: Constant value

• V_min: constant volume flow rate
• V_max: 100 %

Parameters are factory set. The customer defines the required operating mode and the volume flow rates in the order code at the time of ordering.

Commissioning

• On-site adjusting is not required
• When installing the VAV terminal units it is important to assign each room the correct unit based on the ordered volume flow rates
• After successful installation and wiring the controller is ready for use
• The volume flow rate parameters V_min and V_max can be adjusted at a later stage using a potentiometer or an adjustment device

Volume flow controller GUAC-D3

Spring return actuator 361C-024-20-V