TVM

Functional description

The VAV terminal unit is fitted with two differential pressure sensors for measuring the volume flow rates, one in the cold air flow and one in the total air flow.

The control components (attachments) include two differential pressure transducers that transform the differential pressure (effective pressure) into an electric signal, two controllers, and two actuators; the control functions can be achieved with a Compact controller or with individual components.

In most cases, the setpoint value for the dual duct terminal unit comes from a room temperature controller.

The room temperature controller 'leads' the cold air volume flow controller and alters the setpoint for the cold air flow rate between 0 and the maximum volume flow V_max. The controller compares the actual value with the setpoint value and alters the control signal of the damper actuator if there is a difference between the two values.

The warm/total air controller is set to the minimum volume flow rate V_min and controls the warm air damper blade. As a consequence, a corresponding proportion of warm air is added. As the demand for cooling increases, the warm air damper blade closes such that eventually only cold air flows.

An integral attenuator reduces the noise that is created by the restriction of the airflow.

The airflow velocity at the room end is, due to the larger rectangular cross section, about half the velocity in the circular duct.

Order example: TVM/160/BF0/E0/300–900 m³/h/0–900 m³/h

Spigot arrangement	90°
Acoustic cladding	Without
Nominal size	160 mm
Attachment	Compact controller
Operating mode	Single
Signal voltage range	0 – 10 V DC
Volume flow rate, warm	300 – 900 m³/h
Volume flow rate, cold	0 – 900 m³/h

 

TVM-S

• VAV terminal unit for the control of variable supply air volume flows
• Connecting spigots for warm and cold air arranged at an angle of 60°

TVM-S-D

• VAV terminal unit with acoustic cladding for the control of variable supply air volume flows
• Connecting spigots for warm and cold air arranged at an angle of 60°
• For rooms where the case-radiated noise of the unit is not sufficiently reduced by a false ceiling
• The circular ducts for the room under consideration must have adequate acoustic insulation (provided by others) on the fan end
• Acoustic cladding cannot be retrofitted

TVM

• VAV terminal unit for the control of variable supply air volume flows
• Connecting spigots for warm and cold air arranged at an angle of 90°

TVM-D

• VAV terminal unit with acoustic cladding for the control of variable supply air volume flows
• Connecting spigots for warm and cold air arranged at an angle of 90°
• For rooms where the case-radiated noise of the unit is not sufficiently reduced by a false ceiling
• The circular ducts for the room under consideration must have adequate acoustic insulation (provided by others) on the fan end
• Acoustic cladding cannot be retrofitted

Installation and commissioning

• Any installation orientation
• Connecting spigots for warm and cold air arranged at an angle of 60° (TVM-S) or 90° (TVM)
• Return edges of the casing with drilled holes suitable for threaded rods

Upstream conditions

The volume flow rate accuracy ΔV applies to a straight upstream section of the duct. Bends, junctions or a narrowing or widening of the duct cause turbulence that may affect measurement. Duct connections, e.g. branches off the main duct, must comply with EN 1505. Some installation situations require straight duct sections upstream.

Space required for commissioning and maintenance

Sufficient space must be kept clear near any attachments to allow for commissioning and maintenance. It may be necessary to provide sufficiently sized inspection access openings.

Principal dimensions

ØD [mm]

VAV terminal units made of stainless steel: Outside diameter of the spigot

VAV terminal units made of plastic: Inside diameter of the connecting spigot

ØD₁ [mm]

Pitch circle diameter of flanges

ØD₂ [mm]

Outside diameter of flanges

ØD₄ [mm]

Inside diameter of the screw holes of flanges

L [mm]

Length of unit including connecting spigot

L₁ [mm]

Length of casing or acoustic cladding

B [mm]

Duct width

B₁ [mm]

Screw hole pitch of flange (horizontal)

B₂ [mm]

Outside dimension of flange (width)

B₃ [mm]

Width of device

H [mm]

Duct height

H₁ [mm]

Screw hole pitch of flange (vertical)

H₂ [mm]

Outside dimension of flange (height)

H₃ [mm]

Unit height

n [ ]

Number of flange screw holes

T [mm]

Flange thickness

m [kg]

Unit weight including the minimum required attachments (e.g. Compact controller)

Acoustic data

f_m [Hz]

Octave band centre frequency

L_PA [dB(A)]

A-weighted sound pressure level of air-regenerated noise of the VAV terminal unit, system attenuation taken into account

L_PA1 [dB(A)]

A-weighted sound pressure level of air-regenerated noise of the VAV terminal unit with secondary silencer, system attenuation taken into account

L_PA2 [dB(A)]

A-weighted sound pressure level of case-regenerated noise of the VAV terminal unit, system attenuation taken into account

L_PA3 [dB(A)]

A-weighted sound pressure level of case-regenerated noise of the VAV terminal unit with acoustic cladding, system attenuation taken into account

All sound pressure levels are based on 20 μPa.

Volume flow rates

V_nom [m³/h] and [l/s]

Nominal volume flow rate (100 %)

• The value depends on product type and nominal size
• Values are published on the internet and in technical leaflets, and stored in the Easy Product Finder design software.
• Reference value for calculating percentages (e.g. V_max)
• Upper limit of the setting range and maximum volume flow rate setpoint value for the VAV terminal unit

V_{min unit} [m³/h] and [l/s]

Technically possible minimum volume flow rate

• The value depends on product type, nominal size and control component (attachment)
• Values are stored in the Easy Product Finder design software
• Lower limit of the setting range and minimum volume flow rate setpoint value for the VAV terminal unit
• Depending on the controller, setpoint values below V_{min unit} (if V_min equals zero) may result in unstable control or shut-off

V_max [m³/h] and [l/s]

Upper limit of the operating range for the VAV terminal unit that can be set by customers

• V_max can only be smaller than or equal to V_nom
• In case of analogue signalling to volume flow controllers (which are typically used), the set maximum value (V_max) is allocated to the setpoint signal maximum (10 V) (see characteristic)

V_min [m³/h] and [l/s]

Lower limit of the operating range for the VAV terminal unit that can be set by customers

• V_min should be smaller than or equal to V_max
• Do not set V_min smaller than V_{min unit}, otherwise the control may become unstable or the damper blade may close
• V_min may equal zero
• In case of analogue signalling to volume flow controllers (which are typically used), the set minimum value (V_min) is allocated to the setpoint signal minimum (0 or 2 V) (see characteristic)

V [m³/h] and [l/s]

Volume flow rate

ΔV [± %]

Volume flow rate tolerance from setpoint value

ΔV_warm [± %]

Volume flow rate tolerance for the warm air flow of dual duct terminal units

Differential pressure

Δp_st [Pa]

Static differential pressure

Δp_st min [Pa]

Static differential pressure, minimum

• The static minimum differential pressure is equal to the pressure loss of the VAV terminal unit when the damper blade is open, caused by flow resistance (sensor tubes, damper mechanism)
• If the pressure on the VAV terminal unit is too low, the setpoint volume flow rate may not be achieved, not even when the damper blade is open
• Important factor in designing the ductwork and in rating the fan including speed control
• Sufficient duct pressure must be ensured for all operating conditions and for all terminal units, and the measurement point or points for speed control must have been selected accordingly to achieve this

Construction

Galvanised sheet steel

• Casing made of galvanised sheet steel
• Parts in contact with the airflow as described for the product type
• External parts, e.g. mounting brackets or covers, are usually made of galvanised sheet steel

Powder-coated surface (P1)

• Casing made of galvanised sheet steel, powder-coated RAL 7001, silver grey
• Parts in contact with the airflow are powder-coated or made of plastic
• Due to production, some parts that come into contact with the airflow may be stainless steel or aluminium, powder-coated
• External parts, e.g. mounting brackets or covers, are usually made of galvanised sheet steel

Stainless steel (A2)

• Casing made of stainless steel 1.4201
• Parts in contact with the airflow are powder-coated or made of stainless steel
• External parts, e.g. mounting brackets or covers, are usually made of galvanised sheet steel