Application

Application

VARYCONTROL fan assisted VAV terminal units of Type SFTB for supply air control in constant air volume systemsDemand-based mixing of cold primary and warm induced airClosed-loop volume flow control using an external power supplyFor maximum acoustic and thermal comfortShut-off by means of switching (equipment supplied by others)

Special characteristics

Integral differential pressure sensor with 3 mm measuring holes (resistant to dust and pollution)Factory set-up or programming and aerodynamic function testingVolume flow rate can later be measured and adjusted on site; additional adjustment device may be necessary

Nominal sizes

110, 210, 310, 410

Description

Variants

SFTB: Fan VAV terminal unitSFTB-E: Fan VAV with electric reheatSFTB-1: Fan VAV with LPHW coil

Parts and characteristics

Ready to commission unit which consists of mechanical parts and control componentsAveraging differential pressure sensor for volume flow rate measurementDamper bladeIntegral attenuatorAccess door for EC fanFactory assembled control components complete with wiring and tubingAerodynamic functional testing on a special test rig prior to shipping of each unitHigh control accuracy (even with upstream bend R = 1D)

Attachments

TYPE SFTB

SERIES FAN VAV TERMINAL UNITS

For supply air systems with constant volume and mixing of primary and inducedair.

Series fan VAV terminal units take primary and induction air, mix the twothoroughly and provide a constant air supply to the occupied zone of the building.

ErP2015 compliant fans and Part L 2013 compliantHigh control accuracy even with upstream bend (R=1D)Discharge and case radiated sound pressure levels of NR35 can beachieved in the occupied zone

Optional equipment and accessories

Secondary silencer Type TSFB for the reduction of air-regenerated noiseHot water coil or electric heater for reheating the airflow

Compact controller: Compact unit consisting of controller with differential pressure transducer and actuatorTSFB secondary attenuatorHot water coilElectric heater battery

Useful additions

Total volume flow grid in TSFBFor horizontal installation onlyThe SFTB requires site commissioning by a competent person

Construction features

Galvanised sheet steel

Materials and surfaces

Casing and damper blade made of galvanised sheet steelDamper blade seal made of TPE plasticLining is mineral wool and 50 mm thick PU foamDifferential pressure sensor made of aluminiumPlastic bearings

Mineral wool:

To EN 13501, fire rating class A1, non-combustibleRAL quality mark RAL-GZ 388Bio-soluble and hence hygienically safe according to the German TRGS 905 (Technical Rules for Hazardous Substances) and EU directive 97/69/EGFaced with glass fibre fabric as protection against erosion through airflow velocities of up to 20 m/sInert to fungal and bacterial growth

Standards and guidelines

Casing air leakage tested to EN 1751, Class CClosed blade air leakage:NW 125 - 160EN 1751, Class 3NW 200 - 315EN 1751, Class 4

Maintenance

Maintenance-free as construction and materials are not subject to wear

TECHNICAL INFORMATION

Function, Technical data, Quick sizing, Specification text, Order code, Related products

Functional description

The fan assisted VAV terminal unit has a fan running at a constant design air volume and draws a mixture of primary air and induction air through the unit. By adjusting the amount of primary air supplied to the unit the ratio of primary to induced air is changed.

The primary air VAV terminal unit is fitted with a differential pressure sensor for measuring the volume flow rate. The control component (attachments)consists of a VAV compact controller which includes a differential pressure transducer that transforms the differential pressure (effective pressure) into anelectronic signal, a volume controller, and an actuator.

For most applications, the setpoint value comes from a room temperature controller. The VAV compact controller compares the actual value with thesetpoint value and alters the position of the actuator if there is a difference between the two values.

This specification text describes the general properties of the product.

Specification text

Series fan VAV boxes Type SFTB for constant room air supply volume combined with VAV primary air control having high turndown by use of a multi-point flow-grid. Induction of warm air from the ceiling void by forward curved blade centrifugal fan with direct drive motor. Single blade control damper with seal for shut off. Stepless speed controller to enable fan duty to be set to match the downstream duct system pressure.

Construction

Galvanised sheet steelRectangular casing

Spigot connection on the fan end suitable for circular ducts to EN 1506 or EN 13180Connection on the room end suitable for air duct profiles Position of the damper blade indicated externally at shaft extensionThermal and acoustic insulation (lining) minimum 50 mm mineral wool PU foam Class O rated and splitters from polymer foam

Technical data

Nominal sizes 110 - 410Volume flow rate range 50 - 800 l/sVolume flow rate range 180 - 2880 m3/hApprox. 10 - 100% of the nominal volume flow rateInlet static differential pressure 5 - 1000 PaOperating temperature 10 - 50 °C

Attachments

Variable volume flow control with electronic Compact controller to connect an external control signal; actual value signal can be integrated into the centralBMSSupply voltage 24V AC/DCSignal voltages 0 - 10V DCPossible override controls with external switches using volt-free contacts: CLOSED, OPEN, Vmin and VmaxOption to factory set the primary air volume flow rates Vmin and VmaxThe actual value signal relates to the nominal volume flow rate such that commissioning and subsequent adjustment are simplifiedVolume flow rate approx. 10 - 100% of the nominal volume flow rateElectrical connections with cable1 row hot water coilElectric heater battery 1 Phase or 3 Phase

Special Characteristics

Integral differential pressure sensor with 3 mm measuring holes (resistant to dust and pollution) Factory set-up or programming and aerodynamic function testingVolume flow rate can later be measured and adjusted on site; additional adjustment device may be necessary

Materials and surfaces

Casing and damper blade made of galvanised sheet steelDamper blade seal made of TPE plasticLining is mineral wool & 50 mm thick PU foamDifferential pressure sensor made of aluminiumPlastic bearings

Mineral wool

To EN 13501, fire rating Class A1, non-combustible RAL quality mark RAL-GZ 388Bio-soluble and hence hygienically safe according to the German TRGS 905 (Technical Rules for Hazardous Substances) and EU directive 97/69/EGFaced with glass fibre fabric as protection against erosion through airflow velocities of up to 20 m/sInert to fungal and bacterial growth

Sizing data

V Discharge (fan) volume flow rate ---------- [l/s]V Primary air volume flow rate --------------- [l/s]Δp Down stream static pressure ----------- [Pa]Δp Inlet static pressure --------------------- [Pa]NR Guide room NR ----------------------------[NR]

D

I

SD

SI

Variants, Dimensions and weight, Product details

Additional products

Secondary silencer Type TSFB

SFTB: Fan VAV terminal unit

Fan VAV terminal unit for constant volume supply with mixing of primary and induced air for cooling or demand controlled ventilation

SFTB-E: Fan VAV terminal unit with electric reheat

Fan VAV terminal unit for constant volume supply with mixing of primary and induced air for cooling or demand controlled ventilationand heating

Materials and surfacesElectric heaters

The electric heater is available as an integral unit complete with controls including fuses and interlocksIntegral air heater has elements designed for black heat operation and consists of 80/20 nickel chrome wire in a stainless steel tube (Grade 312) filled withmagnesium oxideAutomatic and manual reset high temperature cut out are fitted and a brass earth stud included.Manufactured to British Standards/Codes as applicable and fully factory testedHeater elements are wired back into the control enclosure, including the earth, and heater fuses are suppliedControl of the heater for stepless control is by solid state relay

Technical dataWhen heating is required it is recommended that the primary air should be at Vmin! It is strongly recommended that the BMS is used to monitor the state of the high temperature cut outs! Run-on Time: The control strategy for the heater must allow a minimum of 10 minutes fan run-on time to allow the heater to cool safely. During this time theVmin heating cycle air volume must be maintained for the 10 minute duration after the heater control signal is switched offIt is recommended that the heater output is limited by a supply air temperature sensor to prevent overheating and room supply air stratification

SFTB-1: Fan VAV terminal unit with LPHW coil

Fan VAV terminal unit hot water heat exchanger for constant volume supply with mixing of primary and induced air for cooling or demand controlledventilation and heating

Materials and surfacesHot water coilsHot water heating coil is manufactured from 3/8 inch diameter copper tube with aluminium fins spaced at 1.8 mm (14 fpi)Tubes are formed into circuits to limit water velocity and mounted in a galvanised sheet steel flanged frame with copper headersHeating coils meet the requirements of British Standards/Codes as applicableCoil connections are 1/2 inch BSPT as a standardPlugged air vent and drain points are provided

Installation and commissioning

For horizontal commissioning onlyThe SFTB requires site commissioning by a competent personReturn edges of the casing with drilled holes suitable for M10 threaded rods

Upstream conditions

The effective pressure, which is decisive for the volume flow rate, is recorded and averaged on the control damper blade. Therefore, the volume flow rateaccuracy Δqv is dependent on the upstream section. Duct connections, e.g. branches off the main duct, must comply with EN 1506 and EN 13180.