Type SFTB

SERIES FAN VAV TERMINAL UNITS

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

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

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


Optional equipment and accessories

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

Application

Application

  • VARYCONTROL fan assisted VAV terminal units of Type SFTB for supply air control in constant air volume systems
  • Demand-based mixing of cold primary and warm induced air
  • Closed-loop volume flow control using an external power supply
  • For maximum acoustic and thermal comfort
  • Shut-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 testing
  • Volume 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 unit
  • SFTB-E: Fan VAV with electric reheat
  • SFTB-1: Fan VAV with LPHW coil


Parts and characteristics

  • Ready to commission unit which consists of mechanical parts and control components
  • Averaging differential pressure sensor for volume flow rate measurement
  • Damper blade
  • Integral attenuator
  • Access door for EC fan
  • Factory assembled control components complete with wiring and tubing
  • Aerodynamic functional testing on a special test rig prior to shipping of each unit
  • High control accuracy (even with upstream bend R = 1D)


Attachments


  • Compact controller: Compact unit consisting of controller with differential pressure transducer and actuator
  • TSFB secondary attenuator
  • Hot water coil
  • Electric heater battery


Useful additions

  • Total volume flow grid in TSFB
  • For horizontal installation only
  • The SFTB requires site commissioning by a competent person


Construction features

  • Galvanised sheet steel


Materials and surfaces


  • Casing and damper blade made of galvanised sheet steel
  • Damper blade seal made of TPE plastic
  • Lining is mineral wool and 50 mm thick PU foam
  • Differential pressure sensor made of aluminium
  • Plastic bearings


Mineral wool:


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


Standards and guidelines


  • Casing air leakage tested to EN 1751, Class C
  • Closed blade air leakage:
  • NW 125 - 160
  • EN 1751, Class 3
  • NW 200 - 315
  • EN 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

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


Technical data


  • Nominal sizes 110 - 410
  • Volume flow rate range 50 - 800 l/s
  • Volume flow rate range 180 - 2880 m3/h
  • Approx. 10 - 100% of the nominal volume flow rate
  • Inlet static differential pressure 5 - 1000 Pa
  • Operating 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 central BMS
  • Supply voltage 24V AC/DC
  • Signal voltages 0 - 10V DC
  • Possible override controls with external switches using volt-free contacts: CLOSED, OPEN, Vmin and Vmax
  • Option to factory set the primary air volume flow rates Vmin and Vmax
  • The actual value signal relates to the nominal volume flow rate such that commissioning and subsequent adjustment are simplified
  • Volume flow rate approx. 10 - 100% of the nominal volume flow rate
  • Electrical connections with cable
  • 1 row hot water coil
  • Electric 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 testing
  • Volume 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 steel
  • Damper blade seal made of TPE plastic
  • Lining is mineral wool & 50 mm thick PU foam
  • Differential pressure sensor made of aluminium
  • Plastic bearings

Mineral wool


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

Sizing data


  • VD Discharge (fan) volume flow rate ---------- [l/s]
  • VI Primary air volume flow rate --------------- [l/s]
  • ΔpSD Down stream static pressure ----------- [Pa]
  • ΔpSI Inlet static pressure --------------------- [Pa]
  • NR Guide room NR ----------------------------[NR]


Additional products

Secondary silencer Type TSFB

Variants, Dimensions and weight, Product details

  • Variants
  • DIMENSIONS AND WEIGHT
  • PRODUCT DETAILS

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 ventilation and heating

Materials and surfaces
Electric heaters
  • The electric heater is available as an integral unit complete with controls including fuses and interlocks
  • Integral 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 with magnesium oxide
  • Automatic 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 tested
  • Heater elements are wired back into the control enclosure, including the earth, and heater fuses are supplied
  • Control of the heater for stepless control is by solid state relay

Technical data
  • When 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 the Vmin heating cycle air volume must be maintained for the 10 minute duration after the heater control signal is switched off
  • It 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 controlled ventilation and heating

Materials and surfaces
  • Hot water coils
  • Hot 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 headers
  • Heating coils meet the requirements of British Standards/Codes as applicable
  • Coil connections are 1/2 inch BSPT as a standard
  • Plugged air vent and drain points are provided


Installation and commissioning

  • For horizontal commissioning only
  • The SFTB requires site commissioning by a competent person
  • Return 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 rate accuracy Δqv is dependent on the upstream section.  Duct connections, e.g. branches off the main duct, must comply with EN 1506 and EN 13180. 

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Our department for Service-Requests will contact you asap.
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Tel.: +44 (0)1842 754545 | Fax: +44 (0)1842 763051