HRFL II – Ceiling Void MVHR Unit

HRFL II – Ceiling Void MVHR Unit

Ceiling Void MVHR unit 0.03m3.s-1 (108m3.h-1 ) – 0.57m3.s-1 (2050m3.h-1 )

Applications: Commercial | School | University | Retail | Office Buildings | Hotels | Banking | Leisure

The HRFL II MVHRU is a next generation, all-in-one, ceiling void MVHR unit. This mechanical heat recovery and ventilation system has been specifically designed for false ceiling installation. It is a fully packaged solution which benefits from a compact, slim design to suit the increasingly stringent requirements for local ventilation systems installed in ceiling voids.

Highly efficient, with near silent operation, the HRFL II range is equipped with state-of-the-art plug and play integral controls.

Download the Therm-X Sales Brochure

Download the Therm-X HRFL II Technical Manual

Download the MVHRU Accessories Manual

Download the MVHRU Installation and Operation Manual


The ThermX HRFL II unit casing is assembled from a self-supporting frameless construction, manufactured with double skinned, corrosion resistant, 30mm deep hot dip galvanized sandwich panels (thick.: 0.8mm) packed with high density rockwool (88 kg.m-3) and sealed with a high tightness EPDM closed cell gasket.
The bottom panels are finished with an RAL 9010 powder coated paint to allow exposed installation.


The unit is suitable for indoor installation by suspension on the ceiling void and is supplied as standard with factory fitted support brackets equipped with anti-vibration mounts to ensure a quick and reliable installation.

Access and maintenance

Access to all the unit compartments is available through the bottom tool operated access panels as standard. All access panels are equipped with hinges and handles to facilitate handling during maintenance operations.

All the panels are fully removable allowing access to the plate heat exchanger, drain tray, fan, filter and ancillary coil sections and facilitating access for periodic inspection. The control panel is easily accessible within an enclosure on the outside of the unit.

Heat recovery
  • Highly efficient counterflow plate heat exchanger exceeding the 2018 ErP requirements
  • Operational efficiency up to 93%
  • Eurovent certified performance and tested to EN308:1997
  • Manufactured from high thermal transmittance and corrosion resistant aluminium
  • Face and bypass damper
  • Minimal internal leakage ensured by the double sided inner seals
  • Integrated multi-step anti-freeze logic
  • Single inlet backwards curved radial impellers manufactured from aluminium
  • Energy efficient IE4 electronically commutated (EC) motors with integrated electronic control and silent operation
  • Optimised impellers balanced to DIN / ISO 1940
  • ErP 2015 ready
  • Integral control electronics – soft start, over temperature and short circuit protection
  • Motor insulation class ‘B’, rated IP 54 (acc. To EN 60529)
  • Plastic frame pleated panel filters
  • Synthetic media for low-pressure drop reducing overall unit energy consumption
  • Filtration grade according to BS EN 779:2012/ISO 16890 is F7 (ePM2.5 50%) supply filter and M5 (ePM10 50%) return filter. F9 (ePM2.5 80%) supply filter is available as an option.
  • Filter status monitored by integral digital pressure sensors
  • Installed in slides and sealed for easy replacement and minimised bypass leakage
Controls & communication

HRFL II features state of the art plug and play integral controls with a touch screen wired controller. The interface for BMS connection is via Modbus RS485, Modbus TCP/IP and Bacnet TCP/IP.

The intelligent, inbuilt controls include (not an extensive list):

  • Integral temperature and pressure sensors
  • Touchscreen controller
  • Mains isolator
  • CAV (Constant Air Volume)
  • VAV (Variable Air Volume) – Constant Pressure Supply Duct
  • DCV (Demand Controlled Ventilation)
  • Trickle & Boost mode
  • Time scheduling
  • Airflow offset
  • Supply and room air temperature control
  • Automatic free-cooling regime
  • Modulation of bypass and up to 2 pre-heaters and post-heaters/coolers
  • Modulation of external heatpump
  • Overheat, condensate overflow and frost protection
  • Automatic calibration of fans and filters
  • Service, maintenance and error alarms
  • Commissioning mode with component testing
  • Soft start
  • Fire interlock
  • PID tuning
Optional features

The  following options, if selected, are all fully integrated into the unit controls:

  • Integral electrical pre-heater (frost coil)
  • Integral electrical post heater
  • Integral LPHW post heater
  • External modular pre and post heater/cooler:
    • WCO (Water changeover)
    • DX (Direct Expansion)

Vast range of ancillaries available for the HRFL II range:­

  • Motorised shut off dampers
  • Backdraft dampers
  • Square to round duct transitions­
  • Threaded rods­
  • Duct mounted attenuators­
  • Spare filters­
  • Duct mounted electrical or water heaters­
  • Condensate pump kit­
  • Condensate syphon­
  • Damper actuators­
  • Duct and room mounted IAQ sensors (CO2, humidity)­
  • PIR motion sensor­
  • Valve kits
Tested for your complete peace of mind
  • Performance – ISO 5801:2007
  • Acoustics – BS EN 3744:2010, BS EN ISO 5136:2010
  • Heat Recovery – EN 308:1997
Building regulations and eco-design directive

All models are performance tested, and measurements are made to obtain the power consumption of the units in several operating points. The units can work within the limits of both of these regulations under most conditions. Detailed software selection can be provided to get accurate performance data.

The set-up of the controls on the Therm-X unit can be performed by one of our experienced commissioning teams.
We offer the following options to perform the commissioning of your Therm-X units:

Site attendance for demonstration of controls set-up

With this option one of our experienced engineers will attend to site for one day and demonstrate how to calibrate and set the controls for one Therm-X unit.

Site attendance for controls set-up

With this option one of our experienced engineers will attend to site to check the installation and wiring of every unit as well as calibrate and set up the controls to the required project design conditions.
For additional information about our commissioning options please contact our offices.

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