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Electric Unit Heaters Range – Outputs – 3 kW to 27 kW

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The “LEO EL” Electric Unit Heater range from Flexiheat UK

Electric Unit Heaters -are low noise, electrically powered efficient fan heaters for fixed installation that are suitable for warm air heating, drying and /or ventilation of larger areas such as warehouses, factories, depots, shopping centres or individual shops, workshops, storage areas, garages and production facilities. They are often installed where there is no access to another source of heat such as a gas or hot water powered heating system, or for their higher efficiency, as they are 100% efficient and can be supplied with zero carbon energy if renewable electricity is supplied to the heaters. Electrics heaters may be installed in a number of orientations to provide heating for a wide range of larger areas applications, and have 100% energy efficiency.

People sometimes refer to these units as a “fan coil unit electric heater”, but technically they are an “electric unit heater”.

Commercial and Industrial Electric Unit Heaters

We do an extensive range of electric unit heaters at Flexiheat UK, we have 3 ranges within our commercial offering, these are –

  1. Our “LEO EL BMS” range – This is our most popular and best-selling units. They are a commercial and industrial electric unit heater that is the most controllable on the market. These unit heaters are controlled by an intelligent control called the “T Box”. This controller can control up to 31 electric unit heaters, or a mixture of any of our LEO range of water fed unit heaters or our LEO D destratification fans in conjunction with these electric unit heaters. This controller allows advanced control of heating and ventilating system, controlling the units according to your time schedule and individual needs. The “T Box” controller is also BMS (Building Management Control) compatible allowing a central control system to control the operating times and performance of these unit heaters. The largest output of this range is 22.8kW and it maximum height of installation is 9.5 Metres -thus high ceilings installation is achievable.

Installation picture of our industrial electric unit heaters in a warehouse – Flexiheat UK

  1. The “FHIRX” is more of a commercial electric unit heater – this range is a very basic heater, and lacks the controllability of our other heater units, in that they can’t be linked to a BMS system etc, but it is the most economical in the range of our electric unit heaters. The maximum heating output of this range is 12 kW, and their maximum heat throw is 7 metres or 11 metres at maximum fan speed – dependant on the model. This range must be wall mounted only.
  2. A stainless-steel electric unit heater, designated the “FHLB9KW” – This unit is a particularly suited to applications that require IP54 protection is a requirement such as heating farm buildings or barns etc or in any damp or humid areas. It’s heating output range is between 1.8kW to 9kW.
  3. The largest electric unit heaters that we do at present – the “FHTHERM” range -These industrial electric unit heaters, which can be wall or ceiling mounted have the largest heat output at 27kW. They have additional controllers available, but lack the facility to be connected to a BMS system like the LEO EL BMS units can be.

None of these electric heaters should not be used in areas with flammable gases or vapours or powdered metals etc.

Technical data “LEO EL BMS” – Industrial & Commercial Electric Unit Heaters

Heating capacity [kW]6.0 – 10.88.8 / 16.3 / 22.8
Max. air flow [m3/h]2,0004,250
Power supply [V/Hz]3×400
Rated current [A]*15.633.3
IP Protection Rating 20
Sound pressure level [dB(A)]**56.364.1
Sound power level [dB(A)]***71.479.2
 Horizontal range  [m]****1424
Vertical range  [m]*****5.38.3
Type of casing                   powder-painted steel
Colour  grey
Usage                 Inside buildings
Operational temperature of the room [oC]0 to +50
Position of operationvertically on the wall, horizontally under the ceiling
Weight of unit [kg]19.727.8

*Temperature of 0°C at the inlet, 3rd speed of fan
**Acoustic pressure level at the distance of 5 m from the unit, in the room of medium capability of sound absorption and 1,500 m3 of area
***Acoustic power conforms with EN ISO 3744:2011
****Range of horizontal isothermal air stream, at 0.5 m/s velocity limit.
*****Range of vertical non isothermal air stream, at 20°C at the inlet, 0.5 m/s velocity limit

Download the Electric Unit Heaters Brochure – “Leo EL BMS” – Flexiheat UK

Download the Electric LEO EL Unit Heaters Manual

Industrial electric warm air space heater accessories & options

Customers can request that these Leo industrial electric unit heaters be manufactured with stainless steel casing. Many customers request this option for areas with high humidity or aggressive environments.

We also supply a full range of additional accessories, which allow you to mix a proportion of fresh air and recirculated air through these warm air unit heaters via an external wall.

Our Leo electric fan heaters work in conjunction with the KM-EL mixing chamber to deliver fresh (outside) air into the room. It enables the delivery of external air into the building and heat the air flow based on the temperature requirements and direct it inside the building.

There are three air intakes in the chamber: two for recirculation air and one for fresh air. You can smoothly change the amount the damper opens from 0% to 100%.

Mixing chamber for the LEO electric warm air unit heaters

Air mixing chamber for our Leo electric warm air unit heaters

The picture below shows the LEO industrial electric space heater with a fitted air mixing chamber, which draws and mixes fresh and circulated air through the electric unit heater, ensuring the perfect electric heating system for commercial and industrial applications.

Leo EL Electric unit heater with mixing chamber Flexiheat UK

Electric heater coupled up to a air mixing chamber


Full detail on the air mixing chamber / box for our warm air electric unit heaters can be downloaded here –

Flexiheat Manual for Leo KMEL Air Mixing Box

Thermostat temperature and fan speed control 

These industrial electric heaters have two options for temperature control and fan speed control: a basic thermostat with a manual-selected fan speed (please note that this electric heater range can also be used in a ventilation-non-heating mode too). This controller is designated “TS.”.

Basic controller for temperature and fan speed control for our electric unit heaters from Flexiheat UK

Basic temperature and fan speed controller


The second option is a more sophisticated controller that can connect to a building management system (BMS) and control up to 31 electric heaters. It is a full control system on its own, as such, which will automatically ramp up and down the heat settings and fan speeds to suit the temperature set point. It also has a frost protection mode.

T Box building management system compatible controller for our Leo electric unit heaters Flexiheat UK

T Box – BMS compatible controller for our Leo electric heaters

Mounting heights

These electric heaters can be mounted on the wall or hung vertically from the ceiling, as per the detail below.

Ceiling or wall mounting options for our warm air electric fan heater range from Flexiheat UK

Commercial Electric Unit Heaters – Applications & Function

The FHIRX electric unit heater range of low noise, efficient fan heaters for fixed installation for commercial areas are suitable for heating, drying and /or ventilation of these areas. The heat output and fan speed is set via the control panel on this range of electric unit heaters. The adjustable wall mounting brackets allow the air  stream to be directed to suit the site conditions. All of these electric unit heaters are made of corrosion proof housing of white / grey powder coated steel panels, and are the perfect solution for your commercial or industrial electric heating needs.

The FHIRX 6kW to 15 kW Electric unit heaters are not intended for use other than indoors and are only to be wall mounted and for this reason some people refer to them as wall mounted electric blow heaters, for ceiling mounted units that can blow the warm air down vertically , please see our  LEO “EL” range ( above) or “FHTHERM-E Range” , detailed on this webpage page .These electric unit heaters are appropriate for the heating of warehouses, workshops, storage rooms, show rooms, etc.

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The Flexiheat FHIRX Range of Electric Unit Heaters from 3kW to 12kW

Installation time and costs are minimized when using our electric unit heaters as they are compact and completely factory wired, the unit heater only requires only a power supply connection to the heater. These units come with a control box, which should be mounted at point that gives easy access to the operator of the electric fan heaters. Several electric unit heaters may be control via one control box if so required. The controller makes it possible to control the 3 fan speeds and the 2 heat levels of the heaters. We supply as standard the wall mounting bracket and a wireless controller , as a total package for these electric unit heaters, making them ideal solution as a heater for a garage or car workshops.

Commercial Electric Unit Heaters – Technical Information

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Technical data table for the commercial unit heater range – FHIRX – from Flexiheat UK

Our small electric unit heaters provide a “heat throw” of 7 metres at maximum fan speed for the 6 kW Output model, or 11 metres for the larger unit heaters . The intelligent fan control optimizes fan speed and heat output to quickly achieve and control a comfort temperature whilst maintaining a very low noise level. Provides comfort heating while working in garages, workshops and warehouses and a great solution for commercial heating applications

For more information on this range of what we would class as commercial electric unit heaters, please see the following dedicated webpage on these units here – commercial electric unit heaters

Electric Unit Heater in Stainless Steel IP54 Rated 9kW Output 

We also do a stainless steel cased electric unit heater , which has an IP54 rating for electrical protection , and has a maximum output of 9 KW . This electric unit heater is particularity suited to heating farm buildings etc, where IP54 is a requirement or in any damp or humid areas where durability is required .It is also used in dry environments such as in commercial buildings, warehouses, factories, workshops and other places where the IP54 protection standard is required or any other applications where a fire hazard is of particular concern. The Stainless steel housing and the heating elements are made of stainless steel 316H  ( this stainless steel grade has excellent corrosion resistance when exposed to a range of corrosive environments and media. It is usually regarded as “marine grade” stainless steel but is not resistant to warm sea water) and the IP54 rating provide an increased resistance to destructive dust, and  water drops falling at any angle as well as aggressive gases which can cause accelerated corrosion to a non stainless steel cased heater. This 9 kW commercial or industrial electric unit heater has an inbuilt room thermostat to control the temperature and automatic protection against overheating. The step-less variable thermostat and accurately sized fan ensures an even temperature and good heat distribution. These industrial fan heaters can be controlled to give a 1.8 kW , 5.4 kW or  9 kW heat output as a three phase heater and has an inbuilt adjustable thermostat working in the temperature range from 0-40 ° C . It is also prepared for connecting an external thermostat if so required and can be used in a fan only operation to. They also make a perfect electric heater for a garage or workshop heating application.

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Flexiheat Model ” FHLB9KW” Stainless Steel Electric Unit Heater -1.8 kW to 9 kW Output

Output in (kW): 1.8 kW / 5.4 kW / 9 kW

Mains voltage – (V): 3 Phase x 400 volts

Max mains current -(A): 16 Amps

Air circulation – (m²/t): 700 / 1000

Fan diameter – (mm): 300

Dimensions L X B X H – (mm): 670 x 450 x 600

Weight -(Kg’s): 18

IP Rating – IP54

Industrial electric unit heaters – Up to 27 kW of Heat Output 

Last but not least within our range of electric unit heaters are our “FHTHERM-E” units. This range of industrial electric unit heaters have a couple of features that our other units do not have , these being –

  • The ability to be ceiling mounted, blowing the warm air down, as well as horizontally mounted, blowing the warm air horizontally
  • The ability to have a slot warm air diffuser or a discharge cone or nozzle
  • This range goes up to 27 kW of heat output, which is the largest at present that we have
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Flexiheat FHTHERM-E Electric Unit Heater

These two options that are available for ceiling mounted electric unit heaters are shown below – to the right of the standard single row distribution grid, which the units come as default.

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Electric Unit Heaters complete with a Diffuser for vertical or ceiling mounting

NB – The maximum height at which you can mount these warm air electric unit heaters when using the slot diffuser is 4 metres .The discharge cone can also be fitted to the wall mounted industrial fan heater, to give it a larger air throw, if so required.


These industrial electric unit heaters are available in two sizes, both of which require a 3 Phase / 400 Volt supply –

The FHTERM -E 18 – Which is an 18kW maximum heat output, having three output settings of either – 6kW , 12kW or 18kW

The FHTERM -E 27 – Which is a 27kW maximum heat output, having three output settings of either – 9kW , 18kW or 27kW

The full technical details of  this range of electric unit heater range are listed below –

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We also supply a full range of additional accessories for these electric unit heaters, which allow you to mix a proportion of fresh air and recirculated air through the heaters, either via an external wall or a roof intake.

These include – Roof Intakes, Roof Bases, Wall Intakes, Intake Boxes, Suspension Brackets to suit and Air Filters , we go into more depth in the technical manual regarding these additional items . Below are some of the accessories available for the “FHTHERM” wall or ceiling mounted industrial electric unit heaters

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For the full specification and additional information on the “FHTERM” Industrial Electric Unit Heater range, please see it’s dedicate web page

Electric Unit Heaters for Sale UK & Ireland

Should you require anymore assistance or information on our Electric Unit Heater /Industrial & Commercial Electric Unit Heaters / Electric Unit Heaters , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form