Overdoor heaters and air curtains

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Over door heaters from Flexiheat UK

Over door heaters? what are they and what are they designed to do?

Over door heaters are fan heaters that are designed to provide effective heating with warm or hot air around the location they installed, typically they are used above doorways or even more often an open door, and mounted to the ceiling.

People often confuse these units with air curtain -but these are not the same –an air curtains primary function is to literally provide a high velocity air stream, that prevents the warmed air escaping from an open door or doorways. Thus, they are called warm air curtains by many when they have a heater fitted to the air curtain to heat the wider space.

But, the down side of over door heaters, is that if they are installed on a ceiling over an open door or doorways – then there’s nothing to stop the hot air escaping via that open door! Which means your both wasting money and adding to your energy costs of your building

Over door heaters ensure a warm and welcoming environment for your customers, employees or visitors, not only do they increase the air temperature, but when they also have an air curtain function built into the model like our Elis Duo model (which is both an over door heater and air curtain combined into one model)– then they ensure reduced heat losses which occur with continuous opening of the doors in busy locations, resulting in energy savings and safety benefits too.

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Over door heater and air curtain combined in one unit by Flexiheat UK

Not only do the increase the temperature of the room or area they are installed in, but with the appropriately sized air curtain element of this door heater providing an invisible air barrier you’re ensuring a warm welcome and a cosy environment for customers to walk into, with our door heaters air curtains.

When you’re installing an over door heater, it can help your business attract new customers, as they ensure an enhanced customer experience whilst entering your business, and make a great first impression making them an ideal solution for petrol stations, shops, cafes, restaurants or waiting areas in dental and doctor surgeries, veterinary practices, car garages etc and ensure an open door policy for any retail or leisure business.

We can cover single doors or double doorways or an open front entrance – basically they are suitable for any doors or entrances you may have, with our stylish over door heater / air curtain model.

They can be wall mounted above the doorway space, as they benefit from a compact design, they can be installed in small spaces with their curved end panels they make the over door heater an unobtrusive and aesthetically pleasing addition to any door way, whilst keeping the cold air out with their electric heating elements or hot water heating elements.

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So, let’s look at the two elements that make up our over door heater and air curtain

Door Heaters – hot water heating

The door heater side of the Elis Duo model can provide efficient heating all year round if so required, but predominately used in the winter. They are available with either electric heating elements or hot water heating elements, and can be mounted in a modular format, allowing you cover single doors or double doorways.

The  two types we do are the – “E” – donates electric powered, and the “W” donates warm water fed overdoor heaters units.
100 or 200 is the length of the overdoor heaters in centimetres

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Over door heater and air curtain combined duo range – technical data Flexiheat UK

Download the Over Door Heaters Brochure “Elis Duo” from Flexiheat UK

Overdoor heater – electrical heater / heating element

These electrical heaters require a 3 Phase electric power supply, as this is the only electric supply that has the capability of getting the required heat output from the door heaters – single phase just won’t do the heating capacity to get to the desired temperature for the electric fan heaters, that is the primary function of the electric over door heaters element of the unit. This is ultimately the reason that these electric over door heaters are usually only used in commercial premises that have a 3 Phase electrical supply available to the property.

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An electric over door heater combined air curtain model from Flexiheat UK (air flow for the air curtain is provided by the void above the false ceiling)

These are electric air curtains / electric fan heater combination models , are available in 1 metre long lengths, can be used in a modular configuration, to cover various over door widths.

The electric over door heaters – has two kW output figures – one for the air curtain side – which is 9.9 kW and the overdoor heater output is 14.7 kW

Hot water heat exchanger powered heater range

The heat output for the water heated model, depends on the flow and return temperature to the door heater / air curtain combination unit, and the entering air temperature to the device. Following are some typical heating heating system temperatures, and the heat outputs you will achieve.

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Elis Duo water heating capacity data chart


For other temperatures such as for use with heat pump systems, please contact us and we can run this through our calculation program and produce the performance data for you.

These overdoor heaters have multiple heat settings on the door heating side of the model and can be considered a high level fan heater as such – with a heat output range from 10.1 kW to 33.2 kW, (depending if its electric or hot water heat source) the heat generated by the high level fan heater is blown into the range of environments from small shops, offices, petrol or service stations restaurants, public or office buildings etc.


Air curtain range

The air curtain element of the model, not only supplies a high velocity air stream or invisible air barrier, that prevents air from entering the internal space of the shop. This high velocity air stream not only ensures a warm welcome but also ensures the warm air inside does not escape the room, leading to heat loss from the doorway.

This air curtain with its heating element, provides a warmer welcome with an invisible barrier of warm air, from the ceiling level being pushed down to floor level, over the door or doors of your shop entrance for example.

This ensures the space being protected by the air curtain, doesn’t lose the warm air that the door heater side of the model has produced, resulting in greater energy efficiency, as no warm air is lost through the doorway or entrance being open to the cold air that we experience in the winter periods in the UK.

This keeps the space protected as such, with the fan of the air curtain providing a high velocity air stream or continuous wall of air, that keeps the different temperatures of the two environments separate at the doorway – meaning the internal space of your shop or business retains its heat and prevents the cold air

Alternatively in the summer time, this air curtain range can be used in a non-heating mode, blowing ambient air out via the powerful fan resulting in the entrance being protected from the warm exterior air ingress into your shop, and keeping your customers or staff happy.

The powerful and efficient fan used on these commercial air curtains (sometimes referred to as a screen heater by some customers) mean that they can be used on doors up to 2.5 metres high.

The over door heaters don’t have to be ceiling mounted as we also a wall mounting bracket set.

In the summer the fan can be used without the heaters on – making it an ambient air curtain – and keep insects, bugs and flies out of shops with an open door policy for passing trade.

The over door heaters don’t have to be ceiling mounted as we also a wall mounting bracket set.

install detail for over door heaters; air curtains;

Over door heaters install information – Flexiheat UK


The controls system – the T-box controller is an advanced control system which enables the connection of the over door heaters / air curtains to an intelligent BMS system (Building Management System)

The T-Box remote control can control both the air curtain or over door heater separately or together to suit the customers temperature requirements. This is usually installed in a location that can sense the average temperature of the room being heated.

You can also place the remote control in a shop’s mangers office for example or a building control room, so that access is restricted to the over door heaters control. You can then install a separate thermostat in internal space, which monitors the temperature in the room, and sends this information to the supplied T- box remote control.

You can control up to 31 units from one remote control – should the need arise

Controls system set up schematic –

NB – SQR motorized valves are only used on the water heated versions

Commercial over door heaters;

Elis Duo controls schematic for commercial over door heaters

Over door Heater


Modern design of the heater makes it especially suitable for buildings with high aesthetic values, resulting in a warm and welcoming environment.


Wherever there is a need of heating the room while providing an air barrier for the door opening (which prevents heat loss) e.g., small grocery stores, petrol or service stations, hairdressers, estate agents etc.

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Over door heater and air curtain combination heater from Flexiheat UK

Air curtains control system:

Basic operation of  these commercial air curtains the is ensured by the built-in connection terminal. The advanced external control system enables communication and integration with a BMS (Building Management System)


Functionality the 2-in-1 device ensures an air barrier at the door opening while heating the room simultaneously – via high powered velocity air curtains

Design – the modern design of these commercial door heaters was developed in cooperation with an experienced team of industrial designers.

Construction – the use of aluminium for the construction of the body of the over door heater /air curtain and the fans made of plastic allowed for a significant reduction of weight and noise level of the unit. Adjustable air outlets make it possible to set the suitable angle of both air streams (both the over door heater and high capacity air curtains) to suit the range or throw as required by the customer, to prevent fast heat loss and keep the heated air inside the building.


An over door heater can be an essential device for your shop, business or facility. They have been proven to save your energy costs, when combined with the air curtain element. The installation is not only quick and easy, but also cost effective as you only have one device to do both the heating of the area, and to provide an invisible barrier of air to prevent that warm air escaping from the doorway. Should you require any more information or assistance, please don’t hesitate to contact our sales team a call on 01202 822221 or contact us via our contact form above.