Commercial over door heaters

Commercial over door heaters – the benefits & options

Commercial over door heaters are warm air heaters that are designed to maintain a protective barrier over the entrance to a commercial building or property. Many offices and commercial buildings require doors that are always open and this results in the inadvertent influx of cold (in the winter) or warm (in the summer) air into the building. Using a commercial over door heater or commercial over door air curtain as they are often referred to – will prevent this problem and ensure the separation of the indoor climate from outdoor conditions, in a unobtrusive and quiet manner, that does not disturb. Over door heaters should not be expected to entirely heat a wider space, as this is not their primary function. You can however, provide supplementary warm air heating when using a commercial door heater to provide a warm welcome.

Only properly designed commercial over the door heaters, working over the full width of your open doors will meet the requirements for a functioning air curtain heater. That being the width of the air curtain or over door heater should always be at least equal to the width of the commercial door that the unit is protecting and heating.

commercial air curtain heaters; commercial overhead door heaters;

Commercial air curtain heaters from Flexiheat UK

Over door heaters – What do they solve ? 

The main issues the resolve is – Heat Loss 

When a heated areas room door is opened, the outdoor or external cold air begins to flow through the lower area of the open door and the warm air from the room flows out via the top area of the door. This phenomenon causes an inevitable increase in the heat loss of the commercial building and also reduces the comfort level inside the room due to the penetration of cold air.

The solution ? Installation of a commercial over door heater / air curtain

By installing an energy efficient over the door commercial heater or air curtain, you create a heated air barrier between the indoor and outdoor climate and thus reduce the unwanted effect of cold air leaks into or the building and maintain pleasant heated environment for the occupants.

Operating Principle

The cold air enters the housing of the over door heater and passes over the heating elements ( for electric powered units) or heat exchanger ( for water fed / powered units ), then the heated air is captured by the fan and directs the air flow through special outlet nozzles that forms a thermal curtain over the entrance to the room.

To create an effective warm air barrier, the main role is played by the force of the air flow over the heating elements . For the majority of the UK, a wind speed of 2-4 metres / second is characteristic. Thus accordingly, you need to choose an air barrier, which at the exit of the nozzle, the air speed should be at around 10 metres per second; and at the floor level, the air speed should be at least 2-4 metres per second for the over door heated air curtain to work correctly.

Commercial overhead door heaters

There are two main ways of heating a commercial overhead door heaters, the first and most common is an electrical powered unit. These tend to be three phased powered, although we do have options for single phase if your site only has that voltage available. 

There are no special differences in the design of an electric overhead door heater, as apposed to a water heated heater, only that they use an electrical coiled heat exchanger for effective heating of the air flow. These days , the most effective and reliable electric heat exchangers are  know as “PTC electric coils” – which are a modern and safe solution for an electric commercial over door  or overhead heater – The benefits over the older  technology for the electrical heater elements of these commercial door heaters that used heating wires or spirals are – 

  • Larger heat exchange surface (surface of contact of the heat exchanger with heated air)
  • Lack of voltage on the surface of the electric coil
  • Fully automatic heat control depending on air flow
  • Significantly lower coil temperature in comparison to the older type of electric heaters (e.g. heating wires or spirals)
  • Complete elimination of the risk of system overheating due to self-regulating heating modules (heat capacity automatically reduces when air flow goes down)
  • And last, but not least – Lower energy consumption 
commercial overhead door heaters;commercial over door heaters;

Commercial overhead door heaters from Flexiheat UK

The Pro’s and Con’s of Electric Commercial Over Door Heaters – 


  • Easy of Installation – just extend the electric cable to the electric over door heaters installation site.
  • Ease of maintenance – the heat exchanger is easy to get at for preventive maintenance such as cleaning the heat exchanger.


  • High operating costs – the electric heater will work for heating mainly in the daytime, when the most expensive electrical tariffs are in effect

  • Electric horizontal overhead air curtain heaters spend the first couple of minutes getting up to heating temperature. 

For the full details and range of our electric over door heaters, please click here

Doorway Heaters – Water Heated

The second most popular option is a hot water heated overhead air curtain heater, these are also referred to as hydronic over door heaters or air curtains. They obviously require a hot water source, usually a wet central heating system, that has the required capacity to accommodate the heat output requirements of the units. 

Their operating principle is as follows – The heat medium- in this case the hot water from a central heating system is supplied to the heat exchanger, the cool, air passes over the heat exchanger, and heats up, before entering the fan assembly. The fan then pushes the warm air out at high speed, and pushes it out of the commercial over door heater towards the floor of the door or entrance of the commercial building, and creates an air barrier from above the door. Water heated overhead heaters usually have a heat exchanger with a large surface area to achieve the required heat output required.

Commercial water heated over door heaters; water heated overhead heaters; commercial air curtain heaters;

Commercial water heated over door heaters – you can see the pipework to the right of the overhead heater.

If you have a wet central heating system at your commercial premises, and have the kW capacity in the heating system to use a water heated commercial over the door heater, then they are the best doorway heaters for your site.

Pros: Normally cheaper operating costs in comparison to electric heated over the door heaters.

Cons: Installation costs and complexity – you have pipework to run.

More maintenance- Dosing and venting of the heating system is required. Potential leaks etc.

For the full details and range of our water heated over door heaters, please click here

Commercial over door heater

Commercial over door heaters deliver a continuous wall of warm heated air from the bottom to the top of a doorway or entrance. They have a high air flow rate and are designed to create an invisible air barrier all the way down over a door or entrance. This air barrier separates the air between the two environments of different temperatures. They are widely used at commercial entrances that are more often open than closed.

So what information do we require to select the appropriate over door heater for you ? Basically 2 things – 

  1. What is your door width and height ?
  2. Do you require an electric heated or water heated over door heater ?

Also what can often be handy is a few pictures of the door that requires the heater, to ensure that we know the aesthetics and also to know that the heaters have the correct clearances required and will fit. 

Commercial overdoor heaters

Should you require anymore assistance or information on our Commercial over door heaters / Commercial overhead door heaters for sale in the UK and Ireland, please give us a call on 01202 822222 and our dedicated sales team will be happy to offer advice and assistance or just contact us by mail by clicking here


Electric Boilers for Heating

Electric Boilers for Heating

Electric Heating Boilers, work like all gas and oil boilers –  an electric boiler heats the water, which is then circulated via the flow and return pipework to either radiators or an underfloor heating system, and thus is often called a central heating boiler. The only difference between these boiler types is that it’s fuelled by electricity rather than gas or oil. They are a wet central heating system, just like an oil or gas boiler. Electric central heating boilers have high energy efficiency at 100% , which is higher than any gas boiler installation on the market – be they traditional gas boilers or condensing gas boilers heating systems.

Electric boilers tend to be particularly suited to properties that have no access to a gas supply – be it a mains gas supply or an lpg gas supply

What is an electric heating boiler?

An electric heating boiler generates heat using electric heating elements immersed in water. Electric boilers are highly efficient thanks to their efficiency – which is very close to 100%. They are easy to install in both new houses or flats and whilst renovating older properties, since they require only to be connected to the central heating system and the mains electricity supply. Unlike a gas or oil boiler, they do not produce any products of combustion and therefor no flue gases or fumes, meaning that there is no flue system to install, which results in lower installation costs. You can also lower your energy bills by taking advantage of low tariff electricity such as economy 7 rates.

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Advantages and disadvantages of electric boilers for heating 

  • Installation: is quite easy and often very quick with regards to the time. These electric heating boilers can be wall mounted – (the most common) or floor standing, and are very compact – allowing you to place the electric boiler where you require.
  • Efficiency: these electrically powered heating boilers are an efficient system that has an efficiency close to 100% and allows you to heat your home or flat quickly.
  • Safety: there is no risk of an explosion or carbon monoxide leak which can result in carbon monoxide poisoning that can kill from waste gases.
  • Maintenance: an electric heating boiler requires little maintenance, and isn’t mandatory as compared to gas boilers in landlord properties – this ensures low maintenance costs if any.
  • Space saving electric heating system: these central heating boilers are compact, they are wall mounted and as opposed to an oil boiler, you will not need extra space to store the fuel for the boiler in a tank, eliminating the possibility of an oil spill or the smell associated with the oil storage tank.
  • Ecological heating solution? – if your using electricity generated form renewable energy, such as solar PV / Photovoltaic panels, wind turbines or wave/ water generated electric, that it can be said that you’re not contributing CO2 into the environment, and thus having a CO2 neutral heating system. The same can’t be said for a gas or oil boiler, as both of these are fossil fuels and emit CO2 into the environment.
  • Legislation changes – The current talk is of banning gas heating for new houses by 2025 more info here. Legislation may well force people to change their boilers to electric, whether they have a mains gas network supply or not.
  • The downside – The price of electricity/running costs : at present it’s more expensive than gas and fuel oil, whether it will be lower in relative terms in the future, due to the push for renewable energy- who knows?
  • Any professional heating engineer will be able to fit electric boilers normally in conjunction with an electrician – there’s nothing special about electric central heating boilers as a matter of fact they are easier to install  than a gas boiler for example, as there’s no flue pipes to install, and the lower emissions electric boilers can be placed or fitted in many more locations due to this fact than the average gas boiler.
  • Electric combi boilers are also available that will do the heating and hot water requirements as that what a combi boiler is designed to do- but in reality you need a 3 phase power supply to get useable electric combi boilers – we do have an electric combi boiler solution for single phase boilers /properties/or locations – and these are listed on our dedicated web page here –  electric combi boilers
  • Carbon footprint / carbon emissions can be eliminated or reduced if you are powering the electric boilers from renewable electric power supplies. Unlike gas boilers which produce carbon emissions
  • Running costs can be reduced as our electric boiler range have as standard weather compensation and optimization – built into the units – This can help reducing running cost by 20% as the electric boiler adapts it’s output to the prevailing weather conditions. 
  • Domestic hot water – you can produce hot water via an indirect hot water cylinder with our boilers.

Electric Boiler Heating Systems 

These electric boilers for heating are one of the simplest and most cost-effective solution for central heating. They also ideal for heating flats or houses where there are no or limited possibilities to route a chimney / flue pipe system, for example in buildings of historical value or stone constructed houses. Also, electric heating boilers, are a perfect solution for petrol station heating where only fire-resistant equipment should be used for safety reasons and requirements. They also suit holiday home heating and caravan boiler requirements very well too.

We do a full electric boiler range from 0.5 kW to 45 kW in heating output. These electric wet central heating boilers can be powered by single phase electricity up to 15 kW of output electric boiler , and from there on and up to 45 kW they require a three phase electric supply to the electric boiler. Full details on the range can be found on our dedicated product page here – Electric central heating boiler range

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Electric wet central heating boilers from Flexiheat UK

Electric heating boilers for underfloor heating?

A question we often get asked is can you use an electric boiler for underfloor heating? The quick and simple answer is yes – Our range of electric heating boilers can heat the central heating water from Zero Centigrade all the way up to 80 Degrees Centigrade. Most underfloor heating system will have a flow temperature between 35-60°C, depending on the heat losses from the property or building. If the underfloor heating system operates with thermostatic mixing valves, then commonly they use 45°C temperature for screeded floors and 55°C for timber suspended and floating floors.

Electric central heating boiler systems – UK and Ireland

Should you require any further assistance with our electric central heating boiler systems / electric boilers for heating or any of our products, please click here to contact us via email or call us direct on 01202 822221

Electric Industrial Fan Heaters

Electric Industrial Fan Heaters

They are the big and stronger brothers of classic fan heaters: Electric industrial fan heaters! Ideal for heating large industrial premises, whereby the field of application of these fan heaters is very far-reaching. Of course, this also goes beyond commercial and industrial use, as these electric industrial fan heaters are very versatile and provide a great solution to many electric heating requirements. In the following, we will introduce you to these powerful electric heating systems and how they can be used, what equipment to use, and what to look for when buying an electric industrial fan heater.As a rule, when taking about industrial electric heaters, 230 volt / 1 Phase units will generally be supplied with an output of 3 kW maximum and use a maximum of 13 Amps as this is the maximum that a standard 3 pin “household” type socket can satisfy.The higher output fan heaters above 3 kW need to be connected to a 415 Volt – 3 phase supply, as when using a 3 phase electrical supply the current limits are much higher which allows us to get more heating capability from these types of warm air fan heaters.

Industrial fan forced electric heaters

As the name already makes it clear, electric industrial fan heaters are mainly used in the professional or industrial sector. This ranges from heating, drying and ventilation on construction sites, or in workshops and warehouses and commercial buildings. They are also used as temporary or top up heating for sports halls and social clubs as well as larger event type heating that use marquees etc. As you will see from the detail below, there are electric industrial fan heaters for very specific applications, which meet the specific application requirements, such as mobile units, fixed units etc.

Fixed or mobile Industrial electric fan heaters

Whist the smallest electric powered industrial fan heaters will usually be free standing mobile units and easily carried to where ever it is required, the larger heat requirements can often be delivered from electric fan heaters installed on brackets mounted to walls or columns, or even hung from the ceiling or roof structure.

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Wall or Ceiling mounted electric industrial fan heaters from Flexiheat UK

When the units are to be wall or ceiling mounted, they are often called electric unit heaters. These tend to have a lighter , but still robust casing , as they are not required to have the level of resistance to knocks and bumps that the mobile units tend to receive, as they are mounted at a wall or ceiling height and are out of the way of this type of potential ware and tear that the mobile units are often subject to.Full details on our range of these electric unit heaters can be found here – 

For 6 kW to 27 kW of heat output –

or for the commercial range that goes from 3 kW to 15 kW of heat output

Mobile units – 

Industrial electric heaters , commercial electric heaters

This mobile unit , our “FHNXG” model is available in 9 Kw , 12 kW or 20 kW Output and is a compact yet powerful electric forced fan heater.

The models with up to 30 kW of output are very mobile, and are either easily lift-able or have a wheel’s that allow you to manoeuvre these electric heaters to your required destination. The models up to 20 kW of heating output can easily be transported in a car boot for example.

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Our mobile industrial fan forced electric heaters – 9/18 kW on the left or the 15/30 kW model on the right

Full details on both of the above industrial portable electric heaters electric can be found here – 

When you get to the larger output industrial electric fan heaters, then they can be heavy and large, especially when we are talking about our 42 kW model, which is 130 KG’s in weight. Although this unit benefits from heavy duty braked caster wheels, which allow you to manoeuvre the unit quite easily. This model also comes with forklift slots or pockets as well as lifting eyes, should you wish to lift the unit to a high level.

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Industrial Electric Heater-42kW- from Flexiheat UK

Ductable units – When you want heat into another area from your heater 

If you only require to deliver the heat into the area or room where the space heating is required then it is an easy decision: you’re not going to need an electric industrial fan heater that has a duct spigot fitted to the unit. But if you want your industrial fan heater to deliver heat into a separate area, room or enclosed space then your going to need a ductable electric fan heater. Flexiheat can supply various ductable industrial fan heater models, that can be ducted up to 30 metres in length, as we have units that have high air flow pressure produced by the high-quality fans that are fitted to our units

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Sizing of your heat requirement / heat loss 

The first stage of narrowing your requirement for an electric industrial fan heater is to establish how much heat you need. There are some general rules of thumb, that will give you a good approximation of the heat requirement for you building. You can use 60 Watts per /m2 of floor area.

But using this general assumption has some potential big draw backs, the first being that this “rule of thumb” generally is based on a 3-metre-high room. Many Industrial unit have much larger heights than this, so for an accurate heat loss calculations you would need to calculate the volume of area being heated, adding any heat generated by hot industrial process or machines and then using the U values of the various materials that are used in the make-up of your room or building, along with the desired internal temperature , and normal maximum external temperature ,you calculate an accurate heat requirement for you application.

We have a handy spread sheet / form that you can fill out, along with description of your insulation levels. That we can send you, just fill this form or spread sheet out and we can calculate your heat requirement for you.So just get in touch with us.

Sockets, Plugs and Leads for Industrial Fan Heaters

Single phase industrial electric fan heaters generally come complete with a length of flex and a fitted plug as standard, and whilst in the case of 110 Volt powered electric heaters they come with a standard 3 pin round plug for fitting onto a transformer. For more information on our 110 volt industrial electric fan heater model, please see the following dedicated web page –

With 3 phase heaters there are a greater variety of plugs and some of the smaller heaters come with a flex and plug and some come without, as in the example of our electric unit heaters, as they are designed to be hard wired as they are designed as fixed electrical heaters, and thus come with a connection block.
Some of the larger mobile heaters come with a “CEE” connection socket inbuilt onto the heater, allowing you to have the connecting flex as long as you require, to suite your site conditions

Industrial electric fan heaters UK

The full range of our electric air heaters / fan heating units is robust and totally reliable; These are built with an indisputable high experience and knowledge. Whilst the fan motors of these heaters production cycles, are certified and subject to the strictest technical and dimensional checks and electrical tests according to the ISO 9001: 2015 certified Corporate Quality System and are in full compliance with the latest European and International standards in force.

Industrial electrical fan heaters UK

If you require any further assistance with our electric industrial fan heaters / industrial fan forced electric heaters or any of our products, please click here to contact us via email or call us direct on 01202 822221

Industrial Warm Air Heaters

Industrial Warm Air Heaters – Your Options / Guide 

Industrial warm air heaters work by pulling cold air from the environment and moving it across a heat exchanger. This cold air is heated and via a fan, re-distributed back into the environment until an ambient temperature is achieved, thus heating the building.Warm air heating systems can include floor standing ,suspended units or even mobile units, making them a versatile choice for commercial and industrial premises. 

These warm air heaters come with a wide variety of fuels to choose from, such as oil, natural gas, propane / LPG, electric or even bio-fuels, to power the system.Making these heaters a versatile warm air heating option for any industrial or commercial application.

There are several types of air heaters, these being, gas heaters, oil heaters, hot water heaters, and electric heaters. Each of them has advantages as well as disadvantages.

Thanks to the principle of forced convection, the hot air is renewed and diffused throughout the space. The unique design of these heaters allows you to combine heating and ventilation, which is effective for the treatment of stale air within a building.

Warm air heating can be considered a modern replacement for traditional water or wet heating central heating systems within industrial and commercial premises and works by forcing warm air around the building

Industrial gas warm air heaters

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Industrial warm air heaters from Flexiheat UK

Definitely the most common industrial warm air heaters are the natural gas or propane gas fired units. They come in thee main types, either floor standing, suspended – either from the ceiling or mounted onto a wall, and lastly mobile versions.All of our warm air product range can be seen here –

A free blowing industrial gas warm air heating system is one of the most cost effective and efficient means of heating industrial and commercial buildings. They represent better value than a wet system with boilers and unit heaters or radiators, having a faster speed of response.

Industrial Warm Air Heating Systems

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Industrial warm air heating from Flexiheat UK

For floor mounted Industrial war air heaters- which are commonly known as “cabinet heaters”- are installed on the floor and therefore take up floor space. They come with nozzles or vents to give direction to the flow of warm air – this is known as “free-blowing” — meaning that the warm air is simply projected into the room or they come ready for connection to a duct-work system, that is designed to distribute the warm air around the building or buildings to be heated.

Industrial Warm Air Heating

Warm air heating for any industrial site has some great benefits in that they provide fast warm up times and will heat your area quickly, as apposed to radiant heaters which only heat the area that is covered directly in front of the units.

Warm air heaters industrial are these days incredibly practical as you can control the amount of heat that they produce.They can keep the area being heated at a constant temperature, which improves comfort levels for the employees working in that area, or even to maintain temperatures for application or manufacturing processes that require a certain temperature to aid curing of a product etc.A constant temperature will also be helping to reduce energy costs or bills.You can also help reduce your energy costs even further by using destratification fans, if heating large areas with high ceilings, again another product that we supply. A superb addition as they help to evenly distribute the warm air back down to the area where its required, and are estimated to help save up to 30% on the fuel bill.The latest warm air heaters feature energy efficient burners, which can deliver efficiencies of 91% net, and when used in combination with a control system, optimal design this is the opportunity to lower running costs and gain a more eco-friendly heating system

Industrial warm air heaters UK

Our extensive knowledge of the industrial and commercial heating sector helps us find the right warm air heating solutions to suit your requirements.These industrial warm air heaters are intended for heating large volumes, such as greenhouses, warehouses, factories, supermarkets, and gymnasiums etc that we have in the UK.When heating a large industrial space or warehouse, it can be important that every area is heated with no cold spots, and warm air percolates very well.

In contrast to normal rooms, industrial buildings and warehouses have quite different challenges when it comes to warm air heating. Thus, warm air industrial heating has to be designed for the even distribution of heat and take into account the greater air turbulence of the height in a taller industrial or warehouse building, and take into account the warm air buoyancy currents naturally play a greater role in these applications.

Heating industrial sites with warm air

Should you require anymore assistance or information on our Industrial warm air heatersIndustrial warm air heating systems , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form.

12kw Electric Combi Boiler

12kW Electric combi boiler – What are your options?

12kw electric combi boiler; 12kw electric combination boilers;

12kw electric combi boiler option – Flexiheat UK

An 12kW electric combi boiler can be the perfect solution to your heating and hot water demands for a small house or flat. An electric combination boiler does away with the need for stored hot water but with this comes some things you need to be aware of to decide if a combination electric boiler is right for your application.

Here Flexiheat UK, we have a couple of options for your 12kw electric combi boiler requirements. We do a range of 12kw electric combi boilers, that can either be run off a 240 Volt / Single Phase electric supply (the most common household electrical supply voltage for the UK and Ireland)

 The term “combi” is just an abbreviation for the word “combination” and when used in the context of a 12kw electric combi boiler, this means that the electric boiler will not only do the central heating requirements, but also produce domestic hot water, for your hot water taps within your property or flat. They’re ideal for properties with gas boiler restrictions, such as flueing issues, or no access to the mains gas supply. They are the perfect solution /cost effective alternative for replacing existing solid fuel wet central heating systems with electric boilers.

Ok that’s the good news, but here’s reality

electric combi boilers under 15 kW don’t work – in the real world!

Why? you just can’t get useful hot water performance out of a single phase 240 volt powered unit.

Unlike a gas combi boiler, which does an outstanding job of quickly transferring energy from natural gas to heat water and producing an appropriate hot water flow rate, this is not the case with an electric boiler of this size.

When it comes to an electric boiler, you need the power (Amps) to do this, and a single phase 240 Volt supply can’t generate the Amps necessary to accomplish the requisite hot water flow rate even for smaller properties – if you do have 3 Phase then look at this webpage – Electric Combi Boilers for units that start at 15kW and above.

What’s the solution then?

Essentially, we use a standard electric boiler with the minimum sized indirect hot water cylinder, which is an mains-unvented hot water type – it is only 80 litres in volume.

This results in the lowest water storage level, but enough hot water supply to cope with your properties needs i.e., it not only provides sufficient water volume, but also at the right temperatures as you require 50C to be able to wash the grease of dishes / kitchen utensils. Whilst reducing your energy costs to the minimum for your domestic hot water heating system.

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15kW and below electric combi boilers solution from Flexiheat UK

12kW Electric Combination Boiler Efficiency & Benefits

None of our 12kW electric combination boilers options emit gases or direct pollution when operating as they are not using fuels such as natural gas, LPG gas or Oil and therefore there is no risk of leaks or explosions. All of our electric combination boilers are highly efficient at above 99%, and come with a control panel, and are fitted with the latest ErP low energy rated heating pumps and come with a system expansion vessel. Our electric combi boiler benefits and key features are –  

  • A fully qualified ErP compliant 12 kW Electric Combination Boiler combined with 
  • 80 litres of Domestic Hot Water Storage
  • Heating and hot water superior performance
  • They can be used with a wet underfloor heating system
  • They can be used on a a traditional wet central heating system with radiators
  • They can be used in conjunction with solar heating systems
  • Come with a ErP compliant heating pump
  • Fully modulating power / output regulation
  • Inbuilt programmer or can ban connected to a wireless thermostat
  • A frost / freezing protection system – If the temperature of the water inside the 12kw electric combi boiler is under 5°C, the pump and heating elements will operate to bringing the water temperature up to 35 Degrees Centigrade, ensuring that the boiler is protected against freezing and any potential damage.

They can be installed by any competent electric heating company or a plumber in conjunction with a electrician. 

Domestic Hot Water Performance

One of the most important factors in relation to electric combination boilers is their Domestic Hot Water ( sometimes referred to as DHW) performance. With 12 kW of heating power dedicated to heating the domestic water when required, which ensure a great recovery time of the stainless-steel water tank, which is a very compact unit ,should you use all the water in one go – such as filling a bath.

The recovery time of 80 litre tank, (which can be mounted directly underneath the wall hung electric boiler or in a sperate location to suit site requirements ) from 10 Degrees C to 60 Degrees C is only 29 minutes – and only 15 minutes from 35 Degrees C to 60 Degrees C. The temperature of the domestic hot water can be controlled between 35 to 65 degrees centigrade.

Kitchen taps – flow rates of between 4 to 6 litres per 
minute. These days water efficient taps and showers should have the following flow rates –

Showers – flow rates of approximately 8 litres per minute for a standard shower head.

So with 80 litres of storage of domestic hot water , a standard shower uses 65.1 litres of water blended down to 43 Degrees C and lasts for 8.2 minutes at average flow rate of 8 litres . The 80 litre stainless steel DHW tank will provide 83.3 Litres of water , when stored at 60C and blended down to 43C, which is the highest safe showering/bathing water temperature. Ensuring you have a nice warm shower, at a good water pressure, up to 7 Bar if required.


Electrical Consumption Details  – including fuse & cable requirements :-

These 12kW electric combi boilers can be wired up either with a single phase 240 volt or a Three phase 400 volt electrical supply, 


The following information is relevant when this 12kW electric combination boiler is wired up to a 240 Volt , Single Phase electrical supply –


12kW Electric combi boilers for sale UK & Ireland

The full brochure for this 12kw electric combi boiler and the rest of our range as we also do three phase electric versions that go up to 21 kW of heating output, please download our brochure here – 


Should you require anymore assistance or more information on our 12kW Electric Combi Boiler / 12kW Electric Combination Boilers , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form.

10 kw Electric Boiler

10 kW Electric boiler – What are your options ?

At Flexiheat UK, we have various options for your 10 kw electric boiler requirements. We do a full range of 10 kw electric central heating boilers, that can either be run off a 240 Volt / Single Phase electric supply ( the most common household electrical supply voltage for the UK and Ireland ) or 415 Volt / Three phase electrical supply. These 10kw electric units are suitable for underfloor heating systems or central heating hot water heating applications as well as domestic hot water installations when coupled up to an indirect hot water cylinder.

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Our closest output to a 10 kw electric boiler is our model ” FHEL9″ which is actually just under that value at 9 kw of output, but normally most home heating systems are oversized, as they normally take into account the worst case scenario of it being minus 5 Degrees C, which in the UK winter is vary rarely seen to be honest, thus we’d be very confident that a 9 kW output electric central heating boiler would suffice for your requirements

However should you require 10kW electric output, then we do our model FHEL14 which is rated to an output of 13.5 kW, which is slightly over in output value, but please remember these electric wet central heating boilers have a modulating output, which means it can modulate down to 10 kW of output – for more information on this model and our full range please see this page –

10 kW Electric Boiler Efficiency & Benefits

Our electric boilers have a  99.5% efficiency rating which is better than any gas or oil boiler and benefit from well arranged touch display and control panel for our FHEL9 model. This touch screen ensures both simple and intuitive control of the boiler is achieved.

Fluent regulation in low power output steps of just 1 kW (1,000 Watts ) ensure that the heating load requirement is appropriately matched, also ensuring even greater heating efficiency to the wet central heating electric boiler system, be it underfloor heating or a radiator system.

The modular digital control assures optimal operation of this 10 kW electric boiler in a way that optimizes electric energy consumption with the rated thermal output of the electric boiler.

These 10 kw electric boilers come complete with an integrated “ERP” energy efficient compliant heating pump and integrated 7 litre expansion vessel, making these electric boilers what is commonly know as a system boiler. This allows you to have a “sealed heating system” meaning that no feed and expansion water tank is required in the loft or at high level – which can be prone to freezing or bursting. It also means  installation is made a lot more tidier and compact, as all required components are within the boiler casing.

These electric central heating boilers can be controlled by an “OpenTherm+” thermostat or controller e.g. a nest controller etc ( control your 10kw electric boiler on the go, from your phone) giving your greater control over your electric wet central heating boiler.

They can also be controlled by a standard room thermostat or weekly programmer – the decision is yours to make.

Technical details of our 10 kw electric central heating boilers

Below you can see the technical data for the Flexiheat “FHEL9” and also the next size down and up in this range of touch screen electric boilers for central heating –

Please note as these electric central heating boilers, can be wired in either three phase or single phase, the below table shows both parameters. For example, the maximum rated current for the FHEL9 electric boiler, when wired up using a three phase electrical supply is – 3 x 14 Amps per phase, and when wired in single phase, the figure is 1 x 42 Amps.

10 kw electric central heating boilers; electric boiler 10 kw; electric flow boiler;10kw electric


These boilers are CE marked and approved, and also comply with the directives 2006/95/EC (Low Voltage Directive, LVD) and 2004/108/EC (Electromagnetic Compatibility Directive, EMC) and carry a 2 years parts warranty as standard. So, if you want the best 10 kw electric boiler for sale on the UK market, then we are the company to speak to.

Other features 

  • To reduce energy heat loss, the heat exchanger is completely insulated.
  • Boiler temperature range of up to 80C 
  • Suitable for underfloor heating systems or traditional radiator systems
  • Water level sensor to ensure running dry due to system water loss is not a problem
  • 9 stage heating output steps or levels – for better heat load matching for lower running costs, fuel bills and accurate temperature control
  • The front cover is easily removable for any maintenance purposes
  • Unlike inferior units that have a  temperature control dial – such as the slim Jim electric flow boiler – our units have a nice and easy touch screen control
  • Virtually silent in operation
  • Opentherm control connections – so you can connect a Hive or Nest controller to our unit 


10 kW Electric boilers for sale UK & Ireland

Should you require anymore assistance or information on our 10 kW Electric Boilers / 10 kW Electric Central Heating Boilers , please don’t hesitate to contact our sales customer service team on 01202 822221 or click here for our email contact form. All of our invoices inc vat.

Boiler pressure keeps dropping ? What to check

Why does my boiler pressure keeps dropping ? This is a common question , and following in this guide we’ll take you through the most common boiler problems, what to look for , and actionable things that you can do to fix the dropping boiler pressure. Most of the time these fixes are easy , that can be done by yourself, as you don’t need to be an expert in order to do a little troubleshooting on your own.

By following these simple steps , you should figure out what is causing your low boiler pressure , and why it continually keeps on dropping , in no time at all, before having to call a plumber out. Some of the fixes can be done by you , whilst others you may have to get a plumber or heating engineer out to look at your heating system as you may have a boiler leak causing it to lose pressure.

work through the following table of contents in an orderly manner

Boiler Pressure keeps dropping or continually low – Things to check

Firstly you need to check your boiler pressure gauge , and see what’s it’s reading. This gauge is most commonly built into the boiler, or underneath it and should look like this or similar –

boiler pressure keeps dropping,combi boiler pressure keeps dropping,boiler pressure keeps dropping to 0,ferroli boiler pressure keeps dropping
The Heating System Pressure Gauge – The fist thing to investigate as why your boiler pressure keeps dropping

In the picture above the red marker on the gauge is just an indicator of where the level should be, the thin black marker is the actual pressure of the heating system. A pressurised boiler system or a sealed central heating system needs a certain amount of pressure to work, normally about 0.5 Bar – 1.5 Bar, although some will continue to function with far less pressure. If this pressure reading is lower than the recommend pressure level, this means you heating system water pressure is low and that you have low boiler pressure which needs to be topped up so the level is above the red line on the pressure gauge normally via the filling loop, which will fix fix low boiler pressure.

It is usually best to contact a plumber if you have any concerns about your boiler losing pressure or are unsure of how to re-pressurize the system yourself.

But before that is done, you really need to establish why the boiler keeps losing pressure as you may have pressure loss in the pipework i.e. copper pipe via a leak or even a leaking radiator valve etc.

Combi boiler pressure keeps dropping ?

It doesn’t matter whether your boiler is a heating or heat only boiler or a combi boiler, as we are talking about losing water pressure on the central heating system here .If your combi boiler is losing pressure on your domestic hot water side of the boiler ( this is you hot water that is provided to your hot water taps , showers or bath taps ) then this will be a mains water pressure problem, and you would need to consult your water supplier.

First thing to check –

Is there air in the heating system?

This is an easy thing to check yourself. You just might be able to diagnose your problem with just a few checks,

Before you do anything, try bleeding your radiators. But before you set off to do this, a top tip is to have a towel or rag to catch any drips from the radiator air vent, as the water form the heating system can be black in colour and stain anything that if falls onto. To bleed your radiators, use a radiator key. Find the radiator air vent and slowly turn the radiator key counter clockwise until water starts dripping out, this releases the trapped air and lets hot water fill that void or space in the radiator again, ensuring a nice hot radiator. Always bleed the top floor radiators first and make sure you bleed the radiators in sequence. Bleeding the air from the radiators will then cause the pressure to drop lower again, so check it again after bleeding all the radiators and adjust it accordingly.

If bleeding the radiators doesn’t work, then you may have a bigger issue such as an air lock in the heating system or you may even need to have the heating system itself flushed out. I wouldn’t recommend you doing this yourself , unless you feel completely comfortable, and have the tools and equipment to do it properly. So it’s time to call a plumber for most people.

Second thing to check –

Is there a leak in your central heating system?

Look for signs of a water leak such as a damp floor, leaky pipes, a small hole in a radiator somewhere or a stain on your ceiling, any or all of these signs point to you have a leak on your central heating system, which is causing your boiler to lose pressure. Finding a leak may sometimes feel like finding a needle in a haystack, but it’s worth trying to find it yourself, before calling out a plumber, as most heating engineers charge an hourly rate, which can become quite expensive, should be tasked with finding the leak on you central heating system.

Third Thing to check –

Is the boiler pressure relief valve leaking ?

Is the pipe coming off the pressure relief valve on the boiler continually dripping water ? If so at some point the valve has probably operated and there may be some internal debris that is stop it from properly shutting off again. This faulty pressure relief valve may need to be cleaned or replaced completely and is a fairly cheap repair or you may need to replace this faulty pressure relief valve. This job really should be left to a qualified plumber or heating engineer to do.

Fourth thing to check –

Is the Boiler Expansion Vessel Faulty?

boiler pressure keeps dropping,combi boiler pressure keeps dropping,boiler pressure keeps dropping to 0,ferroli boiler pressure keeps dropping
An external expansion vessel, used in central heating systems

All modern sealed system boilers or pressurised boiler systems use an expansion vessel , either placed within the boiler but can be located externally too , that accommodates any expansion that is created when water is heated up in the heating system. If the expansion vessel is faulty, it normally means that it will not be able to handle the expanding hot water resulting in the pressure in the heating system rising rapidly and this water will be ejected through the pressure relief valve, once it goes beyond 3 bar in pressure. The expansion vessel’s internal bladder, which is normally made from neoprene rubber (Neoprene rubber resists degradation more than natural or synthetic rubber), must be inflated by air or ideally nitrogen ( when the gas side is filled with nitrogen, and not with air, corrosion is prevented and the pressure loss is even more limited). This level of nitrogen or air, commonly known as it’s charge must be maintained through annual servicing of the boiler or eventually it will dissipate completely, eventually causing the boiler to have continual low-pressure problems and ultimately failure of the central heating system

combi boiler pressure keeps dropping,boiler pressure keeps dropping to 0,boiler pressure keeps dropping
Expansion Vessel internal picture, showing the “Bladder”

If that doesn’t seem to be the problem, then the next thing to do is find the Schrader valve on the expansion vessel, which looks like an air valve found on a car or bike tyre. Then depress the valve in the centre using a screwdriver or similar. If water comes out of the valve it means that the diaphragm has failed inside the expansion vessel, and you will need to replace the vessel or with some units you can just replace the internal neoprene bladder.

Dropping boiler pressure from Flexiheat UK; boiler pressure keeps dropping; boiler pressure keeps dropping to 0;
Expansion Vessel Schrader Valve Picture & How to Test

If air comes out of the Schrader valve you need to check the pressure of the charge in the vessel. To do this you will need a suitable measuring device, such as a car tyre pressure checker. The air or nitrogen pressure for an internal boiler expansion vessel should be around 0.8 bar ( but please consult your boiler’s operating manual and check exactly what pressure the vessel should be charged to) but this could be higher for externally mounted expansion vessels. To fix this call your local heating engineer and ask him to re-inflate the expansion vessel. This is done by draining off all the heating system pressure first, then then using a pump (like a bicycle type or similar) the expansion vessel is re-inflated.

So what if the boiler pressure keeps dropping after doing this ?

So after your expansion vessel has been re-inflated keep an eye on the boilers pressure gauge, to see that it’s still correctly holding the system pressure for the next couple of weeks, as sometimes the internal bladder that holds the air or nitrogen has a pinhole puncture and it leaks out over days or even weeks , which isn’t always obvious, until you see your boiler pressure dropping.

Pressurizing your expansion vessel should typically be done as part of an annual boiler service, by a qualified plumber / heating engineer. We highly recommend that any work that is required to be done, is not done by a yourself or a novice, as we are dealing with hot water and pressure here, and these two items can cause physical damage to people or the property

Boilers with low water pressure – other things to consider

One thing that people often overlook is that if your boiler has been under pressured for a long period and you’ve been constantly topping the heating system up via a filling loop, then it would have depleted the central heating inhibitor chemicals within the heating system, it is therefore very important to add more inhibitor to the heating system , otherwise your heating system will start to corrode which can lead to a failure of your boiler, in a relatively short period.

Refilling your low pressure boiler heating system

After diagnosing your problem, and getting it fixed, the final step in getting you low pressure boiler back up to the desired pressure is refilling the heating system with what is called a filling loop . On some boilers the filling loop is internal to the boiler but in most systems the filling loop is an external piece of kit, and should be what is termed as a part “L” of the building regulation compliant and looks like this –

ferroli boiler pressure keeps dropping,combi boiler pressure keeps dropping
Part L Compliant Filling Loop

You should only refill your central heating system when the system has cooled down. You simply open the valves up, slowly and wait for the pressure gauge on the boiler to rise to 1.2 Bar to 1.5 Bar maximum (please consult you boiler manual for the recommended pressure that they stipulate).The process is then finished off by closing the valves , thus sealing the heating system from the mains water

Hopefully this guide “boiler pressure keeps dropping” has been helpful, and shown you some of most common reasons why this happens and how to remedy it.