Electric Boilers / Electric Central Heating Boilers – 0.5kW to 45kW
Electric Boilers – With over 2 million homes in United Kingdom at present are without a mains gas network supply, also many older houses have flue restrictions or are listed buildings that prevent the use of a gas or oil boiler on site. In these situations an electric boiler can be the perfect solution to your central heating needs.Some of the benefits of electric central heating boilers are that they fairly small and compact, so can often fit in a kitchen cupboard or under the stairs etc. The other great benefit is there’s no flue pipe required, unlike an oil or gas boiler which require a flue pipe to evacuate the products of combustion i.e. the flue gases. Thus, there is no risk at all of CO2 poisoning from a faulty flue system or the boiler when you use an electric boiler system. This requirement for no flue pipe, often allows you to install you electric central heating boiler in the appropriate location, to suit your requirements, which is often not the case for a flued gas or oil boiler
Electric Boilers – What are they ?
Electric boilers can be installed in small to medium sized flats or houses to produce the hot water for both your heating system and domestic hot water use ( normally via a indirect cylinder for your domestic hot water requirements). The most commonly installed boilers either use gas or oil to heat the water, an electric boiler will heat the water via an electric element or multiple elements. They are a popular choice for flats and homes where gas is not an option and oil is either impractical or too expensive. They tend to be limited limited as to the amount of Domestic Hot Water (DHW) they can produce instantly therefor we always recommend using an indirect hot water cylinder for the domestic hot water, especially if the property has a bath fitted.The smaller boilers , i.e. from 0.5 kW to 15 kW outputs the electric boilers are available in 240 volt , Single Phase , after 15 kW the units require a Three Phase power supply.They are often fitted in new build homes and flats as they are cheaper to install and maintain. Also, with no gas emissions, they are seen by many as a more environmentally friendly choice, as the electric power supplied can be from renewable sources such as wind, solar or tidal electric production.
Advantages of Electric Boilers
Can be integrated with PV panels to yield further energy savings
Cheap to buy as Electric Central Heating Boilers have no gas valve, fan, air pressure switches, Ignition PCB’s, Ignition leads, electrodes, or burners which keeps the cost down
No yearly servicing is required
No yearly Gas Safe Certificate in relation to rented properties
Cheaper to install
Installing an electric boiler is simpler than gas or oil and so is quicker and cheaper , also as there are no waste gases an electric boiler doesn’t need pipes, flue or chimney so the installation of the boiler will cost you less.
Does not require an external wall for mounting the boiler
As electric boilers don’t need to burn fuel to produce heat they don’t lose energy through waste gases or flues. In many cases this results in efficiency rates of 99% compared to 89 – 95% for most gas or oil boilers
Electric boilers are almost completely silent as there are no moving elements within the boiler
Light and compact
They lack waste gases and thus any flue / chimney means the unit is much more compact and light ensuring you have more flexibility about where in the property you have it installed.This makes them much more versatile in terms of where they can be placed in the property.
Easier to maintain
No annual landlord gas safety certificate is required
Unlike gas and oil boilers which have more mechanics included, electric boilers don’t need annual servicing to keep them functioning
No carbon monoxide threat to the people within the property
No CO detectors are required
Totally safe when the boilers are protected by RCD & MCB
No condensate pipes to freeze up
Electric Boilers For Central Heating
Our range of electric boilers for central heating are fully adjustable in heat output to suit your requirements. For example, we often get asked for a 24kw electric boiler, this heat output is covered by our FHEL30 boiler- which has a maximum output of 30kW. This boiler heats in steps of 5kw outputs, which you can easily set the maximum heating value on the boiler, to 5kW,10kW,15kW,20kW,25kW or the maximum 30kW. Thus, for a 24kW electric boiler output, you can set the boiler to 25kw, which is just slightly over in heat output, by 1 kW. The additional potential power of the 30kW electric boiler is always a handy feature, should you wish add additional heat emitters to your heating system in the future.
Here is a list of the appropriate electric heating boilers to use for a particular heat requirement –
- 10 kw electric boiler – for a 10 kw electric boiler output you can use our “FHELN 15” boiler from the economic range, this is the cheapest option, but only has 3 steps of 5kW heating, and can only be fitted with a standard room stat or room programmer. We would recommend our “FHEL15” electric heating boiler, as it has more heating steps of 6 with 2.5kw increments, which results in better heat load matching, and thus higher efficiency and better control of the heating system. The FHEL15 also can be connected to more sophisticated controllers, such as nest or hive, which allow you to control you electric central heating boiler remotely from you phone, tablet or PC. Ultimately both of these boiler options will give you a 10kW electric boiler. Our last option is our FHEL14, which due to its low minimum performance (1kW) and the modulation option, with heating steps of 1.5kW, can produce 10.5kW of heat output. This electric boiler is the ultimate in electric central heating load matching and recommended for low-energy and passive houses (low minimum power)
- 12 kw electric boiler – for a 12 kW electric boiler output – you can use our FHEL15, which will give you 12.5 kW of output, or our FHEL14 model which will give you 12 kW of heat output
- 4 kw electric boiler – for a 14.4 kw electric boiler – you can use FHEL15, which gives you 15kW of output.
- 18 kw electric boiler – for an 18 kW electric boiler output – you can use our FHEL23 model, which can give you either 17.5 kW or 20 kW of heat output.
- 20 kw electric boiler – for a 20 kw electric boiler output – you can use our FHEL23 model, which will match the exact output of 20 kW.
- 24kw electric boiler – for a 24kw electric boiler – you can use our FHEL30, which will give you 25kW of heat output.
- 30 kw electric boiler – for a 30 kw electric boiler, use our FHEL30, which matches the output exactly.
- 36 kw electric boiler – for a 36 kw electric boiler use our FHEL45, this will give an output of 35kW or 40kW.
Electric Central Heating Boiler Sizing ready reckoner table
The exact heating area mainly depends on the U value for your building – as a basic guide a U value is measurement of building heat lost through the building material by the processes of conduction, convection and radiation. This value is expressed as the rate in Watts [W]) at which heat transfers through 1 square metre [m²] of the surface of a buildings material when there is a temperature difference of 1ºC between the internal and external environments.
An example of this is –
A brick and block cavity wall with mineral wool insulation giving a wall thickness of 312 mm has a u-value of 0.3 W/m – Which this quick selection chart is based on. If you have a property-built from the late 1990’s then you are safe to use this ready reckoner chart.
However, until the late 1990’s, most cavity walls remained uninsulated, and thus an unfilled cavity wall can have a U-value of anywhere between 1.6 W/m2 to 0.6 W/m2, depending on when it was built.
|Power Output of Boiler||Heating area with H=2.7 mtrs & U Value =0.3|
|4.5 kW||~ 55 m2|
|7.5 kW||~ 85 m2|
|9 kW||~ 110 m2|
|13.5 kW||~ 165 m2|
|15 kW||~ 180 m2|
|22.5 kW||~ 278 m2|
|24 kW||~ 300 m2|
If you have a property built prior to late 1900’s or with a different construction to the above mentioned, or just want a more accurate figure, then please use the following heat loss calculator, input all your properties details into this handy online heat loss calculator, add all your rooms / hallways / kitchen etc into it and you will result in the total heat load required to heat your home.
Heat Loss calculator is here
Electric Boilers – Things you need to Consider and Know
The biggest and most important issue with electric boilers is not the boilers themselves, it is the power that they require to operate
Firstly you need to – What’s the difference between a single-phase or three-phase electricity supply ?
Both of these are electricity supplies, it’s the amount of power that is different. A single phase supply is smaller than a three phase supply meaning you cannot use as much power. A typical house will need a single phase supply whilst a larger house, blocks of flats or commercial building will need a three phase supply.
The way to tell what supply a property has is by looking at the fuse on the service head. Single-phase has one 100 Amp fuse ( Although in some older properties this may be a 60 Amp fuse, bit it’s quite rare ) and a three phase supply has three 100 Amp fuses.
So a UK home typically has a 100 Amp supply fuse , this means that all the home electrical appliances , whilst being used simultaneously should not draw over 100 Amps , otherwise the fuse can blow.
Following is a chart showing the electrical ratings of commonly used household appliances –
Firstly Electric Showers- these can have some high loads
Standard Shower Rating Watts (kW) Maximum load from the supply (Amps)
Standard electrically powered items, such as laptops, mobile phone chargers, Televisions (42″ HD), printers and radio’s etc only use approximately 0.5 amps, and don’t generally cause a problem in relation to your electrical loadings, but the following list of appliances and the amps they can draw on a single phase electrical supply, will have –
|Domestic Electric Appliances||Amps Used|
|Radiator ( Electric )||8.5|
|Radiator (oil filled)||13|
UPDATE – We have now solved this common problem So why does this matter ? Well it matters because the larger the electric boiler you go in size , the more Amp’s you need available to power the boiler . You will generally find that in a standard 100 Amp – 240 Volt , single phased supply property , the largest boiler you can use is a 10 kW Boiler ( now a 15kW boiler-see the update below in red ) – why ? because this boiler will draw 45.5 Amps , which is getting close to half of the supply for a standard UK property , even when you consider a diversity factor ( which in layman terms means that not every electrical appliance would be on at the same time ) you are starting to possibly exceed your supply and tripping out fuses etc.
We now do a new range of electric boilers for central heating and / or domestic hot water, designated the “FHEL” range that can now utilise what we are calling the ” maximum current watcher” – it is basically a releasing relay (restriction of current). The relay monitors and controls the electric voltage in the whole house or flat and in the case of exceeding the permitted values of the electric current it reduces the input power of the electric boiler. All of this is done automatically, without any human intervention needed.This system will not only operate on our 240 volt / 1 Phase Electric boilers , but also our 400 Volt / 3 phase units as well. This now means that you can use our 15kW electric boiler model, in a property or flat with standard 240 volt, single phase with no worries or problems that the unit will trip out the main electric board.
For full details on this maximum current watcher, please download the following data sheet / instructions
What are my other options? Well the best solution would be to get your electrical supply upgraded to Three Phase – Is it possible / How much is it to do this? I don’t know , we just supply the boilers – please contact UK Power Network , who are responsible for this here
Or another option may be to get a second 100 Amp supply to your property – Again , contact UK Power Network on the link above – this option may well work out cheaper than having three phase supplied to your property, but again don’t contact us about this, we just supply the electric boilers and this is not our remit.
Electric Central Heating Boilers – Features & Benefits
All of our “FHEL” range of Electric Central Heating boilers benefit from –
- Option to produce domestic hot water via an external indirect cylinder / calorifier and 3-way valve
- An inbuilt energy saving pump ErP compliant heating pump
- Pump Anti-Block Function – Regular spinning of the pump (once every 24 hours) prevents potential clogging of the pump during extended boiler down time
- Very quiet operation due to selected switching relays
- Anti-Freeze protection system – ensuring that these electric boilers are protected against freezing and any potential damage.
- Option to monitor the maximum current drawn to prevent overloading of the consumer board in the building/property – this system reduces the input power to the electric boiler automatically – ensuring that your main fuse does not blow.
- Soft start function – This ensures gradual heat-up of the heating system which is therefore protected against an abrupt temperature rise in the central heating system, that can cause noise due to the expansion of pipes.
- Balanced service load of heating elements – The microprocessor controller measures the operational time of individual heating elements and actuates them in a manner which ensures a thermally balanced loading of the boiler and an even service load of the heating elements, which extends their operational life.
- Each boiler is tested – on water circuit tightness and the function of the regulating and safety components is set and tested as well, before it leaves the factory.
The Standard Range of Electric Central Heating Boilers
The Standard Series of electric Central Heating Boilers -The standard range is available in 7.5kW,15kW,22.5kW,30kW,37.5kW and a 45kW Output models. This electric central heating boiler range goes from 2.5kW to 45kW of Heating Output. These electric central heating boilers work up to maximum temperature of 80°C and minimum pressure of 0.5 Bar to maximum pressure of 3 Bar.The feature the following benefits –
- Fluent regulation ( boiler output ) in low steps of 2.5 kW for the electric boilers up to 30kW, and 5 kW for the electric boilers from 30 kW to 45kW
- Option to connect the boilers to an OpenTherm+ thermostat or controller e.g. a nest controller etc ( control your electric boiler on the go, from your phone)
- Compensated weather control option for boiler – i.e. control / output according to the spatial or outdoor temperature ( a great energy saving feature)
- Option to connect up to 32 boilers in an intelligent cascade boiler configuration, in order to have increased heating power or output
- Outputs of up to 15kW, when using a 240 Volt / 1 Phase electrical supply – and up to 45kW when using a 400 Volt / 3 Phase electrical supply ( up to 1,440 kW when used in a cascade electric boilers configuration)
- All of these electric central heating boilers up to 23kW Output have an inbuilt 7 litre expansion vessel inbuilt, after this size the electric boilers must use an externally mounted expansion tank dependant on system volume and temperature.
- Option of remote boiler control through SMS messages when fitted with the SMS module
- Option to monitor the maximum current drawn to prevent overloading of the consumer board in the building/property – this system reduces the input power to the electric boiler automatically – ensuring that your main fuse does not blow.
Please note the following for the for the rated current of these electric boilers – The smaller electric central heating boilers up to 15kW ,can be wired from either a three phase / 400 volt supply or a single phase 240 volt supply – thus on these units you will see two sets of figures for the maximum rated current – the first number “3 x 12” for example on the FHEL8 Model , is the 3 phase Amps – therefore 3 phases , with 12 Amps on each phase. The second figure in the brackets (1×36) is the single-phase Amps – therefore Single phase / 240 Volt pulling 36 Amps maximum for the FHEL8 Boiler.The same applies for the main circuit breaker figures for the boilers – the first figure is if you use 3 phase supply to connect the boiler up , and the bracketed figure i.e. (the number within here ) is the size require if you use a single phase supply to wire the boiler up.
Standard Series – Electric Central Heating Boilers – Technical Data
Electric Boilers- with touch display
The next option in the Flexiheat UK electric central heating boiler product portfolio is the touch screen range.This range of electric central heating boilers, are available in three sizes – a 4.5 kW output electric boiler, designated the FHEL5, a 9kW output electric boiler , designated the FHEL9 , and the largest unit being the 13.5kW output electric boiler,which is designated the FHEL14.All of this range are suitable for a single phase – 240 volt supply or can also be wired from a three phase -400 Volt supply.This range of electric boilers has all the features of the standard series , with a few notable enhancements,these being –
- Simple and intuitive control of the boiler ,due to the well arranged touch display
- Fluent regulation in low power output steps by 500 Watts (0.5kW) for the FHEL5 model, by 1,000 Watts (1 kW )for the FHEL9 model ,and 1,500 Watts (1.5kW) for the FHEL14 model.These lower power outputs ensure that the heating load requirement is appropriately matched. and brings even greater heating efficiency to the wet central heating electric boiler system.
- Minimum output of the electric boilers is 500 Watts (0.5kW) for the FHEL5, 1000 Watts (1 kW ) for the FHEL9,and 1,500 Watts (1.5kW) for the FHEL14 models , which all helps to increase the efficiency of the electric central heating boiler system.
- Due to the low minimum performance and the modulation option, these boilers are recommended for low energy houses and passive houses ( ultra low energy buildings )
- The modular digital control assures optimal operation of the electric boiler in a way that optimizes electric energy consumption with the rated thermal output of the electric boiler.
Please note the following for the rated current of these electric boilers – These smaller electric central heating boilers up to 13.5 kW in output ,can be wired from either a three phase / 400 volt supply or a single phase 240 volt supply – thus on these units you will see two sets of figures for the maximum rated current – the first number “8” for example on the FHEL5 Model , is the 3 phase Amps – therefore 3 phases , with 8 Amps on each phase. The second figure in the brackets (21) is the single-phase Amps – therefore Single phase / 240 Volt pulling 24 Amps maximum for the FHEL5 Boiler.The same applies for the main circuit breaker figures for the boilers – the first figure is if you use 3 phase supply to connect the boiler up , and the bracketed figure i.e. (the number within here ) is the size require if you use a single phase supply to wire the boiler up.
Touch Screen Series – Electric Central Heating Boilers – Technical Data
Electric boilers for hot water and central heating
By using your central heating electric boiler in conjunction with an indirect domestic hot water cylinder or tank, then you can supply plentiful amounts of Domestic Hot Water for your bathing, be it showering or filling a bath and washing up requirements.
This hot water system ensures that the electric central heating boiler not only heats your wet central electric heating system, be it radiators, under floor or a mixture of both and the hot water cylinder via the cylinders internal heating coil.
You can couple up the boiler to an indirect hot water cylinder, that can also have an electric powered immersion heater in it either as a back-up, or to take advantage of cheaper off-peak electricity to heat the domestic hot water over night.
Using your electric central heating boiler in conjunction with solar hot water heating
An electric boiler can be used as either a “back up” or a “top up” hot water heater for a solar hot water heating system. The boiler can be used to heat up the domestic hot water which is stored in a hot water cylinder, when there is not enough solar energy to get to the desired temperature, which is normally 60 degrees centigrade for stored domestic hot water. This is achieved by using a 3-port valve and a cylinder stat.
Frequently Asked Questions
Are electric central heating boilers expensive to run?
The current electricity cost rate per kWh – (Kilo Watt Hour) is currently 12.376 pence as at 11th August 2019 for the average UK consumer. The average kWh used for heating for low users, which should be considered typically as flats or lower occupancy medium sized houses is around 8,000 kWh per year, thus around £990 per year.
For medium users, which should be though of as a typical 3 bed semi property with the parents and 2 children living there, then this figure is 12,500 kWh per year, which results in a figure of £1,547 per year
Lastly heavy users, which would be a larger property e.g. a 4-bedroom house, parents and 3 teenagers/ young adults, then the consumption figure is 18,00 kWh per year, resulting in a cost per year of £2,228.
NB All prices are quoted ex Vat
Of course, if you are generating your own electricity via solar PV panels, wind turbines, or even water turbines, then these costs can be dramatically reduced, as well as the additional green benefits of adding no CO2 into the environment
Can electric boilers heat radiators?
Yes of course the can- An electric boiler should be thought of as a standard gas or oil boiler, the only difference is that in powered by electricity other than that they work in the same way.
How much does it cost to install an electric boiler?
It should be cheaper than installing a gas boiler, as there is no flue pipe / chimney to install as electric boiler don’t have this requirement. And definitely cheaper than installing an oil boiler, as no oil tank is required as well as the flue/chimney issue. Any competent plumber, who now these days are often qualified in electrical works would easily be able to install the boiler. If they are not qualified in electrical works, then in conjunction with an electrician.
Can you have electric central heating?
Yes- electric central heating in this sense is the same as a conventional wet central heating system but with an electric boiler as the power source, rather than a gas or oil boiler
What size electric central heating boiler do I require ?
The first part of selecting the correct electric central heating boiler is the central heating load or kW requirement. You can do this in a couple of different ways –
1. Consult a plumber or a heating services engineer –
A good qualified plumber will be able to do a heat loss calculation , but probably won’t have the design insurance indemnities ( which means that they have an insurance policy to claim off – if the system they design / recommend doesn’t work as stated.
If you want a “proper job” as they say you need to consult a CIBSE Heating consultant , who will do all the heat loss calculations etc –
Find a CIBSE heating consultant here
But they will probably charge you £100 – £150 per hour of design – probably a minimum of £300 – but they do have insurance indemnities- therefore should the heating system not work / or not be adequate enough you have recompense.
2. The cost nothing , but your time method –
Or you could calculate the load yourself using the following website – which is a heat loss calculation app, this will tell you the heat load for each room, input the rooms,hall ways etc information for your property , add them all up – and you end up with your total heating load required to heat your home or flat.
Heat load calculator is here
This heat loss calculator is very good an accurate if the information inputted is correct , I’m pretty sure that this ( or very similar) is what plumbers and heating consultants use on a daily basis to do heat loss calculations these days
3.Last but not least the ” Rule of Thumb ” , we don’t recommend using these at all , as they make a lot of assumptions and can be very dangerous ! but here we go – and use at your own risk
For underfloor wet heating systems – use 100 watts per m2 for concrete floors , and for suspended timber floors use 70 watts per m2
For a radiator heating systems – use an average of 1.5kW of output for every radiator. Thus if the central heating system has 10 rads – 10 x 1.5kW = 15kW of heating output is required
One kilowatt of heat will be required for heating every 10 square metres of your property. Thus, for heating a 50 square meters property, you would need a 5 kW electric boiler
We really wouldn’t recommend using these rules of thumb methods, use point 2 at the very least in our opinion, these heat loss calculators are very accurate these days, as long as the information entered is correct
Safety and manufacturing standards
All of our Electric Central Heating Boilers / Electric Boilers have been tested in accordance with Directives 2006/95/EC (Low Voltage Directive, LVD) and 2004/108/EC (Electromagnetic Compatibility Directive, EMC) and conform to these regulations in full.
These Electric Boilers are also in compliance with the following norms and regulations:
•EN 50110-1:2003 – handling and operation with electrical installations
•EN 55014:2001 – electromagnetic compatibility -conditions for household devices, electrical devices and similar devices
•EN 60 335-1+ed.2:2003 – electrical household devices
•EN 60 335-1+ed.2 zm.A1:2005 – electrical household devices
•EN 61000-3-2 ed.3:2006 – electromagnetic compatibility(EMC) – the limit for the harmonic current emission
•EN 61000-3-3:1997 – electromagnetic compatibility (EMC)–Law on the limitation of voltage fluctuations and flickering of the low-voltage partition network
Electric Boilers in cascade format option
The boiler electronics enable connection of up to 32 boilers into a single intelligent cascade which modulates the performance ranging from minimum output of the first boiler to the total of maximum outputs of all boilers combined. The interconnection of the master and slave boilers is possible only through a system of intelligent modules – i.e. the same interface must be used for master as well as the slave boilers.In this way the largest output that we can do is 32 x 45 kW Boilers, which equates to 1,440 kW of electrical boiler power output.
Electric boilers for sale UK & Ireland
So should you be after an Electric Boiler System, or Electric System Boilers ( We also hear them be referred to an Electric Flow Boiler or even an Electric Water Boiler ) then we at Flexiheat UK are the people to talk to. We think that we have the best range of Electric Central Heating Boilers in the UK and Ireland for both electrically heating a wet heating system and / or doing your domestic hot water requirements via a hot water cylinder. Should you require anymore assistance or information on our Electric Boilers / Electric Central Heating Boilers , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form