Combi boiler for a large house

Combi boiler for a large house

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Combi boiler for a large house or property – Natural or LPG gas – Flexiheat UK


Looking for a combi boiler for a large house? Here we go through the issues that you need to consider when selecting the best combi boiler for a large house to suit your requirements. Selecting the correct combi boiler size for any home, is critical, especially when your residence is a large house, with multiple radiators, or an underfloor heating system and multiple bathrooms, it then becomes vitally important if you require a high efficiency and economical boiler with exceptional hot water flow rates then we have the perfect gas boilers for your large house / home/ property.

In a nutshell combi boilers heat water for the central heating system and hot water demands, normally without a hot water storage cylinder. For this reason, they can struggle to cope with the hot water demands of multiple bathrooms properties that you might have in a 5 bedroom house for example. But we have a solution to this issue with the best combi boilers for a large property -please read on

What are combi boilers, and what do they do ?

Firstly, we need to establish, what a combi boiler is? Well the boilers official name is a combination boiler – but over the years this has been shortened just to “combi boiler “. These boilers are now the most popular type of boiler for homes, flats etc in the residential market for the UK. A combi boiler not only supplies the heat for the central heating of the home ( i.e. central heating system ) , but also heats the domestic hot water demands instantaneously as a hot water tap is opened.

If you already have a regular boiler installed in your property, that is coupled up with a hot water storage cylinder that requires a cold water tank in the loft space (if the hot water storage cylinder is a vented cylinder), then installing a combi boiler means you no longer need this cold water tank anymore and recover some loft space.

Generally Combi boilers need to be more powerful than regular and system boilers to do the same job, as they use a hot water cylinder to store hot water.

Another benefit of a large combi boiler is that the hot water is fed from the mains water supply, eliminating the need for a feed and expansion tanks, and thus the water pressure is often higher, resulting in better hot water performance and higher energy efficiency, without the need to store hot water.

These factors make a combination boiler one of the highest efficiency boilers on the market, with an attractive low cost purchasing price, along with the lower installation costs and continual lower running costs than the older type system boilers that were extensively used with hot water cylinders in previous times in larger homes or properties with complex heating systems.

There are two main elements to a combi boiler, which need to be considered when selecting the correct size combi boiler –

  1. The central heating side of the boiler– You need to establish how much of a heating load or requirement your large property will have. This is to ensure that the boiler has sufficient capacity to heat your large home
  2. The Domestic Hot Water performance– This is the hot water that you use to bath, wash or doing the dishes / kitchen use – when preparing meals etc

We will look at both of  these issues and give you the guidance to ensure that you have the best solution for your combi for a larger house or property with multiple bathrooms and high hot water demands.

Combi sizing for large house / homes / properties

The first part is the easier bit as they say. It doesn’t matter what heat emitters you are using to heat your home, whether it be a radiator system or an underfloor heating system or even a combination of both. The principle of heat loss sizing for your property doesn’t change for conventional boilers or combi boilers.

Basically, the fabric of your home loses heat, depending on how well insulated the building materials used, such as the brickwork, the floor and the roof. This is known as the “U “value of the materials in question.

This” U “value is official 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.

So, if you have a property built from the late 1990’s onwards then you are safe to use this ready reckoner chart. This ready reckoner table is based on a brick and block cavity wall with mineral wool insulation having a total wall thickness of 312 mm has a “U” value of 0.3 W/mtr. The building regulation from the late 1990’s specify that this “U” value must be achieved, to pass the building regulations.

You need to ensure that you have the total floor area of your home, including the ground level, 1st floor, 2nd floor etc. It is the home’s / properties total floor area you need to calculate.

Power Output of BoilerHeating area with Height of 2.7 Mtrs & U Value of 0.3
4.5 kW~ 55 Mtrs/2
7.5 kW~ 85 Mtrs/2
9 kW~ 110 Mtrs/2
13.5 kW~ 165 Mtrs/2
15 kW~ 180 Mtrs/2
22.5 kW~ 278 Mtrs/2
24 kW~ 300 Mtrs/2

For example – If your 5 bedroom house or large home has a total floor area of 600 M/2, then you’re going to need a 48 kW Combi boiler (2 x 300 m2 = 2 x 24 kW – thus a 48kW output combi boiler)

If your total floor area is 440 M/2, then you’re going to need a 48 kW Combi (1 x 300 m2 =  24 kW  and 1 x 165 M2 = 13.5 Kw –always go up on the chart – you can turn a combi boiler’s power output down , if you have it there , but you can never turn it up , if it doesn’t have the capacity – thus 24kw + 13.5 Kw = 37.5 kW  total boiler output

Our combi boilers for large homes are modulating boilers, which means they will automatically ramp up and down the boiler’s power to suit the central heating ( radiators or underfloor) requirements. They are very clever combi boilers these days !

Domestic hot water performance of the boilers

Ok, now for the second part of a combi boiler for a large house– the domestic hot water performance / sizing – and this these days is the most important factor when selecting the best boiler to suit your requirements.

Traditional combi boilers use a plate heat exchanger to heat the domestic hot water up to temperature, from the “heating water side of the boiler “. They have benefits in that they only heat the hot water when there is a demand, and we do a range of this type of combi boilers up to 50kW of output which is an “A” rated boiler for the heating system and hot water , these are listed on this webpage 50kw combi boilers

A 50kw combi boiler or 50 kw gas combi boiler- which is a combination boiler doing both heating and domestic hot water heating, powered by either natural gas or LPG gas from Flexiheat UK

50kW Combi boiler or Combination boiler – gas fired – from Flexiheat UK

But they also have some minus points, which really come into factor when trying to fulfil the hot water demands when used in larger homes, with multiple bathrooms, or many hot water taps.

Because a combination boiler draws all of its water supply directly from the mains water supply, these boilers struggle to meet high demands for the hot water. An example of this, is when multiple hot water taps are turned on in various bathrooms, the kitchen or other rooms within the house, you will often see a dramatic reduction in the water pressure.

This is caused by the combination boiler not having the benefit of a storage hot water tank, which would meet these levels of demand. This situation used to be resolved by using a regular boiler commonly known as system boilers in conjunction with a hot water storage cylinder.

We’ll we at Flexiheat UK have solved that problem, we basically have a “hybrid combi boiler” or a “combi boiler with an element of storage”, which makes these powerful boilers especially suitable for larger homes, that usually have larger hot water demands via multiple bathroom or showers, that any gas safe registered engineer can install.

Another benefit of having an element of hot water storage is that the larger the property, the longer the hot water pipe runs tend to be, so depending on the property layout you can install a secondary domestic hot water return, which eliminates the delay for the hot water to get to the taps around the home, this also eliminates what is referred to as “hot water dead legs”.

So this brings us to our range, and why our boilers are regarded as the best combi boiler for a large house

We do two models –

the 55 model – which is a combi boiler that modulates its output all the way from 12 to 55 kW for the heating side of the boiler and will produce 54 kW of heating power for the domestic hot water demand

or the largest model – our 65 unit – which is a combi boiler that modulates its output all the way from 13.5 to 65 kW for the heating side of the boiler and will produce 64 kW of heating power for the domestic hot water demand

Each of these boilers are available with a hot water tank in either 60 , 90 or 120 litres of storage , which can handle a domestic water pressure of up to 6 bar ( any more than 3 bar ,and a shower can start to get painful with that pressure , and your taps turn into powerful water jets , often with the water coming out at such a force , that it goes everywhere.

But here is the element which makes the combi boilers the best choice for a large house – the Domestic Hot water performance – it literally is phenomenal, remarkable or exceptional – however you want to call it.

To explain how good it is – here are some stats –


According to BS6700 a standard bath (1700mm x 700mm) full capacity is around 180 litres to overflow level, but most people fill their bath tubs to around half way to allow for the displacement of water when they get into the bath. So, the actual volume of water used is 100 litres.

The normal bath water temperature is around 40 Degrees C

When you have stored water, this is kept at 60 Degrees C to prevent legionella, which is then blended down with cold water to achieve the 40 Degrees C, at a ratio of 60% hot water and 40% cold water, or 60 litres of hot water and 40 litres of cold water to make up the 100 litres.

Thus, a bath cycle requires 60 litres of hot water, stored at 60 Degrees C

The 60 litre tank, would recover it’s hot water in 6.30 minutes, (which means you can start filling a bath 6 minutes 30 seconds after filling the previous one )  the 90 litre in 6.30 minutes ( one and a half baths ) and the 120 litre unit in 6.30 minutes ( two baths simultaneously )  , which is very impressive domestic hot water performance indeed, as these combi boilers have a hot water priority system.


The figures are even more impressive for showers –

According to all the data, a standard 5-minute shower approximately 45 litres of water at 40 degrees C, which uses 27 litres of hot water stored at 60 degrees C – with a standard shower head. From this data – our 60-litre hot water storage tank will do 2 shower – simultaneously – the 6 and half minutes later you could go again

Our 90 Litre – 3 showers, again simultaneously – 6 and a half minutes, you can go again

Our 120 Litre – 4 showers with a little spare, again simultaneously – 6 and a half minutes, you can go again

In reality , we would say , that the persons wouldn’t have even come out of the shower room or bathroom, as they need time to dry off , shave , clean their teeth , do their hair etc, before the unvented hot water cylinder has recovered all of the hot water, in this way you could almost say that you have infinite hot water and all at a great water pressures – no limp or poor showers here !


Water Pressure

As a combination boiler draws all of its water supply directly form the mains water supply, they can often struggle to meet high water demands, especially in large properties like a 4 or 5 bedroom house .We have all seen what happens when a person turns on a hot water tap when someone is having a shower, and the dramatic drop in water pressure , normal followed by a shout “ turn that hot tap off “ I’m having a shower , this is due to the fact that a true combination boiler has no hot water storage tank like our combi boilers, which overcomes this problem, and allows multiple hot water taps or outlets to be used simultaneously, at good pressures.

Full technical output details for our combination boilers with storage for larger properties

These combination boilers for larger properties – can be fired with either natural gas or LPG / Propane Gas

Thermal Capacity – Heating
Maximum Heating CapacitykW555555656565
Minimum Heating CapacitykW12121213.513.513.5
Maximum Heat Discharge for Heating (80°C / 60°C)kW53.453.453.4646464
Minimum Heat Output for Heating (80°C / 60°C)kW9.
Maximum Heat Discharge for Heating (50°C / 30°C)kW57.
Minimum Heat Load (50°C / 30°C)kW9.99.99.911.811.811.8
Maximum Domestic Water CapacitykW54.154.554.764.264.664.8
Thermal Efficiency
Efficiency @ Pmax. (80°C / 60°C)%97.597.397.797.397.297.2
Efficiency @ Pmin. (80°C / 60°C)%98.899.198.20%98.698.398.6
Efficiency @ Pmax. (50°C / 30°C)%105.3105.2105.1105.6105.3105.6
Efficiency @ Pmin. (50°C / 30°C)%107.2107.2107.2107.1107.3107.4
Efficiency @ 30% (30°C)%108.1108.7108.5108.6108.4108.7
Domestic Water Circuit
Domestic Water Temperature Adjustment Range°C10 -6510 -6510 -6510 -6510 -6510 -65
Domestic Water Storage Tank VolumeL60901206090120
Domestic Water Flow Rate in ContinuousL / dT12.218.224.412.318.624.6
Use (∆T=25°C. 20 °C /45 °C)
Heating & DHW Pressures
Maximum Operating Temperature- Heating°C858585858585
Maximum Operating Pressure- HeatingBar444444
Minimum Operating Pressure- HeatingBar0.
Maximum DHW PressureBar666666
Gas Properties
Gas TypeG20-G31G20-G31G20-G31G20-G31G20-G31G20-G31
Gas Inlet Pressure (G20) Nat Gasmbar202020202020
Gas Inlet Pressure (G31) LPG /Propane Gasmbar373737373737
Combustion Values
Maximum Flue Gas Outlet Temperature (50°C / 30°C)°C444444454545
Maximum Flue Gas Outlet Temperature (80°C / 60°C)°C656565656565
NOx Emission  Class (EN 15502-1+A1)555555
Electrical Values
Voltage & FrequencyV / Hz230/50230/50230/50230/50230/50230/50
Energy ConsumptionW210210210300300300
Hydraulic Circuit Properties
Gas Connectioninch1/2”1/2”1/2”1/2”1/2”1/2”
Heating Circuit Flow & Return Connectionsinch3/4″3/4″3/4″3/4″3/4″3/4″
Domestic Water Circuit Flow & Return Connectionsinch1/2″1/2″1/2″1/2″1/2″1/2″
General Features
Net (Dry) Weightkg100115130105120135
Flue Diameter (Ø)mm80/12580/12580/12580/12580/12580/125
** G20 Natural Gas.    G31 LPG
Control options for the boilers

Everyone now wants to be able to control their boiler, when they are out and about, be it travelling or at work or even on a plane – having the facility to turn your boiler on and have the house warm for when you return to it has now become almost standard. Well the good news is that a combi boiler can do this – they have a control panel is also what is called “OpenTherm Plus “compatible, which means you can control these combi boilers, via the use of an “OpenTherm” controller, such as a “nest” type or similar.

This means you can make your life simpler and control these combination boilers from either your mobile phone (android or apple) your PC or tablet, from anywhere in the world, as long as you have an internet connection.

The control panel on these combi boilers also has numerous inbuilt features such as –

  • Frost Protection – Full protection against freezing of the heating and domestic hot water in low ambient temperatures
  • Pump Protection system – Anti-blockage System -The circulation pump is activated automatically once every 24 hours and prevent any blockage
  • Ability to operate according to different heat demands with the variable flow pump control
  • Low fuel consumption and fixed combustion efficiency thanks to the PWM driver, high modulating fan and high modulating gas valve
  • Ability to operate according to different heating system configurations

Last point is that all combi boilers when fuelled by gas should be installed by a gas safe registered engineer, not just a heating engineer to comply with the regulations and to ensure that the combi boilers are safely and correctly installed.

What are you waiting for ! Call us, for the best combination boiler for large properties

So should you be looking for a combi boiler for a large 4 bed house or for a 5 bedroom house , with 2 , 3 or even 4 bathrooms , you can now see why our combi boiler is the best option , as the element of some hot water storage , which is as small as possible , and thus saving on wasted energy , but large enough to cope with the hot water requirements of a large home or property, then please don’t hesitate to contact us at Flexiheat UK for the best combi boilers prices, using the contact us function at the top of this web page, or alternatively give us a call on 01202 822221.As we believe we have the best combi boilers for 4 bedroom house and the best combi boiler for 5 bedroom house for sale on the UK and Irish market.


Fan Coil Heaters

Fan Coil Heaters

Fan coil heaters; hot water heating fan coil; fan coil heater units; fan assisted air heaters;

Fan coil heaters from Flexiheat UK

Fan coil heaters are devices or units that consist of a heat exchanger or coil, which has a fan behind it, to provide a steady stream of fan assisted warm or hot air, which is then used to heat the area quickly and efficiently. They require warm or hot water to feed the coil or heat exchanger, which then transfers it’s heat into the surrounding air, as the fan that is situated behind the coil or heat exchanger pushes the warm air out. Thus, sometimes these heaters are sometimes referred to as fan assisted air heaters or fan coil units. Normally used in large buildings such as commercial and industrial buildings, these fan coil units benefit from temperature control and speed control of the heated air and can be wall or ceiling mounted.

Typical applications for fan coil heating systems include –

  • Factory Heating
  • Warehouse Heating
  • Garden Centre Heating
  • Sport Centre and Stadium Heating
  • Workshop Heating
  • Shopping Centre Heating
  • Church and other places of worship Heating
  • And many other retail outlets, such as car showrooms,
  • Poultry Shed Heating – we do a special unit specially designed for this duty
  • Pig Shed Heating – again, we do a special unit for this application
  • Barns and Storage areas Heating

These are just a few on the many applications these heaters are suitable for. They are very widely used in warm air heating applications that use biomass boilers, that are producing warm water, to transfer that energy produced into warm or hot air.

Fan coil warm air heating system

Using fan coils for heating has been popular and been around for many years – it is a proven method for heating commercial and industrial buildings. They can be used in either re-circulated air from within the building, or can be used to heat in coming fresh air into the building or even a combination of both, via a mixing chamber.

Advantages of these fan coil heating units are –

1.Capability to heat large buildings or areas

2.High efficiency

3.A heating system with low inertia – heating the building in a very short period from initial start-up of the heating system.

4.Even distribution of the heated air – vital to ensuring an effective warm air heating system, using these fan assisted space heaters

5.Relatively low purchasing price – ensuring a competitive solution to the warm air heating of buildings.

6.Also available with cooling coil fitted in conjunction with a heating coil in these fan coil units

7. Fan speed control options

Hydronic fan coil heaters

Hydronics is the use of a liquid heat-transfer medium in a heating system. Thus, these heaters are sometimes referred to as hydronic fan coil heaters, as the heaters use pumped hot water, that flows through the heater coils. These coils have a fan fitted behind them, which blows the air across the coil, and takes the heat from the coil – thus heating the area in which the hydronic fan coil heaters are located.

Water to air space heater construction

We do two ranges of fan coil unit heaters – you can have a steel cased heater or an EPP-cased heater. EPP stands for Expanded Polypropylene, which is a device consisting of plastic that has some unique properties such as multiple impact resistance, exceptionally high strength to weight ratio, high water and chemical resistance and the last but most important point, is that EPP is 100% recyclable. These features and benefits would be difficult to find in any other material.

Both ranges can be either wall mounted or ceiling mounted, ensuring that your heaters are off the floor, and not using up any valuable floor space as well as they are also out of the way of any potential damage from knocks or bangs.

The steel cased heated are suitable for hot water temperatures of up to 150 Degrees C or lower and with the warm water operating pressure of up to 16 Bar. The range of heat output is from 6.5 kW to 344 kW depending on the temperature of the hot water used, and how many rows of heat exchangers or coils that they are fitted with.

We go into full detail on this range of steel cased units , on this dedicated web page –

This page will concentrate on the EPP cased fan coil heater heater range –

Heating capacity from 0.7 kW to 121 kW, which is dependant on the flow and return temperature of the wet heating system feeding the heaters. The output performance is also affected by the entering air temperature to the fan coil heaters, as the colder the air entering is, the more ability that air has to absorb the heat from the heat exchanger. The air flow is from 1, 000 to 5,800 M3/hr, again depending on what fan coil unit model is selected, with a low decibel rating. These fan coil units are detailed on the brochure below –

Download the Fan Coil Heaters brochure from Flexiheat UK

They can also be fitted with mixing chambers, which when connected to our fan coil units effectively creating a heating and ventilating system.

We do a full range of controls, from a simple three step manual fan speed regulation, with a room thermostat all the way up to a full BMS compatible controller, that features automatic three-step air flow regulation, with a weekly programmer, thermostat and the possibility to connect up to 31 fan coil units via single controller. This controller can either stand alone or be connected to a full BMS (Building Management System).

We also offer all the standard accessories such as two or three port control or zone valves – These should be fitted to the pipework just prior to the fan coil unit heater. Thus, when the heater is not required to operate, the warm water flow to the heater is stopped, preventing the heated water flowing through the heating coil, which would generate heat, even though the fans of the heaters would be off. This results in wasted heat energy, and in a higher fuel usage than required.

We also offer flexible stainless-steel pipework kits, that make connecting the fan coil heater to the fixed pipework very quick and easy, reducing the install time.

Heating Coil

The heating coil is constructed from copper tubes with aluminium fins attached to them. The water coil or heat exchanger can be supplied by warm water or a glycol solution up to 60% in strength. The working parameters of these fan assisted water heaters is 16 Bar, and a maximum temperature of the warm water is 120 Degrees C. The fan coil units come with heating coils that have 1,2 or 3 rows depending on the heat output of the model. The flow and return water connections of the heating coil are situated at the back of these hydronic fan coil unit heaters.

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Water to air coil or heat exchanger used in these fan coil unit heaters – They can have 1,2 or 3 rows of coils

Air delivery louvres for hot water space heaters

The air delivery louvres are constructed of polypropylene, and are fully adjustable, ensuring the heat generated from the fan coil heating system can be adjusted in its direction, ensuring that the heated air flow gets to the required areas and does it job.

Fans – Axial Blowing – Fan assisted coil heaters

These hot water fan coil heaters have axial fans fitted to them, to blow the heat generated from the heating coil into the area to be heated. These fans are protected with a strong steel wire grid cover, whilst the fans blades used are made from lightweight, but strong steel. All of these fan heaters are powered by 240 Volt single phase fans. The fans fitted are IP/ Insulation class 54 accredited/ rated ensuring high safety levels.

Mounting Brackets – Rotary

These brackets allow the fan coil heaters to either be wall mounted or ceiling mounted to suit your site requirements. You can choose to mount these heaters with an angle of 45,60 or 90 degrees, and these hydronic heating fan coil units can also be rotated through 170 degrees in the horizontal plane.

hot water heating fan coil; fan coil heater units; fan assisted air heaters; fan coil heaters;

Mounting options for Fan Coil Heating Units / System

Hot water fan coil heater

The Flexiheat range of fan coil heaters are the perfect commercial or industrial air heating solution. These hot water fan coil heaters can be installed to suite the site conditions, be it wall mounted or ceiling mounted. Sometimes these coil heaters are referred to as fan assisted air heaters, hydronic heating fan coil units, hot water heating fan coils. Whatever you call them we have the perfect fan coil heating system for you. For more information either call us on 01202 822221 or email us via the contact form, which is located above.

Electric Combi Boiler UK

Electric Combi Boiler UK

Electric combi boiler UK? – are they available? do they work? Usually when someone says “electric boiler” the majority of people think about the water boilers used to generate instant hot water to a single tap, such as an over or under sink water heater, but these units only produce domestic hot water. Happily, in the UK, electric combi boilers are now a great solution, for not only your hot water requirements, but also your heating requirements.

electric combi boiler uk; electric combi boiler prices uk; electric combi boiler reviews uk

Electric combi boiler UK for sale from Flexiheat UK


As the boiler name suggests, they are an option to a gas or oil combi boiler that uses electricity as the energy supply. Despite the fact that technology is nearly as old as the invention of electricity itself, as of late electric combi boilers have seen expanded enthusiasm from people whose properties are not served by the national gas distribution system or who basically want to dispose of their gas supply and move to a greener energy to fuel their central heating and hot water requirements .

Electric combi boiler vs Gas

Knowing that natural gas is a fossil fuel, and therefore can’t be considered a green fuel source. With regards to electricity, if it is generated via renewable energy sources or if you use a wind turbine or solar panels to generate the electricity, you can go totally carbon neutral on your energy requirements. Utilizing electric combi boilers bodes well to individuals who have installed solar panels or wind turbines onto their property. Recent advances in the technology of solar and wind generation fields now make electric combi boilers a real solution for people who want to get off the national gas grid, or don’t want to use oil either.

Beside the fact that electric combi boilers in the UK, have the capacity to be eco-friendly, the other advantage is that an electric combination boiler is often smaller in size than an equivalent boiler fired by gas or oil, and will often fit in locations that a gas or oil boiler won’t , due to the fact that these boilers require a flue pipe or chimney system to operate.

Individuals who have previously experienced on demand electric water heaters, are usually disappointed with the DHW (domestic hot water) flow rate that they have seen. This is solved with our electric combi boilers as they incorporate either a 50 litre, (for the wall mounted version) or 80 litres (for the floor mounted version) pre heated stainless steel hot water cylinder. This hot water cylinder allows these boilers ensure great hot water performance which are similar to their gas boiler equivalents, with the larger floor mounted boiler delivering 13.8 litres per minute of hot water.

Cost of electric combi boilers in the UK

When it comes to the price of electric combi boilers in the UK, they are very similar to their equivalent gas fuelled equivalents, and are generally cheaper than their oil-fired equivalents, with prices generally in the £1,600 to £2,200 depending on the kW output of the boiler in question.  Obviously, they are more expensive than a heat only electric boiler, but when you add the necessary indirect cylinder required to do the domestic hot water requirements, and the controls required to achieve this, then they generally work out cheaper, than going for a split heating and how water system, that uses a heat only boiler and cylinder combination.

Electric combination boiler installation costs

The installation cost of an electric combi boiler in the UK, is often lower than their gas or oil alternative. No flue or chimney system has to be installed with an electric boiler, which cuts down on the labour required and should result in cheaper installation price. They include an inbuilt heating pump and expansion vessel, for both the heating and domestic hot water requirements, as well as safety valves, that ensure they security of your boiler. All that is required is the appropriate electric supply, with the required amps available, and a water supply and your ready to go as they say.

Electric combination boilers are a great choice in elevated buildings such as high-rise structures, as they don’t require a flue pipe system, as no products of combustion are given off with an electric boiler. Can you just imagine not only the logistical and high expenses associated with installing a gas boiler, in a high-rise block of flats, with scaffolding, and working at height legislation to comply with in the UK, just to name a few problems to overcome. These issues are just eliminated when choosing a combination electric boiler, making them a great solution to a complex problem.

Electric combination boiler reviews UK

When reviewing our range of electric combi boilers that we sell in the UK and Ireland, following are a few brief overview of the range we sell –

Our range of electric combi boiler can be powered by a single phase 240 Volt electrical supply from 4.5 kW to 15 kW, which is the largest power output we know of on the UK and Irish market.

We can go all the way up to 21 kW of boiler output, but from 15 kW to 21 kW you require a three phase 400 Volt electrical supply

We do a wall hung or mounted version, that has a 50 litre hot water internal storage vessel housed withing the boiler, thus ensuring good flow rates, and hot water that is hot enough for doing dishes – you require hot water at 50 degrees C to get rid of grease from cooking utensils and dishes. If you only have a shower in your house or flat, then this is the electric combi boiler for you.

We also do a floor mounted version, which has a larger 80 litre internal hot water vessel, again situated withing the boiler casing, this has enough capacity of hot water to run a bath at mains pressure, just as quick as a hot water cylinder would. If you have a bath in the property, again this is the combination electric boiler for you.

All of the boilers, have 6k W of dedicated electric heating power for the hot water production of the boiler.

These electric boilers can be set to a various output, for example the 45/90 model, can be set with an output of either 4.5 kW, 6 kW, 7.5 kW, or 9 kW to suit your heating requirements. These boilers are available in either wall mounted or floor standing versions.

The 10/15 boiler model, can be set to 10 kW, 12.5 kW or 15 kW output, giving you maximum flexibility to suit your needs

Whichever combination electric boiler you go for, all of them are highly efficient, at almost 100% efficiency (actually 99.8% to be precise)

For more full information, please see the following in depth dedicated web page

Should you require any more information or advice, on what we regard as the best range of electric combi boilers UK and Ireland wide, then please don’t hesitate to call us on 01202 822221 or send us an email via our contact form in the top tool bar

Kroll heaters parts prices UK

Kroll heaters,parts and prices UK

If you require parts or prices for Kroll Heaters, then you need to speak to us at Flexiheat UK, as we were the old Kroll UK, until Kroll pulled out of the UK directly over 3 years ago. So, it’s the same basic team, just with a new name for the company, due to legal reasons. We are the authorized distributor for the UK and Ireland for Kroll products. We stock all of the most common spares / parts for the kroll range of heaters, and anything we haven’t got, we just get from the Kroll factory in Germany for you.

Kroll W401L waste oil burner / heater

This is the most popular waste oil heater that Kroll has done – the Kroll W401L, but also used to be called just the W401 when not fan heater was installed on the top. It was also called the W401VL and just W401L heater when it was supplied with the top fan assembly, which blew out the warm air from the waste oil heater.

Unfortunately, Kroll Germany have now stopped producing this heater. We have other options – please see our webpage on our replacement units – manual fired waste or multi oil heaters- for new replacement units. We also still stock and hold spare parts for the Kroll W401L on the shelf in our warehouse based on the south cost of the UK, and supply these to the UK and Ireland

Kroll waste oil heater

We still sell the Kroll ” SZ” range of automatic fired waste oil heater, which as stated previously is for sale in the UK and Ireland. This range has an output range from 25.5 kW all the way up to 180 kW, and needs to have a compressed air supply to feed the waste oil burner. This automatic waste oil burner can be wired into a programmer, so that it operates on a timer. There is no need to manually fire these heaters up, as long as there’s compressed air available with the automatic range, the Kroll waste oil heater does it all

Kroll waste oil heater for sale

We still sell the Kroll ” SZ” range of automatic fired waste oil heater, which as stated previously is for sale in the UK and Ireland. This range has an output range from 25.5 kW all the way up to 180 kW, and needs to have a compressed air supply to feed the waste oil burner. This automatic waste oil burner can be wired into a programmer, so that it operates on a timer. There is no need to manually fire these heaters up, as long as there’s compressed air available with the automatic range, the Kroll waste oil heater does it all.

The Kroll “SZ” waste oil heater package is actually made up from two components, the KG/UB waste oil burner matched to a Kroll “S” range heater. When coupled together they are designated the Kroll “SZ” waste oil heater package. The “S” range heaters are a well-made warm air cabinet heater, that from the 25kW to the 110kW model are constructed with a stainless-steel heat exchanger and combustion chamber which ensures a long and trouble-free product life cycle.

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Kroll waste oil burners from Flexiheat UK

Kroll waste oil burner spares

Again, we still do all the spares for the Kroll waste oil burner models, known as the KG/UB universal oil burner. This Kroll burner will also burn waste oils such as engine, hydraulic and vegetable oils – such as rape seed, sunflower etc. They will also burn recycled vegetable oils that have had the fats removed from them, and fish oils too! – It really is a universal oil burner, having been at the leading edge of multi oil burners now for many years.

So, if you require any Kroll heaters spare parts, for a burner or a heater, or should you require a price on a new kroll waste oil heater, or require anymore assistance or information, please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form.

Industrial Unit Heaters

Industrial Unit Heaters –

Industrial unit heaters water electric gas oil or steam powered from Flexiheat UK

Industrial unit heaters from Flexiheat UK

Industrial unit heaters come in a wide variety of types for the industrial heating industry, most are versatile in use to cover a wide variety of heating applications, whilst others are designed for specific or niche heating applications.

They are ideally suited to commercial or industrial space heating, as they have an integrated fan, which produces a high volume of air flow which distributes the warm air generated by these industrial unit heaters efficiently and evenly throughout the area of which the units are installed. Depending on the size of the area being heated single or multiple industrial unit heaters may be required, as the effective throw of the warm air has to be considered.

The use of an integrated fan on the unit heaters creates air movement over the heating element surface, quickly and efficiently, this factor ensures that when compared to an equivalent convector type heater, unit heaters are more compact in size, getting more effective warm air heat out of these types of industrial heaters. Our unit heaters are designed to hold up against the typical abuse often seen in commercial and industrial applications or environments being able to withstand dusty and dirty air conditions.

Industrial unit heater – sizing your warm air heating system

Sizing of the most appropriate model and quantity of these industrial unit heaters should always be done on the premises of gaining the optimum efficiency and cost effectiveness both in the initial purchase cost and also the running costs for the warm air heating system.

There are a number of factors, which effective the overall heat load requirement for any commercial or industrial building and the heat that is required to get to your desired working temperatures. The factors that influence this heat load calculation include –

  1. How well insulated the building being heated is.
  2. The amount of air changes per hour this building normally has – i.e. are large roller shutter doors open, and how often they are.
  3. What is your preferred fuel preference – as unit heaters can be fuelled by hot water, electric, steam, natural gas, propane gas or even oil – they choice may be dedicated to you by buildings location and subsequently the available fuel on site.
  4. The efficiency and level of control accuracy of the warm air heating system.
  5. The normal ambient air temperatures you are likely to see in the winter periods – This is an important factor in calculating the size and number of required unit heaters – as you want to ensure that the heating system is adequate to handle the coldest environmental conditions it will endure.
  6. The height of the building will also have an influence on the warm air system, as if the height is large, then the use of destratification fans, to push the warm air back to the ground level where it is required can be used to counter act this natural phenomenon and add to the heating system efficiency.

Should you require any more information on industrial unit heater sizing for your application, then we at Flexiheat UK would be please to help you size your particular warm air heating application. either pop us over an email to or give us a call on 01202 822221 to find out more.

Unit heater types

The heat emitted from these unit heaters can be generated by a variety of fuels, with the predominant factor often being the most readily available and or the most economical fuel source available to the premises.  The most common unit heater types are –

Hot water unit heaters – water fed unit heaters

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Hot water unit heaters for LTHW/MTHW or HTHW systems from Flexiheat UK

Often called a “hot water fan heater” or “hot water air heater”- water fed commercial / industrial unit heaters are very commonly used in factories, warehouses, sports halls or workshops. The hot water is normally generated by a boiler which can be fuelled by gas , oil or electric or even a heat pump which heats the water up to the desired temperature before it is circulated via a piped heating system to the unit heaters often at a low pressure ( 3 bar or under )  – thus the term “low pressure hot water” – or LPHW air unit heaters .

They come with the various control options and ancillaries such as thermostats, which can control the operation of the unit heater fan and also can control the water flow to the unit heater by opening or closing a control valve feeding the unit. Commercial or industrial premises with multiple unit heaters can often be controlled by a single controller, which when coupled to external temperature probe can optimize or compensate for the external weather conditions and adjust the warm air heating system accordingly. This results in higher efficiency levels and reduced running cost of the commercial or industrial heating system.

These industrial unit heaters are available either with units made with plastic (EPP- expanded polypropylene) casings which ensures a modern design with high performance parameters, with outputs from 5kW to 70kW, and air flows up to 4,100 M3/hr or with metal casings with outputs from 6.5 kW to 344 kW in output.

These warm water supplied unit heaters can either be suspended from the ceiling or wall mounted, allowing you to expel the warm air either vertically or horizontally to suite your site requirements

Some of our industrial unit heater range can be supplied with drip pan and drain which means they can be used not only for heating, but also for cooling applications, when supplied with a chilled water supply.

For full information on the range of water fed industrial unit heaters , please see this page of our website –

Industrial electric unit heaters

We do two ranges of industrial electric unit heaters, the first range which in reality is also suitable for commercial applications, is available with outputs from 6 kW to 15 kW. The 6 kW unit is available in either single phase or a three-phase powered model. The electric unit heaters that have a 9 kW, 12 kW or 15 kW output can only be powered by a three-phase electrical supply. This range of commercial and industrial electric unit heaters is controlled by a wireless controller, which can control any number of our electric unit heaters, up to 100 metres away from the controller location. This saves on the associated wiring and installation costs of these unit heaters.

More information and detail on this particular range of electric unit heaters can be found here –

The second range of our industrial electric unit heaters are ideally suited to industrial premises, and are not wireless controlled. They should be used to electrically heat industrial areas with relative humidity of no more than 95% and an air dust concentration of up to 3mg/m3. They come with either a slot air diffuser as standard or can be fitted with a cone air diffuser which increases the range of the warm air stream. This range of electrically powered industrial unit heaters can be installed in either a horizontal position as a ceiling mounted unit heater or in a vertical position as a wall mounted electric industrial unit heater.

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Industrial electric unit heaters from Flexiheat UK

This range has of industrial electric unit heaters, has a large range of accessories, such as roof or wall air intakes and air mixing boxes that allow the unit heater to be supplied with a mixture of fresh and recirculating air to these industrial units. They also have a range of temperature controllers that automatically changes the heat output depending on the temperature in the room and a time programmer for control of unit’s operation in a weekly mode.

For more information and detail on this particular range of electric unit heaters can be found here –

Unit Heater Types – Gas, Oil, Diesel, LPG and Propane Fired Heaters

These differ from the unit heaters mentioned previously as all of these industrial unit heaters have a combustion chamber within the heater, where the fuel is burnt and thus the heat is generated within the heater itself. They are designed for horizontal wall mounting or in vertical suspended configuration, which is useful if you are short of floor space to install a heater, or should you just want the heater up and out of the way. They have as standard an axial fan for free blowing heating applications or can be fitted with a centrifugal fan, that allows duct work to be attached to the heater, and this duct work channels the heat to the desired areas with the building.

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Industrial gas unit heaters, available in either natural gas or LPG/ propane fired from Flexiheat UK

The gas powered unit heaters , (be it natural gas or LPG / Propane) details and further information can be found here-

industrial oil unit heaters

Industrial oil unit heaters

And for the oil / diesel fired unit heaters – pictured above , the full information is here –

Industrial steam unit heaters

Steam as a medium is often seen as an old type of heating system, as it is often associated with the industrial past , but with many industrial factories using steam as part of their process – this steam is a great way of heating an industrial building , as it is exceptionally good at transferring the heat from the steam into warm air and with exceptionally fast warm up times to. Industrial steam unit heaters are very similar to water fed unit heaters, in that they have a heat exchanger coil , casing and fan assembly, but in the instance of a steam powered unit , the heat exchanger or coil itself is designed to changed the steam vapour into usable warm air energy , in in this process the steam often condenses as it transfers it energy into the air. The coils or heat exchangers used in industrial steam unit heaters must therefore be manufactured from steel with a bi-metal fin assembly to accommodate the higher pressures and temperatures associated with steam. We do a full range of steam unit heaters that have an output from 14.6 kW to 459 kW in output, depending on your steam pressure available and the entering air temperature. full detail on the range is here –

Industrial steam unit heaters

Industrial Steam Unit Heaters from Flexiheat UK

Requiring little maintenance, these steam powered industrial unit heaters are extremely tough and highly efficient, and are often wall mounted

Flexiheat UK – Your Unit Heater experts 

As you can see, we do a full range of industrial unit heaters, powered by various fuel sources, so if you have a requirement for heating an industrial or commercial building, then we will have a unit heater option to suit, so please don’t hesitate to contact us at Flexiheat UK