How to size a commercial water heater

How to size a commercial water heater

How to size a commercial water heater by Flexiheat UK; industrial water heating sizing;

How to size a commercial water heater by Flexiheat UK

A commercial water heater is required for supplying warm or hot potable water for showers, bathrooms, kitchens, restaurant sinks, washing machines etc and other purposes in a commercial or industrial building, such as schools, hotels, gyms or hospitals. A commercial water heater uses electrical elements or a burner to heat cold water up to the desired hot water temperature which is used when a demand is placed on water heater. Water heaters may use a tank to store the heated water for when it is required. Sizing a commercial water heater is relatively easy process and not a ” dark art ” as some people may think.

They are also used in many industrial water heating applications, when hot water is required for a production process, such as commercial laundries or other uses, as part of manufacturing a product or service.

If you size or select a commercial water heater with more than the capacity required, you’ll end up with higher capital cost and also higher fuel bills than required, on the other hand If you undersize a commercial water heater, then you run the risk of running out of potable hot water, and upsetting your customers in the case of a hotel for example or your production process failing in the event of a hot water process application. Thus, we have written this “How to size a commercial water heater” guide to assist in the correct selection for your water heater requirements.

Commercial water heater definition

A water heater can be defined as a closed tank used to supply potable hot water, which is either heated by electricity, gas (Natural gas or LPG), or any other source, such as solar. The water heater is intended to be supplied with potable water either from a potable water supply, such as directly from the water mains system (these are referred to as unvented hot water system) or via feed tanks when used in an open vent hot water system.

The three vital elements to bear in mind when sizing a water heater for commercial or industrial applications


Water storage tank capacity: The tank or vessel capacity for storing the hot water required. The tank allows a large volume of water to be drawn at flow rates that can exceed the recovery capacity of the water heater- which is useful for peak hot water demands.

The recovery rate: The amount of water in litres per hour, raised at a given water temperature rise and kW input. Also often quoted is the one hour draw capacity of the water heater, which is the maximum hot water production for one hour, normally required at the peak period of the day when the heaviest requirement of hot water will occur.

The power or energy input of the water heater – The amount energy required, normally measured in Kilowatts consumed by the water heater, which is provided by your preferred fuel, either electric, gas or oil. One kW of energy is 3,412 Btu’s, if you use the old imperial system.

These three factors are used together to select the correct water heater size and power rating.

The best method for selecting a commercial or industrial water heater is on the basis of hot water usage. The selection is a combination of these factors of tank size, recovery rate and heat input.

What size water heater do I need calculation for commercial water heating applications

Following is the European standard for hot water demands to DIN 4708, that is commonly used when sizing your commercial water heater or industrial water heater- whichever you may classify your water heater as.


Commercial Building TypeDemand factorBath tubShowerBidetPrivate wash basinPublic wash basinKitchen sinkSlop sinkBar sink
Hotel & Hostels / B&B’s0.550501010158050100
Sport centre / Gym’s12205158040100
School (Day type not boarding)0.81805208040
Commercial Offices15104040

Calculation example for a commercial water heater hot water demand

A Hotel with 100 rooms = Litres of hot water / Hour at 60 °C

  • 100 Bath tub / showers = 5,000
  • 25 Bidets = 250
  • 100 Private wash basins = 1,000
  • 20 Public wash basins = 375
  • 5 Bar sinks = 500
  • 8 Kitchen sinks = 640
  • 5 Slop sinks = 250

This gives us a total hot water demand of 8,015  x the demand factor for a hotel water heating system sizing of 0.5 = 4,007.5 litres per hour continuous at 60 °C

With a commercial hot water requirement / application like this, due to the volume of water required, the only practical solution is a commercial storage water heater, we do a full range of commercial gas water heaters, that we can match to various storage volumes of up to 5,000 litres in a single storage tank ( more when used in series)  and a power input of 300kW. They are also condensing too, thus you’ll have the maximum efficiency for your hot water commercial system.

We also supply commercial water heaters powered by an oil burner, and this range of oil fired water heaters is fuelled by gas oil which is the preferred oil used in commercial and industrial water heating applications.

As well as electric powered which we speak in more depth below in this webpage

Hot water demands for apartment blocks with a communal / centralized hot water system

A standard apartment or flat according to DIN 4708 is defined as consisting of 4 rooms, with 3 /4 persons living there, a 150-litre bath (with a fill time of ten minutes) with one wash basin and one kitchen sink.

It also specifies, within the standard, that the hot water storage capacity and the performance of the heat exchanger in terms of efficiency are both significant factors in determining the number of apartments a water heater or heaters can serve. A general guide is as follows  –

Number of apartmentscontinuous  requirement (litres per hour)
Domestic Hot Water Temperature60 °C45 °C


Commercial electric water heater sizing

You size a commercial electric water heater, on the exact same principles as a gas or oil powered version, just the fact that you require electricity as the fuel source or power for the water use the above data to establish your hot water requirement, then look at our webpage commercial electric water heaters, for the available sizes and power outputs than we can supply. Just make sure you have the Amps available to power the unit.

Commercial tankless water heater sizing

Sizing a commercial tankless water heater is a different case, as a commercial tankless water heater heats up water on demand rather than storing warm water in a storage tank for later use. This means they are generally more efficient as they only ever heat as much water as you need and are smaller in size than storage water heaters.

But they have a down side as heating water on demand requires using a larger burner in the case of a gas or oil-fired commercial water heater or electrical heating elements than a commercial storage water heater would use, which means that the energy demand while heating the water can be very high. So, you have to ensure you have the power available to satisfy this requirement.

The most common commercial tankless water heater is gas powered, as gas ( either natural gas or LPG gas ) is great at producing a lot of energy via a relatively small supply pipe.

You size commercial tankless water heaters via the number of hot water outlets they have to satisfy, and to what water temperature, we go more into this on this dedicated webpage – gas multipoint water heaters, that are used in commercial tankless hot water systems.


Industrial water heater sizing / calculation

Often industrial water heaters, are sized in a slightly different method, as normally, there are different water temperature rises, specifically required for the process in question
For industrial water heating processes, there are normally 3 elements to sizing your water heater.

These are –

1. The volume of hot water that you require – How many litres of hot / warm water do you require?
2. The temperature rise that you want that water to go through e.g., from the incoming water temperature of 10 degrees C to 70 degrees C etc
3. Lastly your time requirements – how quickly do you want that water to heat up in, or how many litres you require of water per hour your process requires.

When you have established these factors, then you can use the following calculation to establish the kw rating required for you water heater
To heat a specific volume of water by a given temperature rise in one hour.

Volume of water in litres x 4 x the temperature rise in degrees centigrade divided by 3412

(just for note – 4 being a factor and 3412 being a given constant)

Thus, for a 1,000 litre water heater, the calculation would be as follows –

1000 litres of water, to be heated from say 10°C to 70°C, giving a temperature rise of 60 °C would result in-

1,000 x 4 x 60 / 3412 = 70.339 kW per hour

This means that the 1000 litres of water would be heated in one hour by 70.33 kW of applied heat, for the temperature rise of 60°C, whether its by gas, oil or electric

We can use this result to conclude other factors – e.g., to heat the same water volume of 1,000 litres in half the time (i.e., 30 minutes) we would need twice the heating power i.e. 140.66 kW, as 70.339 x 2 = 140.66 kW.

Should the process require a 2-hour period recovery period for the industrial water heater, then we can lower the power input to 36.16 kW
When sizing an industrial water heater and for a commercial water heater, these are the actual power input figures into the water heater, so you need to ensure that the heater has a nett input of this figure, but its also prudent to add a small percentage for standing heat losses, if you are using a storage water heater.

Alternatively, if you have a specific water temperature rise, and you know the kW input rating of the unit, then you can calculate the water flow rate produced, then use the flowing formula –

m (kg/s) = P (kW) / the specific heat of water (Kj / Kg ºC) X ΔT of the water in Degrees C

Whereby –
m = mass flow rate (kg/s) this is litres per second as one litre of water weighs one kilogram
P= Power in kW
Specific heat of water = 4.187 Kj/Kg ºC
ΔT = temperature increase in C

An example
A water heater, with thermal power input of 70 kW, with a temperature rise of 60 degrees C then it would be –
m = (70kW) / ((4.187 kJ/kg ºC) (60ºC))
thus – 70 / 4.187 x 60
70/251.22 = 0.2786 kg/s or 0.2786 Litres a second – times this by 60 seconds to get per minute then by 60 minutes to get the volume per hour – thus 1,003 Litres per hour for a 60 Degree C water temperature rise.

Hopefully this sizing / calculation guide for commercial and industrial water heating applications has provided the information and formulas to help you size the correct water heater for your application. Should you require any more information on our water heaters, please don’t hesitate to contact us at Flexiheat UK

Combi boiler for a large house

Combi boiler for a large house

combi boiler for a large house; large house combi boiler; best combi boiler for large house; best combi boiler for 4 bedroom house;

Combi boiler for a large house from Flexiheat UK


Looking for a combi boiler for a large house? Then 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 combi boiler for your large house / home/ property.

What is a Combi boiler, and what do they do ?

Firstly, we need to establish what is a combi boiler? 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, but also heats the domestic hot water instantaneously a hot water tap is opened.

Another benefit of a combi boiler is that the hot water is fed from the mains water supply, eliminating the need for a feed and expansion tank, and thus the water pressure is often higher, resulting in better hot water performance.

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 extensive used in previous times in larger homes or propeties.

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

1. The 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 combination boiler for a larger house / property.

Combi boiler sizing for large 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.

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 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 boiler (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 boilers 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 their heat output to suit the central heating requirements.They are very clever boilers these days !

Domestic Hot Water Performance of the Combi Boiler for a larger property

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.

But they also have some minus points, which really come in to 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.

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 them especially suitable for larger homes, that usually have larger hot water demands via multiple bathroom or showers.

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 with a  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 three models –

our 45 model – which is a combi boiler that modulates it’s output all the way from 11 to 45 kW for the heating side of the boiler and will produce 44.2 kW of heating power for the domestic hot water demand

the 55 model – which is a combi boiler that modulates it’s 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 60 unit – which is a combi boiler that modulates it’s 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 , is avaialbe 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 ( anymore than 3 bar , and a shower can start to get painful with the water 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 tub (1700mm x 700mm) full capacity is around 180 litres to overflow level, but most people full 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 hot water tank 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 the shower, and the dramatic drop in water pressure , normal followed by a shout “ turn that 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 boilers, which over comes this problem, and allow multiple hot water taps or outlets to be used simultaneously, at good water pressures.

Full technical details for our combi boiler with storage for larger properties

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

TECHNICAL SPECIFICATIONSModelFH-S DHW      45SFH-S DHW      45MFH-S DHW      45LFH-S DHW      55SFH-S DHW      55MFH-S DHW      55LFH-S DHW      65SFH-S DHW      65MFH-S DHW      65L
Thermal Capacity – Heating
Maximum Heating CapacitykW454545555555656565
Minimum Heating CapacitykW11111112121213.513.513.5
Maximum Heat Discharge for Heating (80°C / 60°C)kW42.442.442.453.453.453.4646464
Minimum Heat Output for Heating (80°C / 60°C)kW7.
Maximum Heat Discharge for Heating (50°C / 30°C)kW45.845.845.857.
Minimum Heat Load (50°C / 30°C)kW8.
Maximum Domestic Water CapacitykW44.244.444.854.154.554.764.264.664.8
Thermal Efficiency
Efficiency @ Pmax. (80°C / 60°C)%97.497.397.797.597.397.797.397.297.2
Efficiency @ Pmin. (80°C / 60°C)%98.598.698.798.899.198.20%98.698.398.6
Efficiency @ Pmax. (50°C / 30°C)%105.2105.3105.4105.3105.2105.1105.6105.3105.6
Efficiency @ Pmin. (50°C / 30°C)%107.4107.6107.2107.2107.2107.2107.1107.3107.4
Efficiency @ 30% (30°C)%108.7109108.2108.1108.7108.5108.6108.4108.7
Domestic Water Circuit
Domestic Water Temperature Adjustment Range°C10 -6510 -6510 -6510 -6510 -6510 -6510 -6510 -6510 -65
Domestic Water Storage Tank VolumeL609012060901206090120
Domestic Water Flow Rate in ContinuousL / dT12.118.424.
Use (∆T=25°C. 20 °C /45 °C)
Heating & DHW Pressures
Maximum Operating Temperature- Heating°C858585858585858585
Maximum Operating Pressure- HeatingBar444444444
Minimum Operating Pressure- HeatingBar0.
Maximum DHW PressureBar666666666
Gas Properties
Gas TypeG20-G31G20-G31G20-G31G20-G31G20-G31G20-G31G20-G31G20-G31G20-G31
Gas Inlet Pressure (G20) Natural Gasmbar202020202020202020
Gas Inlet Pressure (G31) LPG /Propane Gasmbar373737373737373737
Combustion Values
Maximum Flue Gas Outlet Temperature (50°C / 30°C)°C424242444444454545
Maximum Flue Gas Outlet Temperature (80°C / 60°C)°C656565656565656565
NOx Emission  Class (EN 15502-1+A1)555555555
Electrical Values
Voltage & FrequencyV / Hz230/50230/50230/50230/50230/50230/50230/50230/50230/50
Energy ConsumptionW190190190210210210300300300
Hydraulic Circuit Properties
Gas Connectioninch1/2”1/2”1/2”1/2”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″3/4″3/4″3/4″
Domestic Water Circuit Flow & Return Connectionsinch1/2″1/2″1/2″1/2″1/2″1/2″1/2″1/2″1/2″
General Features
Net (Dry) Weightkg95110125100115130105120135
Flue Diameter (Ø)mm80/12580/12580/12580/12580/12580/12580/12580/12580/125
** 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 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 also has numerous inbuilt features such as –

  •  Frost Ptotection – 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
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, 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 boiler 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.

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 heating

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 withing 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.

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 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 model.These 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 heaters 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 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 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 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 heaters.

coil heat; heat exchangers; unit heaters; fan heater; coil heating; blower coil unit;fan coil unit heater

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

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.

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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; industrial electric unit heaters;

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

hot water unit heaters;hydronic hot water hanging unit heater

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.

Industrial electric unit heaters; unit heater electric; commercial electric unit heater

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.

Industrial gas unit heaters;industrial gas fired unit heaters

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







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.

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. 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 element 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 heater 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 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 heating 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.

What is an electric heating boiler?

An electric heating boiler generates heat using electric heating elements immersed in water.Electric heating 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 electric meter. 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.

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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 them 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 poisoning that can kill.
  • 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.
  • 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 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
  • The downside – The price of electricity: 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?

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 range that goes 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, and from there on and up to 45 kW they require a three phase electric supply. Full details on the range can be found on our dedicated product page here –

electric wet central heating boiler; electric boiler heating system; electric boiler underfloor heating

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 – 

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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.