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 – 


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Electric wet central heating boilers from Flexiheat UK

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

Electric central heating boiler systems – UK and Ireland

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

Electric Industrial Fan Heaters

Electric Industrial Fan Heaters

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

Industrial fan forced electric heaters

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

Fixed or mobile Industrial electric fan heaters

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

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Wall or Ceiling mounted electric industrial fan heaters from Flexiheat UK

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

For 6 kW to 27 kW of heat output – 


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


Mobile units – 

Industrial electric heaters , commercial electric heaters

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

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

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

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


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

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Industrial Electric Heater-42kW- from Flexiheat UK

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

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

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Sizing of your heat requirement / heat loss 

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

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

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

Sockets, Plugs and Leads for Industrial Fan Heaters

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


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

Industrial electric fan heaters UK

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

Industrial electrical fan heaters UK

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

Industrial Warm Air Heaters

Industrial Warm Air Heaters – Your Options / Guide 

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

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

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

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

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

Industrial gas warm air heaters

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Industrial warm air heaters from Flexiheat UK

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

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

Industrial Warm Air Heating Systems

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Industrial warm air heating from Flexiheat UK

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

Industrial Warm Air Heating

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

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

Industrial warm air heaters UK

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

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

Heating industrial sites with warm air

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

12kw Electric Combi Boiler

12kW Electric combi boiler – What are your options?

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

Here Flexiheat UK, we have a couple of options for your 12kw electric combi boiler requirements. We do a range of 12kw electric combi boilers, that can either be run off a 240 Volt / Single Phase electric supply (the most common household electrical supply voltage for the UK and Ireland) or 415 Volt / Three phase electrical supply. The term “combi” is just an abbreviation for the word “combination” and when used in the context of a 12kw electric combi boiler, this means that the electric boiler will not only do the central heating requirements, but also produce domestic hot water, for your hot water taps within your property or flat.

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12 kW Electric Combi or Combination Boilers from Flexiheat UK

12kW Electric Combination Boiler Efficiency & Benefits

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

  • A fully qualified ErP compliant 12 kW Electric Combination Boiler
  • 50 litres of Domestic Hot Water Storage in the wall mounted version or 80 litres of storage in the floor mounted version 
  • They can be used with a wet underfloor heating system
  • They can be used on a a traditional wet central heating system with radiators
  • They can be used in conjunction with solar heating systems
  • Come with a ErP compliant heating pump
  • Can operate in 2 steps – i.e. half power , or full power output
  • A frost / freezing protection system – If the temperature of the water inside the 12kw electric combi boiler is under 5°C, the pump and heating elements will operate to bringing the water temperature up to 35 Degrees Centigrade, ensuring that the boiler is protected against freezing and any potential damage.

Domestic Hot Water Performance

One of the most important factors in relation to electric combination boilers is their Domestic Hot Water ( sometimes referred to as DHW) performance. With 6 kW of heating elements dedicated to heating the domestic water, which ensure a great recovery time of the stainless-steel water tank, should you use all the water in one go – such as filling a bath. The recovery time of 50 litre tank, (which is used in the wall hung electric boiler) from 10 Degrees C to 60 Degrees C is only 29 minutes – and only 15 minutes from 35 Degrees C to 60 Degrees C. With the floor mounted electric boilers which have an 80-litre tank, the recovery time from 10 Degrees C to 60 Degrees C is only 47 minutes, and only 24 minutes from 35 Degrees C to 60 Degrees C. The temperature of the domestic hot water can be controlled between 35 to 65 degrees centigrade.

ModelPower           (kW)Dimensions  H x W x D   (mm)Weight  Dry     (kg)Domestic Hot Water Storage in Litres
Wall Mounted Model    
FHHSCSM 10/1510kW , 12.5kW or 15kW700 x 600 x 3957150
Floor Mounted Model    
FHHDSC 10/1510kW , 12.5kW or 15kW835 x 600 x 5907680

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

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

So with 50 litres of storage of domestic hot water , a standard shower uses 65.1 litres of water blended down to 43 Degrees C and lasts for 8.2 minutes at average flow rate of 8 litres . The 50 litre stainless steel DHW tank will provide 83.3 Litres of water , when stored at 60C and blended down to 43C, which is the highest safe showering/bathing water temperature. Ensuring you have nice warm shower, at a good water pressure, up to 7 Bar if required.

Electrical Consumption Details  – including fuse & cable requirements :-

These 12kW electric combi boilers can be wired up either with a single phase 240 volt or a Three phase 400 volt electrical supply, and it is the same detail for both our wall mounted model or floor mounted model.

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

ModelOutput in kWDraw Current- Amps -1 Phase 240 VoltCable Section in mm2
FHHDCS or M- 10/1510 to 1547 to 68 25

when the unit is wired up using three phase as the electrical supply 

ModelOutput in kWDraw Current- Amps -3 Phase 400 VoltCable Section in mm2
FHHDCS / M- 10/1510 to 153 x 15.9 to 22.8  6

12kW Electric combi boilers for sale UK & Ireland

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

Download the Flexiheat UK Brochure for 12 kW Electric Combination Boilers

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

10 kw Electric Boiler

10 kW Electric boiler – What are your options ?

At Flexiheat UK, we have various options for your 10 kw electric boiler requirements. We do a full range of 10 kw electric central heating boilers, that can either be run off a 240 Volt / Single Phase electric supply ( the most common household electrical supply voltage for the UK and Ireland ) or 415 Volt / Three phase electrical supply.

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

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

10 kW Electric Boiler Efficiency & Benefits

Our electric boilers are 99.5% efficient and benefit from well arranged touch display and control panel for our FHEL9 model.This touch screen ensures both simple and intuitive control of the boiler is achieved.

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

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

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

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

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


Technical details of our 10 kw electric central heating boilers

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

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

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


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

10 kW Electric boilers for sale UK & Ireland

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

Boiler pressure keeps dropping ? What to check

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

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

Boiler Pressure keeps dropping or continually low – Things to check

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

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

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

Combi boiler pressure keeps dropping ?

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

First thing to check –

Is there air in the heating system?

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

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

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

Second thing to check –

Is there a leak in your central heating system?

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

Third Thing to check –

Is the boiler pressure relief valve leaking ?

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

Fourth thing to check –

Is the Boiler Expansion Vessel Faulty?

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An external expansion vessel, used in central heating systems

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

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

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

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

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

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

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

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

Boilers with low water pressure – other things to consider

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

Refilling your low pressure boiler heating system

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

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

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

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

Oil Combi Boilers

Oil Combi Boilers or Oil Combination boilers are oil boilers that can do both the central heating requirements of your property and your domestic hot water requirements as well, in one combined unit – thus the name combination or “combi” oil boilers. Combi or combination boilers are now the most popular type of boiler install on the UK market , as over 70% of UK households have them installed over other types of boilers.These oil combination boilers , due to their compact size are often the perfect heating and domestic hot water solution for smaller properties within the UK.

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Oil Combi Boilers – Oil Combination Boilers from Flexiheat UK

How do Oil Combination Boilers / Oil Combi Boilers Work ?

Oil combi boilers / Oil Combination boilers work by instantly heating the cold water from the mains supply as soon as there is a demand for domestic hot water, when a hot water tap is turned on, or when a shower is operated. This makes an oil combi boiler highly efficient as there is no requirement to have stored hot water in a cylinder or calorifier. This makes an oil combi boiler installation more compact , freeing up living space withing withing the home or flat.as well as being cheaper and easier to install and more economical to run.

Our Condensing Oil Combi Boiler incorporates a high-tech boiler, similar in principle to most oil fired boilers, which comprises an ultra compact heat exchanger and pressure jet burner. This boiler heats water, known as primary water, which circulates through radiators for central heating. In addition, for increased efficiency, it passes through our patented condensing unit

Our oil combi boiler benefits from a high efficiency plate heat exchanger
which transfers heat from the primary water to the domestic hot water directly from the mains, thus providing domestic hot water at mains pressure. Within the appliance are components such as a circulating pump, heating system expansion-vessel, water temperature control valve and such other controls which you would expect to find in a well designed, efficient modern oil heating system.With our Oil Combi boilers all this is extremely compact and a well engineered package.No need for copper storage cylinders, tanks of water in the loft, and long heat-wasteful pipe runs. Poor showers are a thing of the past, with our oil combi boilers

Oil combi boilers and hot water – Better but different- Condensing oil combi boilers produce hot water in a different manner from traditional systems with a copper storage cylinder. An understanding of the principle will enable you to obtain optimum results for your appliance and realise your level of expectation.

So what is the main difference? an Combination Boiler heats cold water directly from the mains by transferring heat in the boiler (primary water) to the incoming cold mains (domestic) water by means of a highly efficient ‘plate’ heat exchanger. In order to reduce the possibility of excessive water flow, each Combi incorporates a built in flow regulator, carefully sized according to the output of the appliance, in order to stabilise the delivery of hot water. This flow regulator also enhances the performance of its various control thermostats and mixing valves within the appliance which perform better when less subjected to extreme and sudden changes of volume and temperature.

The advantages of the system are:
a). Hot water is delivered at mains pressure (regardless of flow rate) which means that vigorous pressure can be delivered for showers. Typical mains pressure can be 2 Bar – 3.5 Bar compared with say 0.35 Bar – 0.6 Bar from a storage tank in the roof (each metre of ‘head’ produces merely 0.1 of a bar pressure).
b). The hot water is potable – that is, it is fresh from the mains like the cold supply and has not passed through storage tanks in the roof or a storage cylinder.
c). It is more economical and more efficient to produce hot water by this means rather than the old storage cylinder method.
d). Hot water can be produced indefinitely provided that the flow rate is equated to the boiler output.

In order to reduce the possibility of excessive water flow, each of our oil combi boilers incorporates a built in flow regulator, carefully sized according to the output of the appliance, in order to stabilise the delivery of hot water. This flow regulator also enhances the performance of its various control thermostats and mixing valves within the appliance which perform better when less subjected to extreme and sudden changes of volume and temperature.

Why get a new Oil Combination Boiler?

The Top reasons to get an oil combination boiler –

  • As long as you have mains cold water to your property, you can have unlimited domestic hot water – when ever your require it.
  • You don’t require a hot water cylinder or calorifier ,as well as a cold water storage tank in the loft / attic.This means they are particularly suited to being installed in a flat or smaller house
  • They are often quicker and easier to install than other oil heating systems as the system will contain less components.This often makes the heating and hot water installation cheaper to.
  • Environmental groups argue that the burning of fossil fuels is damaging to the environment. Oil Combi boilers make a significant contribution to lessen such emissions by reducing the amount of Carbon Dioxide (CO2) produced.
  • Oil is a more efficient fuel than gas, so you’ll get a good return on every unit of energy used. But,just like gas, the price of oil can fluctuate so sometimes it will be more cost effective.

Oil Fired Combination Boiler Efficiencies

Oil fired combi boiler efficiencies are very high these days with the combustion efficiencies at around 95%. Since the 1st April 2007 all oil fired boiler must have a Sedbuk efficiency of 86% or more – Sedbuk stands for “Seasonal Efficiency Of Domestic Boilers in the UK” and is an energy efficiency scheme devised by the UK government. The Sedbuk rating is calculated from laboratory tests combined with the type of fuel of an appliance, the climate,the hot water system, whether ignition if automatic or permanent and other such factors necessary to produce a meaningful indication of normal efficiency in typical usage.On 26 September 2015 the way boilers are rated for energy efficiency changed; SEDBUK was replaced by the Energy related Products (ErP) directive, bringing a new rating system into effect,to help reduce the impact we all have on the environment, via the EU’s long-term 20-20-20 targets: ErP applies to all residential and commercial heating products across Europe

Oil fired combi boilers Pros and Cons

Pros of Oil combi boilers:

  • Hot water is heated on demand, so there’s no waiting for a tank of water to heat up to run a bath or have a shower
  • Oil combi boilers are highly energy efficient, with most manufactured with an efficiency of 90% or above
  • The Hot water is delivered at the same pressure as the mains water, giving you a powerful hot shower without needing to have a separate shower pump
  • You should be able to save money on installation with an oil combination boiler, since no tank is needed and therefore there’s less pipe work required and a shorter installation time
  • Their compact size means they’re a great space saver; our wall hung oil combi boilers are even small enough to fit inside a standard kitchen or utility room, or you can use our externally mounted version, which take up no internal room at all.
  • Less likely to suffer from scaling up with sediment of calcium, dirt and scale unlike a storage cylinder or calorifier
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One potential problem that storage hot water cylinders tend to suffer from – Calcium,Dirt and Scale build up – this is much less likely with Oil Combi Boilers from Flexiheat UK , as no hot water is stored.

Cons of Oil combi boilers:

  • If your oil fired combi boiler breaks down, you lose both heating and domestic hot water
  • You will experience a decline in water pressure should more than one appliance require hot water at the same time
  • Unlike a domestic hot water storage system, which often has electrical immersion heaters in the event of a boiler breakdown, you don’t have this back up system with oil fired combi boilers

Oil combi boilers for sale

Here at Flexiheat UK, we have some of the best oil combi boilers for sale on the UK market.These boilers are robust and will give many years of trouble free service life. We have two different types of oil combi boilers for sale, the first being a wall mounted unit,which is an internal version, and the second being an external wall mounted unit,which is weatherproof and has been designed to fit on an external wall of the property.

We go into these two option in much great depth on their own individual dedicate pages, but here is a brief overview of the range

  1. There are two models available – The internal oil fired combination boiler has a heating output of 18 kW – or 61,416 Btu’s Output and a Domestic Hot Water performance of 24 kW- which will give a flow rate of 10.5 litres a minute,with a 35 Degrees C temperature rise . The larger unit which is externally mounted has an output of 23kW to 28kW Output- or 78,476 Btu’s to 95,536 Btu’s Output.The Flow rate of this boilers is 12 to 14 Litres a minute, with a 50 Degrees C temperature uplift or rise.
  2. The smaller model,which is an internal wall mounted boiler only is only available in an internal version . The larger boiler is only available as an external mounted version ( particularly useful should space for locating your oil combination boiler be at a premium or impractical)
  3. Both Oil Combi Boilers are what is termed as a “System Oil Boiler” – A system boiler is basically an standard boiler, which includes the pump and expansion tank that are built into the wall mounted condensing oil combi boiler which allows you to have a “sealed heating system”, The benefits of a ” sealed system” are that no feed and expansion tank is required in the loft or at high level ( another benefit is that these tanks were prone to freezing or bursting at the most inconvenient time , often cause major water damage or resulting in a failed heating system ), and that the oil heating installation is made a lot more tidier, easier, and simplifies servicing of the wall hung oil boiler, as everything is in one place , withing the boiler casing.
  4. Domestic Hot Water performance – The smaller oil fired combi boiler will produce 10.5 Litres / minute , with a temperature rise of 35C , also known as a Delta T of 35C – Whilst the larger oil combination boiler will produce 14 Litres / minute , with a temperature rise of 50C

Full technical details on our internal oil combi boilers can be found on it dedicated web page here

And for our external oil combi boilers the information can be found here

Best Quality & Price Oil Combination Boilers in the UK

All of our oil combi boilers have been designed and manufactured to the following standards – OFTEC OFS A100, European Directives BED 92/42 and EEC LVD EN 60335-1 and EMC 89/33C/EEC and are WRAS approved. They are designed to burn Kerosene 28 Class C fuel – to British Standard Specification BS 2869 Part 2 Class C2 , European standard BS EN 2869:2010 Class C2, which is also referred to as Heating Oil, 28 Second Burning Oil or Central Heating Fuel. This grade of Kerosene has clean burning characteristics whilst maintain a high heat output and maximum fuel economy

We have heard our Oil Combi Boilers called everything from Oil Combination Boilers, Oil Fired Combi Boilers, and you can feel free to call them what you like, all we know is that we have a British built, high quality (we think it’s the best oil combi boiler on the market) Oil Combi Boiler, at some of the best prices on the UK market, so should you require any more information on our Oil Combination Boiler range , please do not hesitate to contact our sales team on 01202 822221 or click here for our email contact form

Warm Air Heaters – ErP 2018 Lot 21 Directive Effective January 2018

ErP 2018 Lot21 – Guidelines for Warm Air Heating Systems



What is ErP?

The Energy related Product (ErP) Directive is designed to reduce carbon emissions across Europe. In the same way as on white goods, TV’s and tyres, since September 2015, ErP also applies to domestic and commercial heating products.

The main objective of ErP is to phase out low efficiency products from the market place. ErP also covers electrical powered products, boilers, water heaters and renewable technologies, but for Warm Air Heating applications, where humans are enjoying thermal comfort, then the warm heaters being installed must achieve a seasonal efficiency of more than 72%, from 1st January 2018.

 Requirements :

  • Efficiency requirements (gas and oil)
  • Limit values ​​for nitrogen oxide emissions:
  • Erp Stage 2 for Warm Air Heaters – From 26th September 2018 maximum 100 mg / kWh (180 mg / kWh oil)
  • Erp Stage 3 for Warm Air Heaters – From 1 January 2021 maximum 70 mg / kWh (150 mg / kWh oil)
  • Information must be provided freely and publicly

The importance of being ErP compliant

Since September 2015 the Energy related Product (ErP) Directive has impacted boilers, water heaters and hot water storage tanks. Flexiheat UK are committed to ensuring that all products are compliant and all heating professionals understand ErP regulations.

ErP ObjectivesThe ErP Directive was designed to reduce harmful non-environmentally friendly emissions from energy consuming products. This is to contribute to the European Union’s 20-20-20 targets on climate change and energy.

Targets for 2020 

There are three main objectives for 2020:

  • A 20% reduction in EU greenhouse gas emissions compared to 1990 levels
  • A 20% improvement in the EU’s energy efficiency
  • Raising the share of EU energy consumption produced from renewable resources to 20%

Implementation in two stages:

  1. From 01.01.2018: Space heating annual efficiency η s at least 72%
  2. From 01.01.2020: Space heating annual utilization rate η s at least 78%

 Space heating annual utilization rate :  Definition

The space heating annual utilization rate is a key figure that should take into account the actual operation of heating systems. It is not the firing efficiency. The commission responsible for the directive has recognized that heating works on average 85% in partial load operation – ie in the transition periods – and only about 15% of the full load operation is required and therefore weights the heating efficiencies. Furthermore, inefficient burners, poor insulation and permanent pilot lights are considered with negative factors. Thus, for the first time, different manufacturers can be objectively compared.

Is a Mandatory if –

Warm Air Heaters are being used to provide thermal comfort for human beings – then the heaters MUST comply under the ErP for Warm Air Heaters – Lot 21 of the regulations

 Applications where the  ErP Directive for Warm Air Heaters 2018 are exempt:

  • Door curtains
  • Frost protection of perishable product
  • Horticultural heating (ie glasshouses)
  • Agricultural heating (ie poultry houses)
  • Process heaters/dryers

Information for Warm Air Heating Installers

All Warm Air Heating installers are responsible for ensuring compliance with certain parts of the ErP Directive when carrying out an installation or replacement. Installers have to carry out efficiency calculations for the installed system, provide energy labels and complete the ‘fiche’ document.

Flexiheat UK  is committed to supporting installers with everything they need to complete the fiche and ensure everything is ErP compliant. We strongly recommend that warm air heating installers become familiar with how ErP works.

For more information on the ErP Directive please visit: www.gov.uk/placing-energy-related-products-on-the-uk-market.

You can download a copy of the ErP Directive for Warm Air Heaters 2018 here 

German Electric Heaters – From Flexiheat UK

With the rising costs of gas and oil, we are more and more looking for ways to cut back on heating bills without sacrificing comfort. German electric heaters are a reliable way to heat the areas of a house, apartment or business unit you use the most, without wasting energy trying to heat your entire building. When looking for the right model, consider the advantages an electric heater can provide.

Our range of German Electric Heaters are well engineered being built in the southern area of Germany, which is synonymous with manufacturing excellence. The units are built to an extremely high standard and are some of the most energy efficient and safest models on the market. If you really think you can benefit from an electric heater in your home, garage, or the office this is the type you should get. As the saying goes,  “you to get what you pay for”. That is why, we strongly recommend paying that little bit extra for a German electric heater to give you peace of mind with its high standard of construction.

Our German factory offer a nice range of electric heaters, from a 3kW model up to and 18kW model. The 18kW model has a version that has high temperature capabilities, allowing it to thermostatically controlled up to 70°C. This German made electric heater unit is particularly beneficial for use in the heat treatment, pest control industry. We have found that our 3kW German made unit, after prolonged continuous use, can actually pull 13.1A. We have two options for this. The first being we can supply a dedicated Euro to UK plug adapter, which prevents this or alternatively you can purchase our UK built FF3 unit, which we do not have this problem with. This would be supplied with a standard UK plugGerman Electric Heaters



Why choose to go down the electric heating route

There are several options for heating a room. However, not all options are a practical for some properties. In addition, not all locations have the same energy sources, so that a choice must always be made. For example, for a property without access to gas, one can opt for an oil heating system. What if this property is too remote for regular deliveries? Then a great choice is to opt for electric heating.


Below are just some of the benefits of using one of our German electric heaters; –

Clean and green – an electric heater, unlike oil or gas gives off no emissions.   They are 100% energy efficient; converting every bit of the input energy to heat. They also reduce environmental impact compared to other fuel types:

No installation costsGerman Electric Heaters do not require any installation. You only have to plug the plug into the socket and the device is immediately ready for use

High efficiency –  German electric heaters are very efficient, because the electricity used is directly converted into heat

Additional heating – German electric heaters are ideal when the existing heating system is not sufficient or more heat is required in the short term. Moreover, they are the perfect solution in the transitional period, i.e. in spring and autumn, when the temperatures are not so low that the central heating must be switched on

Safe to Use – German Electric heaters are distinguished by different safety features such as overheating protection

Portability – electric heaters are extremely versatile and more practical in different situations than other heaters. Therefore, they are often preferred

Quiet and discreet – with the exception of the fan, electric heaters have a very low noise level, therefore making them ideal in smaller rooms

Zonal Heating – because of their mobility, an electric heater is perfect for specific areas that require temporary or permanent heat


Make life easy for yourself, with our German electric Heaters, in most instances all you need is a power socket. However, for larger areas three phase models are also available giving large volumes of heat. There are no exhaust gases or smells – just large volumes of safe, fume-free heat. Electric heaters are ideal for virtually any location including


  • Offices
  • Shops and showrooms
  • Hotels
  • Garages
  • Industrial units
  • Classrooms
  • Clinics
  • Building sites
  • Marquees and tents
  • Storerooms
  • Workshops
  • Ships
  • Switching stations
  • Temporary accommodation
  • Modular buildings


The amount of space an electric heater can take care of for you will vary. Make sure you read do plenty of research before you buy one. Generally, this information will be displayed in square footage. You can easily calculate the square footage of an area by multiplying the length of it times the width.

You will find that many of our models of electric heaters also are very nice looking. They aren’t going to stand out like a sore thumb. Many of them are very small in size but you will be surprised at how much heat they are able to emit for you. They also take very little time to heat up so you won’t be waiting in the cold for that warmth to start circulating in the room.

Our range of German electric heaters can definitely offer you the additional warmth that you desire. With their in-built thermostat and two heat settings they will certainly save you energy as well

Should you require anymore assistance or information on our range of  German Electric Heaters , please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form

Commercial Boiler

A commercial boiler is a pressurized system that burn combustible fuel to heat water that is then used to provide heat to your building. Some boilers use the actual hot water itself while others utilise water that has been turned to steam.Be it an hotel, school or hospital boiler, a district heating scheme or any industrial or commercial refurbishment of your heating scheme, you can benefit from our vast experience in supplying commercial heating boilers in the UK and Ireland.

Commercial Boiler

Inside the boiler itself, the burner , wether it be natural gas / Propane (LPG) or Oil  creates heat that is then transferred to the water via the heat exchanger. The process creates either hot water or steam, depending on the type of commercial boiler. The hot water is circulated via pipes throughout your building. The water then enters radiators or other components that divide the heat thus providing the heating you require to keep your indoor spaces comfortable.

Natural gas is probably the most common fuel used in commercial boilers. Other types of boilers are available that burn fuel oil like diesel or heating oil. There are also boilers out there that use electric resistance coils to produce heating from electricity.


Common components of commercial boilers


  • Burner: A burner is a device for the combustion of a fuel. For example, a fuel oil burner can be mounted on the boiler of a central heating system (oil heating). The burner produces a flame by pressing the fuel oil through a fine nozzle and supplying combustion air with a blower. In the burner start, the flame is usually ignited with an electric arc. The hot combustion gases enter the boiler, which effectively serves as a heat exchanger: the generated heat is transferred to the boiler water to a large extent. Similar burners are operated with natural gas. No atomization is necessary here, only a good mixing of gas and air. The correct dosage of the combustion air is important for a clean and efficient combustion. Ideally, the burner supplies exactly the required amount of air to the flame: by no means too little to allow complete combustion (without the formation of soot or carbon monoxide), but not too much to minimise exhaust gas losses


  • Combustion chamber: A combustion chamber is a component in which air and fuel are mixed, ignited and burned to heat the water. The chamber contains the burners and is specially designed to provide a safe and secure area for high-temperature combustion of volatile fuel. The chamber is commonly constructed of steel, cast iron or other heavy-duty metal.


  • Heat exchanger: The heat exchanger is an integral component that carries the heat created by the burners to the water in the boiler. Heat exchangers are commonly made of cast iron, stainless steel or copper.


  • Controls: System controls allow the user to calibrate water temperature, air and fuel supply mixtures, ignition and internal pressure. The controls regulate when and how often the burner fires, the temperature of the water, the rate at which fuel is used and the quality of the mixture of fuel and oxygen. Commercial boilers can also be fitted with appropriate safety controls that make sure that the internal pressures in the boiler doesn’t get too high, the water temperature stays within a safe range and ensures that the system continues to operate properly.


  • Exhaust stack: Also called the flue, the exhaust stack is the series of pipes that divert the exhaust gases away from the inside of the building to the outside. The exhaust stack must be constructed to ensure that any dangerous gases such as carbon monoxide are safely vented away from the interior of your facility.



Boiler Safety and Maintenance

Commercial boilers can be unpredictable systems containing very hot water or steam under high pressure. Therefore, care must be taken to make sure the boiler is clean and working properly and that all safety systems are functional and ready to work if required. Hot water or steam leaks can pose a serious risk of causing injuries or damage. Commercial boilers can potentially explode, which can result in serious injuries or even death as well as significant damage to your commercial facility.

It is imperative that your commercial boiler receives regular preventive maintenance from a professional heating engineer. This maintenance not only ensures the system works correctly and at its highest level of efficiency but that it also works safely.

Here at Flexiheat UK, we realise that finding and purchasing a new commercial boiler is a complicated business. This is made far worse by the confusing terms used to describe boilers. This is our guide to these commercial boiler technical terms, to help make your search easier.



The term condensate is used regularly. Throughout the process of producing heat, the boiler will produce some condensation. This needs to leave your building or premises through an outside wall. In addition, some of the condensation will turn to liquid and need draining away. This is normally through a pipe that connects to your pre-existing drainage system.

Condensing Technology

This term has increased in popularity, as modern boilers are all fitted with condensing technology. This means it is capable of condensing the gas into heat for your business. The benefit of condensing technology is that a lot more of the waste gases are recycled and turned into more heat, which is far more cost effective and better for the environment.

Flow Rate

Flow rate is a term used to describe the amount of hot water that is produced in one minute. This is mainly relevant to combi-boilers. The higher the flow rate, the more water produced which means your boiler can work for less time and use less fuel. Essentially a boiler with a good flow rate will save you money on your bills, but is probably more expensive to purchase initially.

ErP Rating

This term refers to the A++ to G ratings, shown on all new boilers. Referring to the boiler’s energy efficiency as well as its heating and hot water performance, the rating allows you to choose the most efficient boiler. A++ is the highest performing and G is the lowest.


This term means: Seasonal Efficiency of Domestic Boilers in the UK. It is a percentage rating for boiler efficiency and it has been added as part of the overall ErP rating.


We at Flexiheat UK hope this glossary helps make choosing a new commercial boiler a little easier. Don’t let the commercial boiler technical terms give you a headache!

For any help and advice, don’t hesitate to contact us today on 01202 822221 or click here for our email contact form