Whole house electric tankless water heater UK

Whole house electric tankless water heater UK


Whole house electric tankless water heater UK from Flexiheat UK

Whole house electric tankless water heaters from Flexiheat UK an alternative or replacement for tank-type water heaters

A whole house electric tankless water heater has become highly desirable in the UK due to its ability to provide unlimited domestic hot water instantly, without any waiting time or the need for water storage. Instantaneous water heaters have a compact design and can be easily installed in tight spaces, such as a kitchen cupboard or something similar.

While the statements above are correct, it is important to recognise some limitations, such as the limit on the number of outlets that can be used simultaneously, the need for close proximity to hot water outlets, and the need for a three-phase electric supply to power a whole home’s energy-efficient tankless water heater.

Key Point

  1. You require a 3 phase power supply to have a viable whole house electric tankless water heater in the UK

Energy efficient water heating

With rising energy prices, many homeowners in the UK are looking for ways to cut energy costs and make their homes more energy efficient. One way to do this is by installing an electric tankless water heater, also known as an instantaneous water heater or demand-type water heater, is one way to do this. Tankless water heaters provide domestic hot water instantly, as needed, eliminating the need to constantly heat and reheat a tank of water like traditional tank-type water heaters. This can lead to significant energy savings, making whole house electric tankless water heaters an attractive option for eco-conscious homeowners.

How do tankless water heaters work?

Tankless water heaters work differently than traditional water heaters that use a storage tank. When you turn on a hot water tap, cold water travels into the tankless unit. Inside the unit, an electric element heats the water instantaneously before sending it to the tap or shower. The unit directly heats the water without storing it, ensuring you never run out of hot water. Even when hot water isn’t in use, traditional water heaters with storage tanks must constantly reheat and maintain water temperature, resulting in energy waste.

Benefits of whole house electric tankless water heaters

There are several key benefits that make whole house electric tankless water heaters a smart choice in UK homes:

Energy efficient hot water

Instantaneous water heaters only heat water when needed, rather than maintaining a whole tank of water at temperature constantly. This results in major energy savings compared to traditional water heaters. Homeowners can save 20% to 60% on water heating costs.

Continuous domestic hot water

Instantaneous water heaters provide an unlimited supply of hot water on demand. You’ll never run out of hot water for showers, washing dishes, doing laundry, and more. The water heater activates when hot water is needed and shuts off when not in use.

Space Savings

Instantaneous water heaters are compact and mount on a wall, freeing up floor space that standard storage hot water cylinders water heaters use. This makes them a great choice for smaller homes or properties, such as flats, etc.

Long Lasting

Tankless heaters last up to 20 years, twice as long as traditional storage hot water cylinders. The lack of a water storage tank increases their lifespan.

Environmentally Friendly

The energy efficiency of tankless heaters means lower carbon emissions. Less electricity is required for water heating.


With no hot water storage tank that standard water heaters have, there is less risk of leaks or rusting. Tankless water heaters are safer, provide more reliable hot water, and are easier to install.

Factors to consider when choosing an entire house tankless unit

If you’re considering switching to a whole house tankless water heater, there are a few important factors to take into account:

Power Rating: The correct power rating ensures that your tankless unit can handle your household’s hot water demand. Look for a power rating of 18–27 kW for a whole house appliance or even 36kW depending on your demands.

Flow Rate: The water flow rate, measured in litres per minute (LPM), must meet your household’s peak hot water needs. The electric water heater appliance’s power ratings directly influence the heated water flow rate’s capacity or output.

Energy Source: Electric tankless heaters often make the most sense for UK homes. Make sure your electric system can handle the power demands.

Size: Choose the appropriate size tankless heater for your home’s water heating demands, number of bathrooms, etc. An undersized unit won’t meet your hot water needs.

Location: Pick an appropriate indoor location with adequate space and accessibility.

Efficiency Rating: Look for a high energy efficiency rating to maximise savings.

Product range

Our electric tankless hot water heaters have four power ratings, or output ranges, in “one” tankless water heater unit. Except for the 27kW and 36kW electric instantaneous water heaters, which feature a single power setting.

For example, our 9kW to 15kW electric instant water heater allows consumers to pick power ratings of 9kW, 11kW, 12kW, or 15kW in one model, while our 17kW to 24kW instant water heater may be adjusted to 17kW, 18kW, 21kW, or 24kW output.

The cold water mains temperature at the deepest winter times is typically 10 degrees Celsius, thus an average temperature rise of 30 degrees Celsius is necessary to provide hot water for usage in the winter months. The data below shows the performance at a temperature rise or Δt = 30


Power output of the tankless water heaters9kW to 15kW power ratings17kW to 24kW power ratings27kW36kw
Energy efficiency classAAAA
Heat capacity ( power setting options)9/11/12/15 kW17/18/21/24 kW27 kW36 kW
Power supply – All require a 3 Phase power supply 400V 3N~400V 3N~400V 3N~400V 3N~
Mains water supply pressure (Bar) min – maximum1 to 101 to 101 to 101 to 6
Hot water flow rate at  Δt=30 in litres per minute4.3/5.2/5.8/7.28.1/8.7/10.1/11.61317.3
Rated current (Amps)3 x 13/15.9/17.3/21.73 x 24.6/26/30.3/34.63 x 393 x 52
Dimensions – W x D x H (in mm)245 x 126 x 440245 x 126 x 440245 x 126 x 440315 x 140 x 492

Please note that this range of compact instantaneous water heaters requires a minimum flow of 2.5 litres per minute to start heating the water. If the flow rate is lower than this point, they will not operate.

Our 9kW to 27kW instantaneous water heaters feature a LCD display showing the tankless water heaters set temperature

Digital display on our instantaneous electric water heaters from 9kw to 27kW from Flexiheat UK

The digital display on 9kw to 27kW , showing the hot water temperature set on the water heater

and our 36kW tankless water heater has a traditional temperature dial and look like this

36kW electric instant water heater from Flexiheat UK

36 kW Electric instant water heater

Benefits of Going Tankless for Whole House Water Heating

Switching to a whole house electric tankless water heater provides a range of benefits:

  • Save significantly on energy costs by only heating water on demand
  • Enjoy hot water with an unlimited supply of continuous hot water for all your needs
  • Free up extra space by eliminating a storage electric water heater
  • Reduce your home’s environmental impact with an energy efficient system
  • Enjoy convenience, reliability, and safety with an electric on demand hot water tankless unit
  • Get a long-lasting water heater that will serve your property for many years

By going tankless for your whole house, you can gain energy savings, unlimited hot water, extra space, and peace of mind knowing you have an eco-friendly, highly efficient water heating solution meeting your household’s needs.

Installing Your New Tankless Water Heater

Once you select the right electric tankless water heater model for your home, hire a qualified plumber for installation. Proper installation is key to maximising efficiency and providing hot water performance. Key steps include:

  • Select an appropriate indoor location that allows access to the instant hot water heater; they are a very compact design, so this shouldn’t be an issue.
  • Make any necessary electrical upgrades to handle the instant hot water heater requirements.
  • Electricity supply: ensure you have properly sized electric cables and breakers.
  • Connect the water supply pipes with components such as isolating valves and a filter on the cold water feed to the water heater.
  • Insulate water pipes to limit heat loss to sinks or the shower.
  • With a tankless water heater tailored to your specific home set-up, you’ll get the right choice with superior function without wasting energy and benefiting from energy savings for years to come.

Going tankless is the smart choice

With rising energy prices, whole house electric tankless water heaters make increasing sense for eco-friendly UK homeowners looking to save on costs. By only heating water on demand, tankless heaters provide endless hot water while being much more energy efficient than traditional storage tank heaters. Choosing the right size unit with professional installation provides a long-lasting, highly effective hot water solution. Going tankless can make your home more sustainable while cutting your energy bills. It’s the smart choice to enjoy reliable heated water whenever you need it.

So if you require a price, check stock or to purchase one of electric water heaters for entire home hot water needs Please contact us on 01202 822221 or use the email contact form .

Electric tankless water heater range 9kW to 36kW

Electric tankless water heater range – 9kW to 36kW output

Electric tankless water heater range from 9kW to 36kW for on-demand water heating via electrical power - Flexiheat UK

Our Electric tankless water heater range are 100% energy efficient instantaneous water heaters, that provide domestic hot water in a cost effective manner as they heat water only on demand without wasting energy.

Being an electric water heater, they require a three phase electrical supply as you require the Amps to provide hot water at an adequate flow rate for a bath, shower or multiple hot water taps such as kitchen sink taps or bathroom sinks taps in properties or commercial buildings.

Key takeaways

  • The main disadvantage of electric tankless water heaters is that the electrical power ratings set a limit on the hot water flow rate output achievable.
  • This is why generally you require a Three phase electrical supply rather than a single phase electrical supply to power the instant water heater units.
  • Single phase electric can’t supply the Amps (power) required for an electric instantaneous water heater

Tankless water heater electric powered advantages

When opposed to conventional tank-based water heaters, tankless water heaters—also referred to as an on-demand water heater, instant water heaters or instantaneous water heaters or an inline electric water heater—have a number of advantages. Here are a few of the principal benefits:

1. Energy efficiency: instantaneous water heaters only heat water when there is a demand, unlike storage tank-type water heaters that continuously heat and reheat stored water. This on-demand instant hot water heating process can save a significant amount of energy, reducing water heating energy costs by 20-30%.Electric instantaneous water heaters are 100% energy efficient

2. Space-saving: Tankless water heaters are much more compact in size compared to bulky storage hot water tank heaters and are easier to install. This makes them ideal for homes, smaller homes or apartments with limited space, as they can be mounted on a wall or installed in cupboards.

3.No pressure and temperature safety valves or hot water expansion vessels are required to be installed as there’s no hot water storage in the instant water heater appliance – Thus you don’t have to comply with the “G3” unvented water heater regulations that we have in the UK for hot water installation.

3. Unlimited hot water supply: If the capacity of a standard electric storage tank water heater is surpassed, you can run out of hot water if the tank’s capacity is exceeded .In contrast, instantaneous water heaters have an infinite supply of hot water—so long as the demand doesn’t exceed the instant water heaters flow rate capacity.

4. No standby energy losses: Storage tank water heaters constantly lose heat through the tank walls, even when no hot water is being used. Instant hot water heaters eliminate this standby heat loss, further contributing to energy savings.

5. Lower risk of leaks and floods: Since instant water heaters don’t store large volumes of hot water, they have a lower risk of leaks and flooding compared to electric storage tank hot water heater models, which can cause water damage if they fail.

Electric tankless water heaters, with their energy savings and longer lifespan, can make them a cost-effective option in the long run, especially for businesses or households with high hot water demand or and in areas with high energy costs due to their 100% energy efficiency.

Instantaneous water heaters range

Our electric tankless hot water heaters have four power ratings, or output ranges, in “one” tankless heater unit. Except for the 27kW and 36kW electric instant water heaters which only have one power setting .

I.e. Our 9kW to 15kW electric instant water heater allows users to select power ratings of 9kW, 11kW, 12kW, or 15kW in one model and our 17kW to 24kW instant water heater can be set to 17kW,18kW,21kW or 24kW.

The cold water at the deepest of winter periods is normally 10C temperature , thus the standard temperature rise of 30 °C is required to provide hot water for use in the winter period. This is shown as Δt=30 in the data below – 


Power output of the tankless water heaters9kW to 15kW power ratings17kW to 24kW power ratings27kW36kw
Energy efficiency classAAAA
Heat capacity ( power setting options)9/11/12/15 kW17/18/21/24 kW27 kW36 kW
Power supply – All require a 3 Phase power supply 400V 3N~400V 3N~400V 3N~400V 3N~
Mains water supply pressure (Bar) min – maximum1 to 101 to 101 to 101 to 6
Hot water flow rate at  Δt=30 in litres per minute4.3/5.2/5.8/7.28.1/8.7/10.1/11.61317.3
Rated current (Amps)3 x 13/15.9/17.3/21.73 x 24.6/26/30.3/34.63 x 393 x 52
Dimensions – W x D x H (in mm)245 x 126 x 440245 x 126 x 440245 x 126 x 440315 x 140 x 492

Please note that this range of compact instantaneous water heaters require a minimum flow rate of 2.5 litres per minute to start heating the water. They will not operate if the flow rate is lower than this point.

Our 11kW to 27kW instantaneous water heater models feature a LCD display showing the instant water heaters set temperature 

Digital display on our instantaneous electric water heaters from 9kw to 27kW from Flexiheat UK

The display on our instantaneous water heater from 9kW to 27kW , showing the hot water temperature set on the water heater


These range of instant hot water electric heaters use bare wire heating elements in the heat exchanger which are particularly well-suited for use in hard water areas


Our 36kW instantaneous water heater has a traditional temperature dial and look like this –

36kW electric instant water heater from Flexiheat UK

36 kW Electric tankless water heaters with no standby energy losses

Our 36kw tankless water heater uses copper shielded heating elements within a heat exchanger, this dependable technology ensures long lifespan of operation and resistance to air bubbles and water deterioration.

Full manuals are here for these instant water heaters 

EIWH5 Series Electric instant water heaters manual from 9kw to 27kW – Flexiheat UK

EIWH36 – 36kW Electric instant water heater manual – Flexiheat UK

Instant Water Heater

Whether the instant water heater is supplying fixtures such as shower, bath, sinks or multiple taps, our electrically powered units heat water ‘instantly’ as it flows through the appliance.

They can be installed either as inline electric water heater or in series to provide enough hot water to suit all installation requirements.

Energy efficient Hot Water heating

Being 100% energy efficient, with accurate temperature control of water flows you can rely on for daily use in business or domestic water heating applications.

Contact us

Should you require further assistance, check stock, or get a price on the best electric tankless water heater range on the UK market  then please don’t hesitate to contact our sales team on 01202 822221 or click here for our email contact form.

Condensing water heaters

Condensing water heaters

Condensing water heaters with high efficiency domestic hot water heating with storage or condensing tankless water heater options from Flexiheat UK


Condensing water heaters have become the norm since Part L of the UK building regulations came into force in June 2022.

The more stringent water heater requirements of the Part L building regulations apply to both newly built and existing non-domestic building stock.

This basically eliminates the option to swap out existing non-condensing water heaters with the same type of water heater. Any replacement hot water heaters must utilise condensing technology within the domestic hot water heater to produce savings on both a monetary and emission level i.e., carbon emissions, as a condensing water heater will deliver cutting edge efficiencies.

A low emission level hot water system helps the UK achieve our drive to a lower carbon economy and ErP compliant condensing water heaters help this.

However, in the rare event that the Building Control authority determines that replacing a non condensing gas fired water heater water is not suitable or feasible in non domestic buildings, a minimum seasonal efficiency of 80% for natural gas or 79% for LPG may be utilised.

But there are very few circumstances in which you can’t use a condensing water heater, to be fair, so these exceptions would literally be “once in a blue moon,” as they say, if at all.

The energy efficiency benefits of condensing water heaters now mean that the residential hot water systems market has also rapidly moved to this type of water heater’s installation, as they deliver cutting edge efficiencies and produce savings on your water heating bills.

As of yet, there are no regulatory requirements to use a gas fired condensing water heater in a domestic property, but the economic benefits of using less gas to produce domestic hot water for a home or flat through higher efficiency alone have driven the domestic market this way.

However, the commercial hot water regulations or the commercial water heaters market often lead with regards to regulations, and the domestic market then follows, so we can envisage that condensing water heaters will soon be mandatory in this sector before long.

Energy efficient water heating

Condensing gas fired water heaters have a hot water efficiency level of up to 105%. Which is essentially an extra 12 to 15% more performance than an older gas fired non condensing water heater.

A second heat exchanger in a condensing water heater preheats the incoming cold water by using waste heat from the exhaust gases. This process lowers the exhaust gas temperature, boosts energy efficiency, and increases the hot water flow rates of the water heaters.

A cooler exhaust allows for additional possibilities for flueing materials, such as polypropylene plastic flues. Condensing gas fired water heaters need to dispose of the acidic condensation water through a drain and possibly a pH neutralizer because water vapour condenses inside the appliance when the exhaust gas cools, and this is acidic in nature.

Gas fired water heaters

We have a large, high efficiency gas fired condensing water heater range that are direct fired water heaters for small or high hot water demand that can be required in commercial or industrial hot water heating applications such as hotels, leisure centres, and hospitals.

Wall hung water heaters

SFC or SFK gas fired condensing water heater range from Flexiheat UK

SFC or SFK Condensing water heaters range – in natural gas or LPG


Our wall hung condensing water heaters range consists of three models a 28kW, 34 kW or 50 kW output water heaters.

These water heaters benefit from various flueing options: horizontal or vertical flue systems, room sealed or conventional flued with various flue terminal options for easy installation.

The two smallest water heaters come with the option of a pump for a domestic hot water recirculation system (designated the SFK model) or without a pump (our SFC version) for straight through water heating, which are the most common appliances we sell. The larger 50kW model comes with a pump as standard, which is capable of being turned off for straight through direct water heating.

With a large 28mm single-pipe coil heat exchanger made of stainless steel, the SFC or SFK condensing water heater range benefits from very low pressure drops, less chance of blockage, increased thermal efficiency and easier cleaning and delivers high volumes of temperature accurate hot water. Other safety features such as protection to IPX5D rating are standard.

There is no water storage within these units, so there is no heat loss compared to a storage water heating system.

This is the basic rule: the higher the kW output, the higher the DHW flow rate performance

When heating cold water to a certain temperature, this is known as the temperature rise or Delta T (shown as Δt in the charts below). The normal bathing or showering water temperature is 38°C to 40°C, depending on personal preference.

For winter performance

We recommend sizing the water heater on a Delta T of 30 degrees C, shown as “Δt 30” for the majority of the UK, in Scotland, we recommend using “Δt 35”.

During the summer period

You can use “Δt 20” as the temperature rise.

SFK or SFC 28kW Gas fired condensing tankless water heater


Water Temperature RiseΔt 20Δt 25Δt 30Δt 35Δt 40Δt 50Δt 60Δt 75Flow rates
SFK / SFC 2820.6616.5313.7811.8110.338.276.895.51Litres/minute


Download the SFC 28kW Gas condensing water heater with no pump manual

Or with pump for hot water recirculation systems

Download the SFK 28kW Condensing water heater with pump manual 


SFK or SFC 34kW Gas fired condensing tankless water heater


Water Temperature RiseΔt 20Δt 25Δt 30Δt 35Δt 40Δt 50Δt 60Δt 75Flow rates
SFK / SFC 3425.0920.0716.7314.3412.5510.048.366.69Litres/minute


Download the SFC 34kW Gas condensing water heater manual with no pump manual

Or with pump for hot water recirculation systems

Download the SFK  34kW Condensing water heater with pump manual 

SFK 50kW Gas fired condensing tankless water heater


Water Temperature RiseΔt 20Δt 25Δt 30Δt 35Δt 40Δt 50Δt 60Δt 75Flow rate

Download the SFK  50kW Condensing water heater with pump manual 

Please be aware that the highest temperature that the water temperature can be set to is 60 degrees Celsius on the standard water heaters ; on request, we can, however, build a higher temperature unit that can reach up to 85 degrees Celsius. These water heaters are frequently used for the pasteurisation process in the dairy and farming industries, as well as in other applications that call for high-temperature washdowns and water for process applications.

For high demand hot water heating that commercial applications can require, these high efficiency commercial water heaters can be used in cascade for example- we go into more depth on the of this type installation here – Commercial gas water heaters

These on demand high efficiency gas water heaters have various essential safety features, and can be used to top up heat-pump water heaters, which can struggle to achieve the desired water temperatures.

Control options

You can set the water temperature on the control panel of the water heater; however, should you wish the facility to change the water temperature, then we have a remote controller that you can site in your kitchen to boost the water temperature to 50 °C for dishwashing, which is the recommended temperature for removing grease from cooking utensils and dishes.

Easy remote controller from Flexiheat UK; Class 5 modulating boiler or water heater controller that is wired.

Easy remote controller – Wired – for our condensing water heaters from Flexiheat UK


Storage options

We also supply three condensing storage tank water heaters options – which are available as either LPG or natural gas fired water heater and are all ErP compliant water heaters.

We do a 50kW water heater option with a 330-liter storage cylinder

A picture of a gas hot water tank or gas fired hot water cylinder from Flexiheat UK, which are used for water heating in large domestic, commercial, and industrial applications. These units are condensing gas water heaters.

Gas water heaters with storage systems for high volumes at intermittent times demand. These ErP compliant condensing water heaters are energy efficient and cost effective to run.


A 34kW water heater option with a 150 Litre stainless steel storage cylinder

gas hot water tank or gas fired hot water cylinder from Flexiheat UK

or a 28kW water heater option with a 150 Litre stainless steel storage cylinder

internal picture of our hot water heater with storage tank which is gas fired from Flexiheat UK

SFKA 28 or 34 KW Output models – Natural gas or LPG powered

We go into more depth on these storage condensing water heaters that are often used in commercial buildings here – Condensing gas hot water tanks or cylinders

Where are condensing water heaters used?

Everywhere, from residential and smaller business settings such as homes, cafes, hair salons, bed and breakfasts establishments to industrial and large commercial applications such as sports complexes, hospitals, colleges, or schools, we have a complete range of high-efficiency water heaters for every warm water heating requirement.

Contact us

Should you require anymore assistance, information, check stock or get a price / cost on our effective (both in a monetary and emission level) condensing water heaters range please contact our customer services sales team on 01202 822221 or use our email contact above on the web page.

Air Curtain Basics | What is an Air Curtain + How Does It Work?

Air Curtain Basics | What is an Air Curtain + How Does It Work?

Air Curtain Basics _ What is an Air Curtain and How Does It Work

Air curtain basics -What is an air curtain and how do they work ?


A device that creates an air barrier across a door’s whole opening to divide two environments is called an air curtain.

Typically, the air curtain keeps flying insects, odours, humidity, dust, and debris out of the conditioned interior air and keeps it separate from the outside air. Air barriers, fly fans, air shields, and air doors are some other names for air curtains, depending on the sector or even the area in which they are used.

How does an air curtain work?

Typically, an air curtain is installed indoors above a doorway, where it draws air into the device’s intake.

This air can be ambient, i.e., taking the interior air from the inside of the building at whatever temperature that temperature is, or you have the option of heated air curtains, either by electric or hot water heaters, blowing warm air and blocking frigid winter winds.

Air curtains create a laminar airflow, which is produced as a result of this air being driven and accelerated through a small outlet that runs the length of the air curtain. To attain optimal performance, the air discharge angle can be modified using the adjustable blades that come within the air curtain.

Air must travel farther until it reaches the floor when the discharge angle increases.

If the discharge angle is too large, the air curtain won’t be adequate to prevent any wind from infiltrating near the floor because the air’s velocity drops as it moves farther away from the curtain. The air exiting the unit won’t have enough downward force to prevent a substantial gust of wind from entering if the discharge angle is too slight.

Do air curtains really work?

Definitely! All studies and experiments have shown that air curtains work. When an energy-efficient air curtain is correctly installed, it saves a lot of energy while keeping the entrance area temperature protected, comfortable, and free of drafts, insects (this is why air curtains are sometimes called fly fans), smells, and so on from the unconditioned outside air, which can be cold or warm air depending on the time of year.

Air curtains create temperature and environmental separation

In one line, “They create an effective seal on a doorway via a high velocity air flow discharge or air flow stream that ensures environmental separation for doorways or entrances to buildings.” This airflow can be ambient or heated, depending on the requirements of the separate environments.

When are air curtains commonly used?

Air curtains prevent cold air from entering everything, from an employee entrance or customer front door all the way to large loading bay doors. The air curtains create a recirculating, clean air invisible air door as such, resulting in considerable cost savings on the heating energy bills. These energy savings can be up to 40%, depending on the door usage characteristics, as they effectively separate environments.

Used everywhere from food service industries, restaurants, hotels, shops, and cold storage locations to busy warehouses to ensure environmental separation.

Retail applications

In a retail setting, air curtains are frequently placed above a store entryway or other commercial front door. These retailers consistently see foot traffic during peak hours. Even when the business is steady, opening and closing doors all the time could overload the building’s HVAC system and let in insects, dirt, vapours, humidity, and excessive heat or cold.

Warehouses or production facilities

Warehouses are the industrial version of retail. The continuous in-and-out movement of goods is common. The loading dock doors can let in a variety of undesirable elements, such as dust, odours, insects, significant temperatures, humidity, and debris, even if they are opened for a brief period. For those who work close to the doors, it can be unpleasant because they will freeze in the winter and sweat in the summer.

Air curtains for industrial use contribute to a more comfortable environment. They can also lead to increased worker comfort, productivity, and safety. In congested warehouse facilities where forklift traffic is high, visibility is critical, as air curtains create an invisible barrier of air—no dirty strip curtains to create safety hazards and provide a poor air seal.

Food production facilities and restaurants

Facilities that produce and serve food are subject to strict regulations and must maintain the highest standards of hygiene. They are also particularly appealing to insects because of their prep areas and delivery doors. Because insects and strict hygiene standards don’t mix well, air curtains are a great way to significantly reduce flying insects from entering restaurants and other eating places. Air curtains are commonly used to keep hot, humid air out of the interior, in addition to keeping insects out. Air curtains complement these locations very well.

Hospitals, schools, or offices

Despite their distinct differences, all three locations see a steady flow of people entering and leaving through a variety of doors. They are all alike in that they invite outside air, insects, and vapours inside when their doors are open. Entrance doors, delivery entrances, loading docks, and other doors can all benefit from air curtains to keep out the elements, ensure energy savings, and improve workflow.

Ambient or hot air?

Air curtains create an invisible barrier; they can do this with ambient air, which is the air from the room that the unit is installed in. The building’s primary HVAC system provides the heat or chilled air to the room, and this is passed through the unit at a high velocity.

The other option is heated air curtains, which heat the air with a heating element. We have a dedicated webpage here for our electric heated air curtains or hot water heated air curtain units.

Understanding the basics of air curtains

There are three main considerations to ensure that all air curtains work in the correct manner. These are

  • An air curtain unit’s length should never be shorter than the door width if installed horizontally above the door.

  • An air curtain unit’s length should never be shorter than the door height if installed vertically at the side of the door.

  • Depending on the site conditions, the air curtains’ air velocity must meet the specified speed (usually the discharged air reaches a minimum of 2.3 metres per second at floor level). As a result, when selecting air curtain requirements, it is important to consider the height of each proposed door or opening as well as the prevalent interior and exterior climatic conditions that units’ air velocity may have to tolerate.

Energy Savings

A study by Cardiff University showed that in a typical convenience store in the UK, the heating load for the base case was 48 W/m2 per year. Both an air curtain and an automatic door can significantly reduce the heating load to 11 W/m2 per year and 19 W/m2 per year, respectively. This was a 77% reduction in heating energy consumption and considerable cost savings and a great return on investment.

Source Cardiff University- Investigating the Energy and Thermal Implications of Installation of an Air Curtain

Fumes, dust, exhaust, and debris control

Air curtains can provide a barrier that limits the penetration of undesired pollutants in locations with high levels of dust, odours, and debris. Air curtains keep these elements from accessing locations where people work or congregate, improving overall safety. From a customer’s entrance door in a restaurant to shopping centres or warehouses, the ability to block these detrimental substances in the outside air is crucial.

Buying an air curtain? Here’s what to look for:

Negative air pressure

If there is negative air pressure due to mechanical exhaust or stack pressure, the building’s air curtains will experience reduced effectiveness.

Installation requirements

Note the clearance to the ceiling on the side of the opening where the air curtain will be installed, as well as any obstructions above the doorway or entrance. Air curtains often require a minimum distance to work correctly and ensure maximum wind-stopping capability.

Vertical Installations

Mounting air curtains vertically places the unit’s operating noise at ground level, which should be considered. To protect and prevent damage to the air barrier, it is strongly recommended to install a barrier or bollards that shield the air curtains from potential damage caused by forklifts, etc. Here is our dedicated webpage on vertical air curtains.


If you require any more advice or need to clarify anything on air curtain basics, what is an air curtain or how air curtains operate, please don’t hesitate to contact us at Flexiheat UK.

Electric System Boiler

Electric System Boiler – Electric Wet Heating Systems

Electric system boilers from 4kw to 45kw output which are hydronic boilers, that are an energy-efficient electric boiler for central heating and heating hot water via an indirect hot water cylinder from Flexiheat UK

What is an electric system boiler? – In contrast to a conventional electric boiler, which just contains a heat exchanger or chamber, a system boiler incorporates an expansion vessel as well as a circulating pump within the boiler. So, you have all the required components for a sealed wet heating system, also known as an unvented heating system.

Because of the way that an electric boiler system is constructed, there is no requirement for a feed and expansion system in the roof area or circulating pumps exterior to the electric boiler.

The fundamental difference between a system boiler and a regular boiler is how it is constructed.

Types of electric boilers

The earliest boilers ever developed for central heating systems were regular boilers, often known as traditional, conventional, or heat-only boilers.

Due to the low system pressure required by these older types of boilers, they are often supplied via a feed and expansion cistern in the attic, which is known as an open-vent heating system.

With a system boiler, installation is also quicker, simpler, and more efficient thanks to the built-in components, i.e., the heating expansion vessel and a pump.

The boiler’s compact design makes it excellent for heating applications when space is limited, as having the pump and expansion vessel within the boiler casing will eliminate unnecessary external plumbing that would be required if these items were separate components.

The last type of electric boilers are electric combi boilers, which do heating and domestic hot water on demand and these are detailed on this webpage – electric combi boilers

System boilers: electric

Electric system boilers for a wet central heating system are by far the most popular electric central heating boilers, just like they are for gas and oil boilers these days. As sealed heating systems offer many benefits to the customer.

No feed and expansion tanks that must be cleaned on a regular basis; no letting oxygen into the heating system water, which will promote corrosion. To prevent freezing, the pipes from the tank position to the boiler will need to be insulated when using an open vented central heating system.

A central heating electric boiler provides heat for a building

Electric boilers are an energy-efficient alternative to gas or oil boilers for home heating, as an electric central heating boiler has 100% energy efficiency for the immersion heater or heaters . A gas or oil boiler, even a condensing gas boiler, is 90–91% efficient at full condensation efficiency.

Electric boilers

Electric boilers work in a very similar way to gas and oil boilers in that they produce heat via immersion heaters, that is imparted into the hot water of the heating system, providing central heating via radiators or underfloor heating systems for small properties or larger homes.

Our Full Range of System Boilers

First, our touch-screen range of electric system boilers. This range of electric boilers has a fully touch-screen controller (like a mobile phone screen) and can also be controlled by a thermostat, programmer, or suitable “OpenTherm” compatible controller such as your Nest or Hive controllers, which allows you to control the system boiler via the controller or a mobile phone, so you can control your heating form anywhere in the world if you have Wi-Fi and an internet connection.

Electric system boilers touch screen range from 0.5 kw to 13.5 kW output Flexiheat UK

Touch screen range of electric hydronic boilers

These electric system boilers have the lowest power steps on the UK and Irish markets; for example, the FHEL5, which has a maximum output of 4.5kW, has 500 watt or 0.5 kW power increments or steps, which means the boiler will modulate up and down from 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, or 4.5kW, which ensures maximum efficiency by closely matching the central heating and domestic hot water requirements when using an indirect hot water cylinder.

Users can set the maximum output of the electric boiler to one of the power output levels, and the boiler will modulate up and down to that set level. E.g., the FHEL 5 can be set to 3.5 kw maximum output, and the boiler will ramp up and down to that kW output point.

The FHEL9 modulates up and down the power steps in 1 kW increments, thus 1, 2, 3, 4, 5, 6, 7, 8, or 9 kW outputs. The same applies as above, and this applies to all of this electric boiler range.

And finally, the FHEL14, which has a maximum output of 13.5 kW, modulates up and down the power steps in 1.5 kW increments, thus 1.5, 3, 4.5, 6, 7.5, 9, 10.5, 12, or 13.5 kW. The same applies to the boiler, which can be set to a particular desired output kW value and will ramp up and down to this value.

Touch series electric system boiler range from Flexiheat UK

Touch series electric boilers for underfloor heating or radiators central heating – can be powered by either a single phase or three phase electrical supply.

Next is our standard series of electric system boilers:

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

Electric heating boiler from Flexiheat UK – Standard Series – From 2.5kW to 45kW Output

These electric boilers still have a touch control panel, but it’s a partial one that’s still easy and intuitive to use.

electric boilers; electric boilers company; electric heating company

Electric boilers standard series from Flexiheat UK

Please note the following:

  • After 15 kW, i.e., our 22.5 kW to 45 kW electric boilers, require an electrical three phase supply -3 Phase 400 volts, 50 Hz.
  • The 30 kW and larger size electric boilers—we physically don’t have the space within the boiler casing to fit an expansion vessel, but come with the pump integral to the boiler, so you have to fit an expansion vessel external to the boiler (by others) to complete the sealed system and make them system boilers.

electric central heating boilers - Standard series for wet HVAC central heating systems

Electric Central Heating Boilers – Standard Series- Technical data HVAC  – Flexiheat UK

The 7.5kW to 22.5kW electric system boilers modulate in 2.5kW power steps.

  • The FHEL8 has only 3 power steps on this unit, and the output can be set to either 2.5, 5 or 7.5 kW. Use the FHEL9; it’s a much better boiler.

  • The FHEL15 Electric Boiler’s outputs can be set to either 2.5, 5, 7.5, 10, 12.5, or 15 kW.

  • The FHEL23 Electric Boiler’s output can be set to either 2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, or 22.5 kW.

The 30kW and above jump in either 2.5kW or 5kW power steps.

FHEL30 – 30kw Electric Boiler: Output can be set to either 5,7.5,10,15,17.5,20,25,27.5 or 30kW.

FHEL38 – 38kw Electric Boiler: Output can be set to either 5, 10, 12, 5, 17.5, 22.5, 25, 30, 35, or 37.5 kW.

FHEL45 – 45kW Electric Boiler: Output can be set to either 5, 10, 15, 20, 25, 30, 35, 40, or 45 kW.

Download the Flexiheat Brochure For Electric System Boilers

Central heating with sustainable energy

When the electricity supplying your electric system boiler comes from renewable energy sources such as wind turbines, solar PV systems, or wave or water generated electricity systems, you are eliminating your carbon emissions, or at least reducing your carbon footprint, as well as reducing your running costs for your heating and hot water if you generate this electricity yourself.

Are electric boilers efficient compared to a gas boiler?

Yes, electric boilers achieve 100% efficiency by directly converting all the electricity that powers the heating element or elements into heating energy. Sometimes people refer to the overall efficiency as 99.9%, as the control panel of the boiler uses a minute amount of electricity.

A gas condensing boiler efficiency rate can reach up to 90–91% at full condensation (80% from fuel burning and 11% from flue gas condensation) when run at very low return temperatures.

Three phase electricity supply

When you have a three phase electric supply, you can install larger kW output electric boilers, as you have amps available in the electricity to power the electric boiler. We can go all the way up to 45 kW of heating element output.

Alternatives to gas boilers

Electric central heating boilers, especially electric system boilers, are a great replacement for traditional gas boilers, whether it be as a replacement or for a new installation. The benefits are:

  • No combustion takes place in an electric boiler; thus, no flue system is required with an electric boiler to flue the products of combustion that gas boilers installed produce.

  • A gas boiler has to be placed in certain locations, often to comply with flue system regulations—often on a wall that has external access so the flue can go straight out the wall—but with an electric boiler, you can locate them pretty much anywhere you want.

  • No gas supply means there is no chance of gas leaks.

  • There is no risk of carbon dioxide poisoning with an electric boiler installation.

  • Carbon emissions: gas boilers produce CO2 as well as NOx as they use fossil fuel.

  • If you use electricity to power your electric system boilers with renewable sources such as solar PV, wind turbines, or just purchase electricity that is produced by renewable sources, then you can reduce your carbon footprint or even have none at all for your central heating boiler.

  • Quiet operation: electric boilers are virtually silent, i.e., you can’t hear the heating element or elements heating the hot water in an electric water heating system.

  • Electric control panel: our electric boiler range has an inbuilt control panel that can be controlled by a thermostat or programmer. This can be an “OpenTherm” controller, such as a nest or hive type, allowing you to control these electric boilers from a phone, iPad, or computer as long as you have Wi-Fi or internet access.

What size of electric system boiler do you need?

We have a dedicated webpage on this which is here – what size electric boiler do I need ?

Who should consider an electric boiler?

Anyone who wants to have a wet central heating system but doesn’t have a gas supply or doesn’t want an oil tank at home. They are also a good alternative to a heat pump, in particular an air source heat pump in retrofit boiler replacement in wet central heating systems where the radiators, pipework, etc. were previously sized on the traditional flow and return temperatures of 82C/71C flow and return temperatures.

Most heat pump heating systems struggle to produce hot water over 55 °C, requiring the replacement of heat emitters, i.e., radiators, with units that can be up to four times larger and upsizing of pipework to accommodate the required flow rates for heating water. This issue also affects the demand for the domestic hot water tank demand, as domestic hot water needs to be stored at 60 °C to prevent legionella bacteria; thus, an immersion heating element or immersion heater is required to power the domestic hot water to this temperature.

Thus, in older properties, the additional cost of upgrading the wet heating system is prohibitive to many home owners, as the cost of materials and the cost of labour to fit all of the above will run into many thousands (even tens of thousands) of pounds.

This is where electric system boilers, when replacing a gas boiler for home heating and domestic hot water, are a suitable replacement with an easy install, as no heat emitters or pipework needs to be changed.

Electric system boilers for hot water and central heating

Electric system boilers can be installed anywhere in the house, are easy to operate, free from offensive fumes, do not need regular gas checks, do not require the installation of a flue, and have very few moving parts, minimizing the chances of malfunction. Get in contact with us for the best range of electric system boilers on the UK and Irish markets.

Unit heaters for Poultry and Pig farms or swimming pool heating applications

Unit heaters for Poultry and Pig farms or Swimming pool heating applications

Unit heaters for poultry farmers ,pig sheds or swimming pool heating applications

Unit heaters for poultry farmers, pig sheds or swimming pool heating or other arduous heating applications


When warm air space heating certain applications such as indoor swimming pools, poultry farms or sheds and pig breeding facilities it can be difficult due to the arduous conditions that hot air heater need to withstand.

We supply a full range of hot water fed warm air unit heaters that are the perfect solution for these heating requirements. Whether it be heating a commercial poultry shed, farms, greenhouses, barns, nurseries, swimming pools, stables, or other similar livestock buildings or structures.

The “HCF” series of hot air unit heaters are predominantly for heating environments with high-dust or chemical concentrations, as well as for food production or farming company operations.

Warm air space heating for difficult environments

Agricultural farming heating applications often include a high concentration of acids and ammonia (especially relevant to pig sheds / farms), as well as a high quantity of dust in the air (especially relevant to poultry farms / poultry farming)

Swimming pool air heating systems also must be suitable for a high chlorine content within the air, which is very corrosive to warm air heaters heat exchangers.

heat exchanger damaged by ammonia or chlorine atmosphere conditions that are prevalent in poultry, pig farms and swimming pools

High ammonia or chlorine air content damages standard heat exchangers – thus a protective coating is required for a pig farm or poultry houses or air heaters for swimming pools

Air Heaters

These warm air space heaters are fed by hot water, which can be generated by LPG or natural gas, oil or biomass boilers (wood pellets or logs) or alternatively heat pumps either air source or ground source units for higher efficiency to reduce energy costs.

This heated hot water is then pumped around the heating system to the unit heaters which can be wall mounted or suspended from the ceiling of the building to expel the heated air flow.

The heat output is directly related to the flow and return temperature supplied to the unit heater, and the desired air temperature you would like to achieve to overcome the heat loss of the building in question.

Construction of the heaters

This range of unit heaters has the casing manufactured from expanded polypropylene, which is abbreviated to EPP, and is a recyclable moulded foam that a distinct set of characteristics that are hard to come by in any other material:

  • Impact absorption provides strong damage resistance and form recovery. This reduces the likelihood of damage during operation or installation.
  • High resistance to the environment: able to withstand most chemicals, including oils and lubricants.
  • Lightweight: These heaters’ lower weight makes installation simpler.
  • Noise absorption characteristic: which lessens vibration and noise from the heater in operation.
  • Great structural strength and capacity to support loads.
  • Good insulation properties – which means the heat is not absorbed by the heater casing but rather into the areas being heated, ensuring high efficiency in operation

Heat exchanger construction and advantages

The heating coil within this unit heater range is constructed using energy efficient copper and aluminium, which can be supplied with hot water up to a temperature of to 120 °C and a pressure of up to 16 Bar.

hot water heat exchangers with aluminium fins for our warm air heater

The heat exchanger then has a special GOLD EPOXY coating applied to it, which includes an anti-bacterial layer.

We treat the heat exchanger of the unit which has aluminium fins with a Gold Epoxy polyurethane coating, which helps to preserve HVAC equipment from corrosion, reducing energy expenditures, maintenance expenses, and premature replacement.

After this initial coating, the heat exchangers are also having an additional epoxy coating, which is applied to protect the heat exchanger from highly corrosive environments. The epoxy layer has also undergone the salt spray test according to ASTM B 117.

This coating has the following benefits and advantages –

  • Increases the lifespan of the unit heaters in harsh environments by preventing corrosion of the heat exchanger coils.
  • The heating capacity of the unit heaters is also unaffected by the epoxy coating.
  • The epoxy layer has undergone the salt spray test as well.
  • The antibacterial layer stops bacteria from growing within the heating coils of the unit heater.
  • Furthermore, the elastic layer of the epoxy coating prevents cracking when the coil is thermally dilated.

Product range

We do two units, both are equipped with the protected heat exchanger construction for arduous use, and can be either be wall mounted or ceiling mounted in any commercial buildings

The HCF IP54 – 3S industrial unit has a IP54 rated motor, which has 3 speeds – heated output rating of up to 58.5 kW at a flow temperature of 120/90°C and 0°C inlet air temperature.


The HCF IP66 industrial unit has a IP66 rated motor, which has a one speed fan – heated output rating of up to 66.2 kW at a flow temperature of 120/90°C and 0°C inlet air temperature.

Technical data for our water fed heater range for poultry, pig or indoor swimming pool heating HCF IP54 and HCF IP66 units

HCF IP54 or IP66 motor rated air heater

This detail is included in our brochure which can be downloaded here

Download the HCF series of unit heaters for poultry and pig farms or swimming pool heating brochure -Flexiheat UK

and the technical manual is here

Download the Technical Manual – HCFIP54-3S and HCFIP66 hot water unit heaters

Unit heaters for Swimming pools

Swimming pool heating using hot water as the energy source from Flexiheat UK

Swimming pool heting using unit heaters

Indoor pools are often heated all year, the pool area must be kept at a high temperature (about 32 degrees Celsius when the pool is in use), and the structure itself is likely to have a substantial quantity of windows, resulting in poor thermal insulation values.

To keep the humidity in a pool room at a tolerable level and to protect the building’s fabric, you’ll need a good hot air heating system with enough power to quickly bring the air temperature back up to the desired air temperature while the pool is in use.

Our unit heaters for swimming pool heating systems have a EPP plastic manufactured casing which is resistant to air with a high chlorine content. EPP is a robust material and a 100% recyclable product as well.

The Gold epoxy polyurethane coating with its high chemical and high salt spray resistance features ensure that our swimming pool heaters provide the best protection from the chlorinated air and ensure reliable longevity of the product.

The unit heater we recommend for swimming pool heating systems is our IP66 unit, which is a single phase powered heater. This “IP” means the motor has total dust tightness and has protection against a stream of water (100 l/min) from any direction. Water being an obvious potential hazard in a swimming pool environment.

Although if the unit heater is to be placed in a location further away from the pool itself, then the IP54 motor rated units, which can sustain water splashed against the motor from any direction and have no harmful effects should suffice.

If in any doubt, go for the IP66 rated unit is our advice.

Agricultural heaters

Agricultural heaters may be utilised in a variety of settings, including greenhouses to maintain appropriate growth temperatures and frost protection and barns to keep livestock warm through cold weather.

We’ll will break the section of agricultural heaters down to applications.

Poultry heater

With poultry farm heating or other farm animals such as turkeys etc, the biggest issue is the amount of dust that occurs within the poultry houses or farm. This dust can block the heat exchanger up, thus the requirement for easy cleaning is essential.

The “HCF open is fitted with a completely opening casing that allows easy servicing access to the units heat exchanger.

Unlike direct-fired gas or oil-fired heaters, which bring combustion gases into the poultry farm,our air heaters do not introduce water vapour into the building, resulting in drier litter and higher air quality, which leads to greater bird development when using our unit heaters in poultry farming heating.

HCF “Open” Series of unit heaters for poultry farm heating

HCF “Open” series – the heat exchanger is easy to clean, as the unit will pivot open which is essential in poultry farm heating


This unit has gold epoxy coating and an “IP66” rated fan motor to handle these types of site conditions that a poultry heater must endure.

Poultry heaters hot water fed from Flexiheat UK

HCF Open series Poultry heater for a poultry house or shed

Full heat output data are detailed in the following brochure

Download the HCF Open series unit heaters brochure – Flexiheat UK

Greenhouse heating

Thermal conditions that are optimal support healthy plant growth and boost crop efficiency.

The fans of the units make sure that heat is distributed evenly throughout the greenhouse. This ensures that there are no cold or overly hot areas.

Our hot water fed unit heaters allow you to adjust growth conditions, resulting in improved crop quality and output regardless of the size of your greenhouse.

Dust usually isn’t an issue in greenhouse heating – thus we would recommend our HCF IP54 unit or the IP66 unit.

Thermostat and controller options

We can supply this range of high efficiency wall mounted or ceiling mounted space heating units with various control options.

Thermostats and timers: Our selection of thermostats and programmers allows you to regulate the heating zone’s temperature as well as the times that the units run.

A three-speed fan controller with thermostat, a fully programmable controller – designated the “HMI” controller, and actuated control valves.

Three step fan speed controller with thermostat HMI programmer and control valve accessories for our unit heater range

Control and valve accessories for the range

Contact us

Should you require any prices or to check stock on our Unit heaters for Poultry and Pig farms or Swimming pool heating applications, then please don’t hesitate to contact our sales team on 01202 822221 or use our email contact form via the contact tab above to message us.

Destratification – What is it ?

Destratification – What is it ?

Destratification and how destratification systems reduce the inefficiency of a warm air heating system by mixing the layers of air to ensure higher energy efficiency as recommended by the carbon trust in the UK.

Destratification- What is it ?


Destratification is the opposite of the natural process of thermal stratification in HVAC systems, which is the layering of different (usually increasing) air temperatures from floor to ceiling. Thermal stratification occurs when heated air rises to the ceiling or roof space or area because it is lighter than the colder air around it. Cooler air, on the other hand, descends to the floor level because it is heavier than the warmer air around it.

Its basic principles of physics really –as this surrounding cooler air falls to the floor level, and the hot air rises, this is the reverse of what we require when heating. We need to send that heat back down to where it is required, to heat the staff or customers of your business, thus reducing energy consumption and lower energy costs and this is where a destratification system solves this problem by using destratification fans.

Destratification technology can also be used on cooled air supplied by air conditioning systems by ensuring that the chilled air is properly mixing, circulated, and distributed equally throughout the building volume.

What is destratification, and how does stratification make it more difficult to keep the temperature constant?

Here we explore the issues of stratified air which is caused by hot air rising up to the roof space or ceiling level.

How does thermal stratification impact our living and working environments, and what is destratification?

This simple yet important law of nature can pose serious challenges to businesses trying to keep their buildings at consistent temperatures for their clients, employees, and inventory. Heating and cooling systems that are not efficient can be expensive and wasteful. Variations in air temperature can have a significant impact on both the working environment of personnel and the shopping experience. Some may be moaning about the heat in one location while others will be too cold, i.e., hot and cold spots.

In temperature-regulated storage facilities where consistent temperatures are necessary, temperature variations can also seriously affect the design of racking systems. This is particularly true in refrigerated storage facilities, where the cold temperatures are necessary to ensure the commodities’ quality and longevity. Many kinds of commodities’ “shelf life” might be impacted by excessively hot or cold storage conditions.

Thermal stratification

The development of “thermal stratification,” or naturally occurring thermodynamic layers, is the cause of the issue. Warm air rises naturally because it is lighter than cold air. To put it another way, cold air is heavier and denser than warm air. The warmer air is forced upward because the heavier object lowers. Thermal stratification is the result, which is a growing gradient of temperatures from the warmest at the top to the coldest at the bottom. It’s possible that many buildings lack high-quality ventilation systems because naturally, hotter layers develop at ceiling level while cooler layers remain at ground level. Thermal stratification can be more problematic in larger, more open spaces.

Benefits of destratification by Flexiheat UK

Open, high ceilings are common in commercial, industrial, and retail facilities, allowing tenants to arrange the space to best fit their needs. Mezzanine floors are prevalent. They are widely used to divide up employee workspaces and identify the various departments inside the company. The significant temperature variations between the various parts of the structure can make this type of space use problematic.

Temperature difference of the air

The “strata,” or ceiling temperature layers, of buildings taller than four metres differ from those at ground level, where standard thermostats are typically installed. Depending on the architecture and design, the temperature differential between the strata may be significant. A building is more prone to experience problems with thermal stratification the higher and more open it is.

Destratification fan systems can be advantageous in this situation. Effective and efficient heating and/or cooling of buildings calls for a tailored solution with a destratification fan or destratification fans ensuring air movement to eliminate air stratification.

Systems for destratification are intended to increase airflow in an area. Strong targeted destratification fans force the warmer air back down from the roof space to the floor area and prevent the temperature stratification by continuously mixing all the air in the building and reducing the temperature difference between the ceiling and floor. Because of this constant airflow recirculation, any extra heat produced by processes, people, or even solar gain ensures all air temperatures are blended equally and reduce the temperature gradient and lower energy costs for your building.

As a result, the temperature stays more consistent throughout. This lowers the energy consumed and thus the energy bills and makes it simpler to keep all your clients and staff at suitable working temperatures.

The benefits of thermal destratification systems

The benefits of thermal destratification systems are clear:

1.A 20% to 40% decrease in heating bills depending on ceiling heights – i.e., the higher the ceiling height, the larger energy savings.

2.Reduced carbon emissions / footprint – the less energy consumption the less carbon dioxide emissions occur

3. More comfortable environment for your customers or staff as you can maintain a even heating temperature within your building.

4.During the summer, destratification fans can also be employed to create cooling draughts of air.

Commercial benefits for business owners

Here are the issues an air temperature difference can present.

Building fabric heat losses will increase without destratification fans

The hotter air in the roof area influences how rapidly the structure loses heat. For example, the working areas temperature may be 20°C. On a chilly day with an outdoor temperature of -2°C, this would result in a temperature differential of 22°C between the working space and the outside. However, the air in the roof space will be roughly 24°C, resulting in a temperature differential of 26°C between the roof space and the outside air.

This is crucial because the temperature gradient influences the rate of heat loss. The greater the temperature differential between the air in the roof space and the outside air, the greater the rate of heat loss through the roof. Reduced heat loss ( and thus saving energy) via the roof covering can be minimised by lowering the temperature of the air in the roof space by using destratification fans to be more energy efficient.

For example, lowering the roof space temperature from 25°C to 21.5°C would result in a 14% reduction in heat loss through the roof surface. In many circumstances, optimising the circulation of warm air by destratification allows for the right temperature in the working space to be maintained using fewer warm air heaters, lowering both capital and operating expenses.

Losses via airflow infiltration

Another consideration is the influence of temperature gradients on the natural rate of ventilation, which occurs when air enters and exits the structure via leakage locations in the building fabric. It is generally known that part of the warm buoyant air ascending into the roof area will escape through high-level leakage spots. This will result in a slight negative pressure, which will attract additional chilly outside air into the structure via lower-level leakage locations. This low-level cold air entering the building lowers the temperature in the building, requiring the heating system to use more energy to achieve the desired temperature. Fabric heat losses and air penetration are especially problematic in older buildings with insufficient thermal insulation and numerous leakage spots.



Destratification fans, by mixing the air, eliminate stratified layers of hot air, successfully achieving temperature equilibrium across the entire space, and reduce energy consumption for heating systems.

Air stratification in buildings can be avoided by allowing the inside air to mix and move about. The temperature will be balanced by homogenising the air, or mixing it up and giving it all the same attributes. We call this process “destratification.”

Should you require more product information or get a project sizing on our destratification fans then please don’t hesitate to contact our sales team on 01202 822221 or use our email contact form via the contact tab above to message us.

Glass Lined Hot Water Storage Tanks

Glass Lined Hot Water Storage Tanks

Glass lined hot water storage tanks or glass-fused-to-steel tanks for storing hot water produced from water heaters such as tankless water heaters hot water system or indirect water heaters such as gas or oil boilers. From 200 to 6,000 Litres in volume by Flexiheat UK

Glass lined hot water storage tanks, also called vitreous enamel lined hot water tanks, are storage tanks or buffers that are normally used for domestic hot water storage(potable water), although the hot water doesn’t have to be of this quality. They are storage tanks manufactured in carbon steel but with glass or vitreous enamel corrosion protection of the metal surfaces in contact with the hot water.

The glass lining provides a robust internal surface for water storage tanks that must endure the wearing effects of high volume, high-temperature hot water and prevents corrosion of the storage tanks.

Glass Lined Storage Tanks

Our glass lined hot water storage tanks can also be used for cold water storage too, as they are designed to withstand temperatures down to 10 degrees C. The hot water temperature limit is 95 degrees C, depending on the model.

How is the vitreous enamelling or glass lining applied?

All interior linings of domestic hot cylinders must be “Food Grade quality” according to EU Regulation 1935/2004. Our vitreous enamelling has food grade certification at 95 °C, ensuring maximum quality at severe operating temperatures.

Using a sophisticated “surface treatment” on the carbon steel surface, combined with an automated enamel coating procedure, results in much more than a robust mechanical adhesion of the lining. A molecular interaction develops between the steel surface and the applied enamel layer during the curing process.

This maximum bonding of the enamel coating to the steel surface, along with the vitreous enamel’s high level of impermeability, makes the product last longer and keeps it from breaking down in ways that can happen with other types of coatings, like the protective coat coming off or blistering.

When to use glass lined storage tanks

These tanks are the most widely used for storing potable or waste water in building services or process equipment applications, but they are also suitable for dosing chemicals, numerous industrial effluents, or reagent materials since they combine the corrosion resistance of glass with the hardness of steel at a very cost-effective price.

Cathodic protection system via sacrificial anodes

A magnesium sacrificial anode in glass-lined tanks assures potable water quality. These sacrificial anodes guarantee that the domestic hot water is safe to drink by drawing contaminants from the nearby water supply. If the magnesium anode rods strike the glass while lying down, it might cause glass shattering or crazing (fine cracks on the surface of the material). It is critical that they be kept and carried upright.

The sacrificial anodes, through an electrochemical process, are designed to attract particles of limestone, iron, and other minerals present in the water and corrode instead of the glass lined tank. In simple terms, it “sacrifices” itself to help the range of glass lined storage tanks last longer.

Most glass lined storage tank manufacturers advise inspecting and evaluating the sacrificial anode’s condition every year and replacing it when it has been depleted by more than 50%. This is particularly important if you have hard water or use a water softener on your domestic hot water.

Storage Tanks Product Range

We have two ranges of glass lined water storage tanks; these are

Our SAC series

These have capacities ranging from 300 to 5,000 litres, with a maximum water temperature of 95 °C.

With a maximum working pressure of 10 bar for the 300 to 1,000 Litre capacity models

As standard, the 1,500 to 5,000 Litre tanks are 6 Bar rated – with the option of 8 bar manufactured units.

All units come with insulation with ErP energy ratings of “B” or “C” depending on size, to prevent heat loss.

Full details on this series of glass lined storage tanks are here –

Download the Flexiheat SAC Glass Lined storage tanks or cylinders for domestic hot water storage brochure

Finished in grey PVC RAL 9006 colour lining or jacket up to 2,000 litres, and white PVC RAL 9001 above this volume.

They are manufactured to the 2014/68/UE Directive, ART. 4.3, without CE marking Standard EN 12897:2016.
These buffers are designed and built in accordance with the requirements of 2009/125/EC.

Labelling in accordance with the requirements of 2017/1369/EU and Delegated Regulation 812/2013 (EU)

Glass lining corrosion protection to DIN 4753 and come with a 5-year warranty.

Our Coral Vito series

This series of glass lined water storage tanks has capacities ranging from 200 litres to 6,000 litres, with a standard pressure of 8 bar (10 bar optional upgrade) and a maximum operating temperature of 90 °C.

These hot water storage models all benefit from an inspection and clean outdoor or manhole which is 146mm for the 200 to 1,500 and a larger 400mm manhole option is available from 800 litres upwards.


800 to 1500 litre glass lined water storage tanks with large inspection plate or manhole 400mm -CV- RB range Flexiheat UK

RB models with larger 400mm inspection / clean out manhole


Full details are on the following brochure – please see page 10 for 200 to 1,500 Litre tanks , and pages 35 & 36 for the 1,500 to 6,00 Litre tanks

Domestic hot water cylinders and storage vitreous enamelled units from Flexiheat UK

Soft water areas: be aware

Glass-lined storage tanks can succumb to significant corrosive damage quickly under naturally soft water conditions, despite the use of sacrificial anodes.

Purer, soft water has poor electrical conductivity due to a lack of dissolved metal ions; therefore, the electrical flow from the anode to the cathode via the water is decreased. This has a negative influence on the chemical interaction between the sacrificial anode and the storage tank shell, resulting in less protection.

When the sacrificial anode is evaluated in such circumstances, its condition may be exceptionally good, but this is likely to be a significant signal that the anode is failing in its job, implying that the water tank itself is corroding.

An electrically powered anode is a common substitute for the sacrificial magnesium anode rods. A powered anode, which is frequently constructed of titanium, creates a very low current in the water rather than giving up its own electrons and creating an electrolytic current. This should provide a similar level of protection for a glass lined tank while not corroding the anode. However, in soft water conditions, even an electrically powered anode may still be ineffective since the conductivity required by the anode is insufficient.

As a result, in Scotland, west Wales, and the north-west and south-west of England, where the water is very soft, you are almost always going to need a stainless steel hot water storage tank.

Please see more on our range of stainless steel hot water storage tanks

Water heating

These glass lined storage tanks or buffer tanks are often used in conjunction with either tankless water heaters or suitable air source heat pumps, gas, or oil boilers that, via a plate heat exchanger, can provide the domestic hot water and space heating requirements. The glass lined storage tanks provide a buffer volume of hot water to accommodate a variety of peak demands the building or process may encounter.

Hot water system volume

With various capacities of tank sizes available, from a small 200 Litre to 6,000 litres in single tanks (you can also couple the units up in series should you require higher capacities), our range gives us the flexibility to cover all storage capacity requirements you may have.

Glass lined storage tanks

Should you require more product information, check stock, technical support, budget options, prices, or to place an order on our glass lined hot water storage tanks, then please don’t hesitate to contact our sales team on 01202 822221 or use our email contact form via the contact tab above to message us.

120kW Boiler Gas Fired Condensing

120kW Boiler Gas Fired Condensing


120kw Boiler gas fired condensing boiler for central heating be it radiators or underfloor heating and domestic hot water Flexiheat UK


Our gas fired 120kW boiler for heating commercial systems is available in natural gas or LPG gas (LPG biofuel is compatible as well).

This regular boiler can be used for space heating, central heating (radiators or underfloor heating), and domestic hot water production via accessories such as a plate heat exchanger or an indirect domestic hot water calorifier or cylinder.

They are a high-performance “A “rated efficiency , ErP-compliant condensing boiler and offer enhanced performance that exceeds the Part L building regulations for seasonal energy efficiency requirements. With low NOx Class 6, environmentally friendly emissions

Efficiency features: with a broad range of output modulation ratios of 20:1, automatic part load adjustment offers superb outputs down to 5.75 kw of heat output at 80/60 °C or 6.44 kW heat output at 50/30 °C, which leads to better heat load matching of the system, higher energy efficiencies, lower fuel consumption, and energy saving results.

This energy-efficient commercial boiler also has two stainless steel heat exchangers (2 x 60 kW) in one boiler, which ensures redundancy for your heating system; if one heat exchanger module fails, you still have  50% of your heat duty available. This enhanced performance feature can be vital for commercial customers on a site that can’t be without some heat.

120 kW wall hung gas condensing boilers

With the option of installing the boiler as a wall-to-wall solution or arranged on a suitable free-standing frame kit for floor-mounted installation, depending on site requirements.

120kw output gas fired commercial condensing boiler in natural gas or propane gas fuel with high thermal efficiencies for energy savings.

Our 120kW gas fired condensing boiler on a free standing frame kit, with low loss header and plate heat exchanger for Domestic Hot Water production.

We can provide a solution for every commercial heating specification or commercial system, as we can cascade these high performance gas boilers up to 960 kW with automatic part load adjustment with an intelligent fault system that will monitor and report any faults on these commercial specification boilers.

Commercial gas boilers high efficiency condensing boilers for heating either floor standing boilers or wall hung boilers for central heating in commercial applications - Flexiheat UK

Floor standing or wall hung gas commercial boilers from Flexiheat UK


120kW commercial wall hung gas boilers

As each boiler (heat exchanger) has its own flue non-return valve, you can service either boiler heat exchanger module without shutting the space heating system down.

120kW gas boiler with two heat exchangers for energy efficient low carbon central heating and domestic hot water via an indirect hot water cylinder or heat exchanger- R1K120 from Flexiheat UK

Two heat exchangers – redundancy for the heating system – a wall to wall solution


Our energy-efficient condensing gas 120 kw boilers are fitted with fully modulating low NOx burners (Class 6 combustion levels) for lower environmental impact.

R1K120 gas condensing boiler output and energy efficiency figures—Part L building regulations

The latest changes to Part L of the Building Regulations, which went into effect on June 15, 2023, say that all new wet central heating systems should be sized for a maximum heating flow temperature of 55°C (previously, 75°C plus boiler flow temperature was allowed) and preferably lower if possible to get the most condensing heat transfer from condensing boilers, which results in high energy efficiencies.

Thus, our gas boiler will produce up to 125.67 kW heat output when the heating system flow and return temperatures are 50/30 °C.

The unit will also provide 114.64 kW at 80/60 °C heat output if you have a process heating application that is not covered in the Part “L” building regulations.

Full data is shown in the following:


This is detailed in our full manual, which can be downloaded here.

Manual for R1K120 Gas Condensing Boilers, Internal Version, Flexiheat UK

Should you require a larger output gas boiler (we do up to 240 kW in a single boiler and up to 980 kW in a cascade system), then we do a full range of gas condensing boilers for commercial use, which are listed here.

Gas commercial condensing boiler range

Condensing boiler specifications

  • “A” ErP efficiency rating wall-hung boiler designed for commercial use or a very large home domestic central heating system and DHW for multiple bathrooms via a hot water cylinder or plate heat exchanger

  • Low Class 6 NOx flue gas emissions make these more environmentally friendly as low carbon solutions today.

  • Straightforward and easy install: all plumbing connections are at the bottom of the unit, saving installation costs.

  • Energy efficient condensing boilers up to 105.8 %  at 50/30°C flow and return hot water temperature.

  • Stainless steel heat exchanger with 28mm diameter water ways that ensure the boiler benefits from very low pressure drops, guarantees lower risks of clogging (more resistance to fouling up), greater thermal efficiency, and greater ease of cleaning.

  • Can be arranged inline for larger output requirements to cover any commercial specification, but not back to back at present.

  • These 120-kW gas-fired boilers have the identical outstanding efficiency and performance characteristics as their smaller domestic counterparts.

  • Intelligent fault system: it will monitor system pressure, i.e., if the central heating system installation pressure is too low, etc.

System pressure

  • Maximum heating operating system pressure = 3 bar
  • Maximum heating operating system pressure = 0.3 bar


  • An “Opentherm” thermostat controller, such as a “Hive” or “Nest” type, can control the boiler’s operation and temperature either locally or on the go using your phone, tablet, or computer. You can also use a basic thermostat; the choice is yours.
  • BMS compatible with our 0–10 volt free contact kit

Boiler Fuel type

This 120kw high performance boiler can be powered by natural gas or LPG applications

Dimensions of this regular boiler: 120 kW Output for central heating and domestic hot water heating

This boiler has the following compact dimensions: 670 mm wide, 485 mm deep, and 642 mm high.

Dimensions of our 120kw condensing boiler gas fired in natural gas or LPG- ErP "A" rated for central heating (radiators or underfloor heating) and domestic hot water via a calorifier from Flexiheat UK


Connection details at the bottom of the unit: flow and return connections, gas connection, and condensate drain.

Connection details of our 120kW condensing gas fired boiler Flexiheat UK

Free standing frame installation detail

Floor standing mounting kit

Gas fired 120kw condensing boiler on a free standing frame with low loss header Flexiheat UK

Boiler on our optional free-standing floor frame kit with low loss heating system header

120kW gas system boiler

Are these an 120kW gas system boiler? Yes, in that they have a pump (two pumps actually, i.e., one for each heat exchanger module), but at this size of system boiler, we can’t fit an heating expansion vessel within the boiler casing, so one needs to be fitted to the plumbing pipework external to the boiler to make the unit a full system boiler.

Flue options

Each heat exchanger module features its own flue exhaust connection. You can either individually flue each unit with an 80mm or 100mm flue up to 25 or 30 metres, respectively, either vertically or horizontally in range. However, if you use a split flue system, i.e., an 80mm flue diameter for the combustion air and 80mm for products of combustion, you can go up to 40 metres vertically or horizontally in range.

The last accessories option is a 100mm common flue header for the boiler.

R1K120 gas fired boiler with common flue header

Common flue header kit

Gas-fired 120 kW boilers

Should you require more product information, check stock, technical support, budget options, prices, or to order on our 120kw boiler in natural gas or LPG, then please don’t hesitate to contact our sales team on 01202 822221 or use our email contact form via the contact tab above to message us.

Boiler flow temperature for central heating regulations Part L June 2023

Boiler flow temperature

Boiler flow temperature ? hot water heating systems in newly constructed homes or commercial buildings must now be designed to operate at a maximum flow temperature of 55°C as a result of changes to the Building Regulations.

The low flow temperature information

The latest revisions to Part L of the Building Regulations seek to reduce emissions by 31% for both new build houses and home renovations and additions, which is a crucial milestone in the UK’s journey towards net zero.

Since the year-long transition period finished on June 15, 2023 (it did not apply to work subject to a building notice, full plans application, or initial notice submitted before that date, provided the work for each building is started before June 15, 2023), the original measures that went into effect on the 15th June 2022 apply. Heating installers must be aware of the new regulations that now apply without fail.

These modifications served as a significant first step towards the Future Homes Standard, which targets reducing emissions from all new construction by 75–80% by 2025.

Part L of the building regulations

For both new builds and home extensions or renovations, the stipulated modifications to Part L define a 31% decrease in carbon emissions compared to prior requirements. Part L, which places a strong emphasis on low-carbon heating systems, also emphasises a fabric-first strategy. Changes include an improvement in fabric airtightness and insulation standards, better U-values, and thicker insulation in homes.

For buildings, Part L of the building regulations is divided as follows:

New-build homes and buildings: Part L1A Regulations

This document outlines the energy efficiency requirements for new construction. Approved Document, Part L1A

It describes how all new houses will now be valued using the SAP10 Standard Assessment Procedure (SAP) formula. This approach, which was previously derived using SAP 2012, has been updated to SAP 10. Greater insulation needs and a new target primary energy rate, expressed in kWhPE/m2 per year, are defined as a result of the SAP calculation being performed at the design stage. As a result, achieving SAP compliance will rely heavily on good water heating system design.

Additionally, all new wet central heating systems should be sized for a maximum heating flow temperature of 55°C (previously 75°C plus boiler flow temperature were allowed), as required by Part L1A. This will make it much simpler for houses to be retrofitted with air or ground source heat pumps in the future, when they replace a condensing boiler, be they condensing gas boilers or an oil condensing boiler as the radiators and pipework will be sized correctly for the central heating to work at these temperatures and produce maximum efficiency.

Existing properties and buildings, Part L1B

 Part L1B, an approved document, discusses energy and fuel conservation in existing homes.

Even though Part L1B acknowledges that it is not always practicable to achieve new build standards.

Quote: “Where it is not feasible to install a space heating system that can operate at this flow temperature of 55 °C or lower (e.g., where there is insufficient space for larger radiators, or the existing distribution system is provided with higher temperature heat from a low carbon district heat network), the space heating system should be designed to the lowest design flow temperature possible that will still meet the heating needs of the dwelling.

Source: HM Government – Part L 2021 edition incorporating 2023 amendments, for use in England, Page 36

Part L1B specifies that wet central heating systems that are new or being replaced shall, whenever practicable, be sized at a maximum boiler water flow temperature of 55°C.

Importantly, the regulations stipulate that if a thermal element ( wall, roof, or floor) of the home is being renovated or replaced, the work must be done to Part L1A requirements.

Commercial/non-domestic buildings are covered in Part L2a

Again, same regulations for the maximum flow temperature of 55°C or lower, but this document refers to commercial and industrial heating applications that are not domestic dwellings.

Referring document / legislation is here –

Part L2a requirements for energy efficiency compliance for commercial/non-domestic buildings

Low temperature heating advantages

Lower heating flow temperatures are now mandatory in the design of an increasing number of household heating systems, whether they utilise a gas boiler or a heat pump. Installing a condensing gas boiler on a low temperature system will result in cost savings for homeowners and reduce energy bills.

The boiler will always operate in condensing mode while the boiler temperature is set to a flow temperature of 55°C or lower. This makes the boiler and heating system far more effective and guarantees that they are always capturing the latent heat from condensation. As a result, the boiler will run as close to its condensing efficiency as possible, which will result in cheaper energy costs for homeowners.

All radiators and piping installed as part of a new or replacement system must be sized for a maximum flow temperature of 55°C, according to Part L. As a result, it could be necessary to use larger pipework and install radiators of the correct size to adequately heat the space.

When done appropriately, this work can significantly contribute to future-proofing a building so that low carbon technologies like heat pumps, which also employ low flow temperatures, can be installed in the future.

“A gas boiler will function as closely to its condensing efficiency at the boiler’s flow temperature of 55°C (55°C is the dew point temperature at which the condensing mode starts to work in gas boilers, as the flue gases condense and they can recover the latent heat), which will reduce a homeowner’s energy heating bills.”

In short, a lower boiler water flow temperature means reduced heating bills for your central heating system.

How to design and install a low temperature heating system and what to think about

Installers must take into account the wider system as well as the overall design of the building, including heat loss calculations, because the design of a low heating flow temperature system differs from that of a traditional higher boiler’s flow temperature system. By doing this, they can ensure that any future switch from a gas boiler to a heat pump can be made smoothly.

Heating flow temperature

The most important component of the regulations for the majority of installers will be Part L1(b), which focuses on the conservation of fuel and electricity in existing residential dwellings. Part L1(a) addresses the energy efficiency of newly constructed homes (learn more about what Part L means for newly constructed homes here).

It is crucial to note that it specifies that new or replacement wet central heating systems should be built to operate at a maximum flow temperature of 55°C rather than the 75°C typical of conventional heating systems to ensure boiler efficiency in modern boilers that are all now condensing boilers.

Heating system

1. A minimum of insulation All pipes linked to the hot-water storage are subject to thicknesses. Insulation must be at least 5mm thick for pipes having an internal diameter of 10mm, 10mm for pipes with an internal diameter of 22mm, and 15mm for pipes with an internal diameter of 28mm.

2. Thermostatic radiator valves are needed for every installation, with the exception of heat pump installations, which need volume for defrost.

3. For brand-new and completely replaced systems, the maximum flow temperature is 55°C.

4. Insulation is required for all principal hot water pipes used for home hot water.

5. When passing through voids, secondary central heating pipes must be insulated.

6. Multi-zoning is necessary if the total floor space is 150 m2 or greater.

7. When passing through voids, primary central heating pipes must be insulated.

8. In accordance with BS 7593, all primary hot-water and central heating circuits should be properly cleaned, flushed out, and dosed with inhibitor on each installation.

What does this mean for condensing combi boilers?

A combi boiler produces hot water on demand and has no hot water cylinder attached to the boiler, unlike a system boiler. The boiler flow temperature setting on a combi boiler for the heating side of the condensing combi boiler can be set to a thermostat temperature of 55C, and you can achieve the standard hot water temperature required of 40C for the domestic hot water side of the combi boiler with ease with our combi boiler range.

These are listed here

Our fully modulating 24kW combi boiler in natural gas or LPG  

our 35kW fully modulating combi boiler in natural gas or LPG 

or our largest combi boiler 50kw combination boiler in natural or LPG gas 

Hot water cylinders

Lower flow temperatures can cause issues for a hot water cylinder, as domestic hot water needs to be stored at 60 °C to avoid legionella. This means that the boiler flow temperature to the heat exchanger coil in an indirect hot water cylinder must be higher than the hot water temperatures within the cylinder for the heat to transfer to the domestic hot water. Newer boiler models these days have a system that will ramp up the boiler’s flow hot water temperature temporarily to achieve the correct temperature and heat the hot water cylinder.

Alternatively, immersion heaters can be used to top up the heat required for the hot water cylinder


Changing your boiler temperature, or now, as required, designing a lower flow temperature system, is now mandatory. Whether you’re using a combi boiler or system boilers, the boiler temperature settings must be a maximum of 55 °C and the system designed accordingly, as they have to be future-proof for low carbon heating solutions such as heat pumps.

With a boiler flow temperature of 55 °C and a return temperature that is even lower, this allows the boiler to recover the latent heat for the condensing process, lowering the heating bill / gas bills, as recommended by the energy saving trust.