Boiler flow temperature for central heating regulations Part L June 2023

24th August 2023/in News /by flexiheat

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

Conclusion

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.

70kW Boiler Gas Fired Condensing

18th August 2023/in News /by flexiheat

70kW boiler gas fired condensing

Our gas fired 70kW boiler is available in natural gas or for LPG gas fuel (LPG biofuel compatible to). 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.

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

Efficiency features: with a modulation ratio of 20:1, the automatic part load adjustment offers superb outputs down to 3.5 kw of heat output, which leads to better heat load matching of the system, lower fuel consumption, and you’ll save on energy costs.

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

The unit comes with a 2-year warranty for parts , and the heat exchanger has a 5-year warranty if, as required by the building regulations, a dirt and air separator is fitted to protect the system, and the product is serviced annually.

70 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.

Gas condensing boiler, which is a regular boiler on a free-standing frame kit the R1K range 50kw to 120kw outputs from Flexiheat UK

The 70kW gas fired condensing boiler mounted on a free-standing frame kit with low loss header and plate heat exchanger of domestic hot water production.

We can provide a solution for every commercial specification, as we can cascade these high performance gas boilers up to 960 kW with automatic part load adjustment if so required.

70kW commercial wall hung 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.

Our energy-efficient gas 70kw boilers are fitted with fully modulating low NOx burners (Class 6 combustion levels) for lower environmental impact.

70 kW gas boiler with two heat exchangers for energy efficient low carbon central heating and domestic hot water via an indirect hot water cylinder the R1K75 from Flexiheat UK

Two heat exchangers for redundancy in one boiler casing with an output of 70 kW

R1K75 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 effect from boilers.

Thus, our gas boiler will produce up to 79.35 kW when the heating system flow and return temperatures are 50/30 °C.

The unit will also provide 72.83 kW at 80/60 °C if you have a process heating application that is not covered in the Part “L” building regulations.

Full data is shown in the following:

R1K75 gas condensing boiler output and energy efficiency figures Flexiheat UK

Output and energy efficiency figures for our R1K75

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

Manual for R1K 75 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, which are listed here.

Commercial gas condensing boiler range

Specifications

“A” ErP efficiency rating wall-hung boiler designed for commercial use or a very large home domestic central heating systems and DHW for multiple bathrooms via a hot water cylinder.
Low Class 6 NOx flue gas emissions making these more environmentally friendly.
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 100% heat input at 50/30°C
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.
Intelligent fault system: if the boiler has a fault, it will tell you exactly what has gone wrong, i.e., if the heating system installation pressure is too low, etc.
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

Dimensions of this regular boiler: 70 kW Output for central heating and domestic hot water heating

This boiler has the following compact dimensions: 670 mm wide, 495 mm deep, and 642 mm high.

Dimensions of our 70kw 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

A small compact energy efficient gas condensing boiler 70 kW with ErP “A” rated for central heating (radiators or underfloor heating) and domestic hot water via a calorifier.

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

Free standing frame installation detail

Floor standing mounting kit

Gas fired 70kw output condensing boiler on a free standing floor frame kit with low loss header Flexiheat

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

70kW gas system boiler

Are these an 70kW 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 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 a co-axial flue (80mm/125mm) should you wish to go room-sealed up to 10 metres vertically or horizontally in range. However, if you use a split flue system, you can go up to 40 metres vertically or horizontally in range.

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

R1K75 gas boiler with common flue header option

Common flue pipe header option

Gas fired 70 kW boilers

Should you require more product information, check stock, technical support, prices, or to order on our high performance 70kw 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. Follow our business on Facebook or Twitter if you’re interested in being informed of our latest recommend manufacturer product range items deal.

80kW Boiler Gas Fired Condensing

30th July 2023/in News /by flexiheat

80kw Boiler – gas fired condensing

Our gas fired 80kW boiler is available in natural gas or for LPG applications. They are a high performance “A” rated ErP condensing boiler, and offer enhanced performance that exceeds the Part L building regulations for seasonal energy efficiency requirements.

This unit can be used for space heating, central heating, and domestic hot water production via a plate heat exchanger or indirect hot water cylinder or water heaters

Efficiency features: with a modulation ratio of 20:1, the automatic part load adjustment offers superb outputs down to 3.5 kw of heating output, which leads to better heat load matching of the system and lower fuel consumption and energy bills.

This energy efficient commercial boiler also has two stainless steel heat exchangers in one boiler as such, which ensures redundancy for your heating system; if one heat exchanger module fails, you still have up to 50% of your duty available. This feature can be vital in a commercial specification for a building that can’t be without some heat.

Wall Hung Gas Commercial Boiler

With the option of installing the boiler as a wall to wall solution or arranged inline on a free standing frame kit to offer enhanced performance.

Gas condensing boiler on a free-standing frame kit the R1K range 50kw to 120kw outputs from Flexiheat UK

The 80kW gas fired condensing boiler mounted on a free-standing frame kit with low loss header and plate heat exchanger of domestic hot water production.

We can provide a solution for every commercial specification, as we can cascade these high performance gas boilers up to 960 kW with automatic part load adjustment if so required.

For more details on this – please click here- cascading our commercial gas boilers

80kW commercial wall-hung 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.

Our energy efficient gas boilers are fitted with fully modulating low NOx burners (Class 6 combustion levels) and fan for low carbon solutions.

R1K75 gas condensing boiler output and energy efficiency figures – Part L building regulations

The latest revisions to Part L of the Building Regulations that came into force on June 15, 2023, mean 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 were allowed), as required by Part L1A, and preferably lower if possible to achieve the maximum condensing effect of boilers.

Thus, our gas boiler will produce 79.35 kW ( close enough to 80 kW for us) when the heating system flow and return temperatures are 50/30 °C. However, should you require more kW output, please look at the next size boiler up our 100kW boiler which again is available in natural gas or for lpg applications and offers superb outputs up to 106.8 kW.

The unit will also provide 72.83 kW at 80/60 °C if you have a process heating application that is not covered in the Part “L” building regulations.

Full Data is shown in the following –

Output and energy efficiency figures for our R1K75

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

Manual for R1K 75 Gas condensing boiler – Internal version Flexiheat UK

Should you require a larger output gas boiler (we do up to 240 kW in a single boiler), then we do a full range, which is listed here.

Commercial gas condensing boilers

Specifications

“A” rated wall hung boiler – for commercial use or very large home heating applications.
Energy efficient condensing boilers up to 105.8 % at 100% heat input at 50/ 30°C
Stainless steel heat exchanger with 28mm diameter water ways that ensure the boiler from very low pressure drops, guarantees lower risks of clogging (more resistance to fouling up), greater thermal efficiency, and greater ease of cleaning.
Intelligent fault system: if the boiler has a fault, it will tell you exactly what has gone wrong, i.e., if the heating system pressure is too low, etc.
Pressure sensor to monitor system pressure as part of the intelligent fault system
Maximum heating operating system pressure = 3 Bar
Maximum heating operating system pressure = 0.3 Bar
Can be controlled by an “Opentherm” controller, such as a “Hive” or “Nest” type, which means you can control the boiler on the go from your mobile phone, tablet, or PC, just like our full range of smaller domestic counterparts that we supply.
BMS compatible with our 0-10 Volt free contact kit

Dimensions of this commercial boiler: 80 kW gas-fired

This commercial boiler has the following compact dimensions:

Dimensions of our 80kw condensing boiler gas fired in natural gas or LPG- ErP "A" rated for central heating (radiators or underfloor heating) and domestic hot water via an indirect domestic hot water cylinder from Flexiheat UK

A small compact energy efficient gas condensing boiler 80 kW with ErP “A” rated for central heating (radiators or underfloor heating) and domestic hot water via an indirect domestic hot water cylinder.

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

Free standing boiler frame detail

Gas fired 80kw condensing boiler on a free standing frame with low loss header Flexiheat UK

The gas condensing boiler on a free standing frame kit with low loss header.

80kW gas system boiler

Are these an 80kW gas system boiler? Yes, in that they have a pump (two actually, i.e., one for each heat exchanger module), but at this size of system boiler, we can’t fit an expansion vessel within the boiler casing, so one needs to be fitted to the pipework external to the boiler to make the unit a full system boiler.

Flue options

Each heat exchanger module has its own flue exit. You can either individually flue each unit with a co-axial flue (80mm/125mm) should you wish to go room sealed up to 10 metres vertically or horizontally. However, if you use a split flue system, you can go up to 40 metres vertically or horizontally.

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

Common flue pipe header option

Gas-fired 80 kW Boiler

Should you require more product information, check stock, technical support, or prices on our high performance 80kw 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.

Buffer tank with coil or twin coils

28th July 2023/in News /by flexiheat

Buffer tank with coil or twin coils

A buffer tank with coil or coils is used to hydraulically separate a heat source or sources, in the event of a twin coil buffer tank, from the heating system’s hot water. This can be required for mechanical engineering reasons such as flow rate or temperature difference between the heating system and the heating source , which is often the case with heat pump heating systems, be they air source heat pumps or geothermal heating systems.

With a full range of buffer tanks from 260 litres in hot water storage volume all the way up to 5,000 litres of storage capacity, we have the volumes to satisfy any application or performance requirements for your inertia tank.

We do two ranges which will detail below

Why use a buffer with a coil ?

The coil acts as a heat exchanger, separating the hot water generated from a heat pump, boiler, or solar thermal fluid in the event of a solar thermal system from the hot heating water in the thermal storage tanks.

This can ensure that there are no problems with flow rates between the heated water from the heat source and the heating system, and also temperature differences, i.e., some solar system fluids can get up to 200 °C, whereas the storage tank temperature ratings are either 95 °C or 110 °C maximum. Thus, the use of a heat exchanger coil within the buffer tank is required.

The coils used are not a stainless steel coil , like those used in an indirect water heater that produces domestic hot water. We are not producing domestic hot water in a buffer tank with an intermediate heating coil to produce hot water for the heating system. The coils are made of steel, just like the thermal storage tanks.

Which means these buffer tanks must be used on a sealed heating system only, and the heating water must be treated with a corrosion inhibitor.

Domestic hot water production

If you want a Buffer tank with a stainless steel coil to produce domestic hot water, then these are called Thermal store hot water cylinders or Thermal store cylinders – and we go into more detail on this range here: https://www.flexiheatuk.com/product/thermal-store-cylinders/ as these are our units for instantaneous domestic hot water heating or production via a stainless steel coil within the thermal storage tank and are available in volumes from 500 litres of storage to 2000 litres in range or size.

Single heat exchanger models

The first range is the “G” range. These are rated

Maximum working pressure: Coil – 25 Bar – Tank 6 bar

Maximum working temperature: Coil – 200 ºC – Tank 110 ºC

Single coil buffer tanks the G-IF or G-IFS range 260 litres to 1500 litres that are thermal stores to accommodate peak loads for the heating system, using an intermediate coil to hydraulically separate the heat source from the heating system water in a hot water cylinder from Flexiheat UK

The storage tank also has an immersion heater port, should you wish to install an immersion heater as a back up or top up heat source.

Technical data: The “G -IS” buffer tank range has larger tapping ports than the “G – IFS” buffer tank range, which has the standard 40mm (1-1/2″) See “EH” detail on the following:

G range of buffer tanks with single coil or heat exchanger detailing the hot water tapping detail on the buffer tank or thermal stores and heat exchanger detail Flexiheat UK

G-IS and G-IFS Buffer tank with a single coil / heat exchanger technical detail

Larger Size Storage Tank

Thermal storage tanks with hot water storage volumes ranging from 1,500 to 5,000 litres with a single coil.

These buffer tanks are available with an inspection and clean out manhole that is 400mm in diameter and are designated the “ISB” version.

Or as the standard unit without which is designated the “IS” version.

Technical detail

The full detail on the above tanks can be found in the following brochure – pages 12 & 13

Buffer Tanks Brochure Flexiheat UK

Solar thermal heating systems

Some fluids in the solar system can be heated to 200 °C. If this is the case, you need to use our “G” or “MV” range. However, if your water or fluid temperature is less than 110 °C, then we have another buffer tank product with a single coil, and these are detailed here:

Twin coil buffer tanks

Twin coil or two heat exchanger buffer tanks are suitable for applications with two energy heating systems feeding the thermal storage tanks. For example, one coil or heat exchanger can be fed by a thermal solar system, which is usually the lower coil in the buffer tank. The second coil or heat exchanger, which is located in the upper part of the buffer tank, can be fed by heat generated from either a traditional gas or oil boiler or heat pump heating systems, which can be either ground source heat pumps or air source heat pumps.

Our Twin coil buffer tanks from 300 to 2,000 Litres in volume

These units are available from 300 to 2,000 litres in demand capacity.

The twin coil range has a heat exchanger maximum hot water temperature rating of 110 °C and 12 Bar pressure .

The buffer tank’s maximum temperature rating is 95 °C, and the pressure rating varies with the volume; please see the brochure for full details.

Flexiheat brochure for PPS2 Buffer tank with twin coils for sealed heating systems

Buffer tank with a coil or coils

Should you require more product information, availability, technical support, or prices on our complete range of buffer tanks with coil or coils then please don’t hesitate to get in touch. Contact our sales service team on 01202 822221 or use our email contact form via the contact tab above to message us.

1000 Litre Buffer Vessel or Tank

5th July 2023/in News /by flexiheat

1000 Litre buffer vessel or tank

Our 1000 litre buffer vessel or 1000 litre buffer tank is a hot water buffer tank or vessel that is typically installed to increase the volume of hot water in the heating system to store heated water for later use.They are also referred to by some as a 1000 litre thermal store.

They work best with heat pumps because they store the excess energy the heat pump produces during times of low demand and release it during times of high demand.

Our buffer tanks or accumulator tanks are as such a thermal store for hot water systems and this energy is stored for later use, resulting in fewer but longer heating cycles for heat pump systems, wood pellet boilers, gasification boilers or a biomass heating system.

This is 1000 litre buffer tank is just one of our large range of buffer tanks and vessels . Our full large range of other size buffer tanks is detailed on this webpage – Buffer tanks

Heat pump systems

This buffer tank is ideal for use with heat pumps, allow approximately 25 litres of volume per kW of heat pump output if the manufacturer hasn’t specified a buffer tank / accumulator tank volume.

Wood pellet boilers

For wood pellet boilers sizing – allow a minimum of 10 litres of buffer tank volume for every 1 kW of boiler output.

Gasification boilers

For gasification boilers or log fired biomass boilers – allow a minimum of 50 litres of buffer tank volume for every 1 kW of boiler output.

1000 Litre Vessel – Buffer tank product description

This 1000 litre buffer vessel / accumulator tank has a working pressure of 8 Bar and maximum temperature of 95C for sealed heating systems and are not to be used on chilled water.

This 1,000L buffer vessel, or buffer tank is manufactured from mild steel or carbon steel. Please note corrosion inhibitors must be used on the heating water system to protect the product i.e. the buffer tank from corrosion .

Technical specifications of our buffer tanks / accumulator tanks are as follows –

1000 Litre Buffer vessel port details for the buffer plus range from Flexiheat UK to store heating hot water from various energy sources for peak demand use in hot water systems.

1000 Litre Buffer tank or vessel/ Accumulator tank / Cylinder thermal store for heating water

Buffer tanks storage capacity – 1000 Litres nominal – 840 Litres Actual

Buffer tank height – 2,065 mm

Buffer tank pivot height – 2,270 mm

Diameter with Insulation: 940 mm

Diameter without Insulation: 790 mm

Pressure rating – 8 Bar maximum working pressure – not the low 3 bar working pressure that many of our competition offer as standard

Mild steel construction – untreated internal – so the heating system must be a sealed system and water treatment used to prevent corrosion.

This 1000l buffer tank has a removeable insulation system, that allows you to get the thermal store through a standard 800mm wide door.

Product insulation is polyurethane – 75 mm insulation

Rigid expanded polyurethane insulation with 95% closed cells, CFC and HCFC free, fire resistance to class B2 according to DIN 4102-1.

The insulation is removable – which can help to get the buffer tank through doorways or access points

Great quality product at a great price and available from stock or on a short delivery

Buffer tanks weight – 160 Kg when empty – 1,000 Kg’s when full with hot water

Eight tappings – 1 1/2″ female BSP, which enables the installation of immersion heaters as back up or top up heating

Four sensor or thermometer tappings – 1/2″ female BSP

1 x Air vent eliminator or safety valve tapping – 1 1/2″ female BSP

For full dimensions on these buffer tanks please see the following brochure –

Download the Buffer Plus range of buffer tanks and vessels brochure from Flexiheat UK

Contact Us

If you require further information, product availability, check stock levels, delivery times or prices on our 1000 Litre buffer vessel / 1000l buffer tank/ accumulator tanks for sealed heating systems or other sizes from our large range of accumulator tanks, then please contact our sales service team on 01202 822221 or use our email contact form via the contact tab above to message us.

All deliveries are kerbside, and require offloading by the customer, for an extra charge we can offer a tail lift service to get the buffer tanks to floor level.

Please see our Facebook or Twitter pages for our latest product updates and special product prices.

Stainless steel hot water cylinders

15th June 2023/in News /by flexiheat

Stainless steel hot water cylinders

Stainless steel hot water cylinders have rapidly grown in popularity in the UK, as in comparison to conventional enamelled steel hot water cylinders of the same capacity, stainless steel hot water systems are lighter and simpler to install. Long-term maintenance and servicing costs are decreased because a sacrificial anode is not necessary for protection.

With regards to a copper cylinder, they are similar in weight and dimensions, but stainless steel domestic hot water storage tanks can be used at a higher pressure.

Austenitic stainless steel or duplex stainless-steel is a suitable material for a hot water cylinder since it doesn’t need cathodic protection to prevent corrosion on its surface.

Stainless steel pressurised hot water cylinders

There is no feed tank or cold water tank in an unvented system as they use mains water pressure. As unvented cylinders run at mains pressure, sealed hot water cylinders provide substantially superior flow rates, making for more pleasurable baths and showers as they are supplied directly from the cold water mains unlike a vented hot water cylinder.

They can be indirect cylinders, whereby the stainless steel hot water cylinders have an external heating source such as a boiler supplying the heat exchanger, which heats up the unit.

We go into more depth on our indirect unvented cylinders in duplex stainless-steel from 80 to 500 litres on this dedicated webpage –
https://www.flexiheatuk.com/product/indirect-unvented-cylinders/

Direct hot water cylinder range in Stainless-Steel

Or they can be a direct cylinder, whereby the cylinder is heated directly by an immersion element or a series of immersion heaters fitted into the cylinder. An immersion heater requires an electric supply to power this range or type of cylinder. Direct stainless steel hot water cylinders are often used where a gas supply isn’t available.

We go into more depth on this range on their dedicated webpage – direct unvented cylinders in duplex stainless-steel from 80 to 500 litres

Vented hot water cylinder in stainless steel

In UK homes, vented hot water cylinders are still a typical form of hot water system. Vented cylinders operate by drawing cold water from a header tank, which is normally found in the loft, and then utilising gravity to circulate hot water throughout the house.

A vent line connects the vented hot water cylinder to the cold water in the header tank to maintain the hot water pressure’s stability with expansion.

Because the hot water pressure is normally determined by the height of the water tank above the tap or shower feed, the pressure of the hot water can be very poor when using a vented hot water cylinder.

Vented cylinders, however, are easier to install and maintain.

The downside of vented cylinders is that they require more space, with tanks in loft space , and that the water pressure is often low, resulting in poor hot water flow rates, especially upstairs in a property.

To boost the pressure of the hot water delivered under gravity to the showers and taps in homes with a vented cylinder, many individuals install electric pumps to help boost the pressure.

Normally, properties or homes with a system boiler supplying the central heating system require an indirect unvented cylinder, whereas properties with standard or regular boilers require an indirect vented cylinder.

Our vented cylinders are the same as our unvented range, just supplied without the unvented G3 Kit.

Which is better, copper or stainless steel hot water cylinders ?

Copper is one of the most effective heat conductors and allows for greater heat transmission within hot water cylinders, resulting in quicker hot water delivery. Copper is less competitive when compared to stainless steel when it comes to long-term cost savings since stainless steel has a considerably stronger resistance to all types of corrosion than copper, including corrosion in crevices and stress. This makes stainless steel highly durable and promises a longer lifespan when compared to a copper cylinder.

Stainless Steel

However, due to stainless steel’s capacity to sustain extremely high pressure, unvented hot water cylinders are now commonplace. Due to their ability to deliver hot water under mains pressure, unvented hot water cylinders have become increasingly popular.

Since stainless steel is the ideal material for a pressurised system, it has taken over as the standard material to cover all your needs when compared to a copper cylinder. We can supply a pre-plumbed stainless steel hot water cylinder that are part of our range.

Contact us

Should you require any more information or want to check stock or prices on the best stainless steel hot water cylinders on the UK market with a warranty of 25 years (hi-flow commercial units are 5 years) from a trusted brands, then give our sales team a call on 01202 822221 or use our contact us form. Follow us on Facebook or Twitter for our latest offers. We produce full VAT invoices for all sales.

Direct hot water system? features and benefits

26th May 2023/in News /by flexiheat

Direct hot water system ? What are they ?

A direct-fired hot water system is powered by a direct-fired water heater, whereby the water’s heat source is physically contained within the hot water cylinder itself.

As such, a direct fired hot water heater has a built-in gas or oil burner or electric immersion heater elements that directly heats the domestic hot water.

Thus, the water in a direct hot water heating system is heated by heat sources physically located within the hot water cylinder or calorifier as opposed to an indirect hot water cylinder, which generally speaking use a water supply from another heat source to heat the water via an internal coil.

A direct hot water system which is domestic hot water heating via a direct heat source such as electric immersion heaters or gas fired burners- Flexiheat UK

Direct domestic hot water heating systems to heat water

Advantages of direct hot water systems

Direct fired water heaters are devoted to the production of domestic hot water only, allowing for a quicker heat-up and response time than indirect hot water cylinders or systems, which essentially use “heating water” from a central heating system via an indirect hot water cylinder for the purpose of heating sanitary-grade hot water and are by definition less efficient.

Advantages of separating the hot water and heating systems

Direct hot water heaters are frequently placed close to the point of use, which minimises distribution heat losses and lowers the energy needed to supply water over a long pipe run. Additionally, by doing this, the system’s dead legs and portions of inactive or infrequently used pipes that represent a Legionella danger are reduced in length.

The Health and Safety Executive L8: Approved Code of Practise and Guidance for the Control of Legionella Bacteria in Water Systems, which specifies that the distribution pipework should be adequately designed to enable the water to reach all outlets at 50°C within one minute of turning on the taps, supports compliance with regulations such as this.

Gas fired direct hot water heaters

Direct gas fired hot water systems consist of an integrated gas burner that can be powered by natural gas or LPG (propane) gas that heats the water in the storage vessel directly to produce domestic hot water, controlled by a thermostat in the water heater.

They function by delivering heated gases through the heat exchanger, which is normally an internal coil or may be fire tubes located within the hot water cylinder to heat water. The heat from the heat exchanger is then transferred to the cold water surrounding it, thus heating the water to the desired temperature in an energy-efficient manner.

Indirect hot water systems

A dedicated central heating hot water boiler and an indirect hot water cylinder would be installed in an indirect hot water system. The same boiler is now capable of serving both the heating circuit and the domestic hot water system. When no space heating is required, the boiler must continue functioning to produce heat for the domestic hot water system.

Generally, indirect cylinders also come with an immersion heater or immersion heaters as an emergency backup, heating the water directly in the cylinder in the event of a fault with the heating boiler.

What is a direct hot water cylinder?

A direct hot water cylinder: A direct hot water cylinder heats the water using heat sources that are directly located within the cylinder, such as an electric immersion heater. These hot water heating systems are typically found in buildings that do not have access to gas or would prefer to use electricity as the primary energy source for environmental reasons such as low or zero carbon emissions.

Direct cylinders are available for domestic applications. We go into more depth here –

Direct hot water cylinder range from 80 to 500 Litres

or our commercial and industrial direct hot water cylinder range, which can be fitted with large immersion heating elements and store hot water up to 5,000 litres in volume. More on this range here –

Commercial and industrial direct cylinder / tank range

Storage Direct and Indirect Hot Water Cylinders

Direct or indirect heating of your hot water cylinder depends on your requirements and site conditions; either way, Flexiheat UK has a solution for you, as we have both an indirect hot water cylinder range and a direct hot water cylinder range to suit all your calorifiers requirements.

Contact our sales team at 01202 822221 or use our email contact form for further assistance.

Unvented Hot Water System

11th April 2023/in News /by flexiheat

Unvented hot water system

Unvented hot water systems are a well-liked as a reliable source of hot water for home or commercial use. An unvented hot water system uses the mains water pressure to pressurise the system and deliver a high flow rate of hot water to all of the outlets throughout the property. We’ll discuss the advantages of an unvented hot water system in the following article, including their effectiveness, safety, and usability.

Unvented cylinders come in direct and indirect versions. In contrast to an indirect unvented cylinder, indirectly heating the hot water cylinder via a traditional gas or oil boiler or a heat pump heating system, a direct unvented hot water cylinder employs immersion heaters to heat the hot water cylinder directly with electricity.

Unvented hot water systems- How do they work

As they are fed directly from the cold-water mains, unvented cylinders operate at mains pressure.

An unvented system is a closed or sealed system and therefore requires additional devices, such as an expansion vessel, for controlling the pressure changes within the hot water system as the water inside the hot water cylinders heats up, as water is essentially incompressible.

Expansion vessel in unvented systems

Since water expands when heated, it is necessary to account for this expansion. To facilitate this, an expansion vessel must be attached somewhere within the hot water cylinders system. It may be affixed to the cylinder, connected to the hot water system elsewhere, or even integrated into the cylinder.

Efficiency is one of the key advantages of an unvented hot water cylinder. The water is heated and kept at a higher temperature than in vented cylinders because the system is pressurised. This makes it perfect for larger families or homes with multiple bathrooms since it allows for a significantly higher flow rate of hot water to feeding multiple outlets such as your home’s taps and showers, something that a combi boiler will struggle to achieve.

Additionally, the water can be heated more quickly by using a backup immersion heater or immersion heaters in the system, which cuts down on the time it takes for the water to reach the appropriate temperature. The need for frequent heating is decreased by the use of a thermostat which also keeps the water at a steady temperature.

Unvented hot water cylinder

Safety is another another key advantage of unvented hot water cylinders. A cold water tank in the loft is not necessary because the system is pressurised; nonetheless, this can provide a safety risk in the event of a leak or flooding. A safety valve and expansion vessel are also included in the system to guarantee that any excess pressure or temperature is discharged safely via a tundish, preventing system damage to the unvented system.

Easy of use

Unvented hot water systems are also exceedingly simple to operate. The pressurised system results in substantially higher water pressure at the taps and showers than in a conventional vented cylinder, making it quicker and easier to use multiple outlets such as taps and showers. But please note the hot water pressure will only be as good as your incoming cold water mains pressure when using unvented cylinders or a unvented system.

Showering experience is improved with stronger water pressure, from the mains water supply when utilizing an unvented system. Additionally, since there isn’t a cold water tank, frequent maintenance and cleaning aren’t necessary, which saves time and maintenance costs in keeping the system in good operating order as opposed to vented cylinders

Unvented cylinders or an unvented hot water tank can also be installed in a number of places throughout the property, including loft areas or basements, since it is pressurised by mains pressure cold water and does not rely on natural gravitational force / gravity to provide hot water. This gives homeowners more freedom in deciding where to place the unvented cylinder, which can be very advantageous in homes with limited or less space, unlike vented cylinders which need piped access to loft tanks.

Our range of unvented cylinders

The best hot water cylinders must be able to store water under pressure, so they must be durable and as corrosion-resistant as possible. We do a couple of ranges – first our domestic or light commercial range, with cylinder capacity from 80 to 500 Litres ,which are manufactured in duplex stainless steel, which is generally considered a highly corrosion resistant material. There are two options for these mains pressure unvented systems range

Direct unvented hot water cylinders range –

These are fully detailed on this webpage – unvented direct cylinders

Or our

Indirect unvented hot water cylinders

These indirect units , which are installed alongside a boiler or heat pump to feed the coil in the cylinder, having a high heat recovery rate when compared to the direct cylinder range , again with cylinder model sizes from 80 to 500 Litres – these are detailed here –unvented indirect hot water cylinders

We also do a commercial range from 200 to 6,000 Litres in size, which are available as glass lined mild steel or stainless steel vented and unvented cylinders. These are detailed on this webpage – commercial indirect hot water cylinder range

Installation and maintenance of unvented hot water cylinders

Unvented cylinders should come equipped with additional safety measures to protect them against overpressure, such as a pressure-reducing valve to restrict the cold incoming water supply pressure entering the water heating system and a temperature and pressure relief valve are also installed on unvented cylinders for further security, to release the domestic hot water if it becomes too hot.

An unvented hot water system must be installed by a licenced heating engineer (the heating engineers / plumbers need to be certified in building regulations “G3” unvented hot water systems, which covers the safety regulations of an unvented system) , but once they are, they require very little upkeep. The pressure relief valve, thermostats and expansion vessel on any unvented cylinder should be checked annually to make sure they are functioning properly, but other than that, not much more needs to be done to an unvented hot water cylinder.

Unvented cylinder

The system is also significantly more energy-efficient than a vented cylinder due to the use of an immersion heater or heating element, which lowers energy costs and the amount of energy needed to heat the water. In addition, there is less chance of bacterial growth in the system because the water is heated and kept at a higher temperature, which further lowers the need for maintenance.

Conclusion

In conclusion, unvented cylinders have many advantages over vented systems, including increased effectiveness, enhanced safety, and simplicity of operation. These systems are also more energy-efficient and low-maintenance than conventional systems due to the removal of a cold water tank and the use of an immersion heater or heating element. A property, be it domestic or commercial with an unvented hot water system may be the best option if you’re thinking of improving your hot water system.

Gas hot water tank or cylinder

13th February 2023/in News /by flexiheat

Gas hot water tank or cylinder

A gas hot water tank also known as a gas hot water cylinder or gas fired hot water tank are gas fired water heaters that are storage hot water heaters. These water heaters are a solution for high flow rates or high intermittent water heating demands.

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 condensing water heaters are energy efficient and cost effective to run.

These condensing water heaters are energy efficient gas water heaters that are used in heavy domestic, commercial or industrial applications where people want a domestic water heating device that utilizes a hot water storage tank to optimize water heating capacity and supply hot water instantly.

These gas water heaters suit applications where tankless water heaters cannot supply enough instant hot water flow rate or hot water temperature for the water heating requirements.

Sometimes these gas water heaters are referred to as a gas hot water heater tank or a gas water cylinder ultimately, they all refer to the same product, a gas hot water cylinder.

This full range use gas as the heat source and are condensing gas water heaters which reduces energy consumption, lower fuel bills, and lowers emissions.

Water heater applications

Typical applications for this range of gas fired water heaters is health centres, hairdresser saloons, pubs and leisure facilities, hotels and bed and breakfast establishments or larger properties, where hot water demand and good flow rates are essential, and they have a gas supply – either natural mains gas or LPG (liquefied petroleum gas).

These gas storage water heaters allow you to sperate your central heating system from your domestic hot water system, meaning you can achieve greater energy efficiency by only heating water in the summer months and reduce your energy bills or your customers for their water heating.

This gas fired hot water tank range can also cover a vast range of industrial applications as well, such as producing instant hot water with a storage element for food or process manufacturing that require a energy efficient and cost effective gas water storage systems for high volumes at intermittent times.

Gas fired water heaters

Our largest gas fired water heaters is designated the 50/330 – This 50kW condensing gas-fired direct water heater that raises water from 10°C to 60°C on demand, providing domestic hot water at a rate of 871 litres per hour while maintaining outstanding efficiency and low NOx emissions that comply with ErP regulations for heating water. This gas water heater features a 330-liter storage tank / hot water cylinder with a fully enamelled heat exchanger enclosed therein for heating water, and it has a 50kW power output from a pre-mix gas burner (natural gas or LPG options).These are commercial water heaters for high demand hot water applications.

50kW gas fired hot water storage cylinder water heating performance data-Flexiheat UK

Flow data at a storage hot water temperature of 60C – incoming cold water temperature of 10C – mixed hot water temperature of 38C

Features of this 50kW gas water heater with storage hot water cylinder

Energy efficiency class “A” – Load profile XXL – Up to 101.5% nett combustion efficiency
Anti-freeze and Anti-Legionella functions built-in to these water heaters
Fully ErP compliant with low NOx emissions of 39mg/kWh
Mains gas (natural gas) or LPG powered options
20% Hydrogen gas mix compliant
Enamelled lined tank /hot water cylinder with dual impressed current cathodic protection
Multiple flue options for ease of installation

Download the 50kW Gas condensing storage water heater brochure – HY model – Flexiheat UK

Download the 50kW gas storage condensing water heater manual Flexiheat UK

50kW condensing gas fired water heaters components

Flue system outlet Ø 100 / 150mm
Gas valve and regulation
Flue system inspection
Condensate drain
Base of the
Tank inspection flange
Polyurethane foam insulation
Enamelled heat exchanger
Double electronic anode
Combustion chamber
Temperature & Pressure valve
Premix burner

Then our “SFKA” Range of gas water heaters

This gas condensing water heaters range is designed to store 150 litres of domestic quality water at a hot water temperature of 60C or above in the water storage cylinder, this instant DHW is then available to the installation when there’s a demand from the showers, baths, or hot water taps, with good flow rates.

gas hot water cylinder internal picture showing the storage tank with with high thermal efficiency, tankless gas water heater

Internal picture of our storage gas water heaters

We do two main types or models, a 28kW gas water heater or a 34kW gas water heater

Our 28 kW output gas fired water heaters with its 150-litre stainless steel hot water cylinder (storage tank) will provide a continuous D.H.W. supply at a 30°C temperature rise of mixed water with a first 10-minute flow of 305 litres and a one hour flow rate of 984 litres.

Full detail on this gas water heater is here

Flexiheat SFKA 28.150 Condensing gas storage water heater – Hot water tanks Manual

Our 34 kW output gas fired water heaters with its 150-litre stainless steel hot water cylinder (storage tank) will provide a continuous D.H.W. supply at a 30°C temperature rise of mixed water with a first 10-minute flow of 333 litres and a one hour flow rate of 1,167 litres.

Flexiheat SFKA 34.150 Condensing gas storage water heater – Hot water tanks Manual

This gas water heater range is a condensing high-efficiency storage water heater that is room-sealed, meaning these gas water heaters may be installed practically anywhere thanks to its flexible flue / vent pipe options. Making installation of this range of energy efficient condensing water heaters with hot water storage systems quick and easy in any commercial or heavy domestic site.

Condensing water heaters

As our gas fired water heaters range are condensing water heaters, you’re getting many benefits with a reliable and efficient hot water installation, with the benefit of lower energy consumption. They are as such hybrid water heaters, with a tankless water heater which are condensing water heaters combined with a storage tank.

Gas water heater features

Our commercial, or heavy domestic gas water heaters range features

Our heat exchanger is produced in stainless steel and has large single-tube coils with a diameter of 28 mm. Because of this, it has very low pressure drops, which means it is less likely to get clogged, uses heat more efficiently, and is easier to clean.

High DHW performance gas water heater with tank

The domestic sanitary water temperature adjustment ranges from 40 °C to 60 °C
Anti-legionella system;
These are condensing water heaters – being highly energy efficient and thus cost effective to run.
Possibility of recirculation or direct feed for high volumes of demand at intermittent times with our gas water heater with tank range.
Remote management and control of these gas fired water heaters is possible via 0-10 volts or via our Opentherm thermostat and controller with an app that allows you to control the gas water heater from a phone, tablet, or PC.
Integrated post-circulation for excess heat disposal to help save energy.
Self-diagnostic electronic board with frost protection
Integrated recirculation function for immediate DHW delivery;
Fast H2O pre-heating for efficient and instant hot water without waiting.
Electrical systems protection level is IPX5D
Very low NOx emissions, maximum 50 mg/kWh for this gas fired hot water cylinder range.
Suitable Anode to protect the storage tank.
Available in natural gas (mains gas) or LPG
Can even be used in industrial applications for decentralised water heating with our gas fired hot water cylinder range.

Dimensions of our water heaters gas fired

Both water heaters gas fired have the same dimensions occupying a small space or footprint.

Contact us

Whether you a new customer or a trade account, should you require anymore assistance, information, check stock or get a recommended price / cost on our cost effective gas hot water tank or gas fired hot water cylinder range in natural gas (mains gas) or LPG on the UK market with fast delivery times, please contact our customer services sales team on 01202 822221 or use our email contact above on the web page for our email form.

35kW Combi boiler – Combination boilers

4th February 2023/in News /by flexiheat

35kW Combi boiler

35kW combination boiler – “R2C34” from Flexiheat UK – high performance domestic hot water output flow rate of 16 litres/min with a 30C temperature rise for commercial or domestic installations

Our modern 35kw combi boiler is a cost effective heating solution that employs condensing technology to effectively heat the system water by removing latent heat from the flue gases which enables these boilers to have a “A” ErP rating for space heating efficiency and “A” ErP water heating efficiency rating, which means higher efficiency and thus lower running costs and for this gas combi boiler.

A combination boiler is the most popular boiler type in the UK, as the size of a combi boiler is one of its main benefits. As Combi boilers do not require external hot water cylinders / water storage cylinder, this type of boiler provides both hot water and central heating in a single compact unit for more than one bathroom properties.

Having “heating and hot water” in one boiler has many benefits and will save installation space on site and the users or customers will have a lower installation cost as a combi boiler installation is quicker that a system boiler and indirect cylinder installation.

Our gas boiler has a great modulation or turn down ration of almost 10:1 in range, which means the boiler will match or address the central heating load requirement very closely with high efficiency, ensuring you’ll save money on your energy bills for heating and hot water.

With low noise level, this reliable gas boiler, which is available to natural gas or propane gas (LPG) will produce a domestic hot water output of 16 litres/min with a temperature rise of 30C and is up to 108.6 % efficient and provides a cost effective heating solution for domestic installations with tested technology.

35 kW Combination Boilers

A gas burner in the combi boiler is lit when you need hot water or heating. The primary circuit receives the heat from the burner through the main heat exchanger, where it is then either moved straight to the radiators or through a plate heat exchanger to your hot water taps in larger homes.

One of the key features of our 35 kw ErP compliant modern gas combi boiler is a “pre-heat” system, which enables the boiler to contain a small volume of water that can be used instantly for fast hot water response. The water is kept in the boiler all day and kept at the desired temperature so that it can be quickly delivered to the hot water taps.

Fuel options for our 35kw output gas combi boiler

This 35kw combi is available in either natural gas or LPG (propane) gas options depending on local availability of the fuel to the property or house. Should you ever need to change your gas type, just speak to our customer services as we can supply a gas adaptor kit to change the gas boiler to your required fuel type. This is an easy installation and takes less than quarter of an hour to do at most if ever needed as the unit has easy access to all internal components.

Stainless steel heat exchangers in our combi boilers

Our full range of condensing boiler models use stainless steel heat exchangers because of their high corrosion resistance across a broad pH range and are better than a aluminium heat exchanger. Your combi boiler will last longer as a result and has a long warranty period, making them a good choice gas boiler for consumers who require a quality solution and high domestic hot water output.

When discussing our combi boilers dependability, the development of our modern heat exchanger from one single continuous coil permits the water to move through more quickly, efficiently, and at a higher flow rate performance.

This reduces the possibility of debris blockages, increasing reliability and lengthening the boiler’s lifespan. A Stainless steel heat exchanger construction will withstand high flow rates without corroding or wearing out more than a aluminium heat exchanger.

Patented A rated ErP water heating efficiency

Inside the high performance patented stainless steel main heat exchanger is a 12mm diameter internal stainless steel pipe that produces domestic hot water (installed within the 28 mm diameter heating exchanger). This ensures you have a quantity (approximately 7 litres) of “warm water ready to go,” as they say. It’s total length is 8 metres. Because these boilers produce domestic hot water by continuously condensing, which makes them very efficient, gas energy costs and energy bills are reduced.

Additionally, these design features reduce the possibility of scale accumulation, which you can expect in older combi boilers with a plate heat exchanger that many companies still use.

In areas with hard water, this is crucial because our heat exchanger’s high velocity and flexing while in use reduce the potential for scale to build up and prevent it from happening, helping to ensure a long life, trouble-free operation, and a good hot water flow rate for domestic installations.

Good mains water pressure is needed for combi boilers

One potential drawback of a combination boiler is that if multiple showers and taps are initiated simultaneously due to combi boilers pulling water directly from the local availability in the mains cold water supply, the water pressure can drop quickly for example.

Our boiler needs a minimum pressure of 0.5 Bar and will operate up to a maximum pressure of 6 Bar. For good hot water performance we recommend around 3 Bar pressure for your hot water system.

Boiler specifications, features and details

Our 35kw heat output combi boiler has both “A” rated ErP water heating efficiency performance for both heating and domestic hot water, with low noise level outputs and is suitable for weather compensation, when used in conjunction with the external temperature sensor that we can supply for our full range of heating and hot water boilers. Weather compensation reduces the heat output to suit the weather conditions which can vary so much on a day to day basis in the UK.

This 35 kw boiler range is suited for space heating or central heating with radiators or underfloor heating systems with a high efficiency of 106.43% when used on a 50/30C range flow and return system which will save you money and cost on your gas energy bills.

With a useful central heating output of 36.19 kW when used on a 50/30C system , or when used on a 80/60C system the central heating output is 33.35 kW.

We use a Wilo pump rather than a Grundfos pump in our 35kw gas combi, as we consider them a more reliable pump than a Grundfos pump.

Download the Flexiheat R2C 34kW Combi Boiler Manual

For larger homes, or homes that have larger hot water performance demands then please look at our next size up combi boiler our – 50kW gas combi boiler

Dimensions

Our 35 kw combi boiler dimension are – Height = 642 mm , Width = 410 mm and a Depth of 350 mm – with a weight of 44 kg making these robust units easy to fit in any installation.

Flow and return and gas connections – 20 mm

Hot and Cold water connections – 15 mm

Flue lengths and options

With extensive flue options of up to 60 metres in length – when using a sperate 80mm diameter twin flue system, or up to 10 metres in length when using our 80/125mm co-axial horizontal flue system option – both options make this combi boiler a room sealed gas appliance.

Horizontal flue kit co-axial room sealed for our boilers Flexiheat UK

Horizontal flue kit co-axial – the 80/125mm Ø will go 10 metres

Or our vertical flue option

Vertical flue kit co-axial for our boilers Flexiheat UK

Vertical flue kit co-axial – the 80/125mm Ø will go 10 metres vertical

Control options

This boiler can be controlled via the inbuilt digital display, which displays digital operating status and diagnostic display or you can opt for our smart thermostat range option, which is an OpenTherm control system, that allows you to control these combi boilers from an app on your phone, tablet, or computer.

cloud warm app to control the boiler from your mobile phone or tablet

Cloud Warm App – control on the go !

Nest and Hive controllers are Opentherm compatible, so you can use them with what we consider the best 35 kW combi on the market and a cost effective heating solution for homes heating

Common question

35kw combination boiler how many radiators can it run ?

The average size radiator in a new build property is now 1.5 kW (kilowatts) output – so your looking at 23 radiators, but for older properties your looking at around 11-15 radiators on average for this size gas boiler type.

Please ensure that the local area boiler installer or a company engineers are gas safe registered and can provide a labour warranty and service agreement on the install.

Contact us for free boiler quotes for your combi boiler requirements

Should you require anymore assistance, information or best deals/prices on the best 35kw combi boiler with great hot water performance in natural gas or LPG gas on the UK market, please contact our customer services sales team on 01202 822221 or use our email contact above on the web page for our email contact form. All of sales are supplied with a vat invoice.