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

Commercial gas boilers  – 50kW to 1,920kW heat output

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


Commercial Gas Boilers – Available from 50kW to 280kW as single boilers or up to 1,920 kW in a cascade configuration for heating or and hot water heating via indirect cylinders. Commercial boilers work in exactly the same way as domestic boilers, but are designed and manufactured to efficiently cope with the higher hot water and heating demands of a commercial premises or businesses with outstanding performance levels.

Our commercial boiler range all benefit from a stainless steel heat exchanger and condensing technology to maximise the efficiency of the central heating or heating and hot water, for your commercial heating applications. With stainless steel heat exchangers as standard, which carry a 5 year warranty (terms apply) your heating, be it radiators or an underfloor heating system and your hot water production is in safe hands with our commercial boiler range.

New for 2023

Our new modular floor standing boilers for commercial boiler installations, which are available in 180kW or 240kW units, can be cascaded up to 4 units at present (a maximum of 1,920 kW)  and up to 10 units (so a maximum of 2,400 kW) when our new controller comes online by the summer of 2024.

Designated the R1KG 180 and R1KG 240 these commercial gas fired boilers benefit from stainless steel heat exchangers, high efficiency using condensing technology, fully modulating, floor standing gas boilers, made respectively of three, or four, primary heat exchangers of 60 kW output each with condensing technology in one boiler as such.

A picture of a floor standing commercial gas fired boiler – which is available in 180kW or 240kW output models with a modular construction of various stainless steel heat exchangers in cascade which ensures a great heat modulation ratio of 40:1 for the 280kW or 30:1 for the 180kW unit.

Gas fired floor standing boilers with low emissions – the perfect solution for heating commercial applications with great heat output modulation range of up to 40:1 for our 240kW unit.

They have a low environmental impact (with low emissions both CO and NOx emissions) and extremely compact units, because of their vertical design, making them the perfect solution for commercial premises that require outstanding performance levels.

Internal picture of our commercial gas fired floor mounted modular boiler with four heat exchangers for great modulation range with low emissions for heating commercial applications.

Internal picture of our gas boilers, with the side and front panels removed – they are removable for easy access for inspection and maintenance of the gas boilers.

These gas boilers, which are a condensing boiler have low emissions with a Class 6 NOx rating.

Rear picture of the hydraulic connections on our floor standing gas commercial condensing boilers Flexiheat UK

Rear picture of the hydraulic connections on our floor standing gas commercial condensing boilers from Flexiheat UK

Technical data for these floor mounted modular gas boilers


R1KG180 and R1KG240 commercial modular boilers technical information


This range is ideal for blocks of flats with heat interface units, or any other type of commercial applications

Download the Commercial gas floor standing boilers with condensing technology 180kW and 240kW manual Flexiheat UK

The following addition manual for the R1KG range further details the various cascade options – i.e. This commercial heating boiler range can be mounted in line (side by side)

in line commercial heating boiler installation from Flexiheat UK

or alternatively supplied in a back-to-back boiler configuration, enabling several commercial boilers to be installed in a limited area.


This manual is split into 2 parts due to it’s size

R1K Modular gas fired commercial floor standing boilers cascade manual – Part 1 pages 1 to 27


R1K Modular gas fired commercial floor standing boilers cascade manual – Part 2 pages 28 to 56

Gas commercial condensing boiler range

These highly efficient commercial boilers are available in both a natural gas boiler and LPG for the full range, with various commercial boiler models with an output range from 50 kW to 120 kW, in a wall hung or floor mounted when mounted on our free standing or floor standing frame kits configuration. Making them the ideal boilers for commercial heating in any commercial premises or commercial business.

These wall hung boilers work in a fully modulating range, which provides energy saving through 1:10 modulating operation for 50kW and 60kW commercial boilers.

50kw and 60kw gas commercial boilers from Flexiheat UK

50kw and 60kw gas commercial boilers from Flexiheat UK -This gas condensing boiler range can also be floor standing boilers, when using our frame kits or more commonly are installed as wall hung boilers – the choice is yours to suite your site requirements.


and 1:20 for models 75kW, 100kW and 120kW wall hung boilers. As the larger units have 2 heat exchangers within the one casing, should one unit fail, you have 50% of your heating requirement still operational. You can also service one of the units when the other is still operational- so your heating system is never down .This is an important feature and benefit for these commercial gas fired boilers range.

75kw to 120kw output gas fired wall hung boilers or floor standing boilers when a frame kit is used Flexiheat UK

75kw to 120kw Output gas fired wall hung boilers or floor standing boilers when a frame kit is used


These gas condensing boilers can be installed directly on the wall thanks to their reduced size and low weight, freeing up valuable space inside the boiler house of your commercial property or business.

These are wall hung boilers and can be coupled together in a commercial gas boiler modular configuration which you can think of as multiple boilers within “One Total Boiler” as such, this give this range of commercial boilers , a few distinct advantages when compared to others, in that – If one system boiler goes down or malfunctions, you still having the remaining modules to provide you with heat, thus increasing reliability , which can be vital in applications like nursing homes, hospitals or any other commercial applications where your require constant heating and hot water.

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.

Furthermore, multiple boilers, when in a cascaded configuration have power control boards that communicate between them and handle the power output of every module in a uniform and coordinated way in order to guarantee the maximum heating efficiency, matched to the water heating requirement of the installation.

The performance of this commercial boiler range with a wide range of power outputs makes it one of the best gas condensing boilers to use in any commercial boiler installations, be it feeding radiators, radiant panels, fan-coils, underfloor heating etc and to install in any boiler house, in either new or when replacing existing units in any buildings, houses, hotels, schools, factories, or any other industry etc.

With low class leading NOx Class 6 levels for all these commercial wall hung boilers ensuring maximum BREEAM points, which is important for any UK business interest, and something to be expected from leading manufacturers at this date

Gas Commercial Boilers – Compare the Range & Benefits

  • INNOVATIVE DESIGN, COMPACT, POWERFUL, & LIGHTWEIGHT – The devices have been developed and manufactured to be “space-saving”; thanks to their vertical structure they allow space savings in both new installs and to upgrade or replace older failed units or replacing an oil fired system boiler ( or even steam). Due to their light weight they are easy to carry , place and mount. Thus easy to install.
  • Stainless Steel condensing boilers that optimizes the output according to real thermal needs of the installation and business, ensuring maximum efficiency with a working pressure of up to 3 Bar
  • WIDE MODULATION OR TURN DOWN RATIO -wide modulation or turn-down ratio of 1:10 for the 50kW and 60kW and 1:20 for the 75kW, 100kW and 120kW units and up to an incredible 1:160 in cascaded configuration installation of 960 kW for example.
  • STAINLESS STEEL HEAT EXCHANGERS -Each heat exchanger is made without welded joints and is 28mm diameter in size with a industry standard working pressure of 3 bar.
  • ECOLOGIC PREMIX BURNER -The full range of commercial gas fired boilers is equipped with ecologic premix burners made of Fecralloy metal fibre.
  • This range of condensing commercial boilers are suitable for use on sealed systems that fill from a mains water supply and open vented installations ( with a minimum of 0.3 Bar Head) and perfect for both new and retrofit installations.
  • Standard spares consent – all leading brands i.e. Wilo pumps, Honeywell gas valves etc
  • Suitable for radiators or under floor heating systems
  • Domestic hot water can be generated via an indirect hot water cylinder, all controlled via the boiler or via heat interface units (heat interface units are very common in blocks of flats – with a communal commercial boiler in a plant room)
  • These commercial boilers work in a similar way to domestic boilers – so proven reliability and performance.
  • We also do a combination version, which is listed here on our website here-

Commercial combi boilers up to 100kW or a dedicated webpage for our most popular 50kW combi boiler that we supply.

Why choose our Commercial Natural Gas Boilers –

High efficiency and fuel savings at the right price solution for your business

Condensing Boiler Technology

Total flame modulation

Certified efficiency up to 109%

Cascaded sequence control and heat exchangers in rotation – a solution for industrial applications


Quiet in operation

Easy installation and maintenance – in the rare occurrence of a breakdown – access to all essential system components

Reduced size and weight

Construction Quality

Modern, innovative and attractive design to keep your customers happy

large water ways the range benefit from a stainless steel heat exchanger, with industry leading dimensions

Turn down ratio up to 1:20

Ecology / Ecological

Fecralloy fibre premix burner

Reduced gas emissions in the atmosphere

Low CO and NOx levels – Class 6 -industry leading

commercial gas boilers; commercial lpg boiler; wall hung gas commercial boilers; commercial boilers in cascade; Worcester; price; vat; job;

Commercial gas boiler range – Condensing from Flexiheat UK

Wall Hung Gas Boilers – for commercial applications or industrial

The 50kw to 120kW output commercial boilers. The R1K range of commercial boilers , which benefit from high efficiency with premix condensing technology. The technical details of these units are –

50 to 75kW Boiler models – commercial

50kw 60kw and 75kW gas boiler technical data for wall hung boilers – Flexiheat UK

50kW,60kW and 75kW Gas boilers technical information continued


50kw to 75kW gas fired boiler technical data from Flexiheat UK; job;

100 & 120kW Boiler models  – commercial

100kw and 120kw gas boilers technical data from Flexiheat UK

100kW and 120kW gas boilers technical information continued

100kw and 120kw gas boilers technical output information from Flexiheat UK:gas condensing commercial boiler;high efficiency boilers

Gas supply requirements and Flue system details for 100kwe and 120kW Gas Boilers



For the complete technical data on our boiler commercial range to suit your site services, be it Natural Gas or LPG , Please click on the following –

Download Flexiheat R1K Internal 50-120kw gas fired condensing commercial boiler manual

Boiler Control Options

All units can be controlled by an “OpenTherm” compatible controller ,with options for mobile phone control or we can supply a 0-10 Volt connection kit suitable for BMS connection, that is often required in commercial heating and plumbing applications or industrial premises.

Commercial boiler installations in cascade natural gas or LPG

This commercial gas boiler range can be used in a cascade configuration of up to 8 boilers , with the potential of 960 kW of heat output, making them the perfect boilers for Schools , Hospitals , Hotels, or any commercial or industrial site that requires heating via a hot water system. With a turn-down ratio of up to 1:160, these commercial boilers are the ideal boilers when you want to match your heating load, at the very best efficiency levels , giving you the lowest gas costs / gas usage for your commercial heating.

commercial and industrial gas boiler; commercial boiler in a cascade;commercial boiler installations

Commercial gas fired boilers from Flexiheat UK up to 960kW of output – free standing floor standing boilers in natural gas or propane

Easy to assemble pipe work kit for fast install on site for this commercial boiler range to make a floor standing commercial boiler set up.

Commercial Boilers for sale UK and Ireland

To ensure you get the correct commercial gas boiler in either natural gas or LPG, that is right for your water heating requirements, our sales team are here to provide information and advice to help you make an informed decision for your project requirements . With high operational reliability that you would expect from a leading brand that you as a customer can rely on, please call 01202 822221 to connect to our sales team or use our website contact form, to get the latest offers and price.