50kW Combi Boiler – Gas combi boilers

50kW Combi Boiler / Combination boilers

A 50kw combi boiler or 50 kw gas combi boiler- which is a combination boiler doing both heating and domestic hot water heating, powered by either natural gas or LPG gas from Flexiheat UK

50kW Combi boiler or Combination boiler – gas fired – from Flexiheat UK

Our Flexiheat 50kW combi boiler is a well-designed condensing combination boiler with 97% efficiency, making it an “A” rated boiler for heating and hot water. This efficiency allows it to generate enough heat to meet your home’s demand while using less fuel than an older, inefficient boiler. The boiler installation is easy, and we can supply this high performance 50kW gas combi boiler in either natural gas (mains gas) or LPG (propane gas), which is ideally suited to larger homes with high demand and more than one bathroom or even multiple bathrooms, i.e., two or more bathrooms.

Gas combi boilers are a one-of-a-kind, compact, and cost-effective solution that are ideal for houses with limited space. They combine a water heater and a central heating boiler into a single device, eliminating the need for additional water cylinders, immersion heaters, or tanks in your large homes that you require with a system boiler and reducing installation costs.

Boilers account for approximately 60% of a household’s yearly energy costs for domestic use, and they have an enormous impact on fuel bills. With more seasoned older gas boilers, a significant amount of heat that could be used to produce hot water is wasted, making them increasingly expensive to run.

Our 50kW combi gas boiler is more than 97% efficient, so 97p of each £1 you spend on your energy bills for your boiler is utilized. When using an Opentherm internet-connected smart controller, you can control our ERP “A”-rated high performance gas boiler on the go from your mobile, or tablet—the right choice for people with busy lives in large homes and even commercial heating and hot water applications.

ERP “A” rated efficiency rating for both heating and hot water demands, this powerful wall hung boiler is an efficient and reliable combi gas boiler, that can comfortably heat large homes, providing effortless comfort at a reduced running cost. All while you sit comfortably in complete peace of mind, knowing that you have a highly efficient 50kw combi gas boiler, that is also one of the quietest boilers in its class at 52 decibels noise level installed (for comparison, a refrigerator is around 50 decibels noise level).

The best features of our condensing 50kw combi boilers / combination boiler are:


  • Higher kW boiler: compared to the competition, we actually make a 50kW combi boiler that will do 53.85 kW output rating of heating power based on a 50C/30C flow and return system, or 49.19 kW output rating at 80C/60C.


  • The central heating boiler side of this high efficiency powerful combi boiler can be used on an underfloor or radiator heating system. This makes this combi boiler great for large properties; we talk more about this application here – Combi boiler for a large house


  • Modern new design: this gas boiler benefits from aesthetically pleasing looks. With its modern design, and quieter operation with a reduced noise level, it is one of the quietest boilers on the market, with a reduced lift weight compared to the competition.


  • Increased burner modulation ratio of 1:10, which prevents on/off cycling for a lengthy product life for your new boiler and reduces noise level for the user.


  • It’s inbuilt intuitive controller, which benefits from an intuitive menu structure for all the information required for control, commissioning, and fault finding if so required of the heating system, which means no need to search through manuals for fault codes. Resulting in the rapid diagnosis of any issues. Not that you’ll use the fault finding much with our quality range of efficient 50kw gas fired combination boilers.


  • Servicing: With plenty of room within the appliance casing for easy internal access, this 50kW combi gas boiler is an installer’s dream to work on, with pipe connections at the bottom of the boiler and fixing points at the rear of the boiler. Also a benefit for rapid diagnosis and fault finding.


  • Installation of the gas boiler, which must be done by gas safe qualified installers or company – can be in any location, as we offer various flue options, such as a room-sealed range (see details below). Also, being one of the quietest boilers, you’ll have complete peace wherever you locate the boiler.


  • Can be operated on a system with an with an optimum pressure of 0.3 to 3 bars for the heating side and 0.5 to 6 bars for the domestic hot water side of the appliance.


  • This 50kW combi gas boiler is suitable for natural gas (mains gas) or LPG (must be specified at the date of customer order). Sit comfortably, knowing that if you change your gas type, these combi boilers are easily converted over.


  • Provide hot water. The DHW flow rate at a 35 Degrees C temperature rise is a high flow rate of 20.30 litres/min DHW output, or at a 40 Degrees C rise then its 17.5 litres/min flow rate, which is still a high flow rate even in the deepest of the worst winter conditions, which many properties will never endure. The temperature is easily changed with our intuitive menu structure in the in-built control panel.

Central heating system side of the boiler

Central heating output rating: based on flow and return temperatures of 80/60 and the fact that current new build homes have radiators that have an average of 1.5 kw output. Our 50kW gas combi boiler has the capacity to generate 53.85 kW of central heating output power, sufficient to heat up to 35 radiators on the system, effectively serving as commercial heating. Please note that if you are retrofitting, the total number of radiators cannot exceed the boiler’s central heating output rating of 53.85 kW.

Some of our competitors claim a 50 kW combi, but in reality, the heating side of the boiler has only 35 kW of output.

There are not many companies producing a gas fired 50 kW combination boiler. Some people may regard a boiler produced by the Worcester Bosch company, namely the Worcester greenstar 8000 50kw combi boiler range, as a direct competitor to our boiler, but in reality, this boiler and all the information we can find, will only produce:

Central heating output (kW): 33.8 kW at 80/60 °C or 50/30 °C condensing mode: 35.7 kW

While our gas boiler will produce 49.19 kW of heating power at 80/60 °C or at 50/30°C in condensing mode it will produce 53.85 kW at maximum capacity.

Thus, can you really call the worcester bosch greenstar 8000 a 50 kW combi?? You make the final decision, but it seems a bit short to us?

Domestic hot water performance (DHW) –

The Worcester greenstar 8000 is 48.9 kW rated on the dhw side, the output is –

DHW output at the hot tap (35°C temperature rise) – 20.3 l/min hot water flow

DHW output at the hot tap (40°C temperature rise) – 18 l/min hot water flow

With a plus or minus of 15%  quoted ?? umm 

Whilst our boiler will produce the following outputs for domestic hot water

DHW output at the hot tap (35°C temperature rise) – 20  l/min hot water flow

DHW output at the hot tap  (40°C temperature rise) – 17.5 l/min hot water flow

There’s no plus or minus 15% for our data – we will produce those figures quoted above

and this should be more than adequate for more than one bathroom.

Domestic hot water performance of the combi

Main features – Due to its excellent domestic hot water flow rate, with a temperature rise of 30 degrees C @ 23.40 ltrs/min of hot water flow or with a temperature rise of 35 degrees C @ 20 litres /min of hot water, this 50kW combi gas boiler is ideal for a two-bathroom house. Our next size down our 34kW combi boiler will do 16 litres /min just to compare the performance.

Hot water cylinder

As no domestic hot water cylinder is used with a combination boiler, unlike system boilers, you are lowering your carbon footprint and energy fuel consumption for your domestic hot water usage, as gas is only consumed in this ERP A rated efficient combi boiler when hot water is required – it’s one of the key features – your only heating hot water when you require it – which results in lower energy bills / gas bills.

Should your cold mains not have enough flow rate to adequately provide for your hot water needs then a system boiler, which uses a separate hot water cylinder for storing water for larger volume applications or heat only gas boiler (also are also called a conventional, regular boiler or traditional boiler), then please see our webpage here – 50kW Boiler which can be used in a multi boiler cascade system for even larger outputs.

Heat exchanger style / construction

This powerful wall hung boiler is equipped with a stainless-steel exchanger with a large Ø 28mm monotube coils, which not only benefits from very low pressure drops, but guarantees lower risk of clogging, with greater thermal efficiency, and greater ease of cleaning with lower running costs. We guarantee or warranty period the heating water heat exchanger for 10 years, when a good quality magnetic dirt and air separator is fitted to the heating system, and the boiler is serviced annually.

Technical data of our combi boiler – 50kW


50kw gas combi – central heating output / hydronic heating – ErP  “A” energy efficiency rating – energy savings trust approved with high energy efficiency.


50kw combination boiler central heating and domestic hot water technical data

Energy efficient domestic hot water “A rated” ErP energy efficiency rating  – DHW flow rate at various temperature rises 


combi boiler 50kw domestic hot water flow rate at various temperature rises

mains gas and propane gas and electrical requirements for the combination boiler

inc vat; increased power; intuitive menu structure; customers; fantastic new design;company

Download the 50kW Combi Boiler Manual Flexiheat UK

Boiler Flue Options / Spares

We do various flue options / accessories, the most common is a co-axial, which takes the combustion air from outside, and the combustion gases from the device to the outside – making these combi units room sealed when used.

The most common flue kit is our horizontal co-axial kit – both of these can be used up to 10 metres in length

Horizontal flue kit from flexiheat UK;worcester greenstar 8000;ex vat;worcester bosch;ex vat;worcester bosch;ex vat;inc vat;quietest boilers;inc vat;ex vat

Horizontal kit from Flexiheat UK


Or the vertical option

Vertical flue kit from Flexiheat UK;ex vat;worcester bosch;worcester greenstar 8000;ex vat;worcester bosch;ex vat;worcester bosch

Vertical kit from Flexiheat UK


Both of these accessories can be used up to 10 metres maximum vertical flue length, losing 0.8 metres off the length for every 90° elbow used, and 0.5 metres for every 45° elbow used from the overall maximum vertical flue distance.

Or by using a split system, we can achieve routes of up to 60 metres of maximum vertical flue length.

boiler Split flue pipe system;

Split pipe system from Flexiheat UK

Boiler controls

With an easy-to-use display with an intuitive menu structure and greater connectivity with any Opentherm compatible controller, our 50kw combination boiler is made to suit your lifestyle, as well as your home.

One of the new features of OpenTherm – (which is a standard communication system that connects natural gas, lpg gas, oil or even electric boilers with room thermostats). This means that your combi boiler can be used with any OpenTherm compatible thermostats or controllers – the best-known brand on the UK market to date is between Nest or Hive which are , but we also provide a solution from stock, which has extended range, and key features such as the ability to control your boiler from a mobile phone, pad or your computer with wireless connectivity.

This means if your away on from home, you can have controllers that will activate your energy efficient 50kw combi gas boiler based on your postcode location in relation to your property – so it’s nice and warm when you get in or should you be travelling, you can adjust the boiler start time in relation to when your due home on your phone or other device, should you be delayed for any reason you simply adjust the time on your device.

Class 5 modulating controls, can provide an increase of 3% system energy efficiency, as they have a direct impact on the efficiency of the modulating combi boiler, by modulating the flow temperature in line with the internal temperature of the property.

Easy Remote

Advanced class 5 remote control (full colour display), which performs the dual function of a thermostat and remote control of the boiler. This controller must be wired from its location to the gas boiler.

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

Easy remote controller – Wired – from Flexiheat UK

  • Daily / weekly heating and hot water programming;
  • Heating and hot water temperature setting;
  • Reset by remote control in the presence of resettable fault codes – rapid diagnosis
  • Thermoregulation management for reduced running cost of the heating system
  • Appliance parameter programming (technician level)


Cloud Warm WIFI (Wireless) Controller

A free-standing class 5 advanced remote control (full colour display) thanks to the free downloadable app which performs the dual function of chrono thermostat and remote control of the device from a mobile phone or tablet.

Cloud Warm Wired controller from Flexiheat UK; stock;delivery;stock;website;inc vat;stock;delivery;stock;worcester greenstar 8000;ex vat

Cloud Warm Wired controller from Flexiheat UK


  • Daily / weekly heating and DHW programming;
  • Cloud warm application available for free on the Apple Store and Google Play; No annual charges to pay
  • Heating and DHW temperature setting;
  • Push notifications to a mobile device in the presence of any abnormality or fault;
  • Reset from a mobile device in the presence of resettable fault codes;
  • Thermoregulation management for reduced running cost.

Cloud Warm WIFI (Wired)

As above functions, but this unit must be wired back to the 50kw gas boiler

Stock;delivery;ex vat;worcester bosch; inc vat;worcester bosch;ex vat;inc vat; ex vat;inc vat;ex vat; ex vat;inc vat;ex vat;inc vat;ex vat;inc vat

Cloud Warm Wireless Opentherm controller from Flexiheat UK



Brand and Quality manufacturing

With its modern design, with A rated ErP efficiency for heating and DHW (energy savings trust approved) this combi gas boiler with design led product aesthetics , and all installer touchpoints for ease of installation is well suited to larger homes.

Our 50kw combi boiler for larger homes is manufactured in accordance with ISO 9001 and ISO 1400 certified management systems and testing techniques. Should you require more information, best deal, free boiler quotes or delivery times, then please contact our sales teams for the best 50kw gas combi boiler in natural gas or LPG on the UK and Irish market. You can call our office on 01202 822221 or send an email via our contact form.