Gas Safe Engineer

How Combination Boiler Works - Emergency Boiler Repair,Breakdown Repair Engineers in London

The combination boiler description applies to an indirect combination boiler where the domestic hot water is heated in a secondary calorifier. See below for more about a direct combination boiler. Our projects section also contains lots of information about central heating of all kinds including oil fired.


Combination boilers combine the functions of a central heating boiler and an instantaneous multi point water heater. They give priority, in the main, to the supply of domestic hot water (dhw). The combination boiler has all its operating components contained within the casing and is typically designed for use within a sealed central heating system.

Installation is made easier by incorporating an expansion vessel, thus eliminating the need for a feed and expansion cistern in the roof space. Like an ordinary boiler it will have a gas fired burner and a heat exchanger. The waterways of both form part of the central heating system. In most of the early designs of combination boiler, hot water from the heat exchanger passes to a diverter valve, which directs the flow to a domestic hot water calorifier or central heating circuit. The calorifier is tightly packed with small copper tubes, through which secondary water flows the moment the hot water draw off is opened. As the water flows it picks up heat from the surrounding primary water in the calorifier. The central heating system is pressurised and needs a relief valve to protect against any build up of pressure in the system.


A pressure gauge on the appliance indicates the operating pressure. A by-pass, connected across the primary flow and return, ensures that an adequate flow of water is maintained. This by-pass may, or may not be a built in feature of the appliance.


The flue arrangements for combination boilers may be open, room sealed, fan assisted & room sealed, fan assisted open, miniature flue/condensing or se-duct. The primary heating circuit of combination boilers should be pre-commissioned, cleansed and treated with a corrosion protector in the same way as any other heating system. In hard water areas, the secondary domestic hot water should be treated with an in-line scale reducer or water softer (See projects section for info on both of these) This will prevent the build up of limescale on the instantaneous water heater and the accompanying reduction in flow rate and water outlet temperature.


With a direct combination boiler the secondary water is heated in one of two ways. The water may pass through pipes which run down the inside, or next to the primary pipes in the heat exchanger, or by passing through a separate heat exchanger which is bolted on top of the main heat exchanger. A direct combination boiler does not need a diverter valve or a secondary calorifier.


In a domestic hot water system where the (condensing) boiler is a replacement for an existing storage cylinder system or a conventional boiler, it is essential that all redundant pipework is removed to eliminate "dead legs" which can hold air and cause air locks. These can also cause cold spots and slow burner shut off.


Whenever you need a new boiler installed. We makes sure you get value for your money from the top quality. Deciding of installing a new boiler is a big decision, and you have to treat it as an investment. An up-to-date central heating system can add thousands to the value of your home.  We can provide real great installers to your home and we know you are looking for boilers and central heating systems that will serve your needs for many years to come. We never take a ‘here today, gone tomorrow’ attitude to a job. We aim to ensure that any plumbing or central heating installation we carry out will do the job over the long-term. We will still be around to answer your enquiries and offer advice after the job has been completed. That’s why our customers keep coming back to us to take advantage of our expertise and the comprehensive range of services we can offer. When you need work done by a professional, you can just think of us!

Emergency Boiler installation – your reliable boiler installers

When doing central heating installations we will have a team of central heating contractors who know what system is the best for the customer as it will depend on the type of the properties as some will  need bosch combi boiler some are suitable for combi boiler installation and some will be more suitable for condensing combination boilers.

“Leading heating company with leading boiler manufacturers”

Installing a good on boiler like Valliant brand can really make differences to your life. They are designed to give you sufficient performance as a market leader in the UK. This is how we build up our reputation - just by giving the customer the best advice and focus what you get from what you spend.

Our recommended commercial heating engineers are registered and qualifies to do central heating installations even under floor heating system repair and installations they are also heating contractors who take on all work in commercial buildings, offices, homes. When you have problems with heating or plumbing we have heating plumbing specialists who can assist you with heating repair, heating breakdown and some time your heating may be broken because it needs to part like gas filter, gas heat pump , gas valve repair, thermocouple repair, gas boiler spares as they can be important parts that are needed in order to get the heating working

Commercial boiler manufacturers

Not only domestic that we deal with, We also deal with commercial boilers as well so if you are commercial customers from Surgery, Clinic,  Hospital, Cinema, Theatre ,Restaurant, Office, College , University, Schools, Hotel, Guest House, Wedding hall, Factory, Shopping Centre, Superstore, Museum, Building sites or even if you are commercial Landlord, Letting agent & Property , Builders, carpenters, other trade contractors you will have peach of mind that we can deal with bigger stuff like commercial appliances below too.

REMEHA Commercial & Domestic boilers                                            

PEERLESS Commercial & Residential

WEIL MCLAIN GAS OIL Commercial & Residential boilers                

COLUMBIA Commercial & Industrial Boilers

BUDERUS Commercial & Industrial

24Hours Gas Safe Registered

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