What is a combi boiler?
A boiler is like a big kettle, in that it heats up the water. With a combi boiler, when you turn on the hot tap, cold water is taken directly from the mains supply and heated up instantaneously. It also sends the heated water around your heating pipes to warm up the radiators.
A combination boiler can heat up cold water for the hot taps and also for the central heating radiators inside one unit which saves space and time. A powerful boiler can heat up larger amounts of water quickly.
How do you get hot water from a combi boiler?
When you turn the hot tap on, a signal is sent to the boiler to heat up the water. The combi boiler takes water from the mains cold water supply and instantly heats it up. It sends hot water out in the pipes to the tap that is requesting it. By doing this, you don’t need a hot water storage tank.
Why are combi boilers popular?
Combi boilers are the most popular type in the country because they provide heating and instant hot water from the mains from one unit, without needing extra space for a tank. They save space and are very efficient at providing unlimited instant hot water quicker than a conventional boiler can while being less complex than other systems.
Is a condensing boiler the same as a combi boiler?
Rather than being a type of boiler, like a combi, system, or conventional, the term condensing refers to the way it functions – at high efficiency. So all modern gas boilers (installed since 2005) are condensing, including the combi.
What is a gas heating system?
A gas heating system consists of a boiler, pipes and radiators. The boiler uses gas as fuel to heat up water that passes through it. Hot water is then circulated around the pipes to the radiators which heat up the air around them to warm the room. As the water cools, it is sent back to the boiler to be reheated.
The gas used in this system can be provided from the mains Natural Gas supply coming into the house if it’s available in your area, or in the form of liquefied petroleum gas (LPG) that is stored in tanks and needs to be refilled when depleted.
What sizes do combi boilers come in?
Combi boiler sizes vary depending on the number of radiators they need to serve and what the hot water demand is like for a household. The domestic boiler sizes go from 24kW to 40kW for the majority of manufacturers, but some combi boilers can go up to 50kW.
To check what sizes are available right now, click the banner below to go to boilercentral.com which is giving extended warranties for selected boilers.
What is a wet central heating system?
A gas boiler that heats water up before it is sent to the radiators is known as a wet central heating system. Basically, it’s the hot water that heats the room up. This is different from a dry heating system where the air is heated by a heat source like storage heaters and no water is used.
Main components of a gas boiler
Although all components of a boiler are essential, the key parts of a boiler and what they do are:
Burner
The burner is the main component in a boiler that is used to burn fuel to create heat. The combustion process uses fuel, such as natural gas or liquid petroleum gas (lpg), and oxygen to heat the water passing through the boiler.
Heat exchanger
Another key component in a boiler, the heat exchanger transfers the heat created by the burner to the cold mains water passing through the coiled pipe within it. The heat exchanger is designed to envelope the burner so a larger surface area and so more water is heated.
Circulating Pump
A circulating pump helps to keep the central heating system that is switched on at a consistent water temperature. Hot water is pumped out from the boiler towards the radiators and storage cylinders. Cooled water flows back to the boiler to be reheated to the required temperature.
Boiler Flue
The purpose of the boiler flue pipe is to remove exhaust gases and water vapour produced by the combustion process. The flue pipe is attached from the boiler to an outside wall of the house so harmful gases from the boiler are pumped into the air outside and not back into the home. So the flue can be many metres long.
Expansion Vessel
The expansion vessel within a combi boiler maintains the system pressure to a stable working level. The space within the vessel is required to absorb the extra pressure that is created when heated water expands. The vessel is usually charged up to 1 bar of pressure.
Diverter Valve
A diverter valve is seen in a combi boiler and is used to direct the hot water either to the central heating system radiators or to the hot water taps. The valve opens and closes according to where the hot water is demanded.
Gas valve
The gas valve regulates the flow of gas into the burner. It modulates between the high and low volume of gas according to the water flow rate and the desired temperature setting.
Fan
The fan in a non-condensing boiler is located after the heat exchanger and acts as an exhaust to push harmful gases out through your boiler’s flue. In a condensing boiler, the fan is before the heat exchanger and controls the amount of air required to be mixed with the gas, which is sent to the burner.
Printed Circuit Board
The PCB is the brain of the boiler and controls the electronic components of the functioning parts. Internal and external sensors are linked to the PCB to provide feedback on demand, temperature and water flow rate. It also monitors pressure, currents and temperatures to make sure the boiler can’t damage internal parts.
*The information in this article should be used for general guidance only and not as financial advice. Full details are on the link in the footer to our disclaimer page. Always discuss your requirements with a competent and suitably qualified professional before undertaking any work.
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