Combination boiler is a centralized water heater set in a compact unit. This means, all its operating components are stored in a casing. The heater draws its supply directly from the main. In this type of water heater the need for separate storage tank is eliminated. The cold water supply is taken directly from the main supply and heats the water instantly without any need for hot water source. The fuel supply is directed towards the boiler’s burners to heat it up. The burner is activated by the message from the valves in the hot water system and the central heating system. The open tap allows for supply of water whenever asked for. The hot water is sent over the paddle switch that turns the burner on heating the water that comes from the tap.
Once the heating is done, the surplus heat is stored in the heat exchanger within the boiler. The surplus heat is used as a backup when the central heating system is being used fully. It can be used for the home hot water needs or to heat water from the valves. Through the heat exchanger the central heating system and the pipe water can be heated. It can work simultaneously.
When central heating is needed indoors and there is no hot water delivered by the burners then it will take the water from the pipe. In both the central heating or domestic hot water the water compartment in the exchange gets heated up. The heating process for both happens through the heat exchanger. The hot water inside the exchanger is used to heat the pipe water. This process is called indirect heating. So irrespective of where the water supply is drawn from, both the central heating system and the domestic water system are heated through heat exchanger.
Central heating system and the hot water system are never mixed and are completely separate two different entities, so even the water in them are never mixed. Combination boilers can save money depending on the type of lifestyle you are adapted to. For those in a large family where multiple people shower at the same time, combination heating is the not the right option, it can be an expensive proposition. For those who use low amount of water, combination could be the ideal choice.
Combination boiler can be installed by using expansion vessel and removing the need for feed and cistern. It runs on gas fired burner and heat exchanger. In the old design, the hot water passes through a diverter value from the heat exchanger allowing it to move to the domestic heating calorifier or the central heating system. Small copper pipes are packed in the calorifier and the secondary water runs once the hot water is drawn. The water generates heat from the adjoining primary water present in the calorifier. A pressure gauge indicate the pressure and a bypass ensures that adequate flow is maintained.
A word of advice is there is no DIY for gas burner boiler service, since it needs expertise and experience. Boiler exporters provide instruction manuals for safety purpose. Call an expert when you are in need of a service.