Different boilers have their own advantages, but if replacing your old unit, you may decide it is best just to perform a direct replacement with a boiler of the same type. Either way, it’s useful to know which type of boiler you have, and what benefits there may be by changing to a different type.
A Combination Boiler (Combi) is the most popular option for new homes and upgrades. Becuase it combines almost all of the central heating and hot water components into one unit, there are significant space savings to be had, and the potential for greater efficiency and long-term cost savings. You do not require a hot water cylinder to store the heated water, as it is produced on demand and comes through at mains pressure. Additionally, you do not require a cold water tank or expansion tank in your loft, providing the opportunity for more storage space.
Because they run at mains pressure, you can achieve a powerful shower without the need for an additional pump. This also has its disadvantages though, as you are limited by the maximum pressure of your mains water, you could see a drop in performance if you have multiple showers or taps being used at the same time without sufficient pressure coming into the house.
This is the conventional boiler type also known as a heat-only boiler, and relies on external components such as tanks and pumps to perform its job. It heats water in a tank rather than on-demand, and whilst this uses considerably more space, it does provide the capacity for high demands for hot water, such as multiple showers, without being affected by the mains water pressure.
Radiators are normally kept topped up via a feed and expansion tank, at a low pressure. This is suitable for older systems where the radiators or plumbing may not cope with the higher pressure of an external expansion vessel or combi boiler, but at the sacrifice of slightly less efficient heating. This is also often the only system that is compatible with renewable energy sources such as heat pumps or solar energy.
System boilers can provide higher efficiency and space savings by integrating the main components of the central heating system, such as an expansion vessel and pump, inside the unit. They still make use of a hot water cylinder but are often installed without requiring any tanks in the loft.
They can meet the requirements of higher demanding households, whilst providing a neater and often more efficient solution than a conventional system with a regular boiler.