Combination (Combi) Boilers
Combination (Combi) Boilers
Combination (Combi) Boilers
Combination (Combi) Boilers
What are they?
- Combi boilers provide heating and hot water from one unit, typically wall hung.
- The most popular type of boiler in the UK.
- Heat exchanger instantly heats on-demand via combustion (of gas or oil).
Pros?
- Highly energy efficient.
- Compact in size, so they don’t require much space within the home.
- Hot water on demand.
Cons?
- Water flow is reduced when there are two or more outlets in use.
- If the mains water pressure is low, the boiler should not be fitted
- Larger properties with multiple bathrooms cause problems for combis.
Heat Only (Regular) Boilers
Heat Only (Regular) Boilers
Heat Only (Regular) Boilers
Heat Only (Regular) Boilers
What are they?
- Provide both heat and hot water with the use of an additional hot water cylinder and cold water tank
- Pumps and valves are external from the boiler (usually found in airing cupboards due to open pipework)
- Gravity-fed cold water directly into the boiler from the tank, usually in the attic/loft.
Pros?
- Greater flow rate so works better in bigger properties with more bathrooms.
- Suitable for older heating systems as they do not require high pressure from the mains.
- Due to the simplicity of their parts, they are considered more reliable than combi boilers.
Cons?
- Potential to drag air into the system due to the open vents, potentially causing corrosion.
- The hot water cylinder may take a while to heat up, so hot water isn’t instantly available from cold.
- Requires more space than a combi boiler as it needs a cylinder and tank.
System Boilers
System Boilers
System Boilers
System Boilers
What are they?
- Similar to heat only in that hot water is supplied from a cylinder (typically unvented).
- Pumps are within the boiler, and the system is pressurised.
- Water is supplied to the boiler via the mains.
Pros?
- There is a greater flow rate than a regular boiler, so it works better in bigger properties with more bathrooms.
- Less chance for air to be dragged into the system.
- More flexibility in install location due to the pump being internal.
Cons?
- They are unable to be fitted in low-pressure mains water areas.
- Properties with older heating systems may not be ideal due to higher pressure.
- Requires more space than a combi boiler as it needs a cylinder.
