A combination or ‘combi’ boiler is both a high efficiency water heater and a central heating boiler in a single compact unit. Combi boilers heat water directly from the mains when you turn on a tap, so you won’t need a hot water storage cylinder or a cold water storage tank in the roof space.
They are also very cost-effective and energy-efficient as water is heated instantly rather than being heated and then stored in a cylinder. An added benefit is that hot water is delivered at mains pressure, which means that you could get a powerful shower without the need for a separate pump.
System boilers require a cylinder for storing hot water, however the major heating and hot water system components are built into the boiler itself, making it quicker and easier to install. In addition, there is no need for a tank in the loft, so it can be an option in a home with little or no loft space or where the space is earmarked for a conversion.
These boilers are also compatible with solar water heating systems, which deliver environmental benefits as well as lower energy bills.
Regular boilers (sometimes known as traditional, conventional or heat only boilers) are ideally suited to homes that already have a traditional heating and hot water system which is linked to a separate hot water cylinder. These boilers also need a cold water storage tank in the loft to feed the hot water cylinder as well as a tank that maintains the water level of the central heating system.
A regular boiler may be the best option for replacing an existing boiler if the property has an older radiator system, as it might not be able to cope with the higher water pressure that is delivered by system or combi boilers.
Important terms and definitions
Along with heat, when gas or oil is burned within your boiler condensation is also created. This can be seen in the gases which plume out from the boiler, something that is especially noticeable in cold weather. However in addition to this condensate being discharged in the air, condensate also collects inside the boiler and is drained away either inside or outside your home. This is safe and nothing to worry about.
The ErP Rating is a new requirement set by the European Union which is designed to drive improvements in the efficiency and performance of heating and hot water products. The ErP rating introduces new efficiency classes from A++ to G which are displayed on a labels which come with the boiler. ErP labels are already a common sight on washing machines, televisions and other appliances within electrical retailers.
The flue is the part of the boiler which allows exhaust gases to exit the boiler. The flue is typically situated directly behind the boiler enabling waste gases to exit safely straight out of the external wall of your home.
Quoted for Combi boilers, a flow rate represents how many litres of hot water comes out of the tap in a minute. Your flow rate is determined by the amount (and pressure) of water that is entering your property from the water main and the ability of the boiler to heat that water to the temperature you have set. The more powerful a boiler is (represented in kW), the faster the boiler will be able to heat the water coming into your home.
However it is important to recognise a high kW output will not always increase your flow rate. If you have 10 litres per minute coming into your property, you will only be able to receive 10 litres per min of hot water. For example having a boiler that has a maximum flow rate of 14 litres per min will not increase the amount of hot water you receive, if you only have 10 litres per min coming into your boiler.
Standard Efficiency (G Rated)
Old “Standard Efficiency” boilers waste large amounts of heat as they don’t Condense and recycle the heat before it leaves your boiler via the flue. In the current SEDBUK rating structure a Standard Efficiency boiler would be deemed G-rated and is likely to be 30% less efficient* than a new Worcester A-rated boiler.
A system filter is a specifically designed unit which aims to remove and filter magnetic and non-magnetic contaminants from your central heating system before they reach your boiler. Building Regulations always recommends a system filter be fitted to your heating system pipes prior your boiler to prevent any damage to key components.
Thermostatic Radiator Valves (TRV’s) enable you to control the individual temperature of each room in your home, and can be adjusted to the comfort levels you want. The higher the number selected on the TRV, the hotter the radiator and warmer the room. Please note a TRV should not be fitted on a radiator in the same room as a room thermostat.