Air source heat pumps

Air source heat pumps take the latent heat from outside air, using this energy to provide heating within the home. Air source heat pumps can offer substantial carbon savings when compared to other heating sources such as electric storage heaters and oil boilers. Under typical conditions, air source heat pumps operate at average seasonal efficiencies of between 200% and 300%.

Back boiler

Back boilers are small boilers fitted at the back of the hearth of an open fireplace or in a room heater to provide domestic hot water and sometimes to heat radiators within a dwelling.

Biomass

Biomass is biological material derived from living, or recently living organisms. In the context of biomass for energy this is often used to mean plant based material, but biomass can equally apply to both animal and vegetable derived material. Baxi biomass boilers use plant based sources such as pellets or logs.

Boiler

A boiler is a box in which a controlled burn of fossil fuel is carried out and the heat produced is transferred to water.

Combi boiler or Combination boiler

Combi boilers are boilers that heat water instantaneously on opening a hot tap. There are no tanks in the loft and no storage cylinder. The water is fed from the mains so the water pressure is generally stronger. What is a combi boiler?

Combined Heat and Power

Combined Heat and Power (CHP) is the simultaneous production of heat and electricity.  Using a reliable internal combustion engine fed from a single source of fuel, such as natural gas or LPG, a CHP system can produce usable amounts of both heat and electricity.

Controls

All boilers have controls that allow you to adjust the water temperature and space heating temperature (thermostat). Other controls the boiler may have are a water pressure gauge and a digital or electro-mechanical timer.

DHW

Domestic Hot Water

Expansion vessel

As the water in the heating system gets hot it expands; in sealed systems the 'expansion vessel' (a small pressurised container) accommodates the extra volume.

Feed and expansion tank (F&E tank)

Traditional heating system use two tanks that are usually found in the loft. One feeds fresh water to the hot water storage cylinder and the other one (usually smaller) maintains the correct level of water in the heating system. They also allow for expansion of the water in either when it gets hot - hence the name 'feed and expansion' tank.Flow rates

Generally the term 'flow rates' is associated with combi boilers. It refers to how much water (usually measured in litres) can be heated as it flows though the pipes in a given time (usually per minute). A powerful boiler will heat more water therefore providing a better flow rate.

Flue

All boilers have some sort of flue system; there are typically two types:

• Concentric: This system comprises two pipes one inside the other. The internal pipe takes the exhaust gases from the boiler to the atmosphere and the outer pipe supplies air to the boiler. The majority of concentric flues are a maximum of four metres in length and have a wide range of flue bends and extensions. This provides greater flexibility in positioning your boiler.
  
• Twin pipe: This system comprises two pipes. The first pipe takes the exhaust gases from the boiler to the atmosphere and the second pipe supplies air to the boiler. This flue system is useful when the pipes need to be over four metres long. It also has a wide range of flue bends and extensions providing greater flexibility in positioning your boiler. However, this may be less aesthetically pleasing due to the amount of pipe work on show.

Ground source heat pumps

Ground source heat pumps tap into the natural heat found just metres below the Earth's surface.  The heat pump takes the heat at around 10^oC and increases the temperature to a level suitable for a heating system. This stable, consistent energy is then used to provide space heating.

NOx is a mixture of two gasses (Nitrogen Dioxide - NO₂ and Nitrogen Oxide - NO) and is formed when fuel and air are burnt. NOx accounts for approximately 6% of all atmospheric pollution and is more potent than Carbon Dioxide. NOx also contributes to the formation of smog and acid rain. In order to reduce NOx we have invested heavily in burner technology.  We use pre-mix burners which inject exactly the right amount of gas and air into the burner and mix them before ignition.  This means the fuel is burnt very efficiently and we can keep NOx emissions to the absolute minimum. Download our NOx information sheet. 

Open vented

If your heating system has a feed and expansion tank, it's called 'open vented' hot water. A hot water storage cylinder may also be open vented.

Output

The output ratings of boilers are measure in BTUs (British Thermal Units) or kW (kilowatts). A low output would be 30/60,000 BTU's (9 - 17kW). A high output would be 60/100/000 BTU's (17 - 29 kW). Your installer should choose the output best suited to the size of your heating system, the type of property and, in the case of a combination boiler, the amount of hot water you require.

Renewable energy

Renewable Energy or 'Renewables' is the generic term for technologies such as biomass boilers, ground and air source heat pumps, solar and wind and water energy. These all help in the reduction of the environmental impact of heating and hot water systems as well as being economical for home owners.

System boiler

If you have a sealed heating system there's no feed and expansion tank (see F&E tank) in the loft space. Instead a system boiler is filled with water via a temporary connection and expansion is accommodated by a special vessel, which may be inside the boiler (see also expansion vessel)

SEDBUK

SEDBUK stands for Seasonal Efficiency of Domestic Boilers in the UK.  It is the Government's boiler efficiency database and lists the SEDBUK ratings for all domestic boilers in the UK.  For full details see http://www.sedbuk.com/.

Storage cylinder

The storage cylinder supplies hot water for domestic use and is heated by the boiler.  As the hot water in the storage cylinder is used up it is refilled by the feed and expansion tank (see F&E tank).

System

A 'system' is the term used to describe the boiler and all of its components required to provide your home with heating and hot water

Unvented cylinder

The term 'unvented' most commonly refers to cylinders able to store water at mains pressure, thus removing the need for a feed and expansion vessel. Therefore flow rates are usually far superior.

WHB

Wall Hung Boiler

Baxi Renewable Energy
Ground source heat pumps
Air source heat pumps
CHP
Biomass boilers