GLOSSARY
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.
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.
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. Effective heating controls can increase the efficiency of a central heating system. They can also help you minimise energy consumption by ensuring each room is at the right temperature for comfort, while avoiding overheating.
Cylinder thermostat
This thermostat is strapped to the outside of a hot water cylinder near the bottom. It works by sensing the temperature of the water inside the cylinder, switching on the water heating when the temperature falls below the thermostat setting.
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 ?¢‚Ǩ‚Äú 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.
Full Zone Control
Most homes have a single heating zone ?¢‚Ǩ‚Äú the only controls in the rooms are by TRVs (see below). When a new central heating system is installed, it's possible to fit a full zone control that has different pipe loops and separate thermostats for two (or more) areas. This can save significant amounts of fuel in larger houses.
Heat only
A heat only boiler is a conventional boiler which works in conjunction with a hot water storage and cold water top up tanks to provide both central heating and hot water.
High efficiency (condensing)
All high efficiency (HE) gas boilers are environmentally friendly and operate at up to 96% efficiency compared to standard boilers at around 80% efficiency. They recover heat that is normally lost to the atmosphere via the flue gases.
Installation
Depending on the model, your boiler may be wall mounted, floor standing or hidden away in a fireplace.
Intelligent heating controllers
These combine several of the basic controls and can also learn how long it takes for a house to heat up in different weather conditions. They also often allow for different temperatures to be set between day and night.
NOx
NOx is a mixture of two gasses (Nitrogen Dioxide ?¢‚Ǩ‚Äú NO2 and Nitrogen Oxide ?¢‚Ǩ‚Äú 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.
Oil-fired boilers
More than 1.5 million homes in the UK use oil for their heating, and this number is growing as more homes are built in the countryside, away from mains gas.Most UK domestic oil-fired boilers use kerosene. Glen Dimplex Boilers do not sell oli fired boilers. We stock natural gas boilers and have LPG conversion kits.
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 ?¢‚Ǩ‚Äú 17kW). A high output would be 60/100/000 BTU's (17 ?¢‚Ǩ‚Äú 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. Th e rating is now specified by SAP 2009 ratings which are percentages rather than letter. For full details see SEDBUK websit here.
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.
Room Thermostat
This is best located in a living room or bathroom, which you'll probably want to be the warmest room in the house. The thermostat records the room's temperature, and if this is at or above the set level (20?Ǭ?C is usually adequate), stops the boiler from operating the central heating. A programmable room thermostat lets you choose what times you want the heating to be on, and what temperature it should reach while it's on. Some allow you to select different temperatures in your home at different times of the day and days of the week.
Thermostatic radiator control valves (TRVs)
These detect the local air temperature and switch individual radiators on or off, depending on how hot the room is. It's not a good idea to have a TRV on the radiator in the same room as the main thermostat as, if you alter the TRV, the thermostat will adjust itself to be in line with this local radiator.
They usually have a fat valve at one end, marked with a * and numbers from one to five. The * setting is to protect against frost.
Timer or programmer
An electronic timer or programmer decides when the boiler is able to run. A seven-day timer makes it possible to set a different heating pattern for weekdays and weekends. Some timers allow different patterns for each day of the week; this can be useful for people working part-time or on shifts.
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.
Weather Compensators
These measure the temperature, either internally or externally, and delay switching on the central heating on milder days.