Primary Heat Exchanger:
Main Heat Exchanger in a boiler, usually serves the Radiator system.
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Adjustable Damper:
Regulates the temperature in the room by controlling heat emissions.
Air Release Point:
A place where air can be purposely released from a central heating radiator system.
Air Separator:
A device fitted to a central heating system that eliminates any small bubbles of air circulating in the system water. This reduces circulation noise and Corrosion
Airlock:
A blockage in a water pipe caused by a trapped bubble of air, reducing or stopping the flow.
Aluminium Extrusion:
A machine pressed metal component made of aluminium.
Automatic On-Off Switches (Programmers and Timers):
Devices that enable the central heating system to switch on and off at the times you choose.
Backflow:
A flow in a direction contrary to the intended normal direction of flow, usually caused by siphoning. Can also be the result of an incorrectly functioning diverter valve.
Balanced Flue:
This is a system that allows a Boiler to draw fresh air from and expelling gases to the outside of the building.
Ballcock:
Also called a balltap or fill valve. A mechanism for filling water tanks, such as those found in flush toilets, and avoiding overflow.
Banging Sounds:
This is caused by overheating due to a variety of reasons: Blocked Chimney, Build-up of Scale due to Hard Water, faulty Boiler Thermostat, and lack of water in the system or the Pump not working. See our Help & Advice for more details.
Bleed Valve:
Used to release air that has gradually built up inside the radiator, which prevents the panel from heating properly. If this does happen, check out our simple instructions on how to Bleed Your Radiator
Block:
An obstruction that could apply to a pipe or airway in a domestic appliance or central heating system
Blocked Chimney:
Can prevent boiler waste products being safely taken outside of the building. This only applies if you have a Solid-Fuel Boiler. Mechanical defects and debris can also cause blockages.
Boiler:
A boiler is an appliance in which water or other fluid is heated under pressure. The fluid is then circulated out of the boiler for use in heating applications. Faulty boilers should only be dealt with by a CORGI registered expert.
Boiler Flues:
Are devices that safely exhaust the spent fuel gasses from the appliance to the outside of the property. Most are fan assisted.
Boiler Fume Thermostat:
Heating system safety and control feature on a boiler that measures temperature of gasses entering the flue after the burner.
Boiler-Energy Manager or Optimiser:
A device that collects temperature data from sensors inside and outside the building allowing the Boiler to work at maximum fuel efficiency.
Cap-Nut:
A slotted screw in the centre of a water circulating pump. Used to position the pump rota in place and can be used to vent the pump of air.
Check Valve:
Also known as a non-return valve, it allows liquid to flow in one direction only. Commonly fitted to Combination Boilers, they allow water to flow to Radiators and prevents the water returning back into the water main.
Circuit Board Electronics:
Electrical circuitry, often of low voltage and non-maintainable, found in most modern appliances.
Circuit Pressure:
The pressure in which a central heating system operates at. Combi boilers and refrigeration systems have a critical circuit pressure in which they operate most efficiently.
Circulation Pipe:
Are the main water flow and return pipes to and from the central heating boiler for the radiator circuit. The normally smaller diameter pipes to the radiators are known as "branches".
Circulation Pump:
A device used to pump water to the central heating system. A non-ferrous type should be used for the hot water where a standard cast steel pump would quickly rust away.
Cistern:
Is a container holding a small amount of water usually used for flushing toilets.
Cleanser:
This is suitable only for traditional or open-fuel boilers, not Combination Boilers.
Coil:
Is the heating element in a domestic hot water tank. Known as the 'primary circuit' it circulates water from the Boiler to give hot tap water.
Cold Mains Supply:
Is the potable water piped to the premises by the Utilities or Water Company.
Cold Water Storage Tank:
A container for holding water usually used for providing a feed to domestic cold water and/or to a vented domestic hot water system.
Combination Boiler:
Is an appliance that burns fuel to convert to hot water for the central heating system and the hot water supply.
Combustion Chamber:
Is the area within the Boiler where the fuel is burnt.
Combustion Gases:
Are the products produced when fuel is burnt. They consist mainly of Co2 and water vapour.
Compression Fitting:
Forms a joint with a mechanical seal and not soldered, glued or otherwise bonded.
Condensing Boiler:
An energy-efficient appliance that converts its fuel burnt into useful energy cooling most of the vapour present in the combusted gases back into water.
Consumer Unit:
Is a device that splits the incoming electrical supply into switched over current protected circuits.
Convector Heater:
See Skirting Heaters
Conventional Boiler:
Is a water tank fed central heating appliance.
Conventional Open Flue:
A heating appliance that uses the air from within the premises for combustion.
Copper-Lined Waterway:
Is where the primary metals have an additional protective non-rusting skin added to resist corrosion.
CORGI:
Council for Registered Gas Installers. Gas Boilers must be installed & services only by Corgi Registered Engineers
Corrosion:
Central heating system corrosion results from hard-water deposits or from oxygenated water reacting with the system's metal components. Boiler corrosion is the deterioration of boiler components due to reactions with its surroundings.
Corrosion Inhibitor:
A corrosion inhibitor is a chemical compound that, when added in small concentration stops or slows down corrosion in your Boiler
Defrosting Resistance:
This is a heater used to defrost the evaporator in a frost-free freezer or fridge.
Diaphragm:
Is a device used to compare different pressures. Common applications in a boiler are the diverter valve and air pressure switch.
Digital Programmer:
A digital programmer has an electronic display, but does the same job as the Time Clock. It has separate controls for the heating and hot water.
Double Radiators:
A Radiator with two heating panels.
Double-Skinned Pressed-Metal Panel:
Manufactured from two metal sheets for extra strength.
Drain the System:
Term used to purposely empty the water from a Central Heating System.
Draincock:
A valved device to drain a system.
Ducked Duct Warm-Air System (Gas):
A system where the gas is combusted to give hot air which is distributed through the property.
Ducting:
A purpose made passageway to allow the installation of water pipes, electrical cables, etc.
Electrolytic Action:
Different metal types, such as copper and aluminium, act like a battery in the acidic water that is present in some central heating systems resulting in Corrosion
Electronic Ignition:
Most modern Boilers have an electronic ignition that lights the burner automatically when the heating system controls call for heat.
Expansion Tank:
Small tank used in a central heating system to absorb water pressure and extra volume of hot water as it is heated. The tank contains a rubber Diaphragm which squeezes a small volume of air in the tank as the water expands, relieving pressure.
Expansion Vessel:
Expansion vessel is often inaccessible without the help of a Corgi registered engineer. Failure of the expansion vessel can result in a pressure rise as the system heats up too much and the relief valve opens.
Fan Assisted Convector Heater:
Is an appliance where an electric fan is used to distribute the warmed air.
Feed-and-Expansion Tank:
Provide water for the heating system and the domestic hot water cylinder while acting as a reservoir for any overflow as a result of expansion.
Finned Pipe:
Designed to give greater heat output.
Finned Radiators:
Fins give greater area to dissipate heat thus increasing the heat output of the Radiator.
Fins:
Designed for greater heat sink.
Flashing:
A strip of impervious material, usually flexible metal that stops from entering the junction between a roof covering and another material.
Float (faulty or leaking):
A device fitted along with a water valve / Ballcock to automatically maintain a desired water level in a water tank.
Flue Liner:
An insulated liner within an existing chimney that ensures expelled gases are at the right temperature and ensures there is a sufficient draw of outside air to maintain correct combustion.
Flue Outlet:
Is the point where the Boiler flue discharges to the atmosphere.
Furnace:
Used to describe household heating systems based on a central furnace known either as a Boiler or a Heater.
Fuse:
A device to protect an electrical appliance, or circuit, against excessive current flow (in amperes) above the appliance, or circuits, rated value.
Gas Shut Off Valve:
This is usually located next to the gas meter. If the meter box is located outside, then you would usual need a gas key to open the box.
Gauge:
A visual device to obtain the value of a medium. For example, Water Pressure or Temperature. Can be Mechanical, Electrical, or a combination.
Gland Nut:
Is the part of a connection that has to be physically tightened.
Gland Packing:
A seal used to prevent leakage between a fixed part and a moving part.
Gravity Circulation:
Is a water circuit that, being un-pumped, relies on the principle that hot water rises and cold water sinks, therefore, where there is a heating source, circulation occurs.
Gully:
A fitting of the underground surface water or waste water drain over which down-pipes, or other above ground (i.e. Soil & Vent Pipes) drainage, discharge.
Handwheel Valve:
An isolation valve that has a circular grip for turning by hand.
Hard Water:
Is water that contains concentrates of soluble calcium carbonate greater than 20 PPM.
Heat Emission:
Heat energy radiated from any source.
Heat Exchanger Coil:
Is the device used to transfer heat energy to another medium, i.e., hot gasses in a Boiler transferred to the central heating water.
Heat Output:
Is the rated output of an appliance, usually given in KW, BTU, or Therms.
Heating Flow:
Is the hot water pipe from a boiler to the Radiator system.
Heating Return:
Is the cooler water pipe returning the water from the Radiator system to the boiler for re-heating.
Heating-Circuit Controller:
See Zone Valve
Hissing Sounds:
See Banging Sounds
Hopper Feed:
Domestic application not known.
Horizontal Duct:
Service channel that lies parallel with the ground.
Hot Water Circuit:
Is the water circuit from the Boiler to the Hot Water Storage Tank
Hot Water Cylinder:
Hot water passes through the cylinder heating up the stored water.
Hot Water Cylinder Thermostat:
The cylinder thermostat controls the temperature of hot water stored in the cylinder. It is usually fitted to the tank with a temperature sensor.
Hot Water Storage Tank:
Stores the domestic hot water.
Hot Water Thermostat:
This will be fitted to the side of the hot water tank. It controls the highest temperature of the hot water. Some Boiler systems don't need them.
Ideal Room Temperatures:
Assuming an outdoor temperature of -1° (30°F), ideal room temperatures are:
| Living Room | 21°C (70°F) |
| Dining Room | 21°C (70°F) |
| Kitchen | 16°C (60°F) |
| Hall/landing | 18°C (65°F) |
| Bedroom | 16°C (60°F) |
| Bathroom | 23°C (72°F) |