Glossary of Central Heating Terms

Airlock

Trapped air in pipework where, due to its layout, the air cannot escape naturally resulting in no, or very little, flow of liquid along the pipe.

Air vented valve

A mechanical device which automatically releases air trapped within a designer radiator.

Bars

The unit of measurement of water pressure - one bar is approximately equivalent to a column of water 10m high (above the top of the designer radiator) on older water tank systems.
Note: Combi boilers have their own internal pump determining the bar pressure, which is normally listed on the front of the boiler.

Blank Plug

Plug fitted to an unused tapping on a radiator to simply seal and close that opening.

Bleed Central Heating

Where the water is emptied out of the central heating system to allow for the removal or addition of radiators or heated towel rails.

Bleed Valve / Bleed Plug

Plug fitted to the tapping at the top of a radiator which will allow you to release air trapped in the system with the use of a bleed key.

Boiler Noise Silencer

Solution added to a central heating system or an electric radiator (closed unit) to minimise the noise created when the water starts to bubble inside.

BSP

British Standard Piping - A standardised series of screw threads that connects the end of one pipe to another.

BTU

British Thermal Units – This is simply the standard measurement of how much heat is given out by a radiator, heated towel rail, or any other device that gives off heat. The higher the number, the more heat is given out. The BTU figure you see on our website refers to BTUs given off per hour. 1 BTU = 0.29 Watts (W)

CE Marking

Declaration by the manufacturer that the product meets all the appropriate provisions of the relevant legislation implementing certain European Directives. The initials "CE" stand for Conformité Européenne, which is French for European Conformity. There are certain controlled product categories, and products which fall into one of these categories cannot legally be sold in the EU, unless it has passed the tests to receive the CE marking.

Columns

These are the column-shaped hollow chambers that make up the body of Column Radiators. The columns fill with hot water which enables column radiators to give off heat. Some column radiators will have 2 columns or 3 columns or 4 columns and this refers to the number of columns within each section of the radiator. A 4 column radiator will have a greater depth measurement and will also give off more heat than the same sized radiator with only 2 columns.

Combi Boiler

Unit which combines both a central heating water heat exchanger and a domestic water heater in one compact, self-contained unit. Unlike a vented heating and hot water system, a combi boiler does not store hot water, rather it heats water as and when required either directly from the cold mains (for the domestic hot water) or within a pressurised, sealed central heating loop.

Convector

Refers to a class of devices, like a standard radiator, in which the source of heat is not directly exposed. Electric convector heaters are a common type which produces heat by circulating warm air into the room and pulling cold air into the bottom of the unit.

Convector Fins

These are the zig-zagging strips of metal that you find at the back of standard convector radiators. These zig zags help increase the surface area of the radiator and therefore increase the amount of heat it can give out.

Central Heating

Hot water is generated in a central boiler and circulated by pumps through radiators within the building. There are two types: Single-pipe and double-pipe. The single-pipe radiators work with steam, while the double-pipe radiators work with steam or hot water.

Centres

The distance between the pipes inlets on the radiator, which is useful to know if you are fitting a new radiator onto existing pipework. Also known as the Pipe Centre measurements.

Clearances

When fitting radiators it is important to remember to leave adequate clearances for heat circulation and for any installation of radiator valves. The recommended height from the floor to the base of the radiator is 150mm.

Closed System

Central heating system which is closed to the external water supply. Most newer systems are designed this way as it helps prevent oxidization from fresh water. Most closed systems will have rust inhibitor and boiler noise silencer added to it.

Delta

The measurement in which heat output is measured: whereby the temperature of the room is compared against the internal temperature of the radiator. Normally given as either T50 (lowest value, most common), T60 or T70 (highest value).

Dual Fuel

A towel rail (typically) where either an electric element or the central heating system can be used as the heat source, as both are connected through use of a T-Piece. The electric element would most likely be used in the summertime when the central heating system isn't in use.

Element

Probe inserted into a radiator with which it heats the solution on an electric radiator.

EN442

Radiators sold in the UK have to conform and have outputs verified to BSEN442, the European standard for radiators. All radiator literature needs to display BSEN442 compliance, this enables specifiers to show compliance with the European construction products directive.

Farrow & Ball

A British paint manufacturer which is very popular for using when colour matching and finding or replicating an exact colour of paint. Many of our radiators can be customised to any colour you want and, to ensure we get the exact colour, you can quote the Farrow and Ball paint reference name to us. An alternative colour matching system is RAL.

Fins

Waves of metal fitted to the back of standard panel radiators to help convect the heat. Also known as 'convector fins.'

Flat Front Valves

Valve manufactured around a 3 point corner, which gives a flush finish for side and underside entry, pipe through wall installations.

Flow and Return

Central heating system whereby the water flows into the radiators one side and returns to the system to be heated up again out of the other side.

Gauges

Devices used to measure and display pressure levels, temperature, or other parameters in heating systems, helping to monitor and control their operation.

Geothermal Heating

A renewable energy heating system that harnesses the earth's natural heat to warm buildings. It involves using a heat pump to transfer heat from the ground into the building for heating purposes.

Gas Valve

A device that controls the flow of gas to a heating system, regulating the amount of fuel supplied and thus controlling the heating output.

Green Heating

A term referring to environmentally friendly heating solutions, often involving renewable energy sources or high-efficiency systems that reduce carbon emissions.

Heat Loss

The amount of heat lost from a room. Heat can be lost through windows, walls, ceilings and doors. It’s worth taking the amount of heat that each room loses when deciding how many BTUs or Watts your radiator should emit. We’ve made this process easy for you with our Heating Calculator.

Heat Exchanger

A component in a heating system that transfers heat between two fluids, typically between the combustion gases and the water in a boiler.

Hydronic Heating

A heating system that uses water as the medium to transfer heat, often circulated through radiators, underfloor pipes, or baseboard heaters.

Hot Water Cylinder

A storage tank used to store hot water produced by a boiler or other heating source, providing a readily available supply of hot water for domestic use.

Heating Element

The part of an electric heating system that produces heat when an electric current passes through it.

High-Efficiency Boiler

A boiler designed to maximise energy efficiency and minimize fuel consumption, reducing greenhouse gas emissions and energy costs.

HVAC (Heating, Ventilation, and Air Conditioning)

An abbreviation referring to the technology used for indoor climate control, including heating, cooling, and ventilation.

Humidifier

An appliance used to add moisture to the air in a heated space, helping to maintain a comfortable and healthy indoor environment during the heating season.

Heat Pump

A device that transfers heat from one location to another using electricity, providing both heating and cooling capabilities.

IP Rating

An international classification system for the sealing effectiveness of enclosures of electrical equipment against the intrusion into the equipment of foreign bodies (i.e. tools, dust, fingers) and moisture. This classification system utilizes the letters "IP" ("Ingress Protection") followed by two or three digits. Our elements within our electric radiators and heated towel rails are IP54 rated.

Kick-Space Heaters

A kick-space heater is a compact heating unit installed at the bottom of kitchen cabinets or baseboards. It provides efficient and localised heating by drawing in cool air, heating it, and releasing warm air back into the room. Ideal for limited spaces like kitchens or bathrooms.

Kilowatt

A kilowatt is a unit of power used to measure the rate of energy consumption or production. It is equivalent to 1,000 watts and is commonly used in the context of electricity and heating systems. The kilowatt represents the amount of energy used or produced at a given moment, making it a standard metric for understanding power usage or output. In the heating industry, kilowatts are frequently used to measure the capacity or output of heating systems, indicating how much heat they can generate in a specific timeframe.

Locking out

Locking out is a safety feature used by heating thermostats to prevent a boiler from overheating when it reaches a dangerous temperature level. When the thermostat detects excessive heat, it interrupts the communication with the boiler, stopping it from generating more heat. This safeguards the heating system, preventing damage to the boiler and surrounding components. Once the boiler cools down to a safe level, the lockout is automatically reset, allowing normal heating operation to resume. Locking out is a vital safety measure that ensures the efficiency and longevity of the boiler while preventing potential hazards.

Lockshield

Valve fitted at the return side of each designer radiator (coupled with a standard valve) and used to balance the system when it is first installed. Generally, there is no need to adjust lockshield valves once set (they are normally covered with a cap), if they are closed to allow for the removal of a designer radiator, count the turns to the off position so that they can be reset when required.

LST Radiators

Low Surface Temperature Radiators. Radiators are characterised by their surface temperature, which remains relatively low to minimise the risk of burns or injuries if someone accidentally comes into contact with the radiator's surface.

Manual Valves

Manual valves function similarly to taps, allowing direct control over the water flow into the radiator, which in turn regulates the radiator's temperature.

Micro Bore System

A central heating system with 10mm pipes as opposed to the standard 15mm diameter pipes.

Non-TRVs - Non thermostatic radiator valves

These are radiator valves that are not adjustable and keep the radiator or towel rail operating at a single temperature. Depending on the type of radiator, the heat can be at a constant temperature of between 50 - 70°C. Also known as single heat valves.

Open System

Central heating system which is open to the external water supply into a house. Normally older systems are made this way; as it allows oxidisation more easily as the water is fresh and doesn’t contain any boiler noise silencer or rust inhibitor.

Overflow

A pipe connected to a sink, bath, WC, or other water tank, designed to drain away any excess water in case of overfilling, ensuring safe water management.

Panels

If you think of a standard white radiator, the panel is simply the big flat piece that forms the front of the radiator. Sometimes these are completely smooth, sometimes they are grooved and it’s the panel that fills up with water to make the radiator hot. When there is just one panel along the front, this is called a single panel radiator. When there is another one at the back, and making the radiator chunkier, this is known as a double panel radiator. A radiator with two panels will give out more heat than the same sized radiator with only one panel.

Pipe Centres

The distance between the centre points of the two pipes in your designer radiator or towel rail. It’s important to know this measurement so you or your plumber can match up the pipework accordingly. We display the pipe centre measurements in mm on all of our products.

Pressure

Pressure of water running through a central heating system, which is required so the water flows through all designer radiators and fills them to prevent air from trapping in certain places and cold spots in the system.

Pressure Testing

Designer radiators should be high pressure tested to 152.3 PSI (10.5 bar) to perform at a maximum working pressure of 116 PSI (8 bar) at a maximum temperature of 95°C. This enables that whatever the heating application from conventional pressurised domestic to high rise installations or commercial projects the designer radiator can be specified with confidence.

Projection

The distance from the wall to the front of your radiator. Basically, the measurement of how far it sticks out from the wall. We display all projection measurements in mm on all of our products.

PTFE Tape

Polytetrafluorethylene Tape. Sealing tape used around the tapping threads to ensure a water tight seal. 

Radiator

Devices in which a liquid circulates through exposed pipes (often with fins or other means of increasing surface area), notwithstanding that such devices tend to transfer heat mainly by convection and might logically be called convectors.

RAL

Reichs-Ausschuß für Lieferbedingungen. Despite the long German name, RAL is simply a colour matching system that makes it easy to replicate an exact colour using it’s RAL reference number. Many of our radiators can be customised to any colour you want. You can provide us with the RAL colour number so we can ensure the colour is exactly as you want it.

Riser

A component of your plumbing system specially designed to direct water upwards.

Rust Inhibitor

Solution added to a central heating system or an electric radiator (closed unit) to minimise the prevent any material within from rusting.

Single Heat

Where a temperature is pre-set to regulate and remain at the sole setting (i.e. 65 degrees).

Stab (the pipes)

Term used by plumbers where they will stab the pipes through the floor or the wall ready for the designer radiator to be fitted to them.

Stop cock

A valve that enables temporary shut-off of the entire water supply, typically for maintenance purposes.

T-Piece

Accessory fitted to a tapping to allow both a valve and element to be fitted to the same entry point for a dual fuel system.

Tung Fed

Refers to a central heating system where a water tank is used to feed the system with water.

Tails

The copper pipes that are connected to the designer radiator.

Tappings

The thread drilled into the designer radiator where the radiator valves/element will screw into.

Thermostatic

Whereby heat is regulated to reach and maintain a desired temperature.

Thermostatic Valves (TRV)

Radiator control valves which automatically opens and closes as necessary to achieve the pre-set room air temperature. An adjustable valve that sits on your radiator, often with numbered measurements on them, though they can be digital. TRVs are designed to automatically adjust the amount of hot water coming into a radiator according to the temperature in the room, not the temperature in the radiator.

Top Bottom Same End (TBSE) or Top Bottom Opposite End (TBOE)

Where the tappings are duplicated and placed on both ends (both side same end or both sides opposite ends) of the designer radiator. These connections are often used in commercial or elderly applications where top valve mounting is advantageous. A further advantage is that the radiator can be mounted either way up. Most Trade Radiators designer radiators have the tappings at both ends.

Type 11 aka Type K1

A radiator with one panel (single panel) and one set of convector fins (single convector). Sometimes known as a single-single radiator

Type 21 aka Type P+

A radiator with two panels (double panel) and one set of convector fins (single convector). Sometimes known as a double-single radiator.

Type 22 aka Type K2

A radiator with two panels (double panels) and two convector fins (double convector). Sometimes known as a double-double radiator

Valve Entry

The thread created in the radiator where the valves/element will screw into.

Variable Heat

Where the temperature can be manually controlled to reach a desired temperature.

Wall to Centre of Inlet

Distance from the wall to the centre of the tapping or pipe inlet.

Warranty

This refers to cover of your radiator or heated towel rail, should there be a fault caused by an issue with the material used, the manufacturing or the assembly of your product. All of our products have comprehensive guarantees of which further information is available on request.

Watts (W)

Electric rating, which can be used to specify the electric current. A measurement of how much heat is given out by a radiator, heated towel rail or any other heating emitting product. An alternative to the BTU measuring unit. We display the Watts and BTU figures on all of our products. 1 Watt = 3.412 BTUs

Yield Strength

In the context of heating systems, yield strength refers to the maximum stress a material can handle without permanent deformation or failure. This property is crucial in designing and manufacturing heating equipment.

Y-Plan System

A type of heating system configuration that uses a motorized valve to control the flow of hot water to different zones within a property. It is named "Y-Plan" because the pipework layout resembles the letter "Y."

Zoning

Zoning refers to the practice of dividing a building or property into separate heating zones. Each zone has its own thermostat and controls, allowing for individual temperature regulation in different areas of the building. Zoning can lead to more efficient heating and greater comfort as it allows specific areas to be heated independently based on their usage and occupancy. Using electrical equipment in bath or shower rooms need extra care to ensure safety. As a result, IEE Wiring Regulations have identified particular zones within the bathroom to indicate what type of electrical equipment that can be installed and where.