Glossary of Central Heating Terms

Cut through the jargon

Guide to Plumbing Terminology

If you think your heating engineer is speaking a foreign language when using the trade jargon to discuss your central heating system, please don’t hesitate to stop him in his tracks and ask him/her to explain anything you don’t understand.

To help you get to the bottom of some of the most common central heating terminology, we’ve compiled this useful glossary:

  • Angled Radiator Valve – Valves that connect a radiator or heated towel rail to the pipework at a 90 degree angle.
  • Ambient Temperature – the temperature of the surrounding air.
  • Backflow – a flow of water that has reversed because of a loss of system pressure.
  • BAR – a metric measurement of pressure that is equal to the pressure at sea level on earth.
  • Biomass – refers to fuel that originates from plant or animal matter.
  • Blanking Plug – used to close an opening on an unused radiator inlet, available in different diameters, threaded or unthreaded.
  • Bleeding a Radiator – Use a radiator bleed key to open the valve on a radiator to expel excess air to improve radiator efficiency.
  • BTU – This is an acronym for British Thermal Unit, the amount of energy needed to raise the temperature of a pound of water by one degree Fahrenheit. You need to know the BTU of a radiator to make sure it has sufficient capacity to heat a specific room.
  • Carbon Monoxide – an invisible poisonous gas which has no smell created from improperly burnt fuels such as gas, coal and wood.
  • Central Connection – this type of radiator has a valve inlet in the centre of the bottom of the radiator, rather than on each side as is usually the case.
  • Combi (Combination) Boiler – a highly efficient water heater and central heating boiler in a compact unit, supplying hot water directly to taps or radiators without the need for a storage tank.
  • Condensing Boiler – As a boiler burns fuel it produces water vapour or steam which is usually expelled from the flue pipe. A condensing boiler recovers the vapour and recycles the heat from it to stop it from being wasted.
  • Economy Seven – an electricity tariff that offers seven hours of cheaper electricity during the early hours of the morning.
  • Economy Seven – an electricity tariff that offers seven hours of cheaper electricity during the early hours of the morning.
  • Flow and Return – this term is used to designate where water flows into one side of a radiator and out of the other, returning to the boiler to be reheated.
  • Heat Exchanger – A heat exchanger is a device that transfers heat from one fluid to another. In a boiler this means transferring heat from gas to the water that circulates around the radiators.
  • Inhibitor – A chemical liquid that is added to the water in a central heating system to protect it from corrosion.
  • Landlord Gas Safety Certificate – Landlords must have gas fittings and flues in their property professionally checked for safety every 12 months, and share the gas safety certificate with the tenants in the property.
  • National Grid – The network of cables that carries electricity around the UK.
  • Non-Return Valve – a valve that allows a liquid or gas to flow through it, but in one direction only.
  • Panel Radiators – These radiators are filled with heated oil or water which then radiates out into the indoor space. They heat by convection, and can consist of a single panel, double panels or a panel with convector fins on the inside to increase the surface area.
  • Power Flush – A process for cleaning out heating pipes and radiators using water at high velocity but low pressure.
  • Pressure relief valve – This is a safety valve that protects against over-pressurisation by allowing excess water pressure to be expelled.
  • System Boiler – A boiler that can meet high demands for hot water as well as central heating. System boilers take their water supply directly from the mains, using an unvented cylinder to store the hot water.
  • Thermostat – A device that automatically regulates temperature.

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