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Important Boiler Terms & Definitions

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There are lots of important boiler terms & definitions used in the heating industry, but some of these important boiler terms and definitions can be quite difficult to understand so, here at Fixx we thought we would make things easier by putting together the ultimate glossary of all the important boiler terms & definitions you may hear.

Boiler Glossary – Important Boiler Terms & Definitions

Here’s our list of the most important boiler terms & definitions:

“A” Rated – “A” Rated is a measure of efficiency on an Energy Related Product (ErP) label. Boilers which are “A” rated have an efficiency rating of 90% or higher meaning they are the most efficient boilers on the market.

Boiler Modulation – Boiler modulation is a system which lowers the amount of gas being used by your boiler as it reaches temperatures. This helps the boiler be more efficient and save money.

Cast Iron Boiler – The term cast iron boiler refers to the description of an older boiler as the main section of the boiler, the heat exchange was made of cast iron.

Combination (Combi) Boiler – A combination (combi) boiler is one of the different types of boilers installed in UK households. They are called combi boilers because they produce all your home’s heat and water from one compact unit without the needs for a separate water tank or cylinder. They are an increasingly popular choice in households where there is limited space and cannot fit a hot water cylinder. The boiler also only heats the water you use therefore, it is much more economical to run meaning you could save money on your gas bill.

Condensate Pipe – The condensate pipe is usually a grey or white plastic pipe which carries condensate away from your boiler either internally in your home or on an outside wall. If the pipe is located outside then, it may become frozen in extremely cold weather and will prevent your boiler from working. For help on how to take care of your boiler read our handy guide.

Conventional Boiler – A conventional boiler also known as a regular boiler is made up of several parts and components including a boiler, heating controls, a hot water cylinder, a cold-water storage cistern plus a feed and expansion cistern. This type of boiler is normally found in older and larger properties.

Condensing Boiler – A condensing boiler is a high-efficiency boiler which uses gas or oil to generate heat.

DHW (Domestic Hot Water) – DHW is an acronym for Domestic Hot Water which is running water that comes out of your tap and showers for example.

ErP (Energy Related Product) – ErP is an acronym for Energy Related Product Directive. This is a European regulation that sets criteria for boiler manufacturers to report on the efficiency, noise and emissions of a gas boiler and produce energy labels for homeowners to be able to compare like appliances.

Flue – The flue is the ductwork used to carry the gasses emitted from the process of combustion.

Gas Relay Control Valve – The gas relay control valve is a mechanical valve (non-electrical) used in early gas appliances to control the gas and temperature of a boiler.

Heat (only) Boiler – See explanation for Regular Boiler.

LPG (Low Propane Gas) Conversion Kit – An LPG conversion kit is used to allow a boiler to be swapped from mains gas to low propane (LGP) bottled or bulk storage.

Regular Boiler – A regular boiler provides heating and hot water through a hot water storage cylinder. The hot water cylinder is often located in an airing cupboard and the cold-water tank can usually be found in the loft. This type of boiler is perfect for homes with multiple bathrooms due to the ability to provide a lot of hot water at once. For more information on the different types of boilers read our different types of boilers explained.

RS (Room Sealed) – RS is an acronym for room sealed which means the air for combustion and the flue products are moved to outside the property and are not influenced by internal conditions.

Standing Heat Loss – Standing heating loss refers to the amount of energy which is lost through the hot water storage tank and insulation when no water is being used.

System Boiler – A system boiler is one of the different types of boilers. It heats your central heating system and produces hot water for your cylinder. It operates in a similar way to a regular (conventional) boiler. However, it is different as it is a fully pressurised boiler and will need filling via a mains cold water connection (filling loop) and the heating pump that circulates the hot water around your radiators will be included within the boiler case.

Thermostat – A thermostat measures and controls the temperature in a heating system.

User Interface – A user interface refers to the controls on the front of your boiler that allows you to change the temperature settings.

Wireless RF Digital Timer – A wireless RF digital timer is a method of controlling the central eating using an electronic control powered by batteries which doesn’t require wiring and communicates via radio waves.

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