"A" rated

This is the measure of Efficiency on an ErP label which is rated from A to G with A+ being best rating.


Boiler modulation

A system that lowers the amount of gas being used by your boiler as it reaches temperature to help the boiler be more efficient and save energy.


Cast iron boiler

This tends to be the description of an older boiler as the main section of a boiler, the heat exchange was made of cast iron.

Combi/Combination boiler

Combination boilers (combi boilers) are so called because they produce all of your home's heat and water from within one appliance without the need to store water in a cylinder or storage tank. They are extremely popular for all households especially those that are limited for space and do not have room for a hot water cylinder. As they only heat the water you use they are also economical to run meaning you could also save money on your gas bill.

Condensate pipe

The pipe that carries condensate away from your boiler can run internally in your home or on an outside wall and is usually white or grey plastic. If the pipe runs externally, it may become frozen in very cold weather and prevent your boiler from working.



Domestic Hot Water is your running water that comes out of your taps and showers for example

Direct hot water supply

The hot water out of your taps has been directly heated by a boiler (old style), newer systems utilise an indirect method of producing hot water where your boiler will heat a coil in a cylinder that in turn heats your water, or in a combination boiler the primary heating side heats a secondary heat exchanger that produces your hot water.



Energy Related Product Directive. 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.



The ductwork used to carry the gasses emitted from the process of combustion, in simpler terms it is an exhaust pipe for your boiler.

Flue gas heat recovery device

A device utilised in a flue to allow the products of combustion to pre heat the water entering a combination boiler or system that extracts additional heat from the boiler flue system to use elsewhere meaning part of the energy is recycled to offer an energy saving. This technology is used on Ideal's Logic Code Combi ESP1 boiler.


Gas relay control valve

Mechanical valve (non electrical) used in early gas appliances to control the gas and temperature of a boiler.


HCFC insulation

Agents used in the foam insulation manufacture used to insulate many hot water storage tanks.

HE (High Efficiency)

A gas boiler that has efficiency greater than 86% or allows the water vapour contained within the flue gasses to condense back to a liquid improving the boiler efficiency.

Heat (only) boiler

Heat only boilers are also known as 'regular' or 'conventional' boilers. If you are replacing an old boiler and have a small expansion tank and a larger cold water storage cistern in your loft space, you probably already have a heat only boiler. Heat only boilers are usually installed on an open vented system, and will not have a filling loop.


LPG conversion kit

A kit to allow a boiler to be swapped from mains gas to low propane gas (LPG) bottled or bulk storage.


Mechanical timer

A simple time control that operates on a 24hr cycle offering time control to your heating.


NOX class 5

A classification system that gives a measure of potentially harmful emissions with class 5 being the best and class 1 the worst.



A method of keeping a boiler heat exchanger permanently hot on a combination boiler to give a quick response to hot water demand, this system will fire intermittently throughout the day and is generally turned off by most customers; it is useful for customers who have very long distances between the boiler and hot water taps.

Pump station

Transfers the solar energy from the solar panel to the solar storage tank that supplies your hot water.


Rocking grate

A grate in which the bars roll or rock from side to side to break up the cinder and ashes and allow them to drop out.


Room Sealed, means the air for combustion and the flue products are conveyed to outside the building and not influenced by internal conditions.


SE (Standard Efficiency)

A gas boiler that has a seasonal efficiency of 82% or less.

Sealed domestic system

The water within your boiler is sealed from the atmosphere via an expansion vessel, the system will be filled from a filling loop. This type of system offers benefits over an open vented system as less corrosion takes place meaning the boiler and radiators will stay more efficient over their lifespan. (Open vented systems will produce sludge that will affect the efficiency) For this reason all systems are recommended to be cleansed and treated with inhibitor on installation.

Solar collector

A panel that sits either on your roof or integrated into the roof to gather solar energy from direct and indirect sunlight.

Solar controller

The standalone control that ensures the solar gain (increase in temperature resulting from solar radiation) is transferred from the panel via the pump station into the solar coil on the twin coil cylinder.

Standing heat loss

The amount of energy lost through the hot water storage tank and insulation when no water is being drawn.

System boiler

A system boiler heats your central heating system and produces hot water for your cylinder, just like a regular (conventional) boiler. However, a system boiler differs from a regular boiler in some important respects, 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.

System filter

High efficiency, full-flow, magnetic and non-magnetic filters are designed to protect domestic central heating systems by removing suspended black iron oxide. Removing this debris increases the efficiency and reduces energy wastage of the heating system, making it less expensive to run and maintain. Ideal offer their own System Filter which can be used on any boiler system.



Used on mechanical timers to define the on and off periods for the central heating.


Measures temperature.

Thermostatic control

Works in conjunction with an electric solenoid valve or gas relay valve to control the appliance temperature.

Twin coil cylinder

A hot water cylinder with two coils used in an Ideal solar system. The lower coil connects to the solar circuit, whilst the upper coil connects to the normal boiler circuit. The cylinder capability can be determined from household size and number of panels.


Unvented cylinder

A mains water fed cylinder that does not incorporate a vent pipe, the same as a sealed system that allows storage of hot water.

User interface

The controls on the front of your gas boiler that allows you to change the temperature settings.


Weather compensation

Weather compensation can be achieved when the boiler is fitted with an optional compatible outdoor sensor. Weather compensation works by measuring the temperature outside the home and adjusting the temperature (or flow) of the radiators inside. If the weather is particularly cold outside, the outdoor sensor will communicate with the boiler intelligently to increase the temperature inside. This process also works in reverse, as the outdoor temperature increases, the flow to the radiators too will decrease. This process allows the system to operate more efficiently by preventing spikes in heating activity. Smart systems use internet weather temperature and don't need an outside sensor.

Wireless RF digital timer

A method of controlling the central heating using a electronic control powered by batteries that needs no wiring and communicate via radio waves.