Gas Fire Technical Guide

Overview
Choosing Your Gas Fire

Flue Types
Traditional Chimney
Pre-Cast
Class 2 / Pre-Fabricated
Flueless / No Flue
Catalytic Fire

Choosing Your Gas Fire

The main consideration when choosing a gas fire will be the compatibility with your existing flue provision. Whilst the pictures & information on our website may be of help to you, they are in no way a substitute for having an on site professional survey carried out by a Corgi registered gas installer.

Not every gas fire is suitable for every home. In order to choose the ideal gas fire or fireplace for your home, you have to know what type of chimney or flue you have, and what you want from your gas fire. Flue type is the most important starting point, as this determines the depth that you have available for your inset gas fire. There are 3 main flue types, and each can be determined by simply looking at your roof.

Flue Types

Traditional Chimney
Also known as a Class 1 flue, a chimney will accept all types of inset gas fires as well as accepting solid fuel fires. Class 1 flue sizes are 7" diameter (or greater) or 9" diameter square chimney (or greater). In your home, a chimney breast can often be seen clearly with alcoves either side of your fireplace. On your roof, there will be a traditional chimneystack, with either a pot or gas terminal, which relies on the natural circulation of air through the room and up your chimney to expel the combustion gases of the appliance.
Pre-cast
Flue Many new properties that do not have chimneys are fitted with Pre-cast flues. These are made of rectangular hollow concrete or clay blocks that travel vertically, up through the cavity wall of your property. The flue ends as a ridge vent on your roof. Pre-cast flues have a much shallower depth in comparison to a chimney, and so, limit the fires that will fit into this flue type. In your home, you will likely have a flat wall instead of the alcoves of a traditional chimney.
Class 2 / Pre-fabricated Flue
Known as a Class 2 flue, Pre-fabricated flues are usually made of a metal interlocking flue connected to a flue box, with a metal terminal on your roof. The minimum flue size is 5" in diameter. Again, expect to have a flat wall in your room. This flue type will accept the shallower gas fire type.
Flueless / No Flue
In certain circumstances, your home may not have any of these flue types. Instead, the fire may have a flue that goes straight through the external wall. These are termed Powerflue or Balanced Flue fires. With a Powerflue, the emissions from the fire are drawn out through the wall by a fan assembly. Available as a deep or slimline inset gas fire, these look just like an ordinary open flued fire. A 13 Amp fixed fused spur is required for the operation of the fan extraction system. A Powerflue fire can only be fitted where there is at least 2m clearance from the wall, all of which must be classed as your own property. Fan flued appliances use an electric fan for safe extraction of flue gases and, as such, some noise is to be expected. Fireplace World do not retail any Balanced Flue fires.
Catalytic Fire
Another option is a Catalytic gas fire. Instead of the combustion gases being vented out of your home, they are converted into non-harmful gases including carbon dioxide and water vapour. Therefore the fire needs no flue at all. Please note, that flueless gas fire appliances require additional ventilation of a minimum 100cm2. An window which can be opened or louvre is also required in the room into which the appliance is installed.