Electic Fires | Gas Fires | Fireplace Technical Information

Technical Information

Below are some of the most commonly asked "Technical Questions" but if you don't see the answers you are looking for, then simply email our technical team directly using the "Contact Us" section above, who will come back to you by return.


The main consideration when choosing a gas fire will be the compatibility with your existing flue provision. Whether your property has a flue, chimney or none at all, although it is still possible to purchase a fire for all of these situations. We have therefore provided the following information with pictures to explain the different flue types and alternatives available to you.

However whilst the pictures and information below 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 and or Gas Safety Registered installer, which we strongly recommend. This should be done in all cases to check the compatibility of your chimney or flue with the type of appliance you intend to purchase, prior to making any final decision to avoid disappointment and additional unforeseen expense, which we cannot accept, any liability for on your behalf. Furthermore, in instances were a gas basket fire is to be installed in to a large recess or inglenook style of opening then we reccomend that you check the maximum height requirements from the top of the burner to the entry point of the flue or chimney are in compliance with the requirements of BS 5871- part 3.

Brick Chimney ( Class 1 application )

Class 1 Brick Chimney

A brick chimney is easily recognised by a chimney stack, with either a pot or gas terminal on your roof, which relies on the natural circulation of air through the room and up your chimney to expel the products of combustion. The minimum internal diameter will be 7” and it may have had a real solid fuel fire in previously, especially in the case of older properties sometimes identifiable by an existing chair brick at the back of the fire opening.

If you have a chimney you will be pleased to know that you will be able to have most types of gas or electric appliances installed.

Prefabricated flues ( Class 1 & 2 applications)

Class 2 Prefabricated flues

These are usually a metal interlocking single or twin wall flue pipe connected to a flue box, with a gas terminal on your roof. Creating the same circulation of air as a chimney. A flue pipe with a minimum internal diameter of 7” or more is recognised as a class 1 flue and a flue pipe of less than 7” generally around 5” internal diameter is recognised as a class 2 flue.

Again there is both a large selection of gas appliances for class 1 & 2 applications available, dependant on the size of flue and flue box you have in your property.

Precast Flue ( Class 2 application)

Standard Precast Flue This flue is manufactured into rectangular hollow concrete or clay blocks that travel vertically, up through the cavity wall of your property, to a ridge vent or metal flue terminal on the roof. These flues tend to be very shallow in depth, although suitable deeper appliances may be able to be installed with the use of either a spacer kit or deeper rebate on the fireplace.

Power flue (No chimney application)

Power flue

A power flue is an open fronted gas appliance with an electronically driven fan system either semi recessed or surface mounted on the outside of the wall to expel the flue gases and as such a sound is to be experienced when the fan is turned on. When the fire is not in use, some natural air circulation may occur through the flue terminal, which is quite normal.

There are two types of power flue options available, a rear flue or side flue for left and right applications in instances where it is not possible to rear flue through the chosen wall (conditions apply). It may also be possible to install a deep power flue gas fire for added realism, subject to the depth of rebate on a surround if applicable or if installed with a spacer kit where available.

Balanced Flue ( No chimney application )

Balanced Flue

A balanced flue is a glass fronted gas appliance, which is completely sealed from the room into which they are installed and vents directly to an outside wall. Air is drawn in from the outside for combustion purposes increasing its efficiency through an outer pipe whilst the inner pipe vents the combustion gases safely away to the outside of the property.

There is no electric supply required; hence no sound or natural air circulation is experienced as with a power flue appliance. There is also a choice of either outset or inset versions available.

Flue less

Flue less

Flue less appliances have been around for some time and incorporate the latest in gas fire technology using a catalytic converter which the combustion gases pass through converting all harmful gases into carbon dioxide and water vapour. The result is an appliance, which is 100% efficient with low running costs.

Flue less appliances can be easily installed into most rooms providing there is a gas supply, excluding bedrooms & bathrooms and the room meets the minimum size and ventilation requirements. There is a choice of both free standing and inset models available.


Please ensure you take the time to read all the detail contained in this section in relation to your existing flue circumstances before you proceed to purchase any appliance from us. Failure to do so could lead to you incurring additional costs in the return of any goods wrongly ordered by you which we will not accept any responsibility for on our part. If you have any further questions you can either email us or speak to a member of our sales team. We always recommend that you should have a survey carried out by a Gas Safe registered gas installer, HETAS installer or qualified NICEIC electrician (whichever is applicable to the goods you intend to purchase) to check and certify the compatibility of your chimney, flue, property and or circumstances prior to purchase to avoid disappointment. We also recommend that you should wait until you have the goods purchased, onsite, in your possession to take accurate measurements from before proceeding to carry out any building work or create any apertures in the wall to avoid potential costly mistakes being made, as manufacturers reserve the right to alter products or specifications without any prior notice as required.