INSTALLING

For multi fuel appliances up to a rated heat output of 50 KW, you are legally required to:

Either

• Give notice or deposit full plans with the Local Authority Building Control Department and obtain permission to proceed.

Or

• Engage a HETAS Certified and Registered Engineer for the ‘Installation and Maintenance of Domestic Solid Fuel Fired Equipment’.

HETAS Registered companies/engineers must disclose their technical qualifications and have the appropriate level of insurance.

On completion of the installation a Compliance Certificate is to be provided. This can usefully be included in the Home Information Pack (H.I.P.) which some home-sellers are required to provide. A copy of the Certificate is also sent to HETAS, who notify the Local Authority Building Control Department.

N.B. A Compliance Certificate is required for the following:

• Installation of open and multi-fuel fires, either connected to a hot water system (i.e. wet) or not (i.e. dry).
• Chimney relining, either twin wall flexible, rigid section or other.
• Service and maintenance of a domestic solid fuel fired appliance.

Using HETAS-approved installers, who use HETAS-approved appliances and products, ensures compliance with Building Regulations and standards of safe installation. Installers are also subject to HETAS inspections to ensure the competency of their work.

THE FLUE

The air needed for the burning process enters through the air inlet channels of the stove with the hot waste gases travelling up the flue to the atmosphere by the ‘flue draught‘. This is caused by air rising when it is heated and becoming less dense. The quicker the flue heats up the hotter the air the more efficient the flue draught. The speed that the air leaves the stove by the flue also regulates the supply of new air being drawn into the stove. The flue is therefore an important part of the stove’s efficiency.

• The difference in temperature between the air in the flue and outside.
• The flow of wind around the outside top of the flue.

N.B. In the summer months when the outside air is warmer than it is on the inside the flue can work in reverse by drawing the air into the stove. Besides bringing sooty smells into the house when the fire door is open this will make the stove difficult to light and burn. In this case the flue will need to be warmed before lighting so that the flue is drawing the draught to the outside. This can be done by using a fan heater.

Good stove design ensures that the most of the heat is transmitted into the room and not into the flue. To achieve this both the air entering and leaving the stove is controlled. It is important to use the right size of flue to give the smoothest passage for the waste gases and to minimise heat loss in the flue. Manufacturers will therefore specify the smallest flue possible for the stove.

Using a flue liner has advantages as this will match the stove, is smooth, retains the heat and is easily cleaned when required. Flue liners are fitted in one length and sealed on the stove and the chimney top.

The height and location of the flue needs careful consideration. Wind is subject to constant changes of speed and direction and flues can be affected by other potential obstacles that can interfere with this natural flow, eg surrounding buildings and trees. Looking at the flues of neighbouring properties is helpful. If they all have tall chimneys this won’t be because the Builder enjoyed working high up, but due to obstructions to the air flow. However, problems, if any, may be isolated arising only when the airflow is unusual.

Flue Cowls

These are helpful in preventing rain water entering the flue and mixing with any by products of the burning process. However due to the significant variations in weather it is extremely difficult to identify the best cowl for your flue. This is recognised by the fact that most cowl manufacturers guarantee to accept returns if the problem persists.

Generally flue’s function efficiently and so long as the installation accords with HETAS and Building Regulation requirements no problems should arise.

Building Regulations Requirements - Key Points

Please Note:

1. These points are extracted from the Building Regulations Approved Document J – ‘Combustion Appliances and Fuel Storage Systems.’ They are not an exhaustive list and should not be relied on to confirm compliance. The notations in ( ) refer to the point no.’s used in Document J.
2. Where a HETAS registered installer is used, Local Authority Building Regulations (LABR) approval is not required. The installer will self-certify the compliance of the installation, provide the customer with a HETAS Certificate of Compliance, also copied to HETAS, and notify the LABR accordingly.

Applicable for solid fuel installations up to 50 KW rated output and states that the Manufacturers’ installation instructions need to be adhered to.

The installation must ensure an adequate supply of air for burning to prevent the appliance overheating and for the efficient working of the flue (J1). Unless the stove has a direct connection to an external air supply, ALL stoves in excess of 5 KW heat output must have a permanent air entry opening of at least 550mm² per KW above 5 KW (2.1).

There must be adequate provision for the discharge of the burnt products to the outside air (J2).

The burning appliance, fluepipes, fireplaces, chimneys are to be constructed and installed to protect people from the risk of burns and the building from the risk of fire (J3).

Where the hearth, fireplace, chimney or flue is provided or extended a Notice on the performance capabilities is to be provided in a suitable location to enable burning appliances to be safely installed (J4).
After installation spillage tests should be carried out as part of the commissioning process and a Notice left confirming compliance and suitability for intended use (1.53).

For solid fuel use are designed with insulation sandwiched between an inner liner and an outer metal wall (013) and should meet specified British Standards

Chimneys and flues should satisfactorily control water condensation by insulating flues, using lining components impervious to condensates to prevent corrosion and by making provision for draining, avoiding ledges, crevices etc (1.26)

Flues should be formed without cutting, keeping joints to a minimum. Keep sockets or rebate ends uppermost to contain moisture and other condensates in the flue. Joints should be sealed with fire cement, refractory mortar or in accordance with manufacturers’ instructions (1.28 & 1.33)

Should offer least resistances to the flue gases by minimising changes of direction, horizontal length for rear outlets, not to excess 150mm. Where bends are essential, they should be angled at no more than 45° to the vertical (1.47).

Factory-made openings (doors) should be provided which are gas-tight and have the same thermal insulation, should allow easy passage of the sweeping brush and the whole flue should be capable of being swept (1.50).

Should be above the roof of the building to ensure the discharge of the burning emissions whatever the wind conditions (2.10). NB Flue positions and heights are stated in 2/11, generally they need to be at least 600mm above the ridge, but no lower than any other nearby chimney/flue.

Are to be made of solid, non-combustible materials such as concrete or masonry, at least 25mm thick (2.2.4).