Источник: Treloar R.D. Gas installation technology (2010), c. 306-309.
Relevant ACS Qualification Relevant Industry Document HTR1 BS 5871
Flue Termination It is not normally necessary to fit a terminal to any flue system where the flue is greater than 170 mm in diameter. Where a terminal does become necessary, the design will have to meet the requirements of the manufacturer and follow the recommendations in Part 6, Flues and Chimneys.
Connecting Fires and Heaters to an Existing Flue Generally in a traditionally designed dwelling, due to the low heat input of a gas fire, there is no requirement to line the chimney unless the flue length exceeds the distance identified in the table on page 216. However, the manufacturer’s instructions will need to be consulted for clarification. An existing flue will need to be inspected fully to ensure that it is suitable for the installation and of the correct material. It will be necessary to sweep the flue, especially if it was previously used for appliances burning fuels other than gas. Older chimneys will need to be inspected to ensure that there is no evidence of restriction within the flue, such as a damper plate or an old restrictor. Where these are evident, they will need to be removed. In the case of a damper, securing it in the open position will suffice. It is possible to leave old block, back boilers within the opening, providing they do not restrict the void (see below). However, where the boiler has been drained of water, drilling a small 6 mm hole in its base will prevent any pressure from building up inside and causing it to become unsafe. Any existing ventilation from openings into the builder’s opening will need to be sealed off as this may affect the operation of the appliance. The flue will need to be inspected throughout its entire length to assess its condition and to ensure that it only serves the one location. A flue flow test will need to be completed successfully to ascertain its condition. Flue flow testing was described on page 226. Following a check on the condition of the flue, the catchment space and fireplace opening will need to be inspected to ensure that they are adequate for purpose.
Catchment Space This is the opening located behind an appliance, usually as part of the builder’s opening or flue box, in which any debris that falls down the chimney can collect. DFE appliances do not have a catchment space, however conventional radiant convector fires, ILFE and heating stoves do. The size of this void is determined by the flue system. For unlined flues or flues that have been previously used with other fuels, the space should have a minimum depth of 0.25 m and volume of 0.012 m3. For example, if the void is 0.25 m high, 0.16 m deep and 0.3 m wide, the volume will be 0.25 ? 0.16 ? 0.3 m = 0.012 m3 (12 litres). The catchment space can be reduced if the flue system has never been used by other fuels, to 75 mm high with a volume of 0.002 m3 (2 litres). However, the brick chimneys would still need to be lined.
Hearth Construction Where a hearth is required, it must be of fireproof construction and have a minimum thickness of 12 mm. For DFE and ILFE gas fires an additional up-stand is required along the front and side edges of 50 mm, to discourage the placing of rugs on the hearth. This may be achieved by the use of a fender plate. Where a hearth is located at the base of a builder’s opening it will be necessary to extend it forward a minimum distance of 300 mm in front of the fire surround and a distance of 150 mm to each side, beyond the edge of a naked flame or incandescent material. It will also be necessary to extend the hearth beneath any naked flame. See page 201 for details of the hearth notice plate.
Installation of Open Flued Gas Fires 2
Fire Protection Rear-wall:Where the fire is to be located against a surround, additional protection should be provided to minimise the effects of heat transmission unless the manufacturer states otherwise. No combustible material should be placed within the fireplace or builder’s opening.
Side-wall: If the fire is to be located in a corner, it is essential where the construction includes combustible material to ensure that a minimum distance of 500 mm is observed between the wall and the flame or incandescent material.
Shelf: An appliance may only be located below a combustible shelf where the manufacturer’s instructions clearly specify that it is permitted.
Wall-mounted fires: Where a fire is mounted above floor level into a wall, no hearth is needed, provided a distance of 225 mm is maintained between any combustible floor covering and the flame or incandescent material; see diagram on previous page.
Connecting a Radiant or Convector Heater to the Flue Opening Using a secured closure plate, as described on page 302, the flue passes through the slot or hole provided. Where an existing fire back or chair-brick is in place, it is essential to ensure that a minimum distance of 50 mm is maintained and that the void provides the required catchment space as mentioned. Sometimes, due to the design of the fire surround, it will be necessary to fit a flue spigot extension piece as shown or, where the flue spigot passes into a pre-cast flue block system, a cooler device may be required.
Oversized Openings and Voids If a fire or heater is to be put up to an opening that is larger than the closure plate to be put in, it will be necessary to reduce the opening size accordingly. This may be achieved by simply bricking up the opening using non-porous bricks; alternatively, it is acceptable to use a panel of non-combustible material. Materials such as wood cannot be covered in cladding and used as the heat within the opening may result in a fire. As stated above, there should be no combustible material in the opening. Whatever method is used, the final opening should be small enough that the closure plate fits over it and not the size of the fire-flue spigot. Should the builder’s opening or the void itself be too large, as identified by the manufacturer (normally more than 800 mm high, 650 mm wide and 475 mm deep), it may be possible to reduce the size using non-porous bricks or blocks. Insulation blocks, such as ‘Celcons’, should not be used as they will absorb the water vapour from the combustion products and slowly deteriorate. Alternatively, it may be possible to fit a flue box. Flue Box or Collector These metal boxes have been especially designed for the installation of gas fires and heaters where there is no chimney or the existing chimney is unsuitable. The box must be secured in accordance with the manufacturer’s instructions and be positioned on a non-combustible base. When in position, the box can be treated in much the same way as the builder’s opening, however you can only install manufacturer approved appliances into the system with the closure plate secured as necessary. The flue box is connected to a lined chimney or, where a false chimney and breast are proposed, a rigid flue pipe could be used. Pipes should pass into the box at low level and the hole must be sealed with a non-setting sealant.
