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Selkirk flue introduction

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The Selkirk Twin Wall chimney system is designed for use with oil, gas and solid fuel when used with the appropriate fire stopping components. The system is designed for gravity flow application. The Selkirk Twin Wall chimney system is available in a range of diameters and this brochure relates to the 127mm (5") - 203mm (8") range.

The system consists of straight lengths and fittings which are constructed entirely from stainless steel and a 25mm (1") insulated annulus. The external skin is weatherproof and carries the structural load, and the inner liner is resistant to the often corrosive products of combustion, and is free to expand or contract as flue gas temperatures change. The 316 grade inner liner heats rapidly to produce a strong draught which ensures that waste gases are exhausted and condensation of the harmful products of combustion is minimized.
The system can be used internally or externally. The relatively low external wall temperature permits installation with only a 50mm (2") air gap clearance to combustible materials.

Key flue dimensions
Size (internal diameter)
127mm (5 in.) 152mm (6 in.) 178mm (7 in.) 203mm (8 in.)

Maximum outside diameter
175mm (7 in.) 200mm (8 in.) 230mm (9 in.) 255mm (10 in.)

Working lengths
1181mm, 876mm, 572mm, 419mm, 276mm, and 114mm.

Selkirk flue composition

Lengths and fittings are twin-walled with a 25mm (1") cavity. The outer casing is joined to both male and female couplers, while the inner liner is connected only to the male coupler, so gas temperature varies without affecting the structural performance. Selkirk Twin Wall chimney is insulated with rockwool and this high quality insulation has an optimum and carefully controlled density which maintains a relatively high flue gas temperature throughout the chimney lengths.
Lengths and fittings are twist-locked together with a one eighth turn. Locking bands fit over the two rolled seams at joints between lengths and fittings and MUST be used.

Typical applications includes boilers, stoves and heaters. The Selkirk chimney system must be installed in accordance with all appropriate building regulations, codes of practice and manufacturers installation instructions.

Selkirk Twin Wall chimney in diameters 127mm (5") - 203mm (8") are manufactured to comply with BS4543 parts 2 and 3.

Selkirk twin wall flue installation

Installation instructions are provided with all support components. These should be consulted to accurately determine the components that are required to enable any installation to be correctly assembled. Installations should also comply with Building Regulations Document J. If in doubt please contact Stovesonline: 0856 226 5754 or info@stovesonline.co.uk.

Flue clearance to combustible materials
The relatively low external casing temperature experienced in the normal operation permits installation with only 50mm air gap clearance to combustible materials.
Where the Twin-Wall Chimney passes through a combustible floor the appropriate firestoping components must be used.

Jointing flue sections and components
Lengths and fittings are designed to be installed with the male coupling uppermost. Joints are achieved by placing the female coupling over the male coupling and making a one-eighth turn. A Locking Band must be used to secure every joint and to ensure a firm connection.

Connecting to the appliance
The Adaptor is designed to make the connection to the appliance flue gas outlet or to a section of flue pipe to building regulation requirements.

Twin wall flue elbows
Building regulations stipulate that no part of a chimney used with a solid fuel, wood or oil burning appliance should form any angle of more than 45 from the vertical except where necessary to connect to the appliance. 15, 30 and 45 elbows are available.

Floor and ceiling penetration
Where the Selkirk flue penetrates a combustible floor or ceiling a 50mm air gap clearance must be maintained from the outer skin of the chimney to any combustable materials. .

Roof Penetrations

Where the Selkirk chimney penetrates the roof an appropriate flashing should be used. The Seldek range of flashings is specifically designed for this purpose. To fit, trim the E.P.D.M cone to suit the external pipe size using sharp tin snips or scissors, slide down pipe using water as a lubricant. Dress the aluminum or lead base over the profile of the tiles. Providing the cone has been cut to the appropriate size, the use of a storm collar or sealant is not required. If the chimney has a raised seam on the outer skin a small amount of silicone sealant should be applied where the chimney penetrates the E.P.D.M cone of the flashing.

Supporting components
The weight of the chimney may be carried by a number of different support components depending on whether the chimney is installed internally or externally, and whether it is supported by the roof, ceiling, floor or external wall. These components include the Wall Support, Ceiling Support, Roof Support and Telescopic Floor Support. Lateral stability is provided by Wall Bands, Bracing Brackets or Guy Wire Brackets. Supporting free-standing chimneys.
Where the chimney exceeds 1.5 meters (4.9 ft.) beyond the last support it must be braced with a roof brace kit. Guy wires should only be used where this is not possible. In either case, the bracket should be fitted above a locking band and as close to the joint as possible.

Roof support
The Roof Support is designed to support the chimney on the roof joists and is provided with adjustable gimbal plates. Bracing Brackets should be used in the roof space to restrain movement of the chimney due to wind forces on the chimney above the roof. Load Bearing The weight of chimney supplied depends on the support components used. The table below provides details.


The weight of the chimney can be borne in a number of ways and this table states the minimum length of chimney that can be supported by various components.

Ceiling Support6m6m6m6m
Wall Support 
 Side Plates Up15m15m15m15m
 Side Plates Down9m9m9m9m
Telescopic Floor Support16.7m16.7m16.7m16.7m
Roof Support9m9m9m9m

Part of the flue up to a maximum of 6m may be suspended beneath the roof support.
NB: Wall Bands are not load-bearing and must be used at intervals not exceeding 2.5m to provide lateral stability.

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