The front opening of the fireplace must be between 305mm and 440mm
wide, and between 510mm and 650mm high. If the opening is larger
than this, then a surround must be constructed in a suitable non-com
bustible material to create an opening to these limits. Allow a minimum
flat surface of 20mm (10mm each side) around the opening to ensure
that the closure plate can be sealed to the fireplace opening.
Any surround must be sealed to the fireplace to prevent leakage. The
operation of the chimney should be tested as detailed as in section 1.7.
Note. A flue spigot extension of up to a maximum total length of 125mm
may be fitted if necessary, providing that a minimum clearance
50mm between its open end and nearest obstruction is always
maintained.
Fig.1.
Chimney Catchment Space.
1.8.2
Fitting to Pre-Fabricated twin wall metal Flue Boxes.
The appliance may be fitted to a twin wall metal flue box conforming to
the constructional requirements of BS 715, (for example the Selkirk LFE
125 box). The box must have a minimum flue diameter of 125mm
internal and minimum internal dimensions of 160mm deep by 580mm
high by 350mm wide. There are no maximum dimensional requirements
for the box. The top face of the box must be insulated with a minimum
thickness of 50mm of non-combustible mineral wool insulation or similar
material. The flue box must stand on a non-combustible base of
minimum thickness 12mm.
7
