Royal Consumer Information Products U19019 G20 - Manual (Page 13)

INSTALLATION USING A 5" DIAMETER METAL FLUE BOX
Page 6
Important: The Flue restrictor plate must be removed see Fig 10.
When the metal flue box is to be built-in as a false chimneybreast using timber stud work with plasterboard facing,
the flue box should be enveloped with insulation material such as rockwool or similar to prevent a build up of heat
within the structure. An air gap of 75mm should be maintained between any combustible materials and any part of
the flue box or 25mm of insulation between the flue box and the combustible material.
It is important that both the back panel and the appliance are sealed to the gas flue to prevent any leakage of flue
products, or reduction in the flue draught.