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4.7.2 Extract System
The appropriately sized extract canopy located Minimum standard canopy dimensions are to
above the oven installed should be connected be in accordance with the oven manufacturer’s
to a range of ductwork and be complete with recommendations and constructed in welded
an axial flow extract fan (or other suitable fan Stainless Steel.
type) discharging to a convenient location at
high level outside the building. The size of the oven canopy will be dependant
on the type/ capacity of the oven installed
The minimum canopy footprint must be 2000 x beneath.
2500mm and to comply with DW/172 (for any of
the ovens which we currently install). The hood should incorporate a gutter around all
edges with a plugged drain connection at the
The noise level outside the building shall lowest point. Removable grease catch pans
not exceed site specific noise limits as are not required. The canopy must be complete
per LPA conditions or noise survey report with at least 4No. removable mesh type grease
recommendations. If required, any sound filters. Baffle filters are very efficient at grease
attenuators used should be suitable for use in a removal but offer a far higher air resistance than
hot, catering extract environment. the mesh type. Domino’s bake-off operation
produces very little grease and the extract
Air resistance should be calculated by the system is predominantly removing heat and gas
Contractor to suit each installation and the fan combustion fumes. Mesh filters are much more
selected accordingly. The selected fan should efficient at removing any fine flour particles
have a duty nominally 20% greater than the which may be caught in the airflow. The filters
calculated resistance of the system but shall should be of a size which will allow them to be
have a minimum duty of at least 1.5m³/sec (or as cleaned in the sinks available in the kitchen.
otherwise specified by the oven manufacturer). The filters should be arranged within housings at
This is to allow for reduced efficiency as the both ends, as part of a plenum system which
system ages and any ‘as installed’ variation in provides balanced extract over the length of
the ductwork resistance. the oven.
The fan should always be mounted on anti- It is important with the modern ovens that the
vibration mountings and attached to the extract does not draw noticeably from only
fixed ductwork with flexible connections. The one end, or one side. The traditional filter bank
fans should be mounted in such a manner as to running along the back edge only, has caused
be accessible for maintenance and removable problems in this respect, so the preferred option,
in the event of fan failure. therefore, is a filter bank running front to back at
both ends of the canopy (not a central double
Under no circumstances may flexible ductwork faced filter bank) and joined via suitable
be used on the extract system, other than the ductwork or plenum.
fan connections.
4.7.2 Extract System 30 May 2018
