MUAP - Make Up Air Plenum
In order for the kitchen extract system to function correctly, it is essential that allowance be made for the provision of replacement air. This should be achieved either by introducing mechanical supply air or by making provision for natural infiltration. Make-up air may be introduced into the kitchen by means of the canopy or ventilated ceiling, or through the ventilation system or by a combination of all three.

 
         
MUAP Canopies
Canopies are designed generally in accordance with DW/171. Each canopy contains a full length stainless steel grease filter housing. A full length, integral, fully insulated make-up air plenum shall be incorporated inside the front face of the canopy, parallel to the grease filters, with removable stainless steel perforated plate diffusers or double deflection grilles complete with obd’s installed in the outer face. Canopies are constructed from 1.2mm (18G) thick, grade 304 satin finish stainless steel, and have an all welded construction with a 50mm x 25mm perimeter condense channel, complete with drain plug contained with the channel if required. The grease collection system channels grease to the grease collection drawers within the filter housing, which can be removed by the kitchen staff for cleaning. All joints and seams shall be fully welded and/or liquid tight.

500mm x 400mm x 50mm or 500mm x 250mm x 50mm heavy duty washable stainless steel baffle type grease filters are provided, with a 45mm rolled section channel frame with safety edge, and drain holes punched in the bottom leading edge. Removable stainless steel grease collecting draws shall be provided within the apron of the filter housing. Stainless steel vapour-proof twin fluorescent recessed light units are provided or bulkhead type lighting can be supplied within the canopy if required.

   

A fan powered mechanical system provides positive control and therefore should be the preferred method. With natural infiltration the following problems may occur:

  • Unfiltered air will enter the kitchen
  • Air may otherwise be drawn from dirty areas
  • Draughts and discomfort may be caused in cold weather
  • Uncontrolled air movement may affect the cooking process
  • Cooling cannot be provided to persons adjacent to the canopy
 
         

Make up air variations
Replacement air can be supplied into the kitchen via the canopy. A full-length integral fully insulated make-up air plenum can be incorporated inside the front face or perimeter of the canopy, parallel to the extract plenum. Or in the case of island canopies a plenum on each of the canopy faces parallel to the extract plenum. The introduction of supply air via the canopy can be made available with the following methods:

Facia Supply: is the normal method of introducing the replacement air into the kitchen, the air being discharged into the kitchen from the front face of the canopy. Either stainless steel perforated panels or double deflection grilles can be fitted to the front face of the canopy to diffuse the replacement air.

Induction supply air: enables a jet of ambient air to be injected within the canopy via a slot at the lower internal edge of the canopy face, parallel to the extract plenum. This jet of air induces the rising thermal currents toward the extract plenum, simultaneously mixing with the hot air to reduce the temperature of the air as it passes through the filters, thereby increasing the molecular weight of the grease particles.

Perimeter supply air: creates an air-curtain effect, providing operatives with cooling air flow to alleviate the effects of radiant heat and forming a barrier to the rising thermal currents.

Spot Cooling: provides operatives with the benefit of a cooling jet of air from a nozzle, which can be directed towards their work location.

Or any combination of the above options can be incorporated into the face of any canopy.

    Baffle filters
Size : 500mm x 400mm x 50mm
Rated capacity (CFM) = 826
Rated capacity (m3/hr) = 1404
Final PD = 130 Pa

Size : 500mm x 250mm x 50mm
Rated capacity (CFM) = 505
Rated capacity (m3/hr) = 859
Final PD = 130 Pa

Light Units
Stainless steel vapour-proof twin fluorescent recessed light units are available in 600mm (2 ft) long, 1200mm (4 ft) long or 1800mm (6ft) long, which provide an average illumination = 500 lux at working surface.

The supply air system should provide 85% of the total extracted volume, with the remaining 15% infiltrating naturally into the kitchen from surrounding areas. This ensures that the kitchen remains under negative pressure therefore minimising transfer of kitchen odours to areas outside the kitchen.
 

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