Choosing and fitting cooker hoods

There are basically two types of cooker hood – recirculating and ducted. There are also models which are suitable for either recirculation or for direct extraction from the rear or top via ducting to the outside air. With one make of this type there is a wall grille as an optional extra. Each hood is fitted with a fire shield which is kept open during normal use by a fusible cord; this ‘fuses’ in the event of a cooking fat fire and releases the shield.

Apart from a filter to catch dust and grease and, in the case of a recirculating hood, a charcoal filter to catch smells, cooker hoods contain one or more fans and most models incorporate one or more electric lamps to illuminate the hob during cooking. Fans can be either two-speed or three-speed where there is an extra boost speed besides low and normal. Switches, together with a neon indicator, are positioned in front of the hood for easy access and operation.

Buying cooker hoods

  • The position of the cooker hood and the amount of trouble to which you are prepared to go in installing it are among the factors which you should consider when buying a hood. A recirculating hood is simply screwed to the wall or underside of a kitchen cabinet: since no outlet to the outside air is required the hood can be fitted to any wall providing a suitable fixing, giving scope for planning.
  • Where smells and steam are particularly troublesome, a ducted hood is preferable; but ideally this type of hood should be positioned against an outside wall using a short length of ducting which passes through a hole cut into the wall behind or just above the hood.
  • An inside wall, however, should not be completely ruled out: although the ducting should be as short as possible. Lengths up to 6m (or 20ft) can be installed with the ducting fixed to a vertical exhaust in the hood and run up and over to a hole cut in the outside wall. In this case bear in mind you will have to conceal the ducting.
  • Cooker hoods must be positioned at the correct height for efficient and safe operation. It is generally recommended the hood is positioned 600-900mm (or 24-36in) above a hob or 400-600mm (or 16- 24in) above an eye-level grill or top oven; but always follow manufacturer’s instructions on this. The hood should be positioned as near as possible to the minimum height for maximum efficiency in operation.
  • When fixing a cooker hood above an eye-level grill if a special mounting bracket is not provided, it is an advantage to use a mounting block 100- 125mm (4-Sin) thick to site the hood further away from the wall and prevent the airflow being obstructed by the grill.


Remember, where your cooker has an eye-level grill, the cooker hood should be operated at all times when the grill is used: otherwise the heat from the grill could damage the hood.

Size of hoods

Cooker hoods are made in a number of sizes and your choice will depend upon the width of the cooker, since the hood must give adequate cover of the hob. A size which covers most British made standard cookers is 600mm (or 24in); for wider cookers there is a 900mm (or 36in) hood.

Besides these two sizes, at least one make of cooker hood is available in smaller and intermediate sizes of 550mm (or 22in) and 700mm (or 28in) as well. Fan and lights Two-speed models have a single tangential fan located at the rear of the hood to give maximum stability and are powered by a two-speed motor: three-speed models have two tangential motors which provide three-speed facilities. Lighting may be with a single lamp which is sometimes fluorescent some models have two lamps. The fans and lights are switched independently with the fans having multi-switch controls.

Hood finishes

White and brushed aluminium are the most popular finishes, but hoods are also available in a variety of other finishes including stainless steel, teak veneer and oak veneer.

Installing cooker hoods.

The type of installation work required will depend on the model you have chosen. General guidance for fitting typical models is given below, but you should always check with the manufacturer’s instructions.

Fitting recirculating models

A template with relevant fixing instructions is usually provided with each hood. A hood can be screwed directly to the wall or fitted to the underside of a kitchen cabinet. It is sometimes necessary to reinforce the cabinet fixings: so if you decide to fix the hood to a cabinet, first check these fixings. Also make sure the wall construction will provide proper support for the hood fixing screws.

Fitting ducted models

These can also be fixed directly to the wall and some models can be fixed to the underside of a suitable cabinet using the template where provided. Check the cabinet fixings before fitting the hood.

You will need a ducting kit and a length of ducting. One typical kit contains a rectangular-toround adaptor to connect the rectangular outlet in the hood to the round ducting, a louvre flap for the outside and duct sealing tape. The items in this kit are designed for attaching to 125mm (Sin) diameter flexible ducting, although the size of ducting required varies: for example. Another type of hood requires 100mm (4in) ducting. When ordering ducting from your supplier, buy it slightly longer than required.

The duct is fitted to the rearwards exhaust in the hood or to the vertical exhaust, depending on the location of the outlet hole cut in the outside wall and the route of the duct. To fit a duct to the rearwards exhaust of a hood which is either wall or cabinet-mounted using the ducting kit, first make a hole in the wall on the centre line of the hood outlet to take the 125mm (Sin) diameter ducting.

Open up the hood, remove the back blanking plate and fit the outlet in position. Connect one end of the ducting to the circular side of the adaptor and tape the joint to ensure an airtight seal. Push the ducting into the hole in the wall so the fixing plate on the adaptor is flush with the inside wall surface. Make good the plaster and cement round the ducting on the outside wall surface. Fit the foam seal onto the adaptor, locate the cooker hood outlet on the adaptor and fix it to the wall or cabinet. Fit the louvre onto the outside end of the ducting and seal round the joint with mastic or putty. Fit the louvre flaps where relevant.

To fit a duct to the vertical exhaust of a hood which is either cabinet or wall-mounted, using the same type of kit, first make a hole suitable for the ducting on the centre line of the vertical outlet. The hole should be at least 200mm (8in) above the top of the hood so the bend in the ducting will not be too tight. When mounting on a cabinet, cut a hole in the cabinet baseusing the hood or template (if supplied) as a guide. Remove the top blanking plate and fit the outlet in place. Connect the adaptor to the outlet and fix the hood to the wall or cabinet base. Push one end of the ducting through the hole in the wall and bend the other end down onto the adaptor, making sure the bend has a minimum inside radius of 125mm (5in). Tape the joint, make good the wall and fit the louvre in place as before.


Make sure you do not kink flexible ducting since this will restrict the air flow and could fracture the walls of the ducting; keep the number of bends to a minimum and make them with as large a radius as possible. Take care to seal all joints well and keep the length of ducting to a minimum — in any case below 6m (or 20ft). Whenever possible don’t exhaust into a prevailing wind or into existing flues if there is any danger of fumes reentering the house at another point.

Assembling the hood

To assemble the hood and fit the filters on a typical model, you should first remove the filter tray according to the manufacturer’s instructions. Make sure the grease filter completely covers the holes in the grille, remove all internal packing pieces and refit the filter tray. Detach the outlet grille and remove any packing pieces and the plastic bags from the charcoal filter(s). Shake the filter(s) to remove any loose dust generated during transit. When refitting the filter(s) and grille, make sure the filter completely covers the holes in the grille and the charcoal is evenly distributed within the filter(s).

Wiring up the hood

The electrical loading of a cooker hood ranges from about 80 to 220 watts depending on the size and number of fans and lights; but the loading is never more than 250 watts for a domestic model, which means a hood can be supplied from a 5amp circuit or a spur from a ring main with a 3amp fused outlet.

A suitable outlet is a 13amp switched fused connection unit, fused at 3amps, fixed close by the cooker hood and connected to it by 0.75sq mm three core PVC circular sheathed flexible cord. The fused connection unit can be supplied from a spur cable looped out of the ring main at the terminals of a nearby 13amp socket outlet using 2.5sq mm twin core and earth PVC-sheathed cable. Replace the I 3amp cartridge fuse in the connection unit by one of 3amp rating. You could supply the cooker hood from a lighting circuit, providing an earth connection is available, but this is not recommended since it can cause an overload.

Cooker hoods have neon indicators to show when they are switched on, so an indicator on the connection unit is not necessary. A 13amp fused plug and socket outlet may be fitted in place of the connection unit.


On no account put articles on a cooker hood and don’t leave the cooker rings on when not covered by pans, since this may impair the efficiency of the filters and the cooker hood.

Maintaining cooker hoods

Make sure the cooker hood is switched off before cleaning it with warm water containing a mild detergent such as washing-up liquid; don’t use too much water. Activated charcoal filters are effective for 12-18 months depending on use and replacements are available from the hood manufacturer. When renewing them, take the opportunity to wipe clean the inside of the cooker hood. The grease and foam filters should be washed about once a month; allow them to dry before replacing in the hood. Use a soft, short-haired brush to clean the impeller and the outlet grille, together with the circular motor cooling vent.

Before replacing any parts on a cooker hood, disconnect it from the electricity supply by removing the circuit fuse. To replace a lamp, follow the manufacturer’s instructions and use the same type and size of lamp or tube as the original. Faults occurring in a cooker hood should be repaired by a qualified electrician or the hood returned to the manufacturer for repair.

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