Cooker hoods

Cooker hoods are becoming a standard fitting in many new and refurbished kitchens and are certainly a boon in alleviating cooking smells and the reduction of steam from boiling pans.

Extraction is achieved by means of a motor, usually a shaded-pole type, which drives a normal or barrel fan. Variable speeds are often included for coping with different conditions, and a light to illuminate the hob, independently switched, is another helpful addition.

When the hood is switched on, the fan sucks air through a filter system to remove grease particles and cooking smells. Most hoods offer the option of external venting or recirculating the air into the kitchen. Although the recirculating version is useful, better results are obtained through external venting. Kits like the one shown here are widely available and simple to install. All hoods whether recirculating or vented, require regular renewal of the filter. Failure to do this will greatly impair the operation of the hood and could lead to failure of the motor in the long run.

Filters

Some hoods use pre-formed filter replacement cartridges that combine a grease and carbon filter in a disposable unit. Others use a polyester tangle fleece material with an open weave to the exhaust side which may be used in conjunction with a carbon impregnated filter. The open polyester weave removes grease particles from the steam laden air. The air may then pass through a carbon filter or carbon impregnated foam matrix.

The life expectancy of a grease filter is between two and three months, depending on usage. After this its absorption capacity quickly diminishes, the filter becomes brownish in colour and fails to suppress odours. Consult the manufacturer’s instruction for the recommended regular intervals for replacing the filter. If the specific filter unit for your particular hood is difficult to obtain, there are several types of filter kits available that only need cutting to the size required. Follow the instructions in the pack and make sure the filter is fitted the correct way round.

Problems

Problems with cooker hoods are few, the most frequent one being the failure of the hood light. This is usually a straightforward job, but remember to isolate the hood before changing the bulb and be sure to refit all parts correctly. Other problems are motor failure, bearing wear on motor or fan and switch failure. Simple checking for continuity is all that is required to ascertain the fault. This also applies to switch faults.

The first sign of bearing failure is usually an increase in the normal operating noise. This may be gradual and go unnoticed for quite a while. The bearings of both fan and motor are usually more than capable of coping with the light demands upon them, but faults can occur if filter replacement is ignored or irregular. This could allow grease deposits to build up on the fan and finally cause it to go out of balance.

Mounting the cooker hood too close to the hob is a common problem. This could result in a faulty switch, a motor fault due to overheating, trim damage or a sticking switch. It is also dangerous to mount equipment below the minimum height recommended by the manufacturer. Consult your instruction manual and check the correct height of the installation for the hood. Remember, the hob may have four elements in use at the same time. Minimum height requirements also apply to hoods mounted over gas hobs.

It is essential that the hood has its own fuse and isolation switch or socket.

Watch Point

Renew filters regularly - every two to three months, unless otherwise stated in the maker’s handbook.

Consider fitting a vent system if the hood has been fitted for recirculating only. Ventable models have a blanked-off circular hole in the back or top of the hood.

Start the hood fan a few minutes before using the hob to establish an air flow before odours or steam are produced.

Leave the fan running for a few minutes after use of the hob. This will also allow the hood to function much better and remove residual odours and moisture from the atmosphere.

A back flow of air must be provided to replace the air extracted from the room when extractors and vented cooker hoods are installed or are being used.

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