Wiring Accessories
with certain exceptions. One such exception is for maintenance-free accessories suitably marked, conforming to BS 5733, and installed in accordance with manufacturer’s instructions.
It is important that the designer and installer selects those accessories which are suitable for the environment within which they are to be installed. Therefore, as with wiring systems, the factors to consider will include amongst other things, temperature, humidity, the presence of dust and the ‘look’ required (aesthetics).
Consider Scolmore’s ‘Click Definity 20 A Control Switch’. This range has interchangeable faceplates and comes in a series of double-pole switches with or without neon indication. The technical guidance issued by Scolmore details critical factors that should be adhered to. These are detailed such that the products conform to the relevant Standard. Amongst them are included: Voltage/frequency .............................................240 V / 50 Hz Current rating ..............................................................................20 A Terminal size .......................................................5 mm diameter Torque value .........................................................................1.8 Nm Cable size ......................................................................4 x 2.5 mm2 IP rating ..............................................................................................IP20 Operational temperature ........................-5 °C to +40 °C
No accessory should be installed outside of the technical specification of the manufacturer.
wiring system to be adequately supported. This will include support for any trunking/conduit systems along with clips and cleats for cables. Regulation 521.10.202 is a particular example worth considering. This regulation is relatively new and requires wiring systems to be supported ‘such that they will not be liable to premature collapse’. This requirement came about to limit the risk to firefighters from entanglement as they entered premises.
To address the requirement of Regulation 521.10.202, Unicrimp has a range of products that are fully capable of supporting wiring systems and cables. These include, ‘All-round banding’, ‘Fire safe cable clips’, ‘Stainless steel roller ball cable ties’ and ‘Metal LSF cable clips’ (
https://www.unicrimp.com/ products/q-fire/).
Accessories
An accessory is defined in Part 2 of BS 7671 as: ‘A device, other than current-using equipment, associated with such equipment or with the wiring of an installation.’
An accessory, therefore, does not require current to function. Examples of accessories are commonplace and include amongst others: • • • • •
Switches Socket-outlets
Fused connection units Connection units
Cooker control units and the like.
There are several regulations that relate specifically to accessories that a designer and
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installer should be conscious of. For example: Regulation 522.2.201 requires that parts of a cable within an accessory is suitable for the likely temperatures to be encountered. This requires the designer and installer to be conscious of where a rise in temperature may exist and to provide protective measures to mitigate their effects. Manufacturers have data sheets detailing the temperature operating ranges of their products. Regulation 526.3 requires every connection to be accessible for inspection, testing and maintenance
Conclusion
The selection and erection of wiring systems and accessories are the ‘nuts and bolts’ of electrical installation work. The designer and installer should be constantly aware of the requirements of BS 7671 regarding both. Furthermore, manufacturer’s guidance should always be considered, and care given to ensure that they are suitable for their environment.
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