Wiring Accessories
Light reflectance values are a measure of the percentage of light reflected from a surface. For example, at one extreme the assumed light reflectance value (LRV) of ‘black’ is 0% and at the other extreme the LRV of ‘white’ is 100% (Fig 2). This simple chart (Fig 2) details approximate values of LRV for certain basic colours. Using this by way of example and assuming cream painted walls, a 30-point contrast exists between the following: • Cream and white • Cream and blue/red/wood/pink/brown and black
In this same example, a suitable contrast does not exist between: • Cream and silver • Cream and yellow/purple/green/grey or orange
Therefore, in this example, an accessory range of white would be reasonable as would black or brass. Where a 20-point contrast is permitted then the following would apply: • Cream and white/silver • Cream and grey/orange/blue/red/wood/ pink/brown and black
Manufacturers of paint products will typically detail LRVs on their websites. Click Scolmore details the LRV value of its accessories at the back of its catalogue. By way of example, the anthracite grey of the Part M range has an LRV of 8.9.
Mounting heights
The mounting heights above floor level and other recommendations for accessories is detailed in clause 4.30 and may slightly differ to those recommended for dwellings. Some of the key recommendations are detailed below: • Socket-outlets/TV/telephone: 400mm– 1,000mm with the lower value preferred.
• Switches for permanently wired appliances: 400mm–1,200mm.
Fig 2 Example of light reflectance values
• Switches requiring precise hand movement: 750mm–1,200mm.
• Simple push button controls: Not more than 1,200mm.
• Socket-outlets are located consistently and no nearer than 350mm from room corners.
• The operation of switches, outlets and controls does not require the simultaneous use of both hands.
• Switched socket-outlets indicate whether they are on.
• Mains and circuit isolator switches clearly indicate whether they are on or off.
• Front plates contrast visually with their backgrounds.
Conclusion
Designers and installers of electrical installations should be aware of the recommendations of Approved Documents M1 and M2 as they relate to
dwellings and buildings other than dwellings. There are instances where there are differences in mounting heights recommended for dwellings and buildings other than dwellings. The designer should recognise the differences between ADM1 and ADM2.
For each type of premises, designers should carefully consider the mounting heights of accessories and control equipment for accessibility, the nature of the switches (push pads etc where necessary) for their ease of use, colour contrast to be seen, and positions near wall corners and the like.
Care should also be taken to ensure that suitable contrast exists between the light reflectance value of accessories and control equipment and the surfaces they are mounted on. Paint manufacturers will typically provide such data and allow designers to select a suitable range of accessories.
ewnews.co.uk
May 2024 electrical wholesaler | 29
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