Wiring Layout in Loft


Postby John Duncan » Wed Oct 06, 2010 11:07 am

Does anyone have information on Wiring Layout in Loft: how it should appear and be done to comply with legal requirements?

Or are we allowed to run the wiring any old how across joists and piping etc.
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Postby BLAKEY1963 » Wed Oct 06, 2010 9:26 pm

[quote="John Duncan"]Does anyone have information on Wiring Layout in Loft: how it should appear and be done to comply with legal requirements?

Or are we allowed to run the wiring any old how across joists and piping etc.[/quote]

john duncan

BS7671 , 17th edition reg book lists info on this
you could try to access the iet website on regs online
Alternatively your local friendly electrician might have the info in his reg book 4 u 2 look at

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Postby ericmark » Tue Oct 12, 2010 1:03 am

The regulations state things like:- Cable mounted on a wooden wall so that the gap between the cable and the surface is less than 0.3 times the cable diameter. But really there is no precise methods laid down. Normally one considers the length of a hammer stale between each clip. But the BS7671:2008 is not on the net and even if it was is written as shown below:-
522.2.1 In order to avoid the effects of heat from external sources, one or more of the following methods or an equally effective method shall be used to protect it wiring system:
(i) Shielding
(ii) Placing sufficiently far from the source of heat
(iii) Selecting a system with due regard for the additional temperature rise which may occur
(iv) Local reinforcement or substitution of insulating material.
NOTE: Heat from external sources may be radiated, conducted or convected. e.g.
- from hot water systems
- from plant. appliances and luminaires
- from a manufacturing process
- through heat conducting materials
- from solar gain of the wiring system or its surrounding medium.

So running cables next to hot pipes is of course a problem but it does not say you must not do it.
Under
FUNDAMENTAL PRINCIPLES
It states:-
131 PROTECTION FOR SAFETY
131.1 General
The requirements of this chapter are intended to provide for the safety of persons, livestock and property against dangers and damage which may arise in the reasonable use of electrical installations. The requirements to provide for the safety of livestock are applicable in locations intended for them.
In electrical installations, risk of injury may result from:
(i) shock currents
(ii) excessive temperatures likely to cause burns, fires and other injurious effects
(iii) ignition of a potentially explosive atmosphere
(iv) undervoltages, overvoltages and electromagnetic influences likely to cause or result in injury or damage
(v) mechanical movement of electrically actuated equipment, in so far as such injury is intended to be prevented by electrical emergency switching or by electrical switching for mechanical maintenance of non-electrical parts of such equipment
(vi) power supply interruptions and/or interruption of safety services
(vii) arcing or burning, likely to cause blinding effects, excessive pressure and/or toxic bases.

And the electrician needs to interpret this and decide what is OK. In real terms often cables in voids are not fixed as they should be but it is very had to quote direct from BS7671:2008. The guide to 17th Edition is by many considered the same as the regulation and that does state how many cables to a conduit and how they should be clipped but it would be hard to take anyone to task for not following a guide to a guide as even the regulations are not law.
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Postby John Duncan » Tue Oct 12, 2010 9:30 am

Thanks Eric,
The info is a very helpful reply.
The electrician has let the wires run everywhere across hot pipes etc. There is no order to them as they bundle together and criss cross the loft.
We need insulation laying but the state of the wiring would make it difficult.
Do I gather that the regulators allow almost any `layout' in the loft as long as the wiring functions?

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