When doing domestic electrical installation, you are often working alongside old work. Since there is no requirement to bring old up to new standards (apart from things affecting the whole installation like earthing etc), how do you make clear to an inspector what is the new work, and what is old and may not be up to latest regs ? Case in point:
- I have some old electrical wiring passing through the kitchen ceiling (only lighting as it happens) which may not pass the de-rating requirements (grouping, near a central heating pipe). It is for circuits I will not be touching, so I need not change them. But new circuits will be alongside which will obviously be up to the 17th edition.
- I have some holes in joists outside the 0.25 to 0.4 zone. It would be silly not to re-use them, but the building inspector could complain (not strictly electrical here) if they have new circuits installed using them.
One other question: Regarding ambient temperature. I have central heating pipes (high temp, non-condensing setup) in a ceiling, overall ceiling void basically covering the whole house (support under the joists in places). At present not lagged. I could lag it to some extent. How would I calculate the ambient temperature in various parts of the ceiling void in order to work out the de-rating factor ? (Short of building in a probe and closing up the ceiling to test). It is very common to have heating and wiring taking similar routes around a house !
Thanks, Simon.