Cable marking procedure

[Andy Hall]

What is the correct marking procedure when one needs to extend wiring in an existing old colours circuit with cable in harmonised colours? I am fairly certain that I know the answers to these usage cases, but can't find a specific reference describing it.

I think that these examples cover most usage cases of transitioning wiring where both colour standards are in use.

AIUI, there should also be a label on the CU, warning that the installation has both colour standards. Does anybody know who sells these?

Example 1 =========

Addition of a spur to a socket in a ring final circuit where existing wiring is in old colours.

Example 2 =========

Change of wiring in a lighting circuit. Existing circuit wiring (old colours) loops in and then out of ceiling rose to the next ceiling fitting. Wiring in two core T&E from ceiling rose to one way switch. Switch is being located to a different position, so new cable length from rose to switch.

Example 3 =========

As (2) but with two way switch so the switch cable is now three core T&E (black/brown/grey).

Example 4 =========

As (2) or (3) but there is a a fan (bathroom) wired using three core T&E.

Questions ========

A) Should red and black wires from the existing old colour wiring be sleeved in brown and blue at the fitting where the new wiring is being added?

B) For examples (2) to (4) should the switched live (colour in cable, blue), where it arrives back at the ceiling rose be sleeved in brown?

C) For examples (3) and (4) which colours in the section of cable running from rose to the first two way switch? Presumably that is the same as (B) if the cable is two core. What if it's three core? In either case, at the first switch where it transitions anyway to three core, how should each wire be sleeved?

D) For the section from the rose to the fan isolating switch and from there to the fan, which cores for which purpose and sleeving colours for each?

[Cicero]

=============================== Part answer - labels:

[Andy Wade]

For a single phase installation there is no requirement for marking at transitions.

That is all that is required, except for sleeving cores in lighting circuits, etc.

Any wholesaler - e.g.

examples]

That's not a requirement, unless it's a 3-phase installation.

Yes. It should also be sleeved brown where it leaves the switch.

The black and grey cores need to be sleeved brown at all points of termination, since they are phase conductors. I would use the brown core for the permanently 'live' side of the strappers, black for the commons and grey for the second strapper (sw. L to light) - but that's not standardised, AFAIK.

Brown for phase, blue for neutral. The convention here is to use the grey core (sleeved blue) for neutral, the idea being to dissociate the colour black from being neutral. That leaves the brown core for unswitched L and black (sleeved brown) for switched L.

HTH

[Andy Hall]

OK, makes sense - in other words, an unswitched or a switched live marked in brown.

OK, but it makes sense.

OK. That's clear enough.

Yes indeed, thanks.

[Lobster]

I once asked the same question here and IIRC didn't get an answer - so I won't claim this is necessarily correct procedure, but the strategy I've adopted is basically to sleeve the individual wires with old- or harmonised-coloured sleeving according to whether the individual wires are themselves old or harmonised. So potentially mixing old and harmonised sleeving within a fitting, if appropriate.

Only works as long as my stocks of red and black sleeving last, of course!

David