I fear I'm over thinking it, but any way of wiring a lighting circuit
seems to come with disadvantages...
1. standard UK loop-in power at each light fitting
advantages: standard, have unswitched power available at fitting for
future e.g. ceiling fan/light etc
disadvantages: many modern light fittings don't have enough terminals,
or much space to add them
2. loop-in power at each switch
advantages: single wire to each light fitting, have unswitched power
available at fitting for future e.g. timer, neon etc
disadvantages: lots of wires to each switch, need extra terminals
behind each switch
(question: can I use the "unused" terminal of a 2-way switch to join
the neutrals, so that when the switch is "off" the two wires going to
the light fitting are shorted?)
3. junction boxes in the ceiling
advantages: single wire to each light fitting and each switch
disadvantages: junction boxes are supposed to be accessible, but most
won't be in practice. won't have unswitched power anywhere except
4. wire singles: neutral looped into fittings, live looped into
advantages: saves copper! fewer wires in general
disadvantages: induction loop interference, can you still buy cheap
singles, won't have unswitched power anywhere
5. any other options?
6. mix and match the above as convenient
disadvantages: confusing. will probably end up without unswitched
power where I need it!
I know in the past I lived in a house with standard loop-in wiring to
each light fitting, and had to put junction boxes in the ceiling to
nicely accommodate several new light fittings with only LNE terminals.
Fan feed is a fairly big point imho, I'd look to include unswitched
live at the ceiling lighting points whatever scheme is used.
If you did it would suffer one of the 2 downsides of the Carter
system, which was outlawed in the 1930s. Ie that a switch failure is
liable to short out the supply, its a fire risk.
With a tool they could be, ie by unscrewing the light fitting first.
Also one can solder inside the jbox, fit the wires in the screw
connectors as normal, but leaving long tails, and solder those. The
screw cons then provide mechanical restraint for the solder joints.
you can have it anywhere you want by using an extra cable core.
again you get L, swL and N anywhere you want by fitting the necessary
singles to provide it.
well, yes :) ... I doubt its what you'd want though.
Couple more options:
Mains to the light fittings, with the cable to lightswitch being cat5,
run on 12v with a relay
- you can then use anything at all for the switches, which much opens
up the decorative possibilities
- you can also add no end of extra switch ways later if desired
A ring circuit for lighting gives increased safety and reliability.
Its sometimes worth adding extra cable cores, so that later there is
the option to add a greater number of switch ways, enabling easy
switching between differing lighting levels.
When I rewired a house for home automation, I ran all the switch
and lighting point wires back to central connection points (actually
consumer unit shells, because the DIN rail made it easy to mount
X10 dimmers and relays). It's easy to change the way things are
switched, rather like a Cat5 wiring closet, and (important point
for selling) it's easy to strip out the home automation control
and revert to manual operation.
All switch drop cables are triple and earth, which allows either
to get a neutral to the switch or to add a second switch in the
future. Again, many of the lighting points are triple and earth,
for future flexibility.
[email address is not usable -- followup in the newsgroup]
With home automation, all the switches are momentary action
anyway, so I simply wire multiple switches to one of the computer
If I strip out the home automation, I can fit impulse relays
in the consumer unit shell and continue to drive with the
existing momentary action switches.
[email address is not usable -- followup in the newsgroup]
Agreed - don't like this as it bones you if SWMBO gets one of those Ikea
fittings with sod all space for terminals.
Pity they don't do a flush ceiling rose but you could DIY one with a
round dry lining box and terminal strip...
No! There's no guarantee that the switch is break-before-make (unless it
says so) which would result in a rather noticeable bang followed by no
Hager-Ashley maintenance free JBs with spring terminals. The jury is
still out on their longevity but the regs allow these, because the
manufacturer rates them as fit for purpose. But I personally wouldn't
stick then under tiles or laminate just in case! Under floorboards is
fine, and under easily liftable floorboards, you could use a screwed JB
And you'd need either full *continuous* conduit/trunking or double
insulated singles. Unenclosed single-insulated singles (wibble) are NOT
 That means continuous, no 1" gap by the light because it was too hard...
JBs in a more remote but accessible location? Eg group them in a few
locations and have little access panels in the floor. More cable
required, but easier to maintain.
As all my lighting is run mostly on one level, with a dormer conversion,
I've made up 4 large junction boxes with DIN rain and DIN terminals. One
in each quadrant of the house, in the corner voids behind the dormer
room walls (where there are large accessible voids).
Not for everyone - costs more (could have used lots of regular JBs for
the same effect, but I want somewhere to stick relays for a bit of
remote control) and needs more cable. However, not *that* much more in
my case due to the layout.
Another option - permanant power to all lights and fit radio controlled
units to each one. No cables to the switches. Cool, but costs a fortune.
getting more popular though - check out Homebase and B&Q - they seem to
be increasing the range of these units.
Special thanks to you Tim and also to NT for pointing out problems
Fine upstairs (JBs grouped in loft) but _really_ painful for
Downstairs I think I'll just loop into switches, join neutrals using a
chocolate block (one bit of!), and go from switch to fitting with 3-
core + earth to allow me to send unswitched live to fitting later if I
Shall I leave the initially unused strand of 3-core "floating" (I'm
worried about it touching something live and causing problems), or
parallel it to the switched live both ends, or wire it into the earth
both ends to keep it out of harm's way?
Hang on a second - with standard 3-core + earth (brown, black, grey),
I don't have a blue for neutral.
I'm sure I've used 3-core before with one of those colours carrying
neutral (interlinked smoke alarms being the most obvious; brown live, black = neutral, grey - interlink I think) - but where in the
regs does it say that this is allowed?
Specifically, the on-site guide says neutral = blue, and that's it.
Brown obviously works for live, and black and grey obviously work for
switched live - but black or grey for neutral - where does it say I
can do that?!
OK - will just swapping the last 1-2cm of the insulation for blue
insulation (stripped from a blue wire elsewhere) do? That's what I've
done in the past to mark the blue as brown in a switch feed (but back
then, no one was checking!).
Why grey not black? (Just interested).
I was going to use brown for the switched live - but then thought "if/
when I want both switched and unswitched live down this cable, brown
will definately be unswitched live, so grey (or following your advice,
black) will be switched".
Pity there's no proper guide on the use of 3-core colours in various
scenarios, including this one. Am I correct in believing this means it
doesn't actually matter?
Good point. Though it was more like 0.5cm, so was almost in the switch
terminal anyway. I don't like insulation tape, but I agree it's safer
in this context.
Interesting. That's quite funny really - in the old colours, I used
the Blue of 3-core for the Neutral on the smoke alarms precisely
because it was neutral in the "other"(at the time, flex only) colours.
(I hate these new colours - but I know I'm 5 years too late to say
Neutral Grey it is then.
Thanks for all your help.
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