rewiring a light circuit

Hello,

I didn't look close enough at the electrics before I bought this house. I have found that none of the sockets are on a ring: they are all wired as radials, some with spurs. I know you can have a radial with a 20A MCB but they are not wired like that (32a MCB in CU making it look like rings)! I found at least one socket that did not have an earth connection!

The lights are wired curiously. Some of it is red and black T&E. Some of it is T&E that has stranded conductors. And some of it is (if such a thing exists) "single and earth": grey outer insulation, with a red insulated wire inside and an un insulated earth wire. Though earth wires may be present in the cable, they are not always connected; sometimes they are cut level with the grey insulation.

What is frustrating is that a professional firm of electricians fitted a new consumer unit a few months before I bought the house. How did they let the vendor get away with this? Shouldn't they have tested for earths at the sockets, etc? It seems to me fishy that someone should buy a new CU just before moving house. I wonder whether someone else made an offer on the house, had a survey, and withdrew their offer because of the electrics, so the vendor fitted a new CU to give the appearance that everything was ok?

I thought I would begin by rewiring the lights. My house is like this:

ground floor: lounge and kitchen first floor: front bedroom, rear bedroom, bathroom second floor (loft conversion): bedroom and en suite

I thought I would start on the first floor as I am already doing some decorating on that level.

The loft conversion above is making it very difficult to follow wires. What do the professionals do when rewiring houses: remove carpet and cut holes in the floor above or cut holes in the ceiling below?

Rather than move the bed and roll back the carpet in the loft conversion, I went with cut a hole in the ceiling on the first floor. It seems that the builders have run chicken wire between the old ceiling joists and placed rock wool insulation slabs on top of this. This has interfered with me using rods to push cables along. Why would they put insulation between the first and second floors? Surely it would be better to put it above the loft conversion, not under it?

It is very filthy up there, lots of black dirt has fallen onto me.

To make matters worse, the loft conversion is on new joists that run between the old ones (which are still used to hold up the ceilings of the rooms below).

The light at the top of the stairs is on the ground floor light circuit, yet the light in the rear bedroom is connected to that lamp for its live and neutral. It seems the loop connections on the light at the top of the stairs are used for the upstairs light circuit but the switched live for that light comes from the ground floor circuit! I think this is dangerous as you would not expect one fitting to have conductors from two circuits. Do you agree?

What is the best way for me to rectify this? Should I put the light at the top of the stairs onto the upstairs circuit? Or should I leave that light on the ground floor circuit and just remove the first floor live connection to that fitting? What is the common practice with stair lights; what circuit do you put them on, or do you give the stairs a circuit all of their own (perhaps shared with fire alarms?)

Thanks, Stephen.

Reply to
Stephen
Loading thread data ...

Radials are permitted & common. 32A with 4mm^2 is OK. If it's 2.5mm^2 you s hould use 20A MCBs. However these figures change if wire is buried in insul ation. See Wiki 'cable' for full detail.

easily fixed. I'd expect the occasional fault in a building with oldish wir ing.

presumably historic cable. Nothing wrong with that as long as its condition is ok, which with pvc it normally is.

Standard stuff

not good, but easily fixed hopefully

It doesn't sound like the work was legal

probably. It's normal.

why? From what you say it sounds like you only need connect the earths & me asure to check things are ok.

as Phil said that would be from before the loft conversion

I'm not clear how that makes things worse

It's normal practice, millions of houses are wired that way.

Does it need rectifying for some reason? I can't think of one offhand. I ca n recommend getting a bit more familiar with house electrics before setting off on a good deal of work that by the sound of it is 99% pointless. Meanw hile I'd go round reconnecting all the earths - just check they are earths first, not a wire repurposed as a switched live.

And you might want to consider meditation.

NT

Reply to
tabbypurr

Technically you can have a 32A radial, but it is impractical due to trying to get 2 large conductors into standard terminals.

Sounds more like someone forgot to "join the ends".

A new CU would have required full circuit testing afterwards, so none of those faults should exist. So much for Part P!!

Have you got any documentation on the CU fitting - because I would refer it straight to the firm's professional body if there was one!

Reply to
Tim Watts

It's recommended that the 20A radial (usually 2.5 mm^2 cable) should not serve more than 50 m^2 floor area, and the 32 A radial (4 mm^2) no more than 75 m^2. Spurs and branches are allowed, provided the requirements for voltage drop and earth-fault-loop-impedance are met at all points. This is subject to consideration of the likely loading (after diversity)- e.g. the 20A circuit will often not be appropriate for a kitchen.

That was commonly used in the late 60s - early 70s period, especially on low-cost housing. The stranded wire is probably 3/0.029 (pre-metrication ~1969-70).

See

formatting link

...

If you're saying that the supply to the lamp is between the line ('live') conductor of one circuit and the neutral of a different circuit then, yes, that's potentially dangerous - although it can still be found in the form of the 'borrowed neutral' in older installations.

If there are only two lighting circuits in the house they should be on seperate RCDs in the new consumer unit, in which case one or both RCDs should trip whenever that light is switched on.

Golden rule: The wiring of the line & neutral of each final circuit must be electrically seperate from that of any other circuit, in order to permit safe isolation.

Reply to
Andy Wade

ion, with a red

n.

There was also black and earth.

Reply to
DerbyBorn

Much depends on what size cable has been used... also how its been wired. So for example, 4mm^2 T&E radial (with branches in 4mm^2 and / or spurs from it in 2.5mm^2) would be fine. Even multiple spurs in 2.5mm^2 taken from the "origin" of the circuit (i.e. the CU).

Yup, that's never good...

Some older imperial sizes of T&E (and modern large sizes) are stranded. There are even some rare cases of modern 2.5mm^2 T&E that's stranded.

It may be that they actually wanted just a double insulated single... (or its a bodge - again the devil is in the detail)

Not necessarily. They would have tested for ring continuity, and probably insulation resistance, but not necessarily tested every socket.

Could be...

I have even see a place that was "rewired" before sale, where all that was changed was the CU, the sockets and switches and short lengths of visible cable, that were then grafted back on to the existing perished rubber insulated wiring!

Fairy snuff...

Depends on what is easiest and requires least making good. Normally you would lift a floor if its floor boards, but in cases where it say has a real wood floor laid over it, it may be less destructive to get through the ceiling from below.

Yup that is a common building control requirement when adding a second storey, to ensure you have 30 minute fire protection between the floors. I had to do it when I built mine. They get very worried about escaping from second or above storeys since you need to get through lots of existing house!

Par for the course alas... all over disposable bunny suit and a good respirator!

Again, good practice for several reasons... it saves having to pull down the existing ceilings and keeps all the new loft work self contained during the build. When done it also means the new floor is decoupled from the existing ceiling so you get less noise transmission.

e.g.

formatting link

Its probably two way switched, so you may have live wires from both circuits present at the switches.

formatting link

Borrowed neutrals are never a good idea - especially when the circuits are split across multiple RCDs. However it is an unavoidable fact that a lamp switched from more than one storey is at some point going to have live wires belonging to the "other" circuit present. Its just one of those things you need to be aware of.

I would say its best practice to do two way switching in *both* directions - two switches at the bottom and two at the top. So you can switch both lamps from both locations.

formatting link

You may find some useful background in:

formatting link
formatting link
formatting link

Plus plenty more electrical articles:

formatting link

Reply to
John Rumm

The stranded (and red/black)electric cable you mention is the sort used pre the present metric sizes. Single and earth was quite common (as was twin with no earth). So probably dates from the 1960's/70's. Or someone has used a lot of second hand cable. Also all twin cables were red/black. (ie no twin brown/red for use in two way circuits). None of the above matters, except for rodent/heat/mechanical damage, it's pretty indestructable. However the rest of it sounds pretty desperate, a "starting again" job.

Every electrical fitting will have to be removed and each cable tested out to find out where it goes and if it's undamaged.

Without some electrical experience it's a non-starter as a DIY job. It will be an expensive and time consuming job unless you can secure experienced on site assistance.

Reply to
harry

Our 1975 bungalow has the live looped at the the switches rather than the r ossettes it is a red sheathed twin cable with a green stripe, inside the sh eath is a bare solid earth and a red sheathed live. From the switches a sin gle grey sheathed switched live and Earth goes to the rosettes. The neutral is again a single that simply goes from rosette to rosette and does not ne ccesarily follow the route of the main live feed.

My daughters 2015 new build to my surprise is also looped at the switches b ut unlike ours is all done in T&E with the neutrals as well as the live loo ped in the switches. This does seem to result in a lot of wires in the back boxes especially in twin ganged switches and those that involve two way sw itching. All the back boxes are 25mm deep as opposed to 16mm. The walls are dry lined with 15mm PB so the 25mm boxes do not need sinking, the only adv antage I can see to this method of wiring is that replacing the rosettes wi th light fittings is simpler since there is only a single T&E cable with a switched live and neutral.

Richard

Reply to
Tricky Dicky

I think in your situation I'd firstly make all sockets etc, safe as far as earthing etc are concerned, then give more thought to the way in which you want to proceed. I'd wager an awful lot of houses are wired strangely, though actually pretty safely for most usage cases. Might be a serious issue if you plan to resell it though. Brian

Reply to
Brian Gaff

I think that's overcautious. I know someone who rewired her house

30-odd years ago with negligible experience to start with and only occasional on-site assistance - and that mainly in terms of people peering at her work with glass in hand :) What she did have was (a) ready access at work and over the phone to people who did have a clue and (b) the nous to read and follow instructions, and to ask when she wasn't sure she understood what to do.

Of course there's no shame in the OP getting someone in as his time may be better spent on other things, but it could be a "learning opportunity" - helped by the fact that a new consumer unit means he shouldn't need to replace that and that all the circuits should be RCD protected.

Reply to
Robin

Stranded TW&E probably dates back to pre metric days. Using singles was common with some electricians.

Earths on lighting circuits were not required once - even although TW&E cable was used. So the earth wire simply cut off at each end.

You've basically got a real bitsa modified and extended over the years.

If you wish to update to current regs, you'll need to identify and correct things one by one. Or just do a total re-wire. Only you can decide which is best.

Reply to
Dave Plowman (News)

Depends.

Sometimes it cheaper [1] to just rip down/smash to bits the ceilings and then reboard/overboard and then and get a plasterer in.

[1] cheaper is going to be expensive no mater what you do
Reply to
ARW

I've got some rubber insulated wiring in my house which is bad because it perishes.

the cheapest socket tester is like this:

formatting link
i've got lots of them - (it doesnt find all faults)

I'd advise you buying the yellow OnSiteGuide

formatting link

Maybe you should do a wiring diagram of the house - use lots of colours!

Pretty certain whoever fited the RCD was breaking the law by attaching it to dodgy wiring.

[george]
Reply to
DICEGEORGE

IMHO it is still a good way of wiring lights.

Reply to
ARW

I've only seen it once in 'recent' years. On a private estate built in the '80s Given the way they penny pinched on construction, I'd guess it was done to save on costs.

In the unboarded roof space of the one I saw, it looked a right mess. ;-)

But then anything done in a rush can look untidy.

I'm wondering if it's more of a regional thing? The only double insulated singles my local TLC sells is meter tails.

Reply to
Dave Plowman (News)

Dunno how it saves on cost! It more expensive for the materials and labour for the first fix when using singles. The cheapest way is usually loop in loop out at the light fitting using T&E. And the new fad of looping in and out at the lightswitch is not all it is claimed to be - fine for a 1 gang lightswitch in a 25mm box but in say a 3 gang lightswitch you do not really need 5 neutrals and 5 (or more if there are strappers) earth wires in the back box.

I am sure that I have seen just as bad with T&E:-)

Doncaster council insist [1] that their properties are rewired using singles - well single double insulated for the neutrals, the lives of course have an earth.

[1] Not done one of those for 2 years so it might have changed.
Reply to
ARW

CEF stock it, if you need it.

Reply to
charles

Does anyone still use the once common system using junction boxes for lighting? To my mind this gave a simple and neat layout, with only the 230v feed looped between boxes, and just two single T&E's to the lamp and switch.

On moving in here we had a junction box based system from the 70s, and I've continued with this. However, it is a bungalow, so there is no access problem to the junction boxes, which might be why it is less popular with two storey houses, where at least some would have to be between ceiling and first floor.

Charles F

Reply to
Charles F

It's very useful when not using a standard 'loop in/out' ceiling rose. So for those who later change to a different light fitting, easier.

Trying to remember when the 'loop' ceiling roses arrived on the scene.

They, of course, allow just the wires to be run in before plaster boarding and floors are laid. With the connecting up being done at any time afterwards. With JBs, it would have to be done before any floorboards etc went down.

Reply to
Dave Plowman (News)

They are still used by me if I am threading the switch and switched wires down old conduit to save on damage to the walls and lifting too many floorboards. I usually put all the JBs together under a trap floorboard (usually in the airing cupboard) and I label them up.

Reply to
ARW

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.