a query for the electrically minded folk. i have discovered some of this type of wiring in the lighting circuits for my house.the socket circuits are rewired with new cable but the previous owner decided not to bother with removing it for the lights . obviously it will have to be removed but im just interested to know how old this cable would be and how urgently should i get it replaced ( all electrics functioning ok but safety wise who knows?)
It old. In fact as far as electric installations go it's very old!
How old is the house?
Lead cable is probably circa late 1900's up to 30's. It was widely used. Just imagine what it would cost these days!
From a safety angle it will be OK providing you don't overload it too much as the inner current carrying cores may be fractured, especially if it's been disturbed. The cores were usually steel and they can be brittle. According to reg's though it needs to be replaced yesterday. I would make it one of my priorities. It's awful stuff to remove too because it will probably be clipped (with lead straps) to the joists every 1m or so. It's also awful to joint into etc. I don't think it's as bad though as some of the cloth wrapped stuff which is no doubt still in use in many old places. That really is a fire waiting to happen.
At a guess pretty lethal One consolation would be the cash back when you take lead to scrappy.
Why? If it works, use it. Its a lot less likley to catch fire if it shorts out, and anyway, you have MCB and RCD protection don't you?
It isn't current practice (no pun intended) to install lighting circuits with RCD protection, except when using TT circuits.
Christian.
It's at least 60 years old, IRRC. The condition it's actually in will depend on many things, but I'd say that on the exposed ends the insulation will have well and truly perished by now. Cut it back a short way and it might well be in perfect condition.
It's in general much more disruptive to replace lighting wiring than power which is why it often gets left on a bodged job. But I'd replace it sooner rather than later.
I hoiuht it was standard to put the whole house on a 100mA RCD.
"mark al" wrote | a query for the electrically minded folk. | i have discovered some of this type of wiring in the lighting | circuits for my house.the socket circuits are rewired with new | cable but the previous owner decided not to bother with removing | it for the lights . obviously it will have to be removed but im | just interested to know how old this cable would be and how | urgently should i get it replaced ( all electrics functioning | ok but safety wise who knows?)
It may well be in surprisingly good condition if it was properly installed in the first place and not buggered about with since.
However, as the previous owner's rewiring job was rather incomplete it is possible that the lead sheathed wiring was removed from the old fusebox and connected to the new consumer unit without due regard to its earthing, as lead cable is usually earthed by having a termination screwed onto the sheath and then fixed into a conduit box. Also, at all the junction boxes and ceiling roses the lead sheaths had to be bonded together. If this wasn't done properly your lighting circuits and all the cable are unearthed, which could be rather nasty.
What you can do (or get done) is a megger test for insulation between the cores and the sheath, and for conductivity between all the switches and points back to earth. If it passes those tests reasonably well then you probably don't need to rewire before christmas, but the job should be done soonish. If it fails those tests then the cabling should be regarded as an immediate risk and taken out of service asap.
Owain
Lead sheathed cables used pbj (poly-butyl-jute) for insulation. The stuff deriorates over time, and becomes brittle and liable to cracking. Possible loose connections in switches or at ceiling roses, junction boxes, etc, can generate localised heat spots, which in turn tend to make the pbj turn powdery and crumbly, leading to a break-down of the insulation. *Any* movement of the cables should be considered an absolute no-no. I know of two or three house fires that were directly attributed to old lead-sheathed wiring. It's a complete folly to rely on modern protection devices to isolate any possible faults. That's too late when your house is burning down coz a fire has started before the protection operates.
The cables are well-past their life expectancy and should be replaced as soon as posible.
You really are talking through your arse.
Lead cable isn't 100 years old, and I can assure you it deteriorates. The lead sheathing and conductors may be ok, but the insulation which is rubber based will be perished and dangerous where it's exposed. Ie, at every termination.
I've not yet come across any PVC cable in ordinary house wiring which has deteriorated badly with age - assuming it's not been overloaded. But *all* the previous types of cable - yes. PVC has now been on the go just about as long as any other type.
As regards rodent damage, I'd be equally as worried about other things in a house if you're playing host to them.
But it wasn't wrapped in only cotton. And I've had plenty of things made of cotton which disintegrate too.
If PVC was so poor for this job, other things would still be used. Don't think it's a legal requirement.
With regard to the photos, he is confusing longevity with quality (clearly). With regard to lead sheathed cable, the quality was always a bit suspect (if moved about, and in the efficacy of the earth connections). It may be true that lead sheathed cable will "last" 100 years but that doesn't make it good quality in electrical/safety terms.
Its newer than that. I keep unearthing it as I rewire my house and that wasn't built until 1948. Mind you a lot of the building materials used look as if they were left over from before the war so this might be the same. Have also found rubber covered. Don't know if they used both or if one was added later.
Fortunately the previous owner had the house rewired (if one surface socket per room can be called rewiring) so all the lead cable I come across has already been disconnected.
Andrew
As far as I can see from my 1900 house (which was gaslamps originally), the first wiring used lead sheathed for the socket outlets on the ground floor, and rubber sheathed for the lighting. It might be that lead sheath was used where the cable is layed on the earth under the floor -- I haven't seen any remaining signs of old socket wiring for the first floor, or more likely, it was used where earthing was needed (i.e. sockets and not lighting at that time).
Incidently, for amusement I have dissected some of the lead sheathed wiring and it's still in perfect condition, although all the cable ends have been cut. If it was still wired with exposed rubber insulation at terminations, I expect that would have gone brittle, but where protected by the lead, it hasn't.
Likewise.
In message , Dave Plowman writes
Yes I had a length of Lead sheathed cable in this house - part of a ring main (probably of about mid 1960's date), it seemed to have been reused, everything else was PVC.
Certainly the insulation on the exposed cable ends was perished, though not quite so bad as the original 1930's wiring in the lights.
After almost suffering a fire on a connection on the old rubber sheathed cables in the loft I certainly would not want to leave any cables with suspect insulation in place for longer than i had too.
I suppose they must have made lead cable of ring main size, but all the stuff I've come across was lighting only - single core, I'd guess 0.044in.
The oldest wiring remains I've come across were in a dentist's family practice in Tooting. The dentist reckoned his grandfather had had electricity installed and it was the first in the area at the time. It was a sort of cotton and rubber mix insulation, but installed in wooden conduit - rectangular in section split horizontally with grooves for the single cables.
-snip-
Yes, though I would think it a risk whether it passes or not. Exposed PBJ may have powdered away, bare metal conductors exposed and very closely spaced, the mess likely covered with dirt and cobwebs. One small movement, or one more spider, and you could get burnt to death. If it passed a leakage test I still wouldnt want it. Suggest you get it disconnected and use plug in lights.
Regards, NT
A little tale from a colleague I used to work with...
They`d done a rewire in a church and spent happy hours stamping on lots of old lead cables under the flooring which would flatten out in a rather satisfying way.
Then they discovered they were the pipes for the organ...
I've encountered lead-sheathed cables which were so brittle they cracked at the slightest disturbance - a fire waiting to happen, indeed.
--=20
Dave
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