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Topic Title: Lead sheathed wiring
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Created On: 21 April 2017 08:12 PM
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 21 April 2017 08:12 PM
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dickllewellyn

Posts: 1410
Joined: 19 March 2010

Evening All

I've been absent from the forum recently, so I'm pretty sure I've a lot to catch up on, or a lot of repetitive reading of subjects discussed at length in the past, either way, it's good to be back!

I've got a quick question regarding lead sheathed cables still in use. I've never actually seen any still in use on an installation, but I've a client who seems to think they may have some!

I'm booked to sort out a few remedial works in the property, and i wondered what people would advise on circuits with lead still in use which tests OK and is protected by RCD. When I encounter rubber I normally think that if the insulation resistance tests OK and its not disturbed, I'm happy to leave it in service with a recommendation to replace the cable.

It may be that there is no lead. Everything I've seen appears to be 70's PVC. Lighting all seems to have a CPC, although the homemade fittings leave a bit to be desired!

I'm pretty sure the average electrician out the Yellow Pages would imediately say that the house needs urgent rewiring, but I don't like to scare clients into having work done which is actually quite safe, even if it is dated or unusual.

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 21 April 2017 10:00 PM
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AJJewsbury

Posts: 15632
Joined: 13 August 2003

I saw a lot of lead sheathed rubber cables when I was younger - the trick I was taught to identify it was just to try to scratch a small line in the sheath with your thumbnail - if the scratch looks bright it's lead (rubber or PVC will of course look dull).

Lead sheathed is likely to be even older then TRS cables - and I never saw any that didn't look a bit dubious at least at the terminations - 30+ years later I'd be very surprised if it was really still serviceable. You can loose a lot of insulation in dry/clean environments without anything showing up on an insulation test.

- Andy.
 21 April 2017 10:21 PM
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dickllewellyn

Posts: 1410
Joined: 19 March 2010

I'm not expecting much if there is any lead cable. The house is on a TT with no RCD in sight, or even any VOELCB. I was pretty reluctant to poke about too much before isolating!

The good news is that most of the wiring is surface clipped to beams, so if it does need replacing, it's not too horrendous. I've basically quoted to replace the consumer unit, check earthing and bonding, carry out an EICR, and spend two days on remedials. I don't actually think there will be much wrong other than the supposed lead which may or may not still be in use, though there may be a fair few C3s! My theory is that I will know fairly quickly on the first day if there's anything terrible and can quote accordingly.

The homeowners are pretty old and infirm, so anything I do I want to give the least disruption possible for them.

Whats the word on bakelight dome light switches?

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 21 April 2017 10:38 PM
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mapj1

Posts: 9107
Joined: 22 July 2004

Originally posted by: dickllewellyn

....



What's the word on bakelight dome light switches?


probably a fairly short and unrepeatable one... are they the kind which remind you of the girl on the record sleeve of 'My Sharona' ?
If the top unscrews and gives you a handful of live terminals without the use of tools, then joking aside, not really permitted since about 14th edition. If the cover has screws to hold it on, then apart from the fact there will be no CPC and even if there was, nowhere to connect it, it may be just about OK on an RCD.

-------------------------
regards Mike
 21 April 2017 10:54 PM
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dickllewellyn

Posts: 1410
Joined: 19 March 2010

That's my thoughts on the switches. I think most of them have been replaced by plastic reproductions, but there's still a couple in use I think.

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 21 April 2017 10:55 PM
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AJJewsbury

Posts: 15632
Joined: 13 August 2003

What's the word on bakelight dome light switches?

That brings back a memory - many years ago I visited an aunt who'd had her house rewired. As she didn't have much money to spare, they'd kept almost all the original accessories (round switches on wooden blocks, the old tiny ceiling roses and so on) and just replaced the rubber cables with T&E. Given the old accessories were very solidly built compared to today's, it's probably still going strong...

If the top unscrews and gives you a handful of live terminals without the use of tools

Just like a current BC lampholder then? (even the ones at low level like table lamps)

- Andy.
 22 April 2017 08:53 AM
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Jaymack

Posts: 5344
Joined: 07 April 2004

Originally posted by: dickllewellyn
The good news is that most of the wiring is surface clipped to beams, so if it does need replacing, it's not too horrendous.

Perishable rubber cables should be replaced, and I'd expect to see buckle clips on any surface, lead sheathed cable.

Regards
 22 April 2017 11:14 AM
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broadgage

Posts: 2319
Joined: 07 August 2007

IME, most lead covered house wiring cables last indefinitely except at the terminations where the rubber insulation is exposed to the air and perishes.
If however the terminations have become unsafe, then the fact that most of the cable between the terminations is still serviceable does not help much.
In theory one could cut the cable back and re-terminate, but in practice the costs would probably exceed complete replacement.
 23 April 2017 09:07 PM
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antric2

Posts: 1262
Joined: 20 October 2006

Evening Dick,
Good to see you back.
First time I came across lead sheathed cable was about 8 or 9 years ago up here in North Manchester.I wasnt rubber coated or owt like that but actual lead covered and exposed.The outer sheath was the actual cpc .
When new con unit fitted it tripped for fun and customer mentioned they got a tingle when kneeling in the loft and touching some of the light switches.
The outer sheath was live,cant remember what the voltage to cpc was but it was live.
It turned out that 4 other properties on the street had lead cables for lighting circuits.
Is this the type you are talking about or is rubber coated lead cable something different.
Regards
Antric
 24 April 2017 07:29 PM
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dickllewellyn

Posts: 1410
Joined: 19 March 2010

Thanks for the replies everyone.

Antric, the cable is exposed lead sheath rather than rubber coated, I don't know for sure that there is any. When I visited the property I thought everything was grey PVC. (ps. It's nice to be back!)

Broadgage, I kind of though along the lines of what you've said. I expect the runs of cables themselves to be OK, but perrished at the ends. My experience with VIR has been that if undisturbed it seems to be stable, but as soon as you touch it the insulation crumbles.

Jaymack. All the cables are buckle clipped, that seems to be the norm even for PVC up until about the 80's round our way, particularly in cottages. Often the buckle clips can be undone and reused with a bit of care, and I've got a stock of around 30 in case I need to replace any. Hopefully we will see wholesalers stocking buckle clips again soon what with requirements for fixings in escape routes and all!

A J Jewsbury. I know what you mean about lampholders, amazing really that the standards still allow for that where ordinary persons replace lamps, yet consumer units, the realm of the skilled (in theory) must be full of additional guards etc.

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
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