Concealed cables

[ban-all-sheds]

We often see advice here to people who want to remove accessories from defunct circuits when they cannot remove the cable(s) to disconnect the cables at source.

There does not appear to be an exemption in 522.6.101 - 103 for cables which are not disconnected.

[RINGS BELL]

Discuss.

[/AND RUNS AWAY]

 

[JohnW2]

We often see advice here to people who want to remove accessories from defunct circuits when they cannot remove the cable(s) to disconnect the cables at source. There does not appear to be an exemption in 522.6.101 - 103 for cables which are not disconnected.

I'm not sure I understand. When it is not possible to 'disconnect the cable at source' (i.e. if it remains live), I think/hope that we would always advise that the accessories should not be removed if by so doing a safe zone required by the cable would disappear (we seem to accept that 'a joint behind a blank plate' still counts as an 'accessory' in that context).

The more interesting (maybe 'silly') point that you may have unearthed is that it could be said that the regs, as written, still apply to a totally 'dead' piece of old cable' that is connected to nothing. The walls of my house are full of such fascinations

Kind Regards, John

 

[bernardgreen]

The early electricians had the right idea.

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• bernardgreen
• 25 Jul 2014
• 1

( www.rexophone.com )

and more at

http://www.r-infinity.com/Cleats/

I am sure there must be some UK sources but cannot be bothered to look

 

[ericmark]

Let me relate what actually happened to me.
Before I started with a firm a new batching plant was installed. However many of the old cables were sealed in concrete spillages and were not removed.

These cables were causing a problem and it was decided an effort should be made to remove all redundant cables.

The old electrician who had worked there for many years identified the old stuff which included a junction box with no lid with over a dozen SWA cables as being from the old plant so no longer in use.

This old box was a good start point simply if it went into this box it must be dead. So I set to removing these cables moving back from the box after of course checking the box was in fact dead.

This went on for a couple of days and I was sawing through cables to untangle them from cables still in use. Until I was called to a cable sparking.

It turned out there was one odd cable fed an auger which was from the original batching plant and it had be joined using the old junction box but since only energised for about 5 minutes a day had been missed.

After the near miss the removal of cables was only done while the plant was not being used which resulted in one day a month for removing cables.

There is no difference in any switched supply be it a simple light switch or a PLC controlled batching plant there is really only one way to remove cables and that is to spike first. And even then a reasonable time has to be left before continuing in case it still has a supply at some odd time.

both my dad's house and mine have both had one owner and in both cases we have found cables we can't remember every fitting.

I hear people say prove for dead. Clearly from above that means every manual and auto switch must be found and tested. This is one reason I love the neon screwdriver it's that second string to the bow when the unexpected means a cable becomes live while your working on it.

In an ideal world where every circuit has a minor works or installation certificate then there is no real problem. But this is not an ideal world.

It's not only electrics. In Algeria we were moving a 6 inch pipe line and we fired pigs to test line. There was an unknown branch and the pig hit a building similar to a railway hut put a 8 inch hole as it went in and dragged out every bit of furniture with it as it left.

Since I know my house I know the old supply to immersion heater went to kitchen then airing cupboard and when the submersion was removed three sockets replaced it. One is now inside a book case. (Used at Christmas for tree lights) it is so easy to get items like this wrong when removing.

We I am sure are all guilty I know with my sons house I made an error when re-wiring I thought a supply was just to out houses then latter found a live cable clearly teed of that supply.

We all know we should always remove old cables but we also know it does not always happen. However I can't see how we can really protect against the odd cable which becomes live other than neon screwdriver. Even that would not fully protect so my only suggestion is when removing cables all conductors should be connected together so any errors become apparent.

 

[JohnW2]

The early electricians had the right idea.

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• bernardgreen
• 25 Jul 2014
• 1

Ah, you mean like this (photographed for posterity just before being removed from my house - the switch is clearly of a more recent vintage that the moulding/trunking/whatever! - and I'm sorry that someone had painted it!):

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• JohnW2
• 25 Jul 2014
• 1

Kind Regards, John

 

[bernardgreen]

it had be joined using the old junction box but since only energised for about 5 minutes a day had been missed.~~~~~I can't see how we can really protect against the odd cable which becomes live

The short time, once a week, energising of an apparently redundant cable is a hazard when removing old cables.

Temporary wiring a 500 milli Amp 20mm long fuse directly across the supply and leaving it there for a week will indicate ( by blowing ) that the circuit became live at some point during the week. There are better ways but the fuse is a cheap and nasty way of doing it and is not suitable for all situations.

Not recommended

 

[AndyPRK]

The early electricians had the right idea.

Untitled

• bernardgreen
• 25 Jul 2014
• 1

( www.rexophone.com )

and more at

http://www.r-infinity.com/Cleats/

I am sure there must be some UK sources but cannot be bothered to look

I'm more used to seeing them with the red and black conductors in.

Did they not bother with a cpc back then?

 

[bernardgreen]

One house had pare copper conductors for Live Neutral and Switched Live in the wooden molding and no earthing at all.

Provided the wood did not get damp this was probably safe enough in the days when people looked out for their own safety WITHOUT any reliance on Health and Safety regulation to prevent them doing something stupid.

Edited in red

 

[ban-all-sheds]

The more interesting (maybe 'silly') point that you may have unearthed is that it could be said that the regs, as written, still apply to a totally 'dead' piece of old cable' that is connected to nothing.

They would appear to.

 

[JohnW2]

The more interesting (maybe 'silly') point that you may have unearthed is that it could be said that the regs, as written, still apply to a totally 'dead' piece of old cable' that is connected to nothing.

They would appear to.

I suppose we need to remember that the regs are not 'retrospective', hence only really relate directly to newly installed things. No-one would install a bit of concealed cable that they knew was never going to be connected to anything. If it were a 'just in case' installation of a cable which might be needed/used in the future, then it seems reasonable that the usual rules should be applied to it, in the hope that this would increase the chances of it being intact when actually needed!

Kind Regards, John

 

[EFLImpudence]

110.1.2(i)

 

[JohnW2]

110.1.2(i)

Are you taking this to mean that a cable which is not part of a circuit which is 'supplied with a voltage' (e.g. a 'dead' bit of cable) does not come within the scope of BS7671?

Kind Regards, John

 

[EFLImpudence]

Yes.

 

[JohnW2]

Yes.

That's BAS's answer, then! Mind you, it might create new questions - e.g. relating to the previously 'unused bit of buried cable' that subsequently becomes part of a circuit 'supplied with a voltage'!

Kind Regards, John

 

[EFLImpudence]

Mind you, it might create new questions - e.g. relating to the previously 'unused bit of buried cable' that subsequently becomes part of a circuit 'supplied with a voltage'!

Do you mean unintentionally?