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Topic Title: Old installation - mix of stranded and solid cored cables
Topic Summary: Advice required
Created On: 12 January 2015 10:57 AM
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 12 January 2015 10:57 AM
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alphanov

Posts: 3
Joined: 11 January 2002

Hello

I am not from the Electrical Engineering discipline so please excuse my ignorance. (I'm Chartered in EMC)

I visited a friend's house at the same time as an NCEIC electrician. In short the electrician was there to investigate frequently blowing bulbs in a recently installed ceiling unit. He stated that the ceiling junction box was being fed by a flexible cored conductor so "wasn't allowed". He suggested a rewire of the premises to remove the problem. He then looked at the consumer unit which had been replaced by a dual RCD unit about 2 years previously when a building extension had been wired. The unit and the extension wiring had been issued with a Part P certificate. The electrician showed me that the original wiring had been extended using crimps and heatshrink (behind the board) and that the cables were extended using the current colour T&E. A label was on the front of the unit to give a warning to that fact.

The wiring has been tested by an NCIEC contractor about 15 months ago as the house has been rented out by the owner. There were no issues noted on the certificate.

My questions are:
Is the crimp/heatshrink method an acceptable means of joining non accessible cables (if it is done correctly)? (I understand about mechanical strength and heating effects)

Is it OK, on an existing installation, to retain a mixture of solid and stranded cores?

Thanks

Regards

Nev

-------------------------
alphanov
 12 January 2015 11:27 AM
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broadgage

Posts: 2452
Joined: 07 August 2007

My view is that crimped joints covered in heatshrink are acceptable if properly done.
I see no problem in the use of both solid core and stranded core cables in the same installation. Stranded core cables are seldom used these days in the smaller sizes, but are still made, so hardly non compliant or obsolete in any way.
However "flexible" might mean not multi stranded cable, but flexible cord as used on portable appliances. Use of this for fixed wiring was prohibited until fairly recently. It is now allowed, but is rather odd and might warrant further investigation.
Likewise no problem in the use of both old and new colours in the same installation, provided a warning notice is affixed as has been done.
 12 January 2015 01:13 PM
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Zimmerman

Posts: 96
Joined: 31 July 2009

Done correctly with approved crimps and tools should be no problem. BUT I've been on some jobs where Yellow crimps have been used on 2.5 mm solid drawn conductors inside Dado trunking for the extension of ring circuits and they have just parted at the slightest of tugs

Flexible multi-stranded wiring (flex) should be fitted (IMHO) with suitable boot-lace crimps if connected into accessories but if the correct through-crimps are used, again no real problems as far as I can tell.

Above all, do not use the silly 'scissor type' crimpers on the even sillier coloured plastic-toped crimps, they are truly useless.
 12 January 2015 01:15 PM
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davezawadi

Posts: 3955
Joined: 26 June 2002

Hi Alaphanov

Your "electrician" was obviously inadequately knowledgeable as to the regulations.

Flexible conductors may be used in any position in an installation.

Cables may be crimped to join them, and heatshrink of suitable type and thickness may be adequate insulation. The sheath layer may be replaced with more heatshrink to preserve the mechanical protection.

He suggested rewiring on entirely spurious grounds, and was therefore commiting fraud, with intent to get you to agree to presumably pay him money for the work. Trading standards would probably be interested.

Qualified - thats a joke.

-------------------------
David
BSc CEng MIET
david@ZawadiSoundAndLighting.co.uk
 12 January 2015 01:27 PM
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AJJewsbury

Posts: 16104
Joined: 13 August 2003

Use of this for fixed wiring was prohibited until fairly recently.

Flexes for fixed wiring were banned in the 15th Ed as I recall, but I thought were permitted as from the 16th, so about 20-odd years ago?
- Andy.
 13 January 2015 12:46 AM
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mapj1

Posts: 9695
Joined: 22 July 2004

You don't see 1990s as recent ? my local radio station does..

Actually it depends what sort of flex - if its been done in alarm cable or something he may have a point. Its not the flex part that's wrong though, more that it may or may not be a suitable cable for the load or environment.

Get a second opinion, from some one who knows he's not going to get the work if he finds something.

-------------------------
regards Mike
 13 January 2015 03:55 PM
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Zimmerman

Posts: 96
Joined: 31 July 2009

Forgive me but when the electrician said 'ceiling junction box' was he was referring to the ceiling rose fed with a flex or a junction box under the flooring feeding the ceiling rose via a flex? I ask this as you say you are not from a electrical discipline and may have used the wrong term and led us astray.

If it is an underfloor JB feeding the light then the electrician was correct to point it out but perhaps a little zealous in the re-wire option unless all the lighting circuits were wired in this way. There are reasons for asking this as It could be a latent defect.
 13 January 2015 04:00 PM
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Phillron

Posts: 1411
Joined: 18 January 2007

Originally posted by: alphanov

Hello



I am not from the Electrical Engineering discipline so please excuse my ignorance. (I'm Chartered in EMC)



I visited a friend's house at the same time as an NCEIC electrician. In short the electrician was there to investigate frequently blowing bulbs in a recently installed ceiling unit.What type of bulbs and what type of fitting ? He stated that the ceiling junction box was being fed by a flexible cored conductor so "wasn't allowed". He suggested a rewire of the premises to remove the problem.What type and size of flexible conductor ? Is this "rewire" for the supply cable to the junction box only, or a rewire of the whole circuit or of the property even ? He then looked at the consumer unit which had been replaced by a dual RCD unit about 2 years previously when a building extension had been wired. The unit and the extension wiring had been issued with a Part P certificate. The electrician showed me that the original wiring had been extended using crimps and heatshrink (behind the board) and that the cables were extended using the current colour T&E.What was his comment on these extended cables A label was on the front of the unit to give a warning to that fact.



The wiring has been tested by an NCIEC contractor( I supose we can forgive him for that lol) about 15 months ago as the house has been rented out by the owner. There were no issues noted on the certificate.
Was the person who tested the house competent,Niceic is no guarantee that he was

I



My questions are:

Is the crimp/heatshrink method an acceptable means of joining non accessible cables (if it is done correctly)? (I understand about mechanical strength and heating effects)



Is it OK, on an existing installation, to retain a mixture of solid and stranded cores?



Thanks



Regards



Nev
 13 January 2015 04:16 PM
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alphanov

Posts: 3
Joined: 11 January 2002

Sorry it is the ceiling rose. I've no idea if the entire circuit is in stranded cable or not but I suspect that it is as the light switch is also stranded cable. There must be a connection with solid core somewhere though as the consumer unit only has solid cores going into it.

-------------------------
alphanov
 14 January 2015 08:57 AM
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Zimmerman

Posts: 96
Joined: 31 July 2009

If then there is just one 3-core 'flex' at the ceiling rose then there is a high possibility that there is a 'hidden' joint box somewhere under the floor boards or in the attic or wherever. If this is the case with all the ceiling roses then the spark has a point as all terminations should be accessible for inspection testing and maintenance. It could well be that behind/above the ceiling rose there lurks a bunch of 'choc block' connectors. This again is a problem. Happy days :-)
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