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Beware fake electric cable

 
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adam2
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PostPosted: Sat Feb 24, 2018 5:50 pm    Post subject: Beware fake electric cable Reply with quote

This has been a problem for many years, but appears to be a growing problem.

There are several forms of fakery.
1) the copper conductors are smaller than claimed.
2) The conductors are the correct size but made of low grade copper with a higher resistance.
3) The conductors are copper clad aluminium but are claimed to be copper.
4) The insulation or sheathing is of poor quality and less robust than it should be.
5) Cables claimed to be fire resistant are not.
6) Cable claimed to be low smoke in a fire, do in fact emit smoke.

Also be aware that "100 meter" rolls of cable may be 100 chinese meters or about 90 or 91 meters.

In the case of detachable IEC leads as often used with IT equipment, these are often not earthed, or are not fitted with fuses.

It is well to be vigilant and avoid cable from doubtful sources.

In the absence of test facilities, I would go so far as to assume that the stated size is in Chinese mm, and use the next largest size to compensate for this.

YouTube link to a TV programme about fake cable.
https://www.youtube.com/watch?v=ftUdLnxipi4
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Mr. Fox



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PostPosted: Sat Feb 24, 2018 11:51 pm    Post subject: Reply with quote

Cheers for that, Adam.

Worth noting that by using a qualified electrician (with properly calibrated test equipment) you can minimize the risks posed by substandard cable.

To elaborate: when a new circuit is designed and installed, it is then tested to ensure that - in the event of a fault - the resistance is low enough to be able to pass enough current to cause the protective device (breaker/fuse) to operate (trip/blow) quickly enough to prevent any problems (fire).

In other words, even if the cable IS substandard, so long as it's installation is tested in accordance with BS 7671, it's unlikely to give any problems.

As for the (red) bit of fake pyro (BS 6387) cable they test in this video... anyone who has ever handled the 'real' stuff should be able to tell the difference with their eyes closed. Confused

All that said, I've had problems with fake cables from China via ebay... 'du-pont' rainbow/ribbon patch leads for logic level prototyping... I was getting weird problems, tested the patch leads and found no continuity... stripped them open to find absolutely NO conductor material at all! They were just coloured solid PVC string. Mad Rolling Eyes
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vtsnowedin



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PostPosted: Sun Feb 25, 2018 12:08 am    Post subject: Reply with quote

I can't imagine being a purchaser of cable from China after even one such fault is detected. Is the competitions product just as shoddy making it a moot point?
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fuzzy



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PostPosted: Sun Feb 25, 2018 11:32 am    Post subject: Reply with quote

A big quality issue is the insulation. It is often poor fitting, or even slightly porous, allowing damp to travel along wires from their terminations. Not so bad for solid wire, but for stranded flex combined with 2nd grade copper, this is a common headache
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adam2
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PostPosted: Sun Feb 25, 2018 3:10 pm    Post subject: Reply with quote

vtsnowedin wrote:
I can't imagine being a purchaser of cable from China after even one such fault is detected. Is the competitions product just as shoddy making it a moot point?


I suspect that most purchasers of fake cable are not even aware that it is from china. The factories making fake goods, including electric cable, will apply whatever marks and approvals are needed for the intended market.
This would include CE marking, BASEC approval, "made in England" and whatever else is required.

The average small self employed electrician purchases cable in relatively small volumes from the nearest wholesaler or DIY outlet, most check for CE marking.

Larger electrical contractors purchase commonly used types of cable in huge quantities, and might well purchase directly from china subject of course to the cable having all the required approvals and certificates.
Such large firms are most unlikely to listen to employees who express doubts as to the quality of the materials supplied by the employer.

Maintenance contractors primarily maintain existing installations done by others and therefore don't buy much cable.
If they DO need to obtain cable, this is done from the cheapest possible supplier with no regard for quality, beyond checking for approval marks.
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adam2
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PostPosted: Thu Apr 05, 2018 2:44 pm    Post subject: Reply with quote

Mr. Fox wrote:
Cheers for that, Adam.

Worth noting that by using a qualified electrician (with properly calibrated test equipment) you can minimize the risks posed by substandard cable.

To elaborate: when a new circuit is designed and installed, it is then tested to ensure that - in the event of a fault - the resistance is low enough to be able to pass enough current to cause the protective device (breaker/fuse) to operate (trip/blow) quickly enough to prevent any problems (fire).

In other words, even if the cable IS substandard, so long as it's installation is tested in accordance with BS 7671, it's unlikely to give any problems.

As for the (red) bit of fake pyro (BS 6387) cable they test in this video... anyone who has ever handled the 'real' stuff should be able to tell the difference with their eyes closed. Confused

All that said, I've had problems with fake cables from China via ebay... 'du-pont' rainbow/ribbon patch leads for logic level prototyping... I was getting weird problems, tested the patch leads and found no continuity... stripped them open to find absolutely NO conductor material at all! They were just coloured solid PVC string. Mad Rolling Eyes


I do not share your faith in electricians with calibrated test equipment.

Consider as an illustrative example a 32 amp cooker circuit wired in allegedly 4mm cable that is in fact 4 Chinese mm or about 3.6mm actual size.
A competent electrician should test the earth loop impedance of the new circuit so as to ensure that a fault will promptly operate the fuse.
In the case of a relatively short run of cable, then it will still pass the earth loop test, despite being undersized.
The cable is still undersized and if fully loaded might be a fire risk.

The risk is not that great, the regulations do allow a significant safety margin, and cooker circuits are seldom fully loaded for long.
But with millions of meters of fake cable installed the risks add up.

The risk is greater for a circuit that is fully loaded for hours at a time.

The other risk is when through ignorance or penny pinching, the wrong size cable has been fitted.
For example 2.5mm cable on a 32 amp circuit for a cooker is incorrect* In practice one would probably get away with it, unless the 2.5mm cable was in fact only 2.0mm.

And of course no amount of electrical testing will detect "fire resistant" cable that is not fire resistant. No one will know until fire breaks out and the fire alarm/emergency lighting/smoke extract system does not work.

*in general, there may be rare circumstances where it is permissible.
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Mr. Fox



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PostPosted: Thu Apr 05, 2018 9:50 pm    Post subject: Reply with quote

That's why I use words like 'minimise' and 'unlikely'.

Sure, it's conceivable that a very short run circuit loaded to capacity might pose a risk - but with the de-rating factors etc, sizing cable to the 'book' current capacity is rare. If the run is that short, 3.6mm instead of 4mm is unlikely to cause a problem.

More often than not we're sizing (up) for voltage drop.

From memory the 'book' max current carrying capacity of 2.5mm T+E is, what, 31 amps (in free air)? - I'm not aware of circumstances where it is permissible to exceed that (but I'm not infallible!)

The fake pyro would of course not show up in testing - I'm saying that it probably wouldn't even get as far as being installed in the hands of a competent electrician. The stuff they showed in the video was clearly red PVC 3-core, which 'feels' completely different and is different in it construction to pyro.

So all in all I agree that there is a small risk posed by fake cable - just probably not as great as suggested by the TV show - but that this risk can be minimised by using a competent electrician (especially one who has the spectral form of the NICEIC inspector breathing down their neck, looking for that one cable clip you missed because it was 6.45pm on a Friday, you'd dropped the last one you had into the wall cavity of deep, dark oblivion and you had just worked out that the wet feeling on your knees was due to the fact you were actually kneeling in dog piss).
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fuzzy



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PostPosted: Fri Apr 06, 2018 10:31 am    Post subject: Reply with quote

Yes I think the cable diameter is more related to worst case voltage drop, which the IEE rant over to puff up their status. It is true that filament lamps would dim and kettles would take longer to boil with a drop in supply voltage, but any fire risk is likely to start with one of the hundreds of ultra cheap grub screw connections in series in an installation designed to spec. When we moved into our house, I noticed the hot bakelite/phenol smell in our supply cubboard and saw the supply tails were very hot at full load due to a naff block connection. I rang the suggested supplier number and a quick visit from a dude who could work in the dark and he had swapped the cables for fresh ones, a new meter [for no reason], and left the original badly overheated incoming block with the loose connections....
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BritDownUnder



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PostPosted: Fri Apr 06, 2018 12:04 pm    Post subject: Reply with quote

fuzzy wrote:
Yes I think the cable diameter is more related to worst case voltage drop, which the IEE rant over to puff up their status. It is true that filament lamps would dim and kettles would take longer to boil with a drop in supply voltage, but any fire risk is likely to start with one of the hundreds of ultra cheap grub screw connections in series in an installation designed to spec. When we moved into our house, I noticed the hot bakelite/phenol smell in our supply cubboard and saw the supply tails were very hot at full load due to a naff block connection. I rang the suggested supplier number and a quick visit from a dude who could work in the dark and he had swapped the cables for fresh ones, a new meter [for no reason], and left the original badly overheated incoming block with the loose connections....


They do that in Australia too. They need no excuse to install a smart meter when it is of no benefit to the householder and usually leaves them worse off in terms of tariff.

I would think that voltage drop is related to cable resistance (more correctly impedance for AC) and resistance is a function of both diameter of conductor and also length. Which is more significant I can't say as I would have to go and put on my maths hat and we don't want that.
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Mr. Fox



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PostPosted: Fri Apr 06, 2018 5:51 pm    Post subject: Reply with quote

@ Fuzzy:

Yep, loose terminations is a major issue - the whole reason the regs were amended recently to insist on metal cased consumer units was because there were a fair few plastic ones that caught fire... but that was down to 'factory' installed cabling (neutral bus bars, IIRC) not being tightened sufficiently (and installers not checking).

@ BritDU:

Also a function of current, too. Voltage drop tables for each cable cross sectional area (c.s.a.) are given in millivolts (mV) per amp per meter e.g. 2.5mm csa drops 18 mV per metre per amp. The maximum drop limits are 8% for lighting circuits and 6% power for power circuits (for a 'private distribution').

On PV we always worked to 3% on the DC side. I can't remember if that was a reg, guidance or just us. Confused
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adam2
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PostPosted: Tue Nov 06, 2018 4:23 pm    Post subject: Reply with quote

This problem is ongoing.
The latest concern is fake flexible cord

"Ermaks" and made in Turkey.

http://www.aci.org.uk/news/aci-warns-dangerous-turkish-flexible-cord

The alleged 2.5mm copper flexible cord when tested only had a safe current carrying capacity equal to about 1mm of real copper cable.

That could be a significant fire risk in use.

The fake cable contains copper coated aluminium which is not only of much lower current carrying capacity, but is also less robust and liable to breakage.
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