ennel

Posts: 51
Joined: 20 October 2003
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Originally posted by: davezawadi
Another point you might like to try Andy, BS8436 cables do not prevent this problem because the contact cross section of the foil is very small and may well just burn away before the CPD opens. They are intended for fire resistance and electrical screening.
Originally posted by: AJJewsbury
They're meant not to - a nail penetration test is part of the standard (unlike FP etc) and the stated withstand (42,000 A²s for 1.0mm² and 1.5mm² cable and 60,000 A²s for 2.5mm² cables) is actually higher than that for the c.p.c. for equivalent flat T&E cables (13,225 A²s for 1.0mm² and 29,756A²s for a 1.5mm²).
But then we do have reports of c.p.c.s 'blowing away' during a fault, so perhaps even conventional copper ones aren't immune from such possible problems either.
- Andy.
No Dave, BS8436 cables are for far more than just fire resistance and electrical screening, although they do have those properties. And this 'extra feature' is the reason that BS8436 cables are required to be protected by RCD/RCBOs with type B tripping curves, which will operate at fault currents below that at which the earthed screening vapourises under 'nail test' conditions.
However it can be hard to convince a contractor who has installed type C RCBOs instead of the specified type Bs of this necessity, when his QS takes the view "but the Zs of the circuits concerned is less than the maximum permitted for type C breakers - so the circuits comply fully with BS7671".
ennel
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Zoro

Posts: 300
Joined: 31 July 2011
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The problem was not the screw, you will never stop screws being driven into cables. The threat to safety was the circuit had never been tested, but the Certifier the "Electricians Mate" Certified that it had. The prosecution was under HSE Section 7 legislation, not EAWR.
The Qualified Supervisor, who had not supervised the "Electricians Mate" then checked the Certificate, which had multiple errors and then signed the certificate as checked.
The Certifier the "Electricians Mate" had C&G Part 1 and over 35 years experience in the trade, stated that he was not an Electrician.
The Certifier said he did not "IR test " the immersion heater circuit, he Certified that he had. (It was a Heatstore unvented mains cylinder with two immersion heaters).
The QS signed the Certificate with those errors.
The Certifier was given information for the certificate from others whilst in the site hut. Including the supply which he Certified as TN-S, but in fact was TN-C-S, and labelled up as PME at the intake position.
The QS signed the Certificate with those errors.
The Certifier stated that the circuit had an RCD (which it did not) , then certified that that the 3 test results for that RCD were N/A. The installation was under the 16th Edition, so did not require one
The QS signed the certificate with those errors.
The Certificate stated phase/phase IR results, on a single phase installation.
The QS signed the certificate with those errors.
The problem is that the supervision and certification required by HSE legislation, is not met by the NICEIC QS system. This poses the serious question, when are the ESC/NICEIC going to change their position and require that the Certifier is Competent to do so under HSE legislation, not the QS sat in the office.
The stance from the ESC/NICEIC that, this would be to expensive, must concern the public, that people on the doorstep from an NICEIC enterprise could cost a lot, to make them Competent.
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Edited: 02 April 2014 at 10:28 AM by Zoro
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