Testing and Form BS7671


Postby shipyardspark » Wed Nov 12, 2008 9:58 pm

Hi All, My first post so be gentle! Have just completed a major extension to my house and have done the complete electrical installation on my own. I am a trained electrician (albeit I did my apprenticeship in the 60s) and have worked as an Electrical and Electronics Engineer for the past 40 years and am now retired. The work has been carried out under the guidance of the LABC (first fit etc) and I am now at the stage where I will need to call the LABC Inspector in to sign it off. When he last visited he was not sure whether or not he would want to have the installation tested. Reading through the IET website and others it would appear that as a competent person I can sign off the BS7671 as required by Part P. The installation has been checked for polarity, meggered etc. Is this sufficient for the BS7671 or are additional tests required? I don,t have the new Test Equipment but I suppose I could hire it. I am aiming to have a completed set of documents for the LABC consisting of full specifications, pics of first fit cable runs, circuit diagrams and a completed BS7671 etc.

In addition, the installation was drafted under the 16 Editon and has obviously now been completed after the 17th Edition has been introduced. Is this likely to cause me problems

Any thoughts or advice would be most welcome.
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Postby ericmark » Thu Nov 13, 2008 12:18 pm

Many of the items that require filling it say reading can be obtained by Measuring, Calculations or Investigation. But some items I can’t see how any other method other than measuring could be used. Insulation resistance can only really be measured and RCD tripping time and current can only be measured. But earth loop impedance and prospective short circuit current can be calculated. As can the R1 + R2 and R1 + Rn figures.
I know it seems daft to check brand new RCD’s but it is surprising how many fail. I will guess one would hire complete set and as a result you may find measuring the easy way.
As to 16 v 17 Edition in the main the change is all circuits now require RCD protection at 30ma. There are some exceptions where Ali-tube cable is used or cable is run surface and sockets for designated equipment. Lights which are not in bathroom. Etc.
But if designed before June you can still work to 16th Edition.
Building Inspectors don’t seem to know much about electrical installation and seem to grab on a few points often with very little idea of where the rules come from and what the whole rule says. So you may need to be pre-armed with the answers to silly questions. i.e. If you can quote on page 4 of BS7671:2008 it states “BS 7671:2008 Requirements for Electrical Installations was issued on 1st January 2008 and is intended to come into effect on 1st July 2008. Installations designed after 30st June 2008 are to comply with BS 7671:2008.” He will likely back off.
If he does not like your paper work he can re-test the house at his expense, and he is responsible for site safety. So I suppose if you guessed on the reading then he can either accept or re-test.
If you want to upgrade to 17th I can go more in depth on requirements.
Eric
ericmark

Postby shipyardspark » Thu Nov 13, 2008 11:47 pm

Eric,

Thanks for your swift response. I like you, am somewhat bemused by this whole Part P certification process. It seems to take no account of experiences. I can see the sense in ensuring that installations are safe but at some considerable cost to those tradesmen who have lots of years under their belts. I will follow your advice and probably hire the test equipment required, fill in the BS 7671 and see what happens. As the Part P says, it is up to the Building Inspector as to whether he accepts my documentation or not. If not he can have the installation tested at his expense. Your advice on the 16th v 17 Edition is also welcome. I thought that a change in Editions was not retrospective but of course convincing the LABC is another story. Will let you know how it all pans out.
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Postby ericmark » Fri Nov 14, 2008 1:12 pm

Are you aware forms available on IET web site for free down load? If it were mine I would use all RCBO's anyway in fact I am considering changing the base of my consumer unit so I can remove the two RCD's I have at the moment and replace with RCBO's.
Eric
ericmark

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