I'm planning to get my kitchen and bathroom ceilings replastered, and
will be taking the opportunity to fit new lighting. This presumably
falls under Part P. I'm generally fairly relaxed about this, but if I
could comply without too much cost and effort then I'd probably do so.

My council includes on its list of Building Notice prices an entry for

"Work relating solely to an electrical installation where the applicant
undertakes to provide on completion an installation and commissioning
test certificate completed by a person competent but not registered with
a Government approved scheme".

This price I might be prepared to pay (the many-times higher price for
getting them to inspect it, I probably wouldn't).

Is this testing something I'm likely to be able to undertake and have
accepted? I'm not installing a whole new circuit, merely changing a
central rose to half a dozen recessed downlighters or similar.

I currently have a CU with whole-house RCD which, touch wood, doesn't
give any trouble, so I shouldn't end up in the situation where a test
reveals levels of existing leakage that require vast amounts of
unexpected work to rectify.

Cheers,

Pete

Pete Verdon d
wibbled on Wednesday 21 October 2009 16:46


Is this testing something I'm likely to be able to undertake and have
accepted? I'm not installing a whole new circuit, merely changing a
central rose to half a dozen recessed downlighters or similar.


The testing is not brain damagingly hard - provided you can acquire a
multifunction tester, or a group of instruments that can do:

500V insulation test

RCD tests (trip time at 1/2 x, 1x and 5x stated trip current in both
polarities and ideally a ramp test to indicate the actual trip current,
though I don;t think this is compulsory)

Impedance tester (good for measuring fractions of an Ohm)

Optionally an "live" earth loop impedance tester/prospective fault current
tester - though you can state the figures that your electricity supplier
give you which will be the worst case usually.

Some means to test the earth rod if your supply is TT.

A multifunction tester can usually manage all except the last, some can do
that too.

In fact, I would say the inspection side is harder, because you need a
reasonable knowledge of the regs to critique the installation - but you
need these anyway to do the job in the first place.

The IEE OnSite Guide (17th) would be totally worth the money.

In a nutshell for testing, and this isn't a point by point guide - there may
be errors because I'm tired and much is omitted... Merely a gist:

First inspect and test any main bonding (eg water pipes, gas pipes back to
the main earth terminal. Visual inspection of clamps, screw tightness, bind
wire size etc.

Know your supply parameters.

Visual inspection of your circuit - check screw tightness, cable sizes,
terminals, enclosures, cable erection (ooh err) etc.

Test your circuit.

a) Disconnect circuit at CU.

b) Connect L-E of the circuit at the CU end with a terminal block.

c) Measure resistance between L-N, N-E and L-E at every fitting with
switches in every poisition (may need to bridge dimmers out with a wire
link). Obviously L-N and N-E should be offscale (infinite) and not L-E
resistance.

d) Take the highest L-E resistance found for the circuit and write that on
the EIC. Check it is less than that required by your breaker/fuse

Any L-N or N-E results indicate wiring errors and need to be fixed.

With any luck you will also have inherently covered much of the functional
testing (ie do switches work as expected). Dimmers etc will have to be
checked when energised.

The pedantic will repeat that excercise having shorted L-N at the CU end and
removed the L-E short.

Then, IR testing,

a) Remove all lamps and bridge all sensitive equiment out (dimmers, SELV
transformers etc. Disconnect any other loads like shaver sockets, fire
alarms.

b) Do a 500V insulation test between L-N, L-E, N-E at the CU end.

Note the figures and check if they are high enough. Too low = fail.

Remove all the links.

Run an RCD test.

Fill out the form and sign it.

++++++++++

As I say, don't take this as gospel. It's just a rough idea of what you will
need to do - if you to take it on, buy a book on the subject - that will
help iron out the details...

Then you can PIR the rest of your house with the same skills


HTH

Tim

--
Tim Watts

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Tim W
wibbled on Wednesday 21 October 2009 19:53

a) Disconnect circuit at CU.

I should have said, also remove all loads...

--
Tim Watts

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