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Can you wire around corners?

Postby Sam D » Mon Feb 21, 2022 10:33 pm

Hi everyone

Recently I was asked by my son in law to fit a fused socket next to the cooker socket as they didn't have a cooker hood which I've installed. As there is no socket on the wall, I've had to spur from a double socket on the wall closest to the cooker.

Question is, is it legal to take a wire around a corner? Will it meet regulations. I've embedded the wire within white trunking to protect it and have ensured that the double socket I have spurred from and the single metal backbox which the fused socket is housed has been earthed. The extractor works but its worrying me as they are getting someone to sign it off next weekend and want to ensure going around a corner with a wire is legal.

Many thanks in advance.

Sam D
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Simply Build It

Postby ericmark » Tue Feb 22, 2022 10:54 am

If you have installed it, only you can sign the installation certificate, no one else can sign it for you.

There are safe zones, never really worked out why safe at ceiling height but not as skirting board height, but if you take a cable around a single corner the origin socket will give you a safe zone on one wall, and destination socket a safe zone on other wall.

The certificates are a free down load off the IET web site, depending on country or principality within UK there are slightly different rules, if it needs notifying there are two methods, both require you to inform first before starting the work unless an emergency.

So the LABC (local authority building control) has to decide if they think you have the skill to do the work, and the skill to do the inspecting and testing (in England some schemes allow electricians to also do this but unusual.) if they think you can do the work you pay your fee and do it, if they feel you can inspect and test you submit the installation certificate to them, and they in turn send you a completion certificate. If they feel you don't have the skill to test and inspect, they can either do it them selves, or they can appoint some one to do an EICR (electrical installation condition report) they need to appoint some one as they need to tell him how far to go with the inspection and testing, but the LABC can charge you for his time.

Either way you end up without an installation certificate, as only person who can complete it is the person doing the work.

Personally I feel the certificate is a good check list, it means you don't miss checking anything. However on a ring final the earth loop impedance pass mark is 1.37 Ω and the cheap plug in testers with loop test normally pass anything with a ELI of 1.9 Ω so to test with a ring final you need a full blown loop impedance tester, and these are not cheap, also a RCD tester again not cheap, the cost of even hiring the testers for such a small job is likely over what it would cost to get some one to do the job for you, the problem is every time they are hired out, they need re-calibrating.

So in real terms following the regulations you simply can't DIY within a reasonable cost.

So we simply break the rules, if we kept to the rules this part of the forum would be nearly pointless, so a £50 plug in tester with loop as long as there is RCD protection is good enough to show new socket OK to use.

Theory is a B32 MCB/RCBO needs between 3 and 5 times the rating to operate the magnetic part of the trip, which will work within around 0.01 of a second so 5 x 32 = 160 amp add 5% for safety so 168 amp, ohms law 230 volt / 168 amp = 1.37 ohm. But it will trip at over 32 amp in the fullness of time, the 1.37 Ω is only needed for it to trip within the time allowed, so if RCD protected then with an earth fault that only need 30 mA not 168 amp, and will trip in 40 mS so really you don't need it to trip the magnetic part, however the regulations say the RCD is secondary protection not primary except with a TT supply, so they say it should have an ELI lower than 1.37 Ω.

Again in theory the RCD is tested with a machine which measures the time it takes, 40 mS at 5 times tripping current seem to remember 150 mS at tripping current. So the test button only tests it is not stuck, but in real terms if the test button works, I would not worry.

The only problem is with rental property, with owner occupied who is going to find out if not tested to BS 7671?
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