DIY Doctor

CU upgrade

Postby s1bgs » Fri Sep 26, 2008 4:07 pm

Am i right in saying that if I update my CU I will then have to test all circuits, continuity, ring, Ins resistance, earth loop impedence and so on.
I know all bonding is correct size and that it is a TN-S.
just need to be sure.
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Simply Build It

Postby ericmark » Sat Sep 27, 2008 2:52 pm

The answer depends on the skills of “I” to inspect and test requires some skill there are four levels.
Ordinary person
Instructed person
Skilled person
Competent person
Where the safety of others are involved it is considered the highest level “Competent person” is required. There is no single qualification which says you are competent but it is normally considered one should have passed City & Guilds 2391 exam.
The problem is danger can exist while doing the tests both for the tester and ordinary people in the house.
For a consumer change you would only need to test each circuit once i.e. one socket before and after change. But with so near a full PIR I would consider doing full PIR is so little extra work one may as well do full inspection and test then you are clear for another 10 years or change of occupant.
A TN-S supply is not very common and you do need to be careful with 0.8 ohms rather than 0.35 ohms of the TN-C-S system that the Zs readings are still within limits even if the board change the supply transformer. i.e. even if you measure 0.35 you must allow for a 0.8 reading in the future.
There is also Part P and if you had Part P registration you would not be asking these questions.
The fact that the local authority building control become responsible for site safety can be read as they must do inspection and testing. But it can also mean they just need to verify your reading which seems to be how my local council read it and they get someone to look at the reading and consider if they look genuine. If they don’t believe your reading then they can test themselves which is at their expense since I have not had a failure I can’t tell you what is the result if it fails but in theory the power should not be switched back on until a competent person has inspected it and the procedure varies area to area some being very helpful and others being proper jobs worth types.
At the price the council charge for Part P I would not think DIY on changing a consumer unit is worth it. At £70 hire of meters and another £70 plus Part P charge it is often cheaper to pay a registered electrician to do the job.

Postby TOPSPARK » Tue Sep 30, 2008 5:07 pm

When a consumer unit is changed then all of the existing circuits must be tested as it is considered you have changed the working parameters of the circuits.
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