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Electrician condemed existing wiring during extension build?

Postby Customer1 » Wed Sep 09, 2020 7:09 pm

We are part way through our extension and the electrician turns up. He's condemned all cabling because its grey 18 years old and got powder in it. Next he wants to run an armoured cable through the house because of the length of the run (12M) to the new kitchen is so far anything else would be a fire risk. So shocked (not) the builder agrees with him, and guess what its going to be costly!

Anyone out there to advise is there anything in this?
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Postby ericmark » Thu Sep 10, 2020 10:20 am

Pictures, this does not seem right, however maybe some thing missed in the telling, like missing RCD protection or plastic cable clips, etc.

The new rules have a lot of fire protection built in, but I can't think off hand why standard twin and earth should not be used, my question would be to the electrician what regulation does it breach using twin and earth?

131.3.2, 132.7 for example, without knowing why he thinks it needs SWA can't really answer, mother's house had SWA feeding the kitchen as no RCD in consumer unit and the kitchen had it's own sub consumer unit. But not enough info to give an answer.
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Postby Customer1 » Sun Sep 27, 2020 6:50 pm

The house was completely rewired, new consumer unit rcd ecy in 1998 signed off by building control to the code current at the time.

This guy has condemned the twin and earth saying its a white cable (sheathing) so cant use it. I apparently need armoured cable to the kitchen due to voltage drop, its 10 m and another mcu in the kitchen.

Is this just rubbish?
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Postby Mr White » Sun Sep 27, 2020 7:39 pm

Since we (Anyone reading this) can not see anything, I would suggest you get another electrician to visit site and give you his opinion.
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Postby ericmark » Sun Sep 27, 2020 9:30 pm

White twin and earth normally thermal setting cable rated at 90 degs C where grey is thermal plastic rated at 70 degs C so in the main white is higher spec to grey.

But need to be on site, so you need another electrician on site to advise.
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Postby Customer1 » Mon Sep 28, 2020 1:49 pm

Thanks, that is useful, so then do I really need an armoured cable and additional consumer unit in a kitchen 10 to 12m from the existing, and in perfect working order MCB because of voltage drop?
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Postby ericmark » Mon Sep 28, 2020 5:12 pm

To measure volt drop within the installation we measure the loop impedance at incoming supply and at the furthest point that circuits goes to, and take first reading from second reading, then multiply the result by the amps used, and this gives us the likely volt drop, we are allowed 11.5 volt for sockets, however it is rare to actually test the volt drop, as today there is not much equipment affected by volt drop.

In the main we are more worried about the earth loop impedance, if that is exceeded then a MCB may fail to trip in time, however a 2.5 mm cables will have same volt drop be it twin and earth or steel wire armoured, so something does seem wrong.

However your not going to work it out on a forum, your going to need an electrician.
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