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The neutral meter tail incoming to the consumer unit is made up of 10 x 1.5mm cables. is this safe or should it be a single core insulated 25mm cable?

This is a new building.

4 Answers from MyBuilder Electricians

single core 25mm tails must be used. to BS7671 regulations


Answered 22nd Feb 2012

I'm assuming here when you say they used 1.5sq mm cables that these are 1.5mm twin & earth?

Not sure about safe, and I can't image why it was done this way other than laziness - I guess they ran out of 25sq mm double-sheathed neutral and couldn't be bothered to get any more.

In terms of electrical capacity, if they've used all 3 conductors - line, neutral and earth - on each of the 10 cables as neutral conductors, then that would add up to 25sq mm. However, there's a BS7671 requirement (514.3) that cables be correctly identified by colour at their terminations, so if the line and earth are all left without blue sleeving, then it doesn't comply.

Regulation 523.8 does permit parallel conductors under certain circumstances, though it does require all parallel conductors to be the same cross-sectional area. So if the 1.5 sq mm cables used are twin and earth, then it wouldn't comply as the cpc is smaller cross-sectional diameter.

To me though, the safety killer is that the cpc (if twin & earth cable) is unsheathed along its length and where the sheath is removed for terminations, you're left with exposed live conductor - which can't be considered safe at all. Even if the cpc has been blue-sleeved, there's still the risk of some bare conductor showing at the pont where it enters the sheath.

If they've not used twin & earth, but used 3 core flex, then that doesn't comply with regulations because you're not allowed to use green/yellow conductors for anything other than as a protective conductor (Reg 514.4.2).

If they've used 10 single 1.5sq mm conductors, then that would only give 15sq mm total (You'd need 16.7(??) 1.5sq mm conductors to total to 25sq mm).

I guess I've taken a long about way of saying you should get the installers back to correct it, but given you the justification for doing so.


Answered 24th Feb 2012

Realisticly You can only have this for a very short term. It should be the same size as the live conductor.
The tails are starting from 16mm


Answered 5th Mar 2012

You really need a professional to look at this.


Answered 25th Oct 2013

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