Replacing section of ring main

iep · 20 Sep 2010

The wiring for one of the ring mains for my house has become damaged about a meter above where it exits the fuse box (all circuits exit through top of fuse box and run up the surface of the wall). No electrical damage I just took a chunk out of the insulation while moving some furniture through the garage.

I'm not sure how ring mains are normally terminated, but in our house both the ends of the ring terminate in the fuse box itself. Both cables of the ring have been 'nicked' so I need to replace the first meter of both.

As it happens though, I have a length of 6mm cable spare. Since it can easily carry 32A, is it acceptable to run a single length of this cable the first meter from the fuse box and then crimp connect it to both the cables of the ring main from there?

Cheers,

iep

PrenticeBoyofDerry · 20 Sep 2010

Really the cable should be the same CSA as that of the existing circuit, it's not expensive to buy a 2 meter length of 2.5mm T&E from the wholesalers, I'm sure they will cut to length, mine do!
If I lived near you I would give you some.
How do you intend to terminate the joint in the repair?
if the joint is accessible a 30A Junction Box would be acceptable. You will need two!

iep · 20 Sep 2010

Thanks, I was more curious of the regs than anything (and it's always nice to use up materials that you have where appropriate). There's a place up the road that I'm sure will sell me the cable.

I guess then that it is normal practice to terminate the two 'lives' of the ring at the fuse itself (and the neutrals together on the neutral bar)?

The joint is easily accessible. I was planning to use crimp connectors and then to heatshrink the joint. Is this not advisable?

Cheers,

iep

holmslaw · 20 Sep 2010

iep · 20 Sep 2010

I guess I could do that but it seems a bit of a bodge.

Having said that, we're planning to have a new CU put in at some point in the next few months so it would only be for a while.

iep.

sparkwright · 20 Sep 2010

Electrically I suppose you could use the 6 mm, but I wouldn't recommend it as it just complicates things in the future. It isn't really recognised as a standard ring circuit.

You would not get a satisfactory joint by crimping, as the cables are different sizes; and you have three of them.

You could take this opportunity to re-route the cables and use 13 amp sockets to form joints, giving you more sockets in your garage to use. Use 2.5 mm cable.

You could only do this if you can confirm both cables are directly on the ring; and not spurs from the ring.

iep · 20 Sep 2010

sparkwright, that's not a bad idea. I am a bit light on garage sockets as it happens.

For the record, is it acceptabe to use crimp connections like these provided cables are of equivalent size?

http://cgi.ebay.co.uk/50-BLUE-HEATS..._Cabling_ET&hash=item255a09b652#ht_896wt_1137

iep

iep · 20 Sep 2010

Out of curiosity, is this stuff illegal?

http://cgi.ebay.co.uk/30AMP-Connect..._Supplies_ET&hash=item1e584daa7d#ht_500wt_928

I'm not planning to use it but I'm curious as to whether it's ever an acceptable solution.

Cheers,

ip

plugwash · 20 Sep 2010

No it's not illegal but it is often used inappropriately. To comply with BS7671 it needs to be placed in a suitable enclosure and furthermore it needs to be accessible for inspection.

RMS · 20 Sep 2010

If all the cables exit the consumer unit at the top and there is sufficient slack, why not fit some appropriate size plastic trunking?

ban-all-sheds · 20 Sep 2010

iep said:
I guess I could do that but it seems a bit of a bodge.

What's damaged? Just the outer sheath?

If there are no bare conductors showing then just enclosing it to reinstate the protection that the sheath would provide is OK. Yes - it's a bit bodgey, but if you're having the CU replaced soon anyway.... He says, mindful of the fact that there's nothing as permanent as a temporary fix

If you do want to cut and join the cables, why not do it at the point of the damage? That way you won't need new cable.

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Replacing section of ring main

holmslaw

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