Ring extension junction box

29 Sep 2006
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United Kingdom
Hi all,

I am planning to extend my main ring into a new "box room" home office. As there are no existing electrics in the room and the new sockets aren't physically between 2 sockets in a circuit I need to break into the nearest socket in an adjoining room instead. This will necessarily involve the use of a junction box, although I know it is not ideal.

To briefly explain the extension, I am planning to do the following (following the circuit round, not in chronological order!):

1) Disconnect one of the cables from socket on the ring circuit. Connect it to a junction box.

2) Run a cable from this existing socket to the two new sockets and back again into the junction box to complete the radial circuit.

Ideally, I want this junction box to be as accessible as possible, so I am planning on putting in a flush mounting box where the cables are connected via a choc block. I would then fit a blanking plate so that it could be accessed at any time. My questions are :

1) Is this set-up OK?

2) Is there any guideline saying where the junction box can or can't be located?

Thanks in advance.
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Much will depend on the existing installation.
Read Additions and alterations are going to be costly
You will see the whole idea of breaking into a ring main is being talked about and it's pro's and con's and what ever the outcome you will need to know the earth look impedance before alteration before you start.
Also to extend a ring whole ring will need RCD protection.
Thanks. I didn't realise the whole ring needs RCD protection (it doesn't have it now). It's an old style re-wire-yourself fuse. I understand you can get RCD devices that fit in these old fuseholders though?

I will check earth loop impedance before I start.

Also, any thoughts on the JB location?
Until the debate which is on going I would have suggested using spurs. If more than 1 double socket then use a
or with double socket only then with Ali-tube cable not twin and earth use these
the fuse box you talk about will likely take a MCB instead of fuse but not RCD or RCBO and you would need something like this
to add RCD protection. At which point is it really worth it and should you not get a new consumer unit?
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Yes, of course it's just the MCBs that connect to the old Wylex, but no RCD protection (I did know that!).

I do need to replace the CU at some stage, but I need to get a proper spark to do it and it's likely to cost a fair bit. Especially if they find other problems (which you want them to of course!).

In the meantime, maybe adding a spur as you suggest is the way forward. I'll follow the debate with interest.
why bother with a surface junction box with a blank plate?
just put another socket next to the existing one and use that instead or the JB.. gets you an extra socket in the other room as well then...
why bother with a surface junction box with a blank plate?
just put another socket next to the existing one and use that instead or the JB.. gets you an extra socket in the other room as well then...

Genius! Now why didn't I think of that? Great idea, thanks.
also tlc do a maintence free junction box by ashley/hager which i have used when breaking into a ring and these dont need to be accessible
you sure about that?

I don't think it falls under any of the categories of connections which do not need to be accessible..

its not..
(i) a joint designed to be buried underground,
(ii) a compound filled or encapsulated joint,
(iii) a connection between a cold tail and the heating element as in a ceiling, floor or trace heating system,
(iv) a joint made be welding, soldering, brazing or appropriate compression tool
(v) a joint forming part of the equipment complying with the appropriate product standard.

from what i understand these are pushfit type connectors which rely on spring tension of a metal "prong" to hold the wire in place..
Maintenance Free Junction Boxes

Suitable for use in inaccessible locations

Maintenance free terminals provide one solution where accessibility is an issue.

Tests, including long term vibration, shock test, long term connection test,
pull out, voltage drop, temperature rise and exposure to corrosive atmospheres
validate the suitability of these terminals.

Equally suitable are solutions such as a ‘joint made by a compression tool’.
Maintenance free terminals have the additional advantages of allowing the
direct insertion of solid, stranded or flexible conductors,
and allowing the connection of up to four conductors from 0.5mm2 to 4.0mm2.

this is what is said on tlc website
however BS7671 does not recongnise them in it's list of termination methods suitable for inaccessible terminations. So if you were to use them in such a situation it would not be compliant with BS7671.
therefore this is false advertising?? as it clearly states they can be used for inaccessible locations, surely ashley would have looked into this?? im thinking this product may have come on to the market after the regs were written?
they might think it comes under (v) above, part of the equipment complying with the appropriate prodict standard..?

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