Extending a ring main

[Stevep3577]

Hi All
I intend to extend my ring main into a bedroom and add 2 extra sockets. I am following this guide (Please see link) http://www.diynot.com/pages/el/el014.php

I have run all the cable's, fitted the two sockets and im about to break in to the ring and make the connections using the two 30amp junction boxes. However am i aloud to complete this, as i know all the regs restrict people from completing some tasks. I have been told that extending a ring main and adding spurs do not require certification, unless its in a special area, like a kitchen, bathroom or outdoors. Is this the case?

I have recently had a new consumer unit installed and certified so the whole house is protected by RCD and the ring protect by an MCB.

 

[PrenticeBoyofDerry]

A few things you should be made aware of Stevep3577,
Firstly: any junctions or connection made in the circuit must be easily accessible for inspection and testing purposes, this is a requirement. So you cannot use the standard 30A junction boxes, if they are being hidden under floor/ceiling void with no access available (ie trap door/hatch) You cannot make joints and bury in wall either.
The requirements do specify other methods of making joints that can be hidden/buried but the easiest method of compliance is by the use of an MF/ maintenance free connections.
I would personally try to avoid any joints and extend the RFC in away that joints can be eliminated.
Secondly: All alterations/additions to existing circuits should be inspected, tested and certificated, regardless of whether it is deemed notifiable work.
Also if you are routing cables, are you aware of the permitted safe zones, the regulations concerning the holing of joists and the depth of chases in walls ( 1/3rd of leaf/wall depth, on vertical chase and 1/6th on the horizontal chase)?
Useful links:
http://www.diynot.com/wiki/electrics:inspection_and_testing
http://www.diynot.com/wiki/electrics:installation_techniques:route
http://www.diynot.com/wiki/electrics:installation_techniques:walls

 

[Taylortwocities]

You should not need to use junction boxes to extend the ring.

See the excellent WIKI for how to achieve this
http://www.diynot.com/wiki/electrics:extend_ring

 

[ericmark]

Step one before even planning to extend a final ring circuit must be to measure the earth loop impedance. There is a limit with a B32 MCB this is 1.44 ohms measured from centre of the ring. With a TT system this will be higher but the Line - Neutral impedance should still be within the 1.44 ohms limit. This will ensure should there ever be a fault the magnetic part of the MCB will operate disconnecting the supply in a fraction of a second. Once the limit is exceeded the disconnection time jumps to seconds rather than fraction of a second even if only exceeded by 0.1 ohms.

To add to any circuit the added parts must comply with current regulations even if old parts can still only comply with regulations current at the time it was installed.

With a ring this means in practice the whole ring will need RCD protection or the new wiring will need to be Ali-tube not twin and earth and all new sockets will need RCD's built into them.

If it's not in a special location and it's not a new circuit no need for LABC to be informed. However the rules should still be complied with which means full testing and inspecting.

This I see as a problem with all DIY and no one has the meters required. You may have an inspection report should be done every 10 years or change of occupant and it may have the readings so you can add the amount of cable used and calculate new readings. 2.5mm sq twin and earth is 0.018 ohms per meter so for example if the orignal reading was 1.2 ohms then you can add 0.24 ohms of cable that's around 13 meters. But without readings you can't really start.

Since a fused spur can have an impedance of 4 ohms because of the 13A fuse assuming installation is correct before you start you can add a huge lenght of extra wire before you hit the limit so this would be the safer method with lack of test equipment. Also a RCD FCU could be used so even the RCD problem is addressed.