extending ring main methods

I want to add extra sockets in my kitchen. I have numerous double sockets on the ring with the two mains cables embedded in plaster and descending from the ceiling. However, I need to add more sockets at a couple of these locations.

A sparkie mate of mine says that this must be done by extending the ring main - no more than one spur off each socket. Ok - understood. The way to do this, he told me was to take one of the descending cables from this master socket and use choc block to connect it to a cable going to the first new socket. The return cable from this secondary socket will connect to the terminals of the master socket, together with the other descending cable, thus keeping the ring intact.

Does this sound OK - just sounding this idea out. Or do I have to do complete new cabling and have the floorboards up upstairs?

Reply to
Kaiser Sose
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Going to ignore the obvious Part P implications and the choc block implications.

Think you might have slightly misunderstood something your sparkie said....

Not quite. You can have one spur off each ring connected socket. No need for choc block if done that way. What you sparkie explained was how HE would extend the ring.

Jim A

Reply to
Jim Alexander

On Wed, 07 Mar 2007 06:09:43 -0600 someone who may be Kaiser Sose wrote this:-

Nothing wrong with using terminal blocks in this way, though the box needs to be large enough to accommodate them and the socket.

Any ring circuit that has been extended should be tested properly to ensure that it is still a ring.

Reply to
David Hansen

It sounds like you may be confusing two different ways of extending the circuit... (there is also a third - which we will come to)

an unfused spur:

Here you can feed one (and no more than one) socket (single or double) via a single cable from an exiting socket (or other appropriate accessory) on an exiting ring. These are simple to wire and require no cable to cable joints, however you may not be able to get enough sockets added in this way.

Extending the ring:

If you need to add many new sockets then this is a better solution. The technique described by your sparkie is one way (I usually use crimped connections since they take less space in the back box, and are more "permanent"). Splitting the ring elsewhere with a pair of junction boxes would be another way.

A fused spur:

A third way to add several sockets is via fused spur. Here you wire a fused connection unit to the existing ring as a spur. Then wire as many sockets as you require from this. It is often an easy way to get extra sockets, but the big limitation is that all the added sockets will have to share the single 13A fused supply - so it is not appropriate for sockets that you anticipate carrying heavy loads.

Reply to
John Rumm

OK, here's another angle. You have numerous double sockets and want more sockets at a couple of these locations. Actually the addition process is more to do with the ring connection between existing sockets that the dropper. You need to work out where the run is. Assuming the socket boxes are also embedded in plaster, initially assume horizontal or vertical cabling but the socket boxes may yield a clue. If so maybe you can insert a socket box between two existing sockets and chase between the sockest to repair the ring. Understanding the route of the ring is the key.

Jim A

Reply to
Jim Alexander

Yes very true, and I would test it before extending as well. You can open a right can of worms if you only test afterwards.

Adam

Reply to
ARWadsworth

Thanks for the updates guys.

If I were to use choc block in the way I described, would I have to wrap it in insulating tape before pushing it to the back of the (metal) 45mm deep socket box? If so, do the regulations prescribe a particular colour of tape?

Also, how to test the continuity of the ring as mentioned? Just buzz it out with a bleeper? On that note, how to tell whether the ring is complete before I even start? I would guess that if I disconnected the two main cables from an existing ring socket and put a buzzer lead on each one of the three conductors in turn they should still buzz out at 0 ohms back through the consumer unit?????

Thanks,

Steve

Use ROT13 for my email: snipped-for-privacy@ogvagrearg.pbz

Reply to
Kaiser Sose

No need since it is already contained in an enclosure.

Yup, that is the sort of idea...

The following procedure is not a replacement for the full tests descibed in the On-Site Guid, but will give you a good confidence check on the new wiring.

Let's assume you have installed the new bit of ring and wired it all up but not connected it yet.

Turn off the power to the circuit, and unplug (or otherwise isolate) all the things plugged into the circuit. Disconnect the existing socket, then separate out the wires. Using a multimeter on a low ohms resistance range you can measure the resistance between the two lives, neutrals and earths. You would expect live to live and neutral to neutral readings to be the same as each other, and the earth to earth may be a little higher (since the wire is thinner). Note the resistances.

Now carry out the same test on the new ring and note the results. You can also do a R1+R2 type test where you measure the combined resistance of the live and the earth wire together. This will enable you to compare your results against table 9A in the OSG. Since you probably have a good idea how long the new ring section is, you can use this as a sanity check. If you have access to a megger you could also use this on the new section of circuit to check its insulation resistance is also ok.

Now make the cable join between old and new wires (using up two of your four free cables). Check the round trip resistance between the remaining ends. This should now be checking the resistance of the whole circuit. You would expect a reading equal to the sum of the previous readings that you made for the old and new bits in isolation. You should now have good confidence that the new cable to cable join is good. Finally replace the original socket and connect the remaining two cables to it in the normal way.

Reply to
John Rumm

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