Upgrading from radial mains to two ring main circuits

[Keefa]

I am currently planning to upgrade the mains circuit in my Victorian house. I currently have an old style (fuse wire) board and it seems that all of the sockets throughout the house are on a single radial circuit.

I am intending to get an electrician in to upgrade my fuse board to a new CU with RCDs, plus running some earthing cable from the bathroom, however I would also like to change the mains radial setup to two (up and downstairs) ring circuits.

Assuming that I get an extra RCD fitted to the CU is there any problem with me simply locating the last of the upstairs sockets and running cable back to the CU on one RCD. Then disconnect the cable between this upstairs socket and the downstairs socket and run another cable from the downstairs socket to a new RCD at the CU. Finally I would then need to locate the last socket on the circuit and run a cable from there back to the second RCD.

Does this make sense to you? Is there anything I am thinking wrong?

 

[Steve]

If you have an old electrican install, which radials would suggest, you should change ALL of the cables, as they will most likely be in poor condition. When our house was rewired, you only had to look at the insulation and it fell off. Seriously though, get an electrician to have a look at the old cables, if you are doing all this work, it is a shame not to do it properly and safely.

 

[plugwash]

the big question is what size and type is the cable and is it in good condition?

 

[ban-all-sheds]

Another big question is:

I would also like to change the mains radial setup to two (up and downstairs) ring circuits.

Why?

Not why two circuits, but why two rings?

 

[ban-all-sheds]

If you have an old electrican install, which radials would suggest,

I think young electricians also install radials?

Seriously though, get an electrician

But not an old one, eh?

 

[Steve]

If you have an old electrican install, which radials would suggest,

I think young electricians also install radials?

sorry, meant "electrical", but you already knew that didn't you ban?

 

[ban-all-sheds]

 

[Keefa]

Sorry for the delay in responding to my own question...

I agree that checking the wiring is a good idea although the condition of the wiring I have seen so far seems pretty good.

The question I have is which is better: ring or radial?
Modifying to two radial circuits would certainly be easier and require far less cable but if I'm doing the job then I might as well do it right. I may need to add a few extra sockets here and there but nothing major. Does anyone know which config I should use?

Thanks in advance.

 

[Adam_151]

I agree that checking the wiring is a good idea although the condition of the wiring I have seen so far seems pretty good.

While to a certain extent you can judge cable from looking at it, you can never be 100% sure, it should never be used to justify re-using of the cable*, you need to do an insulation resistance check

*obviously no harm can come from using just a visual check to justify throwing the cable in the nearest skip

EDIT: typo fixed

 

[ban-all-sheds]

I'd say stick with the radials - there's not much to be said in favour of rings. They were introduced as a quick (and dirty?) fix to the problem of increasing demand at a time of a shortage of copper. So a 15A radial had its capacity doubled by running another piece of 7/.029 from the last socket back to the fuseboard.

If that had never happened, I doubt that anybody today would be suggesting that the introduction of ring-final circuits would be a Good Idea™, nor that the IEE would be adding exceptions into the Wiring Regs to allow them to exist.

 

[Adam_151]

FOR RINGS:

20A 2.5mm² radials and 32A 4mm² radials run the cable nearer full capacity than a ring (unless its very unbalenced), so installation methods would have more of an influence on radials than rings.

You can also go further with the ring, volt drop does't come into play as quickly as it does for radials.

Rings are easier to impliment H/I earthing on.
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AGAINST RINGS:

Broken rings only show up during testing

The whole spurring issue
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I would argue that both rings and radials have their place, a radial is ideal for a relativly small area where there will be a lot of demand (eg. kitchen), and a ring for a bigger area where demand is usually low, but could be high at times* (upstairs)

* C/H broken, mid january, portabale heaters come out


We could discuss this for months on end, same with TNC-S earthing, the justifcation behind part P, etc,

 

[Keefa]

Thanks for the help guys. I'll get the current wiring checked out and then decide what to do from there, although sticking with the radials does seem like the far easier/simpler option.