Can I join 2 radials to make a ring?

[Longhorn]

...put each on a 20A MCB

Each on its own MCB or can they share?

 

[telectrix]

better on separate MCBs so as to split them, this helps with division of circuits as per 17th edition, esp. if each is on a separate RCD/RCBO.

 

[Sparkingmad]

Each radial goes on its own mcb longhorn

What he was saying is if one radial has a fault you leave that one off and the other still works, if it was a ring main you would lose all the sockets until a professional can get out and test and locate fault and fix it

 

[Longhorn]

I don't have nearly enough MCBs for that. Apart from the kitchen (ring) the whole house is on radials, many of which are sharing MCBs. This is another reason for the ring idea. If I could join those newer radials to form a ring I could eradicate many of the older radials and free up some MCBs.

 

[Sparkingmad]

Sparkingmad; you're absolutely right, simply extending the radials to add extra sockets would be marginally easier than creating an actual ring as it would save me joining them together, but I didn't know this was possible. My theorising, and the reason for the question, was based on my longterm believe of 2 things: 1) You can't spur off of a spur, and 2) the ring main was designed just after the war when copper was at a shortage and a ring can be made in 2.5, thus saving copper (I infer from this that radials were heavier gauge before the ring was invented).

Based on those 2 points I reasoned that as these radials are 2.5 (and thus similar to a spur in handling capability, albeit directly from the CU and not from an existing socket) it would be safer, and indeed more in keeping with ring spec, to just join them together and form a ring, which would also allow me to add more sockets ad hoc.

As far as loading goes, they are all upstairs right now, so mostly bedroom stuff (phone chargers, toothbrush charger, etc, and periodically the vacuum). Heaviest draw would be my iMac and standard lamps plugged into the walls. Although there is a possibility to incorporate a connection to my shed, so there may be a little heavier draw on it with certain power tools.

This is way way before my time and the cable was imperial and not 2.5mm. I think the recommendations then still allowed the use of the BC plug adaptor to connect your iron to the light pendant . Plus the wire was tin plated back then and let's be honest you would only have had 1 maybe 2 single sockets in each room. Most people now have more sockets behind their TVs than they had in the whole house in the 40's and 50's. I'm sure there are a few here that remember those days

 

[Longhorn]

Well, I guess that's true of many of us here. If I'm safe just to extend the radials ad nauseam then it looks like we're in business. I'll make sure there's a 20A MCB on each.

 

[telectrix]

Well, I guess that's true of many of us here. If I'm safe just to extend the radials ad nauseam then it looks like we're in business. I'll make sure there's a 20A MCB on each.

best option would be a bigger CU. if you have. say. a 6 way, get a local spark to quote you for a 10/12 way dual RCD or RCBO board.

 

[Longhorn]

The board we have is a 10-way dual RCB MK board.

 

[telectrix]

that should be big enough for most houses. where you live? fawlty towers?

 

[Sparkingmad]

Might be worth getting a sparks in to test some of the other radials you may be able to convert some of those to ring mains to free up some room in that board. Lol

 

[Longhorn]

We seem to be going around in circles.

There are 10 MCBs, but one is the kitchen ring, one is the cooker, one is the alarm. So now we're down to 7. If each radial should have it's own MCB then theoretically we should have no more than 7 radials. Surely it would be better to have, say, an upstairs ring and a downstairs ring and maybe an outbuilding ring, and still have 4 MCBs left over for other things?

If I can connect the two newer radials as referenced in my original post I can add at least 3 more sockets along the way in very usable places, I just wanted to know it it was safe and legal to do this and whether it constituted notifiable work.

 

[telectrix]

altering circuits is not notifiable. a new circuit is.

 

[Deleted member 26818]

When rings were first introduced, sometimes two 15A radials were joined together to make the ring. If you were lucky, the two 15A fuses would be replaced with one 30A fuse.

 

[Mark42]

Hi Longhorn
What no one has explained yet is why radials can be safer: what you've heard about not spur-ing off spurs only applies to ring circuits, because rings are protected at 32A, so long lines of 2.5mm cable running spurs might mean - if multiple loads are plugged into the spurs - overloading that run of single 2.5mm cable. Genuinely possible, and genuinely dangerous.

Whereas radials on 2.5mm are never protected above 20A (sometimes 16A) so even if you have a hundred sockets on the thing, you can't overload the cable as the breaker would trip first. (Assuming the circuit is not stupidly long, but that's enough detail for now.)

Personally I dislike ring final circuits, and consider them outdated. Others will disagree. In your case I'd definitely go for keeping the two existing radials. You may add as many extra sockets locally as you wish. Make sure you have (or add) 30mA RCD protection. And do NOT connect the two radials together at any point.

Note: In my own house (which is 500 years old and made of wood) I did the opposite to what you're suggesting. I inherited only two 32A rings for the whole place. I started by splitting these rings, junking the 32A MCBs, and converting them to four radials, each with a 16A RCBO.

 

[Deleted member 26818]

Outdated?
If RFCs are outdated, what does that make Radials, which RFCs replaced?
It's not fashion week.