Radial Circuit in Garage - Change to Ring?

crappy · 23 Jan 2022

Evening folks,

I have a radial circuit in the garage which is fed from a single 16A breaker through 2.5T&E. It has 6 x 2-gang sockets on it. CU is in one corner of the garage and the final socket is the opposite corner. Total run is around 30m I estimate.

The garage CU is fed from the house from a 40A MCB over 6mm armoured and into the CU which has a 63A ELCB.

I want to put some more sockets on the "blank" wall and easiest would be to have another run from the CU through to the new sockets (I will add 3 x 2 Gang) and then on to the end of the radial.

Can I simply do this and change the radial to a ring and the 16A to a 32A?

C

JohnW2 · 23 Jan 2022

crappy said:
... I want to put some more sockets on the "blank" wall and easiest would be to have another run from the CU through to the new sockets (I will add 3 x 2 Gang) and then on to the end of the radial. ... Can I simply do this and change the radial to a ring and the 16A to a 32A?

You could do that.

However, if a total of 16A (at a time) is enough for your needs, you could run another radial ('a branch') from the CU and leave the 16A MCB as it is. Wiring-wise, the only difference would be that the 'ends' of the two radials (strictly, two branches of one radial circuit) would not be joined together to make it a 'ring'.

Kind Regards, John

crappy · 23 Jan 2022

Thanks.

Truth be told - it's unlikely I will be using that much that a ring really needed. Power tools etc and it's only me.
I thought of making it a ring because it would be safer.

Another radial would also work - I have one spare space in the CU for another 16A MBC so doable.

I would safe around 3m of T&E so not really a cost thing.

crappy · 23 Jan 2022

I just re-read your comment and see you and I talking different things. So you can have multiple radials of a single 16A breaker but clearly you're always limited to 16A.
It's not a spur off the radial but direct from the CU.

Ok, that might work too then and I can keep my one spare space in the CU.

thanks

JohnW2 · 23 Jan 2022

crappy said:
I just re-read your comment and see you and I talking different things. So you can have multiple radials of a single 16A breaker but clearly you're always limited to 16A. ... It's not a spur off the radial but direct from the CU. .... Ok, that might work too then and I can keep my one spare space in the CU.

The thing is that a radial can 'branch' anywhere along its length, and that includes 'at the CU'. Hence, if you have two cables, each supplying a number of sockets, originating from (the same MCB in) the CU, then that is just one "radial circuit" which happens to 'branch' st the CU.

However, as we've both said, if you did it that way, you would be limited to a total of 16A, across both 'branches' and all sockets.

Joining the ends of those two branches of the radial together would make it a ring, and you could then upgrade the MCB to 32A.

Kind Regards, John

333rocky333 · 23 Jan 2022

Bear in mind though some 240v power tools or even 110v transformers can trip 16a mcbs despite the running load being substantially less, due to the start surge

crappy · 23 Jan 2022

Thanks. Appreciate it.

I'll take a look over the weekend again and see where I need the sockets and decide to make it a ring or just branch or extend the radial.

@333rocky333 - noted.
If I end up with the radial and it gives me issues on tool start-up when there is other load on (I have a few Pb battery chargers etc) then I will be forced down the ring route.

JohnW2 · 23 Jan 2022

crappy said:
Thanks. Appreciate it. I'll take a look over the weekend again and see where I need the sockets and decide to make it a ring or just branch or extend the radial.

Fair enough. You're welcome.

crappy said:
@333rocky333 - noted. ... If I end up with the radial and it gives me issues on tool start-up when there is other load on (I have a few Pb battery chargers etc) then I will be forced down the ring route.

As I said, if yopu find yourself in that position (unlikely, since you presumably haven't had the problem so far), then, as I said, you would simply need to join together the end sockets on each of the two 'branches' (to 'create a ring') and then upgrade the MCB to 32A.

Kind Regards, John

EFLImpudence · 23 Jan 2022

Or - don't do that and upgrade to 20A or 25A anyway.

Or - have two radials of 20A or 25A.

JohnW2 · 23 Jan 2022

EFLImpudence said:
Or - don't do that and upgrade to 20A or 25A anyway. ... Or - have two radials of 20A or 25A.

Yep, that's two more possibilities.

Kind Regards, John

crappy · 24 Jan 2022

EFLImpudence said:
Or - have two radials of 20A or 25A

Can a radial be 25A?

plugwash · 24 Jan 2022

There is no fundamental reason why not.

But 25A is pushing pretty close to the limit for 2.5mm² T&E, pay careful attention to any grouping factors or adverse installation methods.

EFLImpudence · 24 Jan 2022

crappy said:
Can a radial be 25A?

I think you are getting the words mixed up.

Do you have a cooker or electric shower?

flameport · 24 Jan 2022

crappy said:
Can a radial be 25A?

Radial circuits can be any rating, provided the cable is suitable for it. Almost all circuits are radials.

A ring is just one specific circuit design created to meet very specific requirements that existed many decades ago.
There is nothing magical, safe, useful or desirable about it. It's not the normal method of installing wiring, and in most modern installations it's totally pointless.

crappy · 24 Jan 2022

I guess my statement on "can it be 20/25A" meant "on existing 2.5mm".

I thought a ring was required to allow for higher loads (up to 32A) on 2.5mm as larger becomes expensive / cumbersome. Totally appreciate that it could just be a radial (as in, open ended).
So it's ok then to a another radial, using standard 2G sockets, with 4mm and do 20A on that?

Yes, cooker, power-shower, lights(?) are all radial.

Why are rings pointless today?
I know the argument that should there be a cable break then the user won't know and the 2.5mm could be taxed beyond 16A designed and therefore a fire hazard.

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Radial Circuit in Garage - Change to Ring?

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