Extending socket circuit to a ring?

I have a workshop with its own small fusebox. There are two double sockets wired like this with 2.5mm^2 T&E:
Fusebox (30A fuse) -> T&E -> first double socket -> T&E -> second socket.
Is there any reason I shouldn't continue the circuit from the last socket back to the fusebox (adding the odd socket here and there) to turn it into a ring?
Thanks,
Chris
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No reason why not to. Just make sure that all the cable is properly protected.
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The existing cable is neatly clipped to the wall near the ceiling, and comes down vertically for each socket at chest height. (The walls are bare brick) Is that "properly protected", or should it be shielded?
Thanks for your answer!
Chris
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I'd certainly run it in conduit in a workshop, and use metal clad fittings. But IMHO only the vertical runs would need protecting.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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That's what had been done (and I continue to do when I extend) in my garage/workshop. Everything within reach is in trunking, wires across the ceiling on joists or trusses are just clipped/tied.
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Chris wrote:

No - that should be fine.
In fact I would suggets that you _should_ extend to a ring since you are quite likely to exceed the current limit for the cable before the fuse blows should a fault occur (a 16A or 20A fuse would be more normal on a radial circuit like this). As a ring however, the 30A fuse will be fine.
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Ok, thanks.
The fuse situation seems a bit unusual to me anyway: The garage is fed from a 30A fuse in the house by a heavy duty outdoor cable. In the garage is a small CU, with the workshop feed on a C20 MCB. Finally in the workshop is a small CU with two circuits; the 30A socket circuit and a 15A lighting one.
So if I understand correctly, the garage fuses are pretty pointless, unless/until the MCB (and probably cable) in the garage are upgraded.
Chris
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That does seem a bit of a 'growed like topsy' setup. It's not particularly bad or dangerous though. The most significant problem will be the lack of discimination between the workshop CU and the garage CU (and/or the lighting circuit, see below).
Given that the whole of the outside wiring is fed from a 20 amp MVB in the garage you are OK extending the sockets wiring without making it into a ring as a 20 MCB is the correct rating for a radial circuit of this sort. I see little point in changing it to a ring unless you really need to uprate the total load capability.
The 30A MCB (or is it a fuse?) in the garage is, as you say, superfluous but the lighting one isn't. That's my one worry about the system, a 15 amp circuit isn't correct for lighting and most lights are only rated to be used on 6 amp or (sometimes) 10 amp circuits.
Personally I'd retire the CU in the workshop, leave the power circuit as a 20 amp radial protected by the MCB in the garage and run the lights from an FCU with a 5 amp fuse in it.
Is the wiring in the garage and workshop protected by an RCD? It certainly should be. The neatest solution (if it isn't protected) would be a combined 20 amp RCD/MCB in the garage CU.
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Ok.
Ok. We may end up putting washing machine/dryer in there at some point, as well as an electric heater, so I'll have to work out how much load that all comes to.

There's a 30A fuse in a carrier at the house end, and a rewirable 30A cartridge in the workshop. The garage in the middle has MCBs - not very consistent!

I see. These are a pair of striplights (which need replacing anyway, but that's another job).

That would certainly simplify things a bit.
If I need to up the load in the workshop, I'd then presumably need to do something like wiring it as a ring starting and ending at the garage CU.

Yes, the garage unit is an RCD.
Thanks very much for the detailed reply!
Chris
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That might total more than 20 amps but are you likely to have both on at the same time? Assuming 3kw (12 amps) for the washing machine and dryer then a 1kw fire would be fine, a 2kW one would be marginal.

Assuming the feed to that point is OK, yes. In fact since there's a 30 amp fuse in the house protecting the feed the garage CU is possibly redundanat though it's probably worth keeping it. I think (as I said before) I'd get rid of the workshop CU and keep the garage one with the MCBs as they will give you discrimination with the feed being from a 30 amp fuse in the house.
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In fact, you must do this to make it compliant. A 2.5mm radial clipped direct should be fused at 20A. A 2.5mm ring can be fused at 30A. Better still, use a B32A RCBO instead of a fuse. Much safer, particularly for power tools.
Christian.
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Actually, thinking about it, it might just be regarded as compliant anyway (although certainly not best practice). Because you are allowed to assume 13A from a double socket, the maximum current flowing can be assumed to be below 26A. A single 2.5mm clipped direct can carry this. It is still vastly superior to fold back into a ring.
Christian.
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... but it turns out that the whole thing is protected by a 20 amp MCB in the garage so that 30 amp one in the workshop is a red herring really.
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wrote:

anyway
assume
be
vastly
Is it about now someone will start quoting the reg that forbids this set up.
Adam
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wrote:

<snipped>
up.
All I'd say is, the best and safest way to go is to take a proper switched sub main from the house and make the consumer units in the outbuildings a separate installation in their own right. That way, anything happening in the outbuildings will not have as big an impact on the house system.
But that's just me. :-))
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wrote:

HEE HEE !!!! Sorry !!! Wrong thread.
(i'll get me' coat) :-))
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No, the general rule is to assume 20 A load on a double socket (per the BS 1363 test requirement). That stacks up with the 'double socket ton a 2.5 mm^2 unfused spur' rule for standard final circuits.
In the current case in question it's unlikely that more than 5 kW would be required overall and I'd recommend changing the fuse to 20 A.
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Andy



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