Does the following installation require a fused 13A switched spur.

Does the following installation require a fused 13A switched spur before the SWA.

2.5mm T&E from ground floor ring to IP rated box on outside wall.

then

SWA 2.5mm from Ground floor ring to garage unit (40A RCD) 16A MCB.

then

from the garage unit to two metal clad double socket outlets.

Thanks

Yes. Otherwise your spurring off with 16 amps

Yes as you are effectively spurring more than one point from the ring final.


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Yes because you are spuring to two double sockets.

If i was to change the 16A in the garage unit to a 10A would this meet regs?

The 16A MCB is irrelevant.
It's the two double sockets that are a problem.
Your options are:
Use a larger cable 4mm˛ or 6mm˛.
Use one double socket.
Make the spur an extension to the ring.
Use a 13A FCU.

Don't get me going about 4mm radials off a ring!

Mmmm. sorry Im well confused??!!?

Why would a 10A mcb be irrelevant?
The two skt outlets would be protected by 10A instead of 13A??

Its been a long day sorry

Sorry yes, if the distance from the origin of the spur is less than 3m, then yes you could use the 10A MCB.
I was assuming the distance would be greater than 3m.

It is about 8 meters. Does it make any difference that it is SWA 2.5mm Ref Method C.
??
I dont mind adding a 13A FCU next to the double socket at origin, just more mess for the customer.

I could even take out one of the metal clad skt outlets but its all been done in SWA and looks rather nice!

IMHO, as far as the spur from a spur issue is concerned, I think I would be hard pressed to find a regulation that says it can't be done. There are a few other issues that may be relevent.
1)The existing socket ring should already be RCD protected at 30mA. Adding another RCD would not provide any discrimination for that circuit.

2)If the use of metal clad sockets is an indicator that the garage is subject to external influences that would require more protection than a standard white outlet offers, then I would personally not want to suffer the potential inconvenience of the main board RCD tripping due to garage earth leakage.

3)The garage is presumably a detatched building and may require it's own earth system.

Originally Posted by sivoodoo

It is about 8 meters. Does it make any difference that it is SWA 2.5mm Ref Method C.
??
I dont mind adding a 13A FCU next to the double socket at origin, just more mess for the customer.

I could even take out one of the metal clad skt outlets but its all been done in SWA and looks rather nice!

Where there is a reduction in current carrying capacity of a conductor, either because of reduced CSA or a change in installation methods, overcurrent protection should be provided within 3m of where the reduction occurs. This can be ommited if appropriate overcurrent protection is provided at the origin of the conductor.
You can omit overload protection if there is no likelyhood of overload occuring, and fault protection is provided at the origin of the conductor.
As such, if you beleive that there is no likelyhood of overload occuring due to the use of a 10A MCB, and the conductors are protected against fault current by the ring CPD, then yes you could use the 10A instead of the 16A MCB.