Fused spurs

[DominicB]

Hi guys,

I understand that when you spur off a circuit if you have a 1 socket then you do not need to have it fused but if you have 2 or more it needs to be fused.

What is the principle behind this?

Thanks

 

[Leesparkykent]

so you cant overload the section of wiring between the ring final and the 1st socket you've spurred off to.

 

[Pete999]

Hi guys,

I understand that when you spur off a circuit if you have a 1 socket then you do not need to have it fused but if you have 2 or more it needs to be fused.

What is the principle behind this?

Thanks

What he said

so you cant overload the section of wiring between the ring final and the 1st socket you've spurred off to.

 

[Pete999]

What he said

What he said

 

[DominicB]

Thanks for the replys so I get that it would be over loaded but why was that?

 

[Darkwood]

Ring mains are protected traditionally by a 30amp or 32amp overload protection, this is more then a standard 2.5mm cable can carry but because it's in a ring, the current is divided down both paths meaning the protective device would see an overload and trip before any or the cable in the ring is overloaded. The issue though is if you introduce a spur, it is then possible to overload that stretch of cable given that it's been protected by a 32amp so to ensure this is minimised, regulations will have you fuse down when multiple points are present on the spur thus usually limiting it to the 13amp fuse or what ever appropriate size fuse you fit (nothing stopping you fitting a 16 or 20amp inline if the cable calcs are met on that particular spur but requires a bulky point for your mcb as oppose to a traditional cheap 13amp fused spur).

 

[DominicB]

That makes sense, thanks!