fused spur of a fused spur from ring main

n180 · Apr 13, 2016

Hi guys,

whats the regs regarding fused spurs?

Is it ok to have, from the ring main, a fcu, feeding another fcu, feeding another fcu etc or is it only one fcu per socket like a normal spur?

I've got a fcu spur from the ring main for a fan in the bathroom. I need to fit in an electric radiator in the bathroom. I'm thinking of taking the feed for the radiator from the FCU spur of the fan. Will that be ok?

Thanks in advance.

vwes59 · Mar 31, 2021

Ive just done this very thing. 13A FCU off a ring for outside socket, then 5A FCU off that for a 20W security light and PIR

timhoward · Mar 31, 2021

I’m not suggesting that the OP takes this post too literally but it’s interesting how readily we all comment about radials off a ring not being permitted. Being totally pedantic it’s not quite the right language. I’ve never found a reg saying that (look at 433.1.204 carefully). The appendix diagram seems to be the main guidance that is followed.
The main issue is that the person installing it can’t be in control of the loads for the lifetime of the installation so wise practise is not to run multiple socket points off a spur but I don’t believe it is explicitly prohibited.
Ducks for cover!

timhoward · Mar 31, 2021

Flanders said:
Just a thought but i know the regs says you cant feed more than one point from a ring but what is the difference between two 13 amp fcu and 1 twin socket especially if you are only putting small loads on them and fitting 3 amp fuses

I'd have said the regs do let you have more than one socket on a radial off the ring if the loads are known (though I accept it is rarely done, not widely understood to be the case and I've never done it), and there is therefore no difference if it is FCU's or sockets.
It's incredibly rare to see this done - I've seen it once in a hotel lobby with single floor sockets and a 40w table lamp on 4 tables, all on a spur of a RFC. It blew my mind at the time, but my conclusion was that it is allowed. Had they all been wired into FCU's that actually makes it safer as the loading is even more locked down.