Shed

[antighsiothail]

Ok got that use a switched fcu instead of an ordinary light switch and use a3amp fuse in it and yes I understood to use what I said in the feed to the shed namely the weatherproof rcd fcu. Think I'm sorted now, thanks again.

 

[deadshort]

It's sunny outside ! what the hell

DS

 

[Taylortwocities]

I understood to use what I said in the feed to the shed namely the weatherproof rcd fcu..

Just I am not sure what you mean there. You said that the ring final was already RCD protected. you do not need another one.
You need a 13A FCU before the socket and a 3A FCU as the light switch.

Like this

JB on ring ------ 13A FCU ------ socket ------- 3A FCU ------ Lights

The 13A FCU stops you creating the naughty spur off a spur syndrome.

 

[antighsiothail]

That ....JB on ring ------ 13A FCU ------ socket ------- 3A FCU ------ Lights

Was my intention to a T, but then I saw the combined unit rcd/fcu for an extra fiver and thought what the hell, always been a bit of a belt and braces sort.

 

[Taylortwocities]

Up to you, but it wont give you any more protection.
There's no guarantee that the shed RCD will trip before the house one.
Operating the test button on the shed RCD will trip half the hoiuse electrics too.

I cannot see there's any point.

 

[antighsiothail]

Ok got you, thanks for all the advice on here.

 

[JohnW2]

Up to you, but it wont give you any more protection. ... There's no guarantee that the shed RCD will trip before the house one. ... I cannot see there's any point.

There's obviously 'no point' if the existing RCD works satisfactorily. However, the OP said that (given the small marginal price difference) he was proposing to use an RCD FCU as 'belt and braces'. Given the suggestion that maybe some 7% of in-service RCDs may be faulty (i.e. not work when they should), I would not necessarily knock the idea of 'belt and braces' protection, if the OP would feel more comfortable with that.

Operating the test button on the shed RCD will trip half the hoiuse electrics too.

It might. As you know, the test buttons of 'standard' RCDs (as used in CUs, and as standalone devices) do not introduce faults to earth, so that pressing the test button should not affect any other RCDS in the circuit. However, for some reason, it seems that at least some RCD sockets and RCD FCUs do introduce a fault to earth, so would/could cause other RCDs to operate.

Kind Regards, John

 

[Iggifer]

However, for some reason, it seems that at least some RCD sockets and RCD FCUs do introduce a fault to earth, so would/could cause other RCDs to operate

Always tempting when I see RCD FCU's and sockets in public places to press the test button, knowing full well it's likely to take an upstream RCD out with it