Fused spurs

[greenstarthree01]

Hi all, bit of an ‘is this ok’ question, or could you suggest a better way....!?

Want to add a socket in a hallway, but the tidiest socket to spur from already has a fused spur from it, supplying an alarm. The alarm spur is fused at 3A so not suitable for a double socket, but I don’t want to lose protection of the alarm either.

Could I add a 13A fused spur before this, and supply the new socket directly from that, plus the original 3A fuse? So it would be:

Socket on ring

\/​

13A fused spur
\/‘’’’’’’’’’’’’’’’’’’’’’’\/​

New socket - - - - - - 3A fused spur

\/
alarm​

Sorry if that doesn’t come out visually, tried to use punctuation so it spaces right, hopefully it’s understandable!
I’ve read that 2 spurs from one isn’t allowed, but I’ve also read that with a fused spur you have a lot more options.

what do you think, is there a better way I’m missing?!
Thanks all

 

[terryplumb]

You can go from the socket to a FCU and from the load side to a second fcu ( for alarm) .The second FCU would have the alarm connected to its load side and from its supply terminals take a cable to the new socket. All cables to be 2.5mm² T&E on the supply side (So all cable from the original socket ) the first FCU fused at 13 amp ,so limiting the total current running thru the spur cable.

 

[AndyPRK]

This is where I try and use common sense !

Having 2 spurs from the same point, where one is such a small load (eg light or alarm) I put 2 spurs from the same point in my own house.

Assuming I can get the 4 cables into the same point of course.

 

[greenstarthree01]

@terryplumb
Just to clarify, you’re saying spur from the supply side of the second FCU, as opposed to the load side of the first?

Is there a technical / regulation difference between doing this and spurring both off the load side of the first as in my example? Seems like it does the same thing but just curious


@AndyPRK
It does seem overkill to my relatively untrained eye, but I’ve seen 4 cables in a 13A socket before and it.... didn’t fill me with confidence!
Everything is in a cupboard under the stairs so I don’t mind if 2 FCUs is the answer. It can be inelegant, as long as it’s right!

 

[terryplumb]

@terryplumb
Just to clarify, you’re saying spur from the supply side of the second FCU, as opposed to the load side of the first?

Is there a technical / regulation difference between doing this and spurring both off the load side of the first as in my example? Seems like it does the same thing but just curious

The first FCU introduces a 13 amp fuse ,so all downstream is connected to its load side across the fuse. Hence limiting the current drawn thru the spur.
If you connected the socket to its supply side ,you would be negating that protection.
If you took a spur from the ring final socket to a FCU and then ,from its supply terminals to a socket ,you would be running a spur from a spur which the regs don't allow.

 

[winston1]

You don't need a fused spur for your new socket, it can be spurred direct. As Andy says your new socket and fcu for the alarm can both be spurred from the existing socket.
There is no rule saying you can't have 2 spurs from the same point.

 

[greenstarthree01]

If you took a spur from the ring final socket to a FCU and then ,from its supply terminals to a socket ,you would be running a spur from a spur which the regs don't allow.

Oh, but isn’t that what the alarm is doing now? Spur from ring socket, to FCU, to alarm? Different rules for a wired appliance as opposed to a socket?

 

[winston1]

Oh, but isn’t that what the alarm is doing now? Spur from ring socket, to FCU, to alarm? Different rules for a wired appliance as opposed to a socket?

No that is one spur feeding one fcu.

 

[JohnW2]

Oh, but isn’t that what the alarm is doing now? Spur from ring socket, to FCU, to alarm? Different rules for a wired appliance as opposed to a socket?

No, just one set of rules.

As has been said, you can have as many spurs as is physically achievable from one socket on a ring. If a spur supplies a socket (with no intervening FCU), then you are only allowed that one socket on that spur (although, if you could get all the conductors into the socket's terminals, you could have a second socket on a second spur, originating from the same place as a first spur).

On the other hand, if a spur supplies (the supply side of) a FCU, then you can connect whatever you want (and as many of them as you want) to the load side of that FCU, since the total current in that spur is 'limited' (albeit not literally!) to 13A by the fuse in the FCU.

Kind Regards, John

 

[aptsys]

You don't need a fused spur for your new socket, it can be spurred direct. As Andy says your new socket and fcu for the alarm can both be spurred from the existing socket.
There is no rule saying you can't have 2 spurs from the same point.

Exactly. The OP is overthinking this - Just spur for the original socket on the ring. There's no issue with two spurs from one point on a ring.

 

[sparkwright]

Another option is to simply extend the ring from the original socket, so both the new socket and the alarm point will have two cables feeding them. (There would have to be a joint at the original socket to achieve this.

This may seem like effort, but will make future additions simpler.

To be fair to the op, just about every textbook will tell you only to spur from a point on the ring only once.

 

[greenstarthree01]

Thanks everyone for the replies, sorry haven’t been able to check in until now.

So the consensus seems to be the new socket can be added without an FCU, if I can get 4 cables into the terminal of the original socket.

If not, could I still add a 13A FCU just to ‘spread’ the terminals? So like @terryplumb suggestion, from the load side of a new 13A FCU to the supply side of the 3A alarm one. Then from the supply side of the 3A alarm FCU to the new socket?

I wonder what’s the reason that there’s so much written advice to not take multiple spurs from the same point? Is it related to the guidance about not having more spurs than ring sockets?


@sparkwright i have thought about extending the ring but wouldn’t that be notifiable? Thought I’d read that somewhere...

 

[terryplumb]

In my opinion the potential issue ( Although not in your case ) with adding two spur cables from a ring final circuits socket ,and connecting double sockets to each spur cable ,is the donor sockets terminals ability to cope with the combined potential loads. If I recall correctly most are rated 16 to 20 amps.
Would be interested to know others opinions.

Edited to include terminals.

 

[winston1]

I have thought about extending the ring but wouldn’t that be notifiable? Thought I’d read that somewhere...

No, not notifiable. Even more ignorance.

 

[winston1]

from the load side of a new 13A FCU to the supply side of the 3A alarm one. Then from the supply side of the 3A alarm FCU to the new socket?

No, if you do that the new socket would only have 3 amps available.

I wonder what’s the reason that there’s so much written advice to not take multiple spurs from the same point? Is it related to the guidance about not having more spurs than ring sockets?

Ignorance.

There is no rule saying you can't have more spurs than ring sockets. It is possible to have a ring round the loft with every socket dropped down as a spur.