Cable sizes

[JohnW2]

Is it better when taking a spur to use a fused box? ie cut the cable which is currently a spur install a fused box and then run the new spur from that?

I'm afraid that doesn't help. An FCU that could take a 13 amp fuse is really no different from a single socket with a 13 amp fused plug in it.

I'm not totally sure what everyone is saying here. If the OP is suggesting inserting a 13A FCU fairly close to where the spur joins the ring (and before any sockets/loads), then he can (within reason) run as many sockets as he wishes from that FCU, and even in 1.5mm² cable (after the FCU) if he so wishes. Indeed, that's explicitly one of the arrangements shown in Appendix 15 of the regs.

What he cannot do is add a FCU after any load/socket on the spur.

Kind Regards, John.

 

[Risteard]

≥2.5mm²

Even >=2.5 would have done.

 

[ban-all-sheds]

By >2.5mm I mean greater-than-or-equal-to. ASCII does not have greater-than-or-equal-to sign.

But there's one in the Special Characters set available just two mouse clicks away - why couldn't you be bothered?

 

[Space cat]

If the OP is suggesting inserting a 13A FCU fairly close to where the spur joins the ring (and before any sockets/loads), then he can (within reason) run as many sockets as he wishes from that FCU, and even in 1.5mm² cable (after the FCU) if he so wishes. Indeed, that's explicitly one of the arrangements shown in Appendix 15 of the regs.

What he cannot do is add a FCU after any load/socket on the spur.

I find that rather odd. If a socket, especially a double, and an FCU are connected to the same spur, it makes no difference which is closest to the ring. The cable between the ring and the first load is potentially overloaded either way.

One way it can be done is by breaking into the cable before any sockets or other loads (like JohnW2 says) but transferring the rest of the spur to the load side of the FCU. After that you can add your new socket - and more if you like - to the load side and do it with 1.5mm cable too.

There are a few things to beware of:

1) Make sure that the cable you cut into really is a spur and not part of the ring. You'll create no end of problems if you insert a 13 amp fuse into your ring.

2) Having located a spur cable, make sure you put the FCU in the right way round, ie with the Line side towards the ring.

Also be aware that the total load on all the sockets fed from the FCU cannot exceed 13 amps or you'll get through a lot of fuses!

 

[Monkeh]

AIUI ring circuits must be in >2.5mm cable and that includes unfused spurs. Except for MICC of course.

So your saying you cant use 2.5mm cable for ring final circuits.

By >2.5mm I mean greater-than-or-equal-to. ASCII does not have greater-than-or-equal-to sign.

So? ASCII is archaic and inadequate. Stop using it.

 

[JohnW2]

If the OP is suggesting inserting a 13A FCU fairly close to where the spur joins the ring (and before any sockets/loads), then he can (within reason) run as many sockets as he wishes from that FCU, and even in 1.5mm² cable (after the FCU) if he so wishes. Indeed, that's explicitly one of the arrangements shown in Appendix 15 of the regs.
What he cannot do is add a FCU after any load/socket on the spur.

I find that rather odd. If a socket, especially a double, and an FCU are connected to the same spur, it makes no difference which is closest to the ring. The cable between the ring and the first load is potentially overloaded either way.

I think that either I wasn't clear enough or else you have misunderstood me. If the entire spur circuit is fed from the ring via a 13A FCU, that limits the total current in that spur circuit to 13A, hence won't even overload 1.5mm² cable, let alone 2.5mm² cable. Most people would use 2.5mm² cable between the ring and the FCU, but even that is not strictly necessary, since (under most circumstances) protection by the downstream 13A fuse is regarded as acceptable - so 1.5mm² could usually theoretically also be used for that. However, if the FCU came after the first socket, the totally current in the first run of cable from the ring could be 13A PLUS the load on the first socket (theoretically 13A max, although we all know that some people plug more than 13A worth of load into a double socket!).

One way it can be done is by breaking into the cable before any sockets or other loads (like JohnW2 says) but transferring the rest of the spur to the load side of the FCU. After that you can add your new socket - and more if you like - to the load side and do it with 1.5mm cable too.

That's what I was proposing - so I'm still a bit confused by what you say above.

Kind Regards, John

 

[EFLImpudence]

By >2.5mm I mean greater-than-or-equal-to. ASCII does not have greater-than-or-equal-to sign.

Do you have Windows?

Start > All programs > Accessories > System tools > Character map

 

[Space cat]

I think that either I wasn't clear enough or else you have misunderstood me.

Maybe both. The first time I read your post, I interpreted the phrase "inserting a 13A FCU" as "adding a 13A FCU" in the same way as you would "add" a socket to a spur. I've just read it again and, with the benefit of (subliminal) hindsight, it's obvious what you meant.

 

[JohnW2]

I think that either I wasn't clear enough or else you have misunderstood me.

Maybe both. The first time I read your post, I interpreted the phrase "inserting a 13A FCU" as "adding a 13A FCU" in the same way as you would "add" a socket to a spur. I've just read it again and, with the benefit of (subliminal) hindsight, it's obvious what you meant.

No problem. That being the case, I think we're both saying the same thing!

Kind Regards, John.