Does this wire diagram meets regulation?

[Whynot123]

We've recently moved house (well, it was in April and we're still decorating so I still like to think of it as recently).

I'm doing some like for like replacements in the kitchen (old for new sockets) and I'm wondering if this set up meets the regulations. It was like this when I got here, promise.

Here's a diagram to describe it a little easier. The issue is from a double socket on a ring main. There is a spur from it that goes to a SFCU, which powers the boiler. This seems fine but then from the SFCU there is a single socket. From the single socket we then leave the kitchen and go through to the conservatory where there are two further SFCU's that go on to power double sockets.

Is this all above board? If it is, that's great and I was wondering what the regs were for powering the socket off the Boiler FCU? For example, can it come from the Line IN and therefore turning off the boiler SFCU will not turn off the power to the socket next to it and the conservatory. Or does it need to come off the Load?

Thanks for any help.

 

[EFLImpudence]

No, this is what you must have:

The 13A FCU must protect everything. That is turn on and off everything.
The 3A will, as you asked, just turnoff the boiler.

 

[JohnW2]

Is this all above board? If it is, that's great and I was wondering what the regs were for powering the socket off the Boiler FCU? For example, can it come from the Line IN and therefore turning off the boiler SFCU will not turn off the power to the socket next to it and the conservatory. Or does it need to come off the Load?

It is 'above board' (but not very practical), since everything is on the load side of the initial 13A FCU.

With that arrangement, if the single socket is fed from the load side of the boiler SFCU, the total amount of current available for the boiler and the 5 socket outlets (1 single + 2 doubles) will, of course, (by virtue of the fuse in the boiler SFCU) be limited to 3A - which is unlikely to be adequate for your needs. It would be better (allowing a total of 13A for bolier + sockets, which may still not be enough for you) to feed the single socket (hence also the two doubles) from the load side of the first SFCU (or, equivalently, and probably more conveniently) the supply ('in') side of the boiler one. The SFCUs feeding the two double sockets are redundant and unnecessary, and could be removed.

Edit: I made a mess of that, because I was unwittingly looking partially at EFLI's diagram, not yours - hence the reference to the 'first/initial SFCU'! I'll edit this accordingly in a moment!
Edit2: OK - I agree with EFLI's diagram, but would point out that the single socket should be fed from the supply (not load) side of the boiler's FCU (otherwise boiler+sockets would be limited to 3A total). As above, even 13A (total) may not be enough for all your sockets - only you will know thgat.

Kind Regards, John

 

[Whynot123]

Thanks very much for your replies.

That's great, and if the worst comes to the worst I just need to add the 13A FCU. However, is there any chance of slightly jigging the existing set-up to solve the problem?

From what I understand we can spur off a socket to a another socket without a FCU. Anything further we would need FCU's. I'm wondering if there's anything I can do to the existing circuit. How about if the spur from the double kitchen socket went straight to the single socket instead of the boiler SFCU. Then from that single socket onto the Boiler FCU. Then from the single socket (or boiler FCU) to the conservatories FCU's.

This way, the only thing that isn't protected is the first single socket (the spurred socket) and everything else is projected by it's own FCU.

 

[JohnW2]

.... However, is there any chance of slightly jigging the existing set-up to solve the problem?

From what I understand we can spur off a socket to a another socket without a FCU. Anything further we would need FCU's. I'm wondering if there's anything I can do to the existing circuit. How about if the spur from the double kitchen socket went straight to the single socket instead of the boiler SFCU. Then from that single socket onto the Boiler FCU. Then from the single socket (or boiler FCU) to the conservatories FCU's.

Unfortunately not. If you have an 'unfused spur' (i.e. straight from the ring, with no FCU), you are only allowed to supply one 'thing' (single socket, double socket or FCU) from that spur - i.e. you can't extend to anything else from that first 'thing'.

It makes a fair bit of sense. The idea is to restrict the total current that can flow from the ring down a spur. With a fused spur, the first thing the spur hiots is an FCU, which limits the total current to 13A, regardless of how many sockets/whatever you connect downstream of that FCU. With an unfused spur, the current limitation is achieved by restricting you to supplying just one socket (single or double), or a downstream FCU. What EFLI has proposed is probably the simplest solution.

Kind Regards, John

 

[Adam_151]

From what I understand we can spur off a socket to a another socket without a FCU. Anything further we would need FCU's.

Thats correct, an unfused spur may feed one point only.

I'm wondering if there's anything I can do to the existing circuit. How about if the spur from the double kitchen socket went straight to the single socket instead of the boiler SFCU.

That is alright so far

Then from that single socket onto the Boiler FCU.

That would then be technically incorrect according to standard circuit arrangements, however as the load of a gas fired boiler is near here no there, you could probably justify the arrangement

Then from the single socket (or boiler FCU) to the conservatories FCU's.

That certainly cannot be permitted

This way, the only thing that isn't protected is the first single socket (the spurred socket) and everything else is projected by it's own FCU.

You are looking at it the wrong way, you are not protecting the sockets with FCUs, you are protecting the spur cable leaving the first point, which for arguments sake is rated at 20A. Having multiple loads connected by their own FCU does not acheive this

 

[Whynot123]

Thanks John and Adam, that does make perfect sense and I understand the logic behind this now. Although I hoped for the existing set up to be valid adding the 13A FCU is a great solution and luckily nothing major needs to happen to the kitchen or conservatory.