Running two appliances from a fused connection unit

muckybutt

asbokid wrote: »

yawn yawn!

"If it is part of a ring with 2.5mm cable and this is the first spur from that ring then you should use the same size cable unless you go through a Fused connection unit (correctly rated) in which case you can use 1.5mm." Appendix 15 of BS7671 (17th edition)

there's a simple diagram if that will help you!!

Pish !!! utter pish

Homersimpson

"If the feeding socket on the ring main is just a single, then by law the spurred socket must be a single, too."

I can tell you two things wrong with that statement, one the IEE wiring regulations dont make any reference to a twin socket only being connected to another twin socket (i.e if a single outlet is on the ring you can take a spur from this point to one twin socket, one single sockt or a fused connection unit) and two the IEE wiring regulations are not in themselves law although they are refered too by other documents which are (first thing they teach you at college when you study the IEE wiring regulations which I have done and still do).

asbokid

Well that's what was related to me. So bully.. It's trivially wrong on semantics on the one part, and perhaps should have distinguished best practice from regulations on the other.

It's curious that none of the qualified electricians who commented on this thread have been willing to offer the OP any advice whatsoever. Yet there is a gloating eagerness to condemn others suggestions as wrong. I've always found there to be a certain arrogance and an uncomfortable protectionist mindset to electricians. It's unwarranted since it's not likely any electrician here will lose any money by offering the OP some free advice.

So, instead of pooh-poohing.. what do you propose the lady should do? If she can DIY the work herself, how would she go about it? If she wants to pay for the work to be done, what options does she have, and at what cost?

Homersimpson

The OP's options are:-

If they can do the work themselves

1. Ascertain whether the spur is on the ring (by removing it and it should have two cables coming into to it) and if it replace it with one of those semi recessed single socket to twin socket converters or chop out the wall, change the back box and fit a recessed twin socket.

2. If the spur isn't on the ring then find where it has been connected to and if its wired in 2.5mm2 cable and is the only thing connected to the spur do one of the two things listed in one above.

3. If you find the cabling is a 1 or 2 above you could also connect a socket to the spur, in fact you can connect as many sockets as you like as long as the spur has a 13A fuse in it.

4. If the OP can't find the point of connection or isn't sure whether theres more than one socket connected to the sput then call an electrician.

If the OP Can't do the work themselves then call an electrician then I would imagine that this should cost around £100 - 150 sort out but i'm not too sure as i've never paid anyone to do any electrical work.

I'm not an electrician and I don't believe that Part P is a good idea at all (unless your an electrician in which case its marvelous).

The reason a ring main is wired like it is, is historic and the IEE Wiring regs contains lots of odd regulations to allow their use to continue (I don't think many if any other countrys use rings). The cables on the ring must have a current rating of at least 0.67x the protective device (i.e in A 32A ring each leg of the ring must be wired in a cable which is at least 21.44A). Lets say that you calculate a piece of2.5mm2 Twin and Earth cabes ratings as 24A that would be fine.

Now onto spurs. You can connect one item to the ring either using a junction box (which must be accessible) or into one of the other sockets the cable used must be the same as (or larger than) one leg of the ring. This would allow you to connect a double socket or a single socket or a fused connection unit (fused spur). In the case of a double socket you could in theory plug in two items of equipment which would each have a fuse rating of a maximum of 13A and hence could have a maximum load of 26A which is 2A over the cable rating, this is allowed under the regs and is one of the odd quirks. I wouldn't however advise putting this sort of load onto a spur from a ring (or even the ring its self as 26A is around 6kw which should really be on its own circuit).

If you connect into the ring via a fused spur unit or take a radial as decribed above to a fused spur unit with a 13A fuse you can connect as many sockets as you like to the output side of the fused connection unit as the 13A fuse is intended to protect the upstream cable I.e the cable feeding it. Any sockets fed from the 13A fuse are therefore protected by the 13A fuse so you could plug in a lot of low powered equipment.

Radials from rings are one of the odd quirks and one of very few situations where you use a downstream fuse to protect an upstream cable. I'm not sure whether there are any distance limits on spurs from rings to the first fuse point but I would suspect they intend it to be 3m as this is a dimension used for a similar situation on much larger industrial and commercial installations (In those case busbar chambers and fused switches/switched fuses and or busbar trunking and tap off units).

muckybutt

good post homer :T

keystone

Homersimpson wrote: »

.........that Part P is a good idea at all (unless your an electrician in which case its marvelous).

Thats not true many of them think Part P is an anti-business pain in the backside.

Radials from rings are one of the odd quirks and one of very few situations where you use a downstream fuse to protect an upstream cable.

A circuit can be a radial or a ring. It can't be both or a combination.

Cheers