Spurs, how many?

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magica
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Spurs, how many?

Post by magica »

Please clarify and advise, can I run 2 spurs to 2 SINGLE sockets from a double socket currently only used for kettle and toaster with no other spurs? The spurs are to supply 1. washing machine 2. extractor hood therefore not in constant use. Many thanks.
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ultimatehandyman
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Post by ultimatehandyman »

Hi Magica.

I'm not a sparks but I would not do it!

Electricians do not like spurs and tend only to put one in if they really have to and you can only run one spur from a socket that is on a ring main, if you have a radial socket you cannot run a spur from it!

You could run a single spur from a socket that is on a ring main as long as it is not a spur itself for the washing machine. (if that makes sense, you cannot run a spur from a spur! You might only be plugging an extractor in it but the next people that buy your house might plug a 3kw heater in it)

Is it not possible to take a feed for the extractor from the lighting circuit via a fused, switched connection unit?

Markysparky might be on later he Knows his stuff and will probably be able to advise!
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Post by markysparky »

UHM is spot on magicia.

It ain't good practise to have more than one spur off a ring main. And you can't spur of a spur as already pointed out.

And as UHM suggests! Is there any chance of wiring the fan from an existing lighting circuit this would solve your problem.

But if you feel that 2 spurs is your only option! you could have both spurs protected by an unswitched fused spur.
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Nothing wrong with doing it this way as it will prevent the cable from doing any more than it should.

Good luck with whatever you decide! :-)
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Post by ban-all-sheds »

ultimatehandyman wrote: you can only run one spur from a socket that is on a ring main, if you have a radial socket you cannot run a spur from it!
:?: :?: :?:
With a radial circuit, rather than a ring, you can branch off as many times as you like, and each branch can have as many sockets as you like.

It's only because ring finals use cable that is too small for the size of fuse/MCB that there are restrictions on branching off from them.


I'm sorry - I can't come in to work today, the voices are telling me to stay at home and clean the guns.

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Eccles
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Post by Eccles »

What really matters with all these kind of problems is do you know what thickness of cable you should be using to prevent overheating and possibly an electrical fire. I am not a registered electrician but did an extremely good course a few years ago on domestic electrics where the technology was very carefully explained. I now realise why some friends of ours had a disastrous fire in a cafe they were running: They actually managed to plug about five heat using devices into a double socket which was "radial" but only fed with 2.5 mm twin and earth. The cafe was old and they did not know what they were doing. The supply cable would take up to about 4 kw at most and they were putting nearly 6 kw through it at times = very hot cable = fire. Actually I recently again had to do a spur off a main ring, which I also do not like for reasons explained above but it was done in order to supply an under counter built in fridge using about 120 watts so dead safe unless someone tries something different in the future. To obviate any future problems I have once again permanently marked the socket that it is a spur and the load must not exceed 2.5 kw. Why can't sparkies do this?, it seems such an obvious safety measure to adopt to me.
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sparkydude
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Post by sparkydude »

The reason we do not do this is because there is no need to, If a spur is taken from a ring main in 2.5 T+E cable which it is supposed to be , It can only be used to supply one item of equipment IE one double socket,one single, or a spur. The cable is rated at 28A so that allows for a 3kw appliance to be plugged into each socket. The protective device in the distribution board on a ring main will be either 30-32A so the extra 4Amps of overload may cause the cable to warm but never overheat as it will trip or blow before then. the chances of you getting a 6kw load on a ring main is remote as there will be other items of equipment on the ring main using power at the same time. The radial circuit is better because it loops in to one pont then onto the next and so on, but as this will be protected by a 16 or 20A protective device then it will never allow an overload situation to last for long before opening.

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Andrew
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Post by Andrew »

Can someone please explain a more about spuring off a spur to me. I understand that it's "bad", but how and why?

I have a spur to a twin socket and from that I have another spur to another twin socket ("it was like that when I got here"). It's in a slightly inaccessable place, which is why it's probably like that.

Is it an immediate fire hazard or just bad practice? Should I be worrying?

Should I remove the second spur (leaving the legitimate first spur) and connect this second socket to the main by extending the ring circuit? If so, is there a page on this site for extending the ring main? I can't find it! Or...could I not just interupt the ring main with a junction box a bit further on and spur off that? There's no harm in having a spur anywhere else on the ring main as long as it's not from an existing spur, and there's no limits to the amount of spurs, et cetera????

Many thanks!

Ta.
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Post by markysparky »

What size fuse/breaker is protecting it?
Eccles
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Post by Eccles »

What some of these sparkies don't realise is that there is still circuitry out there which is not going through an MCB but in fact old type fuses and some of those old type fuses have been rigged with bits of wire so that they don't blow. I actually found such a set up in a pre-war bungalow in Brighton a couple of years ago. The old boy who had lived there had no idea that his bungalow was all radial circuits and as he knew that you had to have a wire across the fuse connectors to "make things work", he had done precisely that. Moreover, someone had fixed him up with a extra double socket in the bedroom which was a spur and he occasionally plugged a hefty electric fire into it and an electric kettle. He had no idea of the risk he was taking. I personally think that this sort of thing goes on not because of cowboy sparky activity but because sparkies like to keep everything as a big technical mystery when it is really schoolboy stuff which most folk can understand if they are told. I also think it should be taught in schools.
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Post by tim'll fix it »

eccles are you suggesting that electrical theory is simple

how dare you, go and stand in the corner :wink:
:lol:
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Andrew
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Post by Andrew »

In repsonse to your question, markysparky, I've had a look at the fuseboard. Nothing is ever simple, but here's the answer:

There are two fuses (not MCBs) marked up as "sockets". Both of these are 30amps. It's only a flat so no idea why there're two, unless they've been marked up incorrectly (which is always good!). I've not taken them out one at a time and gone round to see which sockets either one affects.
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Post by markysparky »

Eccles wrote:What some of these sparkies don't realise is that there is still circuitry out there which is not going through an MCB but in fact old type fuses and some of those old type fuses have been rigged with bits of wire so that they don't blow. .

You don't say! Think I've never seen that before? :lol:

Backstreet workshops are the best for that sort of thing.
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Post by markysparky »

If you have a look at my 1st response to this thread it will tell you the best way to do this.

If it's a spur of a spur protect it with a 13amp fused spur
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Andrew
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Post by Andrew »

I've never come across fused spurs, so I think I'll give that one a miss. Instead I'll leave the original spur coming from a socket (unfused?). I'll remove the other one and wire it up as an extended part of the ring (30amp junction boxes?).

If what you say is true ("It ain't good practise to have more than one spur off a ring main"), then why do people put spurs on systems in the first place when extending the ring main is (in my eyes) as simple as spurring? I'm sure there is a good reason.

Also, just out of curiosity, if I was going to extend the ring main and began by splitting the cable and putting both ends into separate junction boxes, and then turned the power back on, all sockets should continue to work on a ring circuit as power is fed both ways round that type of circuit - correct? With a radial, however, all power to the sockets along the line would be lost, right? Would that be another way of telling what type of setup you had?
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Post by markysparky »

Yes that is right. If you remove the socket and keep both cables apart, restore the power! and if both cables are still live that particular socket is on the ring. If only one is live then it's either a radial or a spur of a spur.

And yes it is just as easy to keep it on the ring but not all the time.
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