So many Spurs it's like the wild west

[motorbiking]

Why do electricians favour spured twin sockets now rather than extending the ring. 10 years ago I had some work done and all the sockets were extensions on the ring, now I'm having work done and unless told otherwise the sparkies are putting Spurs in? I've told them to change them and they are moaning. Surely it's not that much quicker to be worth a spur? have the rules changed ?

 

[deadshort]

No. But the price of cable has!

DS

 

[DaveHerns]

Laziness ?

 

[EFLImpudence]

Why do you think they should?

There is no advantage electrically to extending the ring to a single point.



Edit - It could indeed be disadvantageous.

 

[EFLImpudence]

If it were a radial circuit would you insist the cable be run to single points, then back up and on to the next point?

 

[motorbiking]

I can see the advantage of Spurs from a fault tolerance point of view, but it's a weak argument. I.e if a wire becomes lose you get a failure rather than not knowing that your ring has split.

I'd prefer extension to the ring, to be consistent with the rest of the house - there are no Spurs anywhere else and of course future proofing to allow further expansion, as well as allowing more potential load.

I was more curious as to if there were other reasons. e.g preventing DIY electrics. etc or benefits.

 

[EFLImpudence]

I can see the advantage of Spurs from a fault tolerance point of view, but it's a weak argument. I.e if a wire becomes lose you get a failure rather than not knowing that your ring has split.

Safety is quite a big argument.

I'd prefer extension to the ring, to be consistent with the rest of the house

Absolutely irrelevant.

there are no Spurs anywhere else and of course future proofing to allow further expansion, as well as allowing more potential load.

Ok. You could always add another spur.

I was more curious as to if there were other reasons.

You are merely disagreeing with the present electrician who disagrees with you.

e.g preventing DIY electrics. etc

I don't follow.

or benefits.

Well, you have already dismissed the biggest benefit as a week argument.

Others will disagree but there is, for example, no point in extending the ring to an under-worktop socket.

 

[flameport]

The real question is why people are installing ring circuits in the first place.

 

[motorbiking]

I think creating a spur off the ring for a fault/safety point of view is a weak argument because the spur also requires a junction on the ring which could also fail in the same way as the socket. Though perhaps with a maintenance free box its less likely. My question is why opt for a spur over an extension to the ring? I thought best practice was that you extend the ring where possible? It seems current practice is you spur when possible - just wondering why? The same electrician has also wired an outside porch light using an existing fused isolator switch that feeds PIR switched outside lights, which is obviously a bit dim - though the light won't be as currently there is no way to switch it off other than the isolator.

 

[ericmark]

The ring allowed the house to be wired using less cable, one is permitted 106 meters of 2.5mm² in a ring however not sure with the rules about 1/3 in from end of beam if that is still true? I have wired a warehouse using all spurs from the ring, it had a 6mm² ring with a junction box above every socket with a 2.5mm² cables down to the socket, it was done this way to reduce the cable used in the ring and so keep the earth loop impedance within the required limits.

The installation needs to be designed, not simply thrown together, and step one before fitting a new socket is to work out if the ring can be extended. The Ze with a TN-C-S should be better than 0.35Ω but as to if you can rely on it being better is another thing, the street supply can change without notifying you so we work on 0.35Ω, so the line - neutral impedance at centre of the ring can drop to 0.94Ω and still be just within the volt drop limits.

The problem is measurement measure with any loop impedance tester three times and you will get three different readings, so if I read 1.35Ω the question is do I flag as a fault or not? Likely not as it could be my meter is slightly out. Even with a 0.90 reading am I sure I am in the centre of the ring. The only sure way would be to use a low ohm meter using at least 200 mA to measure with which would require the whole circuit to be cold. So switch off and then return in an hours time to measure.

If the loop showed as 0.85Ω OK I have some leeway and extending the ring is likely the best method. But you have only given half the story, without the test results no one can say if extending the ring is possible. In the main meters measure line - earth when set to impedance and line - neutral when set to prospective short circuit current, at least the better ones do. So looking for at least 244 amp. But some meters don't auto switch between line - earth and line - neutral I have been caught out myself and since the earth wire is thinner than the neutral one can believe the volt drop is exceeded even when really it is not. In theroy we should test both line - earth and line - neutral for the tripping current of the MCB we take the worse reading, and for the volt drop the line - neutral reading.

The testing is time consuming and you pay for that time, plus the cable costs and you pay for that cable, so often there is quite a jump in price between doing all the testing to extend a ring then use extra cable, and to simply fit a fused spur where if the ring was correct to start with then near impossible to get fail results when testing, the ELI jumps to 2.42Ω from 1.44Ω and similar with PSCC so that is the route many electricians go for.

When putting the ring in it is easy, 100 meter role and you know you must return to CU without starting a new role. But unless that electrician says on the paper work 85 meters of cable used, working it out latter is not so easy.

 

[motorbiking]

Thanks for the very comprehensive reply, everything make sense - this is exactly why I want them to extend the ring - they have testing kit I can't justify buying and therefore if all sockets are off the ring, I am pretty sure I can add sockets later without needing advanced testing kit e.g. diy sockets as spurs. I totally get that electrical work is 80% testing and that 90% of diyers "pass" the circuit based on if the appliance works or not. I've located the junction box - looks like a 20A chocbox was used to spur the ring, its only 2m from the consumer unit. I didn't realise you could use a 20A chocbox for 3 x 2.5mm cables - I thought they didn't have sufficient amp rating?

I'm now in 2 minds to nip out and buy a couple of wagoboxes and refit, or ask the sparks to refit. The problem I have is the sparks are taking instructions from builder and he's practically gone awol, so they get one set of instructions from him and then agro from me, because its wrong. I'm having the same problem with the plumber, who's installed mains surface mount pvc water pipes on my garage floor, where they can easily get tripped or damaged. With plumbing I can rip out and refit, myself, but electrics needs sign-off.

 

[AndyPRK]

Sadly when adding sockets it is common to use spurs. You really should have specified RING if that is what you wanted, for the sensible reasons you give of adding sockets later.

But to be honest, unless its a kitchen, spurs should be fine

 

[EFLImpudence]

I think creating a spur off the ring for a fault/safety point of view is a weak argument because the spur also requires a junction on the ring which could also fail in the same way as the socket.

No more than the connections to the next socket on a ring.
I had assumed all the spurs were connected to sockets; surely you don't have junction boxes fitted on the kitchen wall.

Though perhaps with a maintenance free box its less likely.

There are no MF sockets.

My question is why opt for a spur over an extension to the ring?

Because it makes absolutely no difference.

I thought best practice was that you extend the ring where possible?

Did you? Why would that be?

It seems current practice is you spur when possible - just wondering why?

It depends on the situation. If the continuation of the ring has to return to the same point then it is of absolutely no advantage.
Are you thinking there are no spurs fitted before 19whatever?

The same electrician has also wired an outside porch light using an existing fused isolator switch that feeds PIR switched outside lights, which is obviously a bit dim - though the light won't be as currently there is no way to switch it off other than the isolator.

Then, have a switch fitted. That is obviously a mistake.

 

[EFLImpudence]

Sadly when adding sockets it is common to use spurs.

Why sadly? If suitable, what difference does it make?

But to be honest, unless its a kitchen, spurs should be fine

It could be a bungalow where all the sockets are on spurs.

Best not live there.

 

[ericmark]

At 2 meters from the consumer unit I would have likely have gone back to the consumer unit, it is permitted to take a spur from there and it would reduce the chance of over load.

I have always found it hard to write a request for work without either telling the tradesman his job or allowing too much leeway. I had however a few standard phrases I would use, one was "The current BS7671 shall be complied with unless written permission is given to deviate." the other was "The health and safety aspects of the plant shall be no worse than it was before starting." and "Risk assessments and method statements shall be written where required to satisfy any HSE inspectors visits, should they arrive while the work is being completed." I still got the odd time where tradesmen would over step the mark.

As an electrician I don't tend to employ electricians, whoever on the odd time I have needed to. I also found a problem where the electrician is a sub-contractor so any faults you need to speak to the main contractor and they in turn talk to the electrician. The last was a very simple job, I had fitted a new door bell to my mothers house, it had 4 x HP2 dry cells in the bell push which has gone flat when the social services visited. They offered to hard wire it so it would not go flat again. We in real terms wiring was already there all it needed was the 8 volt AC transformer to be swapped for a 12 volt DC power supply. I really could not believe how they could get it so wrong.
1) They swapped the 8VAC transformer for a 12VAC transformer. Got them back.
2) They swapped the transformer for a socket with a walmart power supply plugged in.
I asked for the minor works certificate again and again, no sign, I stuck the RCD tester on the socket and it failed to trip. I reported it and again nothing happened. And this when the county council was the client, I think they must have sent the apprentice and in the end I gave up. I intend to get a rewire soon so all will be corrected. However I can understand how one can feel you banging your head against a brick wall. You do however have one advantage, you can withhold payment until corrected.