Two spurs from one socket

[JohnW2]

Yes, you are correct about the terminal on a modern MCB not having a screw connecting directly to the conductors - but either way, it seems the more conductors you have, the greater the chance of one conductor slipping the net.

As I said, with the MCB type of terminals, I think that it's not so much the number of conductors as their relative sizes that matters most. As I said, if, with just three conductors, one of them is smaller than the other two, that is a potential 'killer' situation.

Kind Regards, John

 

[sparkwright]

You could always do it properly and ensure that does not happen.

And how do you do that?

I could have 4 conductors, and a modern MCB where the screw doesn't directly screw into the conductors.

I can arrange them in the terminal all nice and straight. No kinks. No crossing over. All side by side.

Tighten it up, no movement.

Ah, a loose conductor.

Ok, let's try two side by side. With another two side by side 'on top'.

Bugger. Another loose wire.

Ok, lets try doubling the ends over.

All nice and straight. All the same way round. Can't really be sure if they ARE the same way round, as no X-ray glasses today.

All in all, it's a bit of a faff, when this problem didn't exist as much with the old round terminals where the screw made direct conduct with the conductors.

I am constantly working on existing consumer units, done by others, where I find loose connections. I generally like to make sure all the wires are secure while I'm there, because I'm the last person to be working on that board, and whenever I see an MCB with two, and especially three or more conductors, I tend to give them a gentle tug because I KNOW there is a very good chance they are going to be loose. And sure enough, they often ARE.

I also feel the amount of testing that has to be done on some existing installations means the disconnecting of once secure conductors, only to be put back sloppily by someone in a desperate hurry to do his next job.

Now that would be poor workmanship by the person putting it back, no question really - but he thinks he's putting it back as it was. He sort of is. Only now the wires could be loose if he hasn't checked. You have to check. You can check once, and they appear fine. You can check a second time, only to find they are loose.

Personally, I wouldn't be to offended if an electrician ran one short wire (over-sized in the case of a ring circuit) and joined the three or four circuit wires to a 5 way wago, I really wouldn't.

 

[JohnW2]

I also feel the amount of testing that has to be done on some existing installations means the disconnecting of once secure conductors, only to be put back sloppily by someone in a desperate hurry to do his next job.

Yes, that's one of the ironies. The fact that a lot more testing is now done than would have been the case several decades ago means that there is a lot more 'interference' with connections at terminals than there used to be, hence more opportunity for connections to be left 'loose'.

This way of thinking is probably now 'just history' but, in terms of terminals in which one screws directly onto the conductor, many decades ago I was told/taught that one should not re-tighten onto the same bits of copper more than 3 times but should, instead, cut the end of and 'start again' with an intact bit of copper conductor!

Personally, I wouldn't be to offended if an electrician ran one short wire (over-sized in the case of a ring circuit) and joined the three or four circuit wires to a 5 way wago, I really wouldn't.

I wouldn't be 'too offended', either. In fact, such an arrangement (with 'sprung terminals') presumably considerably reduces the risk of joints being left 'loose' following testing.

Kind Regards, John

 

[rrodd]

Hello, thank you all for your comments, I appreciate your passion and perhaps frustrations, even though a discussion of terminal design doesn't help me much, and comments and discussion of MCBs and consumer units are not relevant to me here. But I do understand how easy it is to get carried away.

I wasn't sure it was permissible to take 2 spurs directly from one socket, but thanks for clarifying that. The problem with that approach is as someone said, the backbox is a little small, and whoever wired up the sockets was stingy with the cable so there isn't much movement in the faceplate. I think it would be very difficult to get all the cables into the box and terminals.

My logic for what I proposed is that a 13A FCU would allow an additional socket to be fitted at a later date, perhaps by the next owner. If it was switched, it would also allow the outside socket to be switched on (and whatever is plugged into it) from inside.

A FCU for the light would allow 1mm2 cable to be used to the (inside) switch which is be easier to get behind the plasterboard. The lights would be a couple of low wattage, enough to light the path to the bins.

Both FCUs would also allow the circuits to be isolated in the event of problems.

So, that was my idea of a reasonable way to get things done.

However, looking at the area today, I realised it's not possible to go straight through the wall from behind the socket because there is something on the other side of the wall. I'll have to take the cable along the inside of the wall before it goes through it.

Because a short section of the outside cable goes under my decking I propose to use SWA in case of rodent damage - I do have pesky squirrels come into the garden but they only seem interested in the bird feeders, though there's no certainty that they might explore other areas at any time.

So, would any of you kind gentlemen suggest a suitable arrangement?

 

[securespark]

The worst were the Wylex NB breakers. The later type were OK, but the early type had a screw behind which was a metal washer. Getting 3 x 2.5 securely fixed was tricky....

See the one on the left.

Wylex - Mem Mcb 5 -15 Amp Type NB And HB Range Type 2 6KA | eBay

Find many great new & used options and get the best deals for Wylex - Mem Mcb 5 -15 Amp Type NB And HB Range Type 2 6KA at the best online prices at eBay! Free delivery for many products.

www.google.co.uk

 

[rrodd]

securespark, with respect, I've already said that discussions or complaints about various terminal designs are not helpful here, especially MCB or CU. If you would like to create a thread specifically to discuss such features, you may do so and discuss and complain, or merely inform to your hearts content.

In the meantime, it would be appreciated if the same passion and depth of knowledge could be demonstrated to something that would benefit me - my installation query.

 

[ebee]

On a bog standard ring final then then two spurs of say a single socket each used to be permitted. The problem then envisaged was a common practice of each of those single sockets being converted to twins at a later date. Therefore in some circumstances 4 outlets on the spur(s) from one point of a ring final might cause problems.

Note - a spur is allowed at the origin of a ring final but in practice if you had a ring final with not one but say fifteen spurs each of one twin socket at the fuseway then what danger could occur unless someone added spurs to spurs? none, but how many of you would boke at seeing so many conductors of 2.t T & E at the fuseway and if the ring final was then removed you`d have a multi-radial circuit of 2.5 T & E cables with one point on each leg and a 30/32A MCB of 30A fusewire, again what danger? I am of course assuming that you can adequately connect 15 or some such silly number of conductors in the particular fuseway and maintain mechanical and electrical soundness of the circuit.

 

[JohnW2]

On a bog standard ring final then then two spurs of say a single socket each used to be permitted.

I'm not sure why you say "used to be". Provided only that their origin is a point/accessory 'on the ring', one is still 'permitted' to have two (or more, if conductors would fit in terminals!) double sockets as (separate) unfused spurs with a common origin - and 'permitted' even in terms of the guidance of Appendix 15 of BS7671 (there are no actual 'regulations' about this).

The problem then envisaged was a common practice of each of those single sockets being converted to twins at a later date. Therefore in some circumstances 4 outlets on the spur(s) from one point of a ring final might cause problems.

There is a general requirement that rings should be designed such that overloading for long periods of any part of the wiring in "unlikley", but a potential theoretical issue will only arise if the 'point' from which multiple outlets originate is close to one end of the ring.

The same people who are uncomfortable about two double sockets being spurred from one point on a ring usually have no problem if they are spurred from two different 'points' a few inches apart!

Particularly with Method C 2.5mm cable, the difference between 27A and 32A is so small, as is the probability of >27A load being applied close to one end of a ring, that there really is (at least in my opinion) not much reason for 'lost sleep'!

Kind Regards, John

 

[rrodd]

Sigh.... is there anyone on this site who actually knows anything about my query and who wants to share his/her knowledge?

I'm not interested in hyperthetical debates. It's unfortunate I have to be so blunt, but obviously, my polite reminder earlier today is easily overlooked.

I retired from teaching a long time ago because it got to be such a chore controlling, rather than teaching all those little darlings. This thread is like deja vu all over again.

I've had great advice on this site before and I hope this thread can be rescued so that the resulting advice will rival what I've had before.

 

[rrodd]

Provided only that their origin is a point/accessory 'on the ring', one is still 'permitted' to have two (or more, if conductors would fit in terminals!) double sockets as (separate) unfused spurs with a common origin - and 'permitted' even in terms of the guidance of Appendix 15 of BS7671 (there are no actual 'regulations' about this).

Thanks for this. It's helpful and backs up what was said in the second post. Unfortunately, for reasons I mention above, it would be difficult to install in this way.

 

[EFLImpudence]

Thanks for this. It's helpful and backs up what was said in the second post.

Thank you.

Unfortunately, for reasons I mention above, it would be difficult to install in this way.

Then bearing in mind:

(there are no actual 'regulations' about this).

What else would you like to know?

 

[ebee]

various guidance makes it clear that two spurs from one point is best avoided. however as John correctly pointed out "The same people who are uncomfortable about two double sockets being spurred from one point on a ring usually have no problem if they are spurred from two different 'points' a few inches apart!" yes you are right about that John, in the same vein I mentioned the "multiple spurs at origin" scenario and indeed removing the ring (or not having one in the first place) but having a radial or multiple radials of 2.5 T & E each to one twin socket and the fuseway is 30/32A immediately has some folk jumping up and down ranting about dangers/overloads whereas not even flinching about a spur at origin of a ring. Especially if ring not present but a circuit with only a 2.5 radial has now become suddenly dangerous by removing the ring . I`ve witnessed such thinking a few times. The mind boggles.

PS John, a double yes ref the absurdity of two spurs from ring a few inches apart being seen as a no fuss scenario to the same folks too.

PS - I would not feel as happy if the loads unevenly spread or at least not within the mid one third of total ring length approximation.

In fact it reminds me of another one with the cooker circuit diversity approximation - again some folk think that you must not do the diversity calc on three separate appliances that youd do on one combined appliance = oven, grill, hob in a bog standard domestic setting of mum and dad and 2.4 children. The good old, first 10A plus 30% of remainder plus 5A if a socket intended for occasional use of a cooker equation, has pretty much stood the test of time. Whether a total of 3,2 or 1 appliances with similar intended type of use does not make the usual ready reckon type formula to become suddenly no good

 

[JohnW2]

You seem a little 'trigger happy'. In (I presume) response to my immediately preceding post, you wrote:

Sigh.... is there anyone on this site who actually knows anything about my query and who wants to share his/her knowledge?

... and then, explicitly in response to my same post, five minutes later you wrote ...

Thanks for this. It's helpful and backs up what was said in the second post.

Kind Regards, John

 

[JohnW2]

various guidance makes it clear that two spurs from one point is best avoided.

A good few people say that, but is there actually any such formal 'guidance'? Even Appendix 15 does not explicitly address that question.

...... Especially if ring not present but a circuit with only a 2.5 radial has now become suddenly dangerous by removing the ring . I`ve witnessed such thinking a few times. ....

I would say that the problem is that such people do not (or cannot) "think"

Kind Regards, John

 

[ericmark]

I used the Screwfix LAP grid system so a double socket became a single socket, switch and fuse, and I could then add as many sockets as I wanted.

The idea of only three wires in a termial is good, once you have 4 the chances of one not being firmly gripped increases.

But OK for double socket and not two singles, was claimed to be because you could then swap the singles for doubles or think the first one is part of a ring final. But that assumes a lack of inspection and testing after fitting, and to condone not testing is a slippery slope, we all know we should test, and OK in my own house where I have tested many times before and I know what sockets are on ring finals and with are spurs and radials I may not follow testing to the letter, but I know I need 1.38 ohm line - earth and around 0.98 ohms line - neutral loop impedance with an incomer of 0.35 ohms. And to add without testing is a little silly.