How many is too many?

[morpheus83uk]

Is there a general rule which states how many cores you can put into a single opening on a ceiling rose, the back of a plug socket, light switch or choc block?

I have seen various diagrams showing two and three cables going into a choc block on one side and only one coming out the other would this be ok or would it be classed as dangerous?

In a celling rose I have always had one core one opening can you put two cores into a single opening on a ceiling rose? or is it better to still have a single core going into the ceiling rose opening and then have two cores into a choc block?

I have seen wiring diagrams showing 3 cores into the back of a light switch where I presume they are looping is this perfectly fine or would this cause problems or anything dangerous?

I personally have only ever used a choc block for two cores maximum on a single side and celling roses and switches having a single core into each opening.

I am just curious as its what I have always done but I have seen diagrams showing different things... is it perfectly safe to have 3 or 4 cores going into a single side of a choc block or the back of a single gang switch?

What would people say the maximum is?

Thanks

James

 

[JohnW2]

Is there a general rule which states how many cores you can put into a single opening on a ceiling rose, the back of a plug socket, light switch or choc block?

I suspect that you may get quite a range of opinions. One conductor per terminal/screw is the ideal, but, in general I would say that it's probably OK to have as many 'as will fit easily' (which obvioulsy depends upon their size). One problem is that the insulation can get in the way close to the terminal, so attempts to get several conductors into one terminal can result in the temptation to leave some exposed copper visible outside of the terminal - which you should not do!

Manufacturers of sockets, roses etc. will generally quote what they regard as the maximum cable capacity of the terminals.

Kind Regards, John

 

[morpheus83uk]

Thanks John I have never seen (granted never looked either) for the maximum capacity when looking on B&Q. Wickes and Screwfix for sockets etc but something I will look for in the future now I know its there!

So basically there isn't really a maximum which is dangerous to put into a terminal unless its exceeding the manufacturers cable capacity?

James

 

[OwainDIYer]

It varies widely.

MK will happily take 3 x 2.5mm (possibly even 3 x 4mm which would be required for a 32A radial) and the terminals are recessed deeply and widely enough so that copper isn't exposed

Wickes own brand will not take 3 x 2.5mm imperial equivalent.

On the other hand some makes don't handle small conductors well and need the conductor to be doubled/tripled or even more up to stop it sliding about in the hole.

 

[JohnW2]

Thanks John I have never seen (granted never looked either) for the maximum capacity when looking on B&Q. Wickes and Screwfix for sockets etc but something I will look for in the future now I know its there!

I couldn't tell you whether its on the packaging or websites of the likes of the places you mention, but the information exists in the technical datasheets and, I would imagine, the instruction sheets included with reputable brand products. For example, from the datasheet for MK Logic Plus sockets:

Untitled

• JohnW2
• 11 Sep 2014
• 1

So basically there isn't really a maximum which is dangerous to put into a terminal unless its exceeding the manufacturers cable capacity?

As I said, opinions will probably vary. There's probably no doubt that the more conductors one puts in one terminal, the greater the risk of the screw not gripping them all properly, or subsequently working loose. Also, as above, the manufacturers will often specify maximum terminal capacity.

Kind Regards, John

 

[RF Lighting]

You can fit 4x 2.5mm² in an MK socket.

 

[EFLImpudence]

So basically there isn't really a maximum which is dangerous to put into a terminal unless its exceeding the manufacturers cable capacity?

It would be foolish in the extreme for a manufacturer to state a maximum which was for electrical safety reasons but still supply terminals which could accommodate more than that.

 

[JohnW2]

It would be foolish in the extreme for a manufacturer to state a maximum which was for electrical safety reasons but still supply terminals which could accommodate more than that.

You say that but, as RF has partially pointed out, if MK say that 2 x 6mm² conductors will fit in their socket terminals, I'm quite sure that this means that they "supply terminals which could accommodate more than" the 'maximum' of three 2.5mm² conductors which they state!

Kind Regards, John

 

[EFLImpudence]

You say that but, as RF has partially pointed out, if MK say that 2 x 6mm² conductors will fit in their socket terminals, I'm quite sure that this means that they "supply terminals which could accommodate more than" the 'maximum' of three 2.5mm² conductors which they state!

That is my point. It cannot be for electrical safety reasons.

 

[JohnW2]

That is my point. It cannot be for electrical safety reasons.

Oh - I see - I thought you were saying the opposite of that! Whatever, I suppose it depends upon what one means by 'electrical safety reasons'. I would have thought that it would be pretty inevitable that the 'mechanical security' of conductors would theoretically decrease as the number (of essentially round c/s conductors) secured by a single screw increased - and that, if true, could clearly have an impact on 'electrical safety issues'. Maybe it actually is the number of (round) conductors secured by a single screw which is the main issue, rather than their CSAs (provided they fit)?

Kind Regards, John

 

[EFLImpudence]

No, I don't agree. Surely the more you fill the terminal, the better.

I would bend back the ends of two 2.5mm²s making four.

After all, two 6mm²s have fourteen round conductors.

 

[JohnW2]

No, I don't agree. Surely the more you fill the terminal, the better. ... I would bend back the ends of two 2.5mm²s making four.

I don't really know - I was thinking more of the geometry of fitting together (relatively large) circular conductors, and getting the single screw to hit them where it would ensure good and stable contact between all of them.

After all, two 6mm²s have fourteen round conductors.

Yes, that's true, but I think that's perhaps a bit different - lots of small conductors will 'pack' pretty well.

In any event, going back to the OP's question, I suspect that many of us probably adopt similar approaches - namely the one I mentioned of happily putting in as many conductors 'as will easily fit'.

Kind Regards, John

 

[ericmark]

As an apprentice I was taught one hole one wire if it needed more wires add more terminals but when I moved from industrial to domestic I realised this was not the case with domestic. However as one tries to put 6 wires in one hole you find some are often not clamped and over heating results.

The standard 13 A socket is limited to one spur and I have considered this is really because any more than three wires in any hole is likely to mean one is not clamped firmly.

So I would always limit it to three wires per hole. With a ceiling rose using 1mm cable not even sure if you would get three wires in the hole.

There are may types of ceiling rose many have limited room but some mount onto a conduit box giving loads of room inside like these

I used these where it was hard to reach the lamp and I would remove whole lamp for re-bulbing.

 

[JohnW2]

The standard 13 A socket is limited to one spur and I have considered this is really because any more than three wires in any hole is likely to mean one is not clamped firmly.

As often discussed, I don't think there is actually any regulation which says that, and I suspect that most of us have seen two spurs originating from one socket (or other point) on a ring. In any event, there are certainly no corresponding 'rules' (or electrical arguments) about radial circuits - so that, if the conductors would fit in the terminals, one could have as many branches as one wanted originating at one socket.

However, having said that, and as I said in my previous post, I do wonder whether the manufacturers 'terminal capacity ratings' may be more to do with the number of conductors (e.g."3 maximum") than to considerations of CSA.

Kind Regards, John

 

[OwainDIYer]

You can fit 4x 2.5mm² in an MK socket.

Dead handy when you want to figure-of-8 extend a ring.