Joining elecrical cable

[Aitch]

I need to reposition the 2 lights in the ceiling in the main room to a central position before the insulation and plasterboarding is done. I need to extend the existing wiring a distance of about 3-feet for both lights. What is the best way of joining and/ or extending the cable to the new position? (the existing wiring is brand new and meets all the regs etc.).

Thanks,

Aitch

[Gyn_Paul]

My understanding is that you can extend an existing gaine (via either side of a junction box) and bury it in the ceiling void ONLY if it is possible to replace/extend the existing wires in one piece. That is, if it's possible to pull them back to their source, replace them, and pull them back to their new position. If that's not possible, and you need to join on new bits, then the box in which you have joined the wires needs to remain accessible.

As for how.... I favour bornes: the little plastic blocks into which you push bared wires which are held in place by a spring-loaded edge, as opposed to domino or choc-block connectors with screws. With the latter I find it's quite possible to screw the thing tight and still have one of the wires not caught properly, giving ample scope for arcing if it's carrying a high current.

p

.

[tj]

If the wires are currently run in gaine, you should pull them out and replace them back to point of origin at the length you require, and join a new piece of gaine to the old.

Sounds easy, but it is my experience these professionels are not averse to running gaine in and out of stone walls,  running up a wall by hacking out the pointing and running the gaine in the speaces between the stones. There is no way you can rewire in such circumstances.

So, if its not practical to rewire then put in a junction box, I prefer bornes too! and leave it you, as to whether or not to leave it accessible ( wouldnt worry too much about that ), its extremely rare that when an electrical fault occurs it is something hidden like a junction box, it is generally the exposed elements switches, sockets, light fittings etc.  

[Gluestick]

GP:

Where I need to fix more than one wire into a circuit block with flat ended screws (and I do agree they can fail to bear down correctly and pull out!), I tend to solder them and allow the screw to tighten into the soft solder.

This approach also prevents high contact point resistance as well as arcing.

 

[Nick Trollope]

[quote user="Gluestick"]

GP:

Where I need to fix more than one wire into a circuit block with flat ended screws (and I do agree they can fail to bear down correctly and pull out!), I tend to solder them and allow the screw to tighten into the soft solder.

This approach also prevents high contact point resistance as well as arcing.

 [/quote]

But, as the solder oxidises over time....

[Gluestick]

Silver solder? [blink]

(Gold Dipped)

[Www]

[Gyn_Paul]

[quote user="Gluestick"]

GP:

Where I need to fix more than one wire into a circuit block with flat ended screws (and I do agree they can fail to bear down correctly and pull out!), I tend to solder them and allow the screw to tighten into the soft solder.

This approach also prevents high contact point resistance as well as arcing.

 

[/quote]

Yes, that's an excellent solution which I too have employed  - especially where I needed to join 3 or so together in a larger block. Complete peace of mind when - having soldered them together - the domino is essentially reduced to the role of an insulated container!

All this hysteria about arcing stems from a small 2-disjoncteur unit in a barn comprising a 20A and a 16A distributing power and lighting.  It was partially obscured by a growing pile of removals boxes. I was standing in the barn one day scratching my head ("now what did I come in here for?") when I heard the sound of arcing. Investigation revealed the entire side of the box and one of the disjoncteurs was black and melted. Cause? Tightened screw not catching both the wires.

That was in my own place. I have also been helping to renovate a small council building,  formally a schoolroom, in a block of pre-fab-like pavillion buildings.

One of the convector wall heaters didn't work and upon investigation it turned out the problem was a junction box. The arcing in which had not only melted the connector and the surrounding box, but also charred the wall (wooden, of course) above it. How it hadn't set the place alight I don't know.

p

[Gyn_Paul]

[quote user="Nick Trollope"][quote user="Gluestick"]

GP:

Where I need to fix more than one wire into a circuit block with flat ended screws (and I do agree they can fail to bear down correctly and pull out!), I tend to solder them and allow the screw to tighten into the soft solder.

This approach also prevents high contact point resistance as well as arcing.

 [/quote]

But, as the solder oxidises over time....

[/quote]

Only on the outside...

[bejay]

When  it is appropriate  I like to try feed both wires under both screws in terminal  blocks. This is easy with two single strand conductors but much more difficult  with multi strand wires. I agree that is impossible to know just how many strands are actully clamped by a screw connection.

I recently invested in a pair of decent quality crimping pliers and the necessary colour coded connectors and terminals. As it happens I have only used them on 12V DC  systems so far but I have found that they work very well on on multi strand conductors becuse they compresss straight across all the strands. They are not foolproof and you do need to match the cable to the connector but the end result is very neat.

 One rarely sees solder joints these days in heavy current (as opposed to electronic) work.

bj

[Gluestick]

Because we used to do quite a lot of automotive wiring and even making looms and sub-looms 30 years ago, I invested in some of the original Ampex crimped terminals for Lucas (Spade) as well as round ends.

They were very good.

The cheaper ones around now aren't so good, I've found and often pull off!

Yer pays yer money...........................