I want to break into the ring main and add a couple of sockets but what is the current best or the recommended method of jointing the cables - a "traditional" junction box like this
TIA
cut the cable, install 2 sockets, each cut end goes to one of them, and add a linking bit of cable. Otherwise you can use a jbox or crimps. Soldering's also allowed, but with that you should still use a jbox to enclose it.
NT
The official party line says that you should only use screwed connections - such as the junction boxes which you reference - in places which are readily accessible for maintenance, and that elsewhere (e.g. behind plaster) you should use crimps or soldered joints.
Wiring under floorboards is somewhat moot. It's probably best to regard it as 'inaccessible' and use crimps - but I've got a hell of a lot of junction boxes under mine!
Under floorboards is considered accessible so a JB is fine.
Ah, that's great, thanks folks :o)
Providing you are able and willing to lift them if needed during an electrical inspection. So generally, they are not regarded as accessible because it could mean damaging any floor covering (which might be applied at a later date).
If a new installation - or works which have to be checked - then it would make sense to do this before laying any covering. If a *thorough* inspection of an existing installation, floorboards would have to be lifted anyway. If just a test, the existence of a JB or any cable connector wouldn't show up - unless faulty.
Which means some LV transformers etc can't be sited under floorboards either.
cut the cable, install 2 sockets, each cut end goes to one of them, and add a linking bit of cable. Otherwise you can use a jbox or crimps. Soldering's also allowed, but with that you should still use a jbox to enclose it.
Can anyone point me to a recourse about soldering power cables? I'm not planning doing any myself, but clearly it must involve more than twisting the wires together and applying the lead-free equivalent of 60/40.
Fair enough for ring mains. But there are other circs in which the existence of a JB will be manifest. Eg I have a hall light which is two-way switched using a traditional junction box under the first floor floorboards. (I wish now I'd re-done it without but there were time constraints - plus the constraint that the light hangs via a 6x4 joist and I did not fancy drilling a big enough hole through that to feed a junction box.) AIUI any PIR which looks at that light will show the existence of the junction box and expect it to be available for inspection. So do I have a way now of avoiding the potential need to lift the boards?
I had wondered about placing the junction box in a further enclosure which I then fill with a pourable epoxy. (ISTR doing something of the like with electronics for use underground many moons ago.) But that still does no prove to the inspector that there were good and tight connections before the resin was applied - or indeed that the resin is really there (despite eg photos). The same seems to be true with soldered joints. So am I basically stuffed (or whatever the correct term is under BS 7671:2008) unless I can provide access?
No need for lead-free - leaded stuff is easier and lower temp to reduce melting of insulation. Main think is to use an iron (not blowlamp!) that can pump enough heat into the joint quickly enough.
Absolutely. There could be all sorts of hidden nasties on an installation that only a visual inspection plus tests would show. Including joints made specifically for where they can't be inspected. ;-)
melting of insulation.
the joint quickly
Soldering isn't commonly used in the field -- it's not a skill that many installation electricians have nowadays.
I have done it a few times. I've used a normal junction box to make the connections as you normally would. Then solder the terminals/conductors, so they're being held by both the normal screw terminals (which you can't any longer turn) and the solder. Normal thermosetting plastic junction boxes will survive soldering temperatures for plenty long enough to solder the terminals (although they won't for hours on end, e.g. overheating terminals).
Don't do this unless you are already very competent at soldering. You'll need a reasonably large iron (I used a 50W temp controlled). You need to solder quickly to avoid damaging the insulation, and you need to layout the conductors in the JB so there's no stresses/forces on the insulation (e.g. wires not pressing on each other or anything else, and no tight bends).
Really, unless you are already very competent at soldering and have exactly the right kit, use crimps. They'll give better results in less skilled hands, providing you use a proper ratchet crimper and correct sized crimps.
Can you pull down any of the wires to the existing ring?
- eg, run in capping or oval or loose in holes if behind skirting
In which case break the ring & just extend accordingly.
- so maintaining the ring structure
- so having all junctions directly accessible
Lifting floorboards sounds easy, but not when covered with a heavy bed, carpet, fitted furniture or wood.
If redecorating it should be a non-issue to do it "properly". If you do use a JB, note it on the CU re I&T.
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