Terminal blocks

I've just fitted some new sockets in a bedroom. The cable was just a little too short to reach the socket, so I had to extend it using a few terminal blocks (chocolate block) and some spare cable.

Trouble is, I used a 15 amp terminator block. I've got a couple of questions:

- I seem to recall that 30 amp should be used (FWIW I've no reason to think my house is anything other than a standard ring main). But will I be OK with

15 amp?

- comparing 15 amp and 30 amp terminal blocks side by side, the 15 amp appears to have MORE metal than the 30 amp. I guess 30amp is like that to allow fatter cables in, but surely this means I'll be OK with a 15amp?

- In another bedroom, I had to chisel out the ring main cable from a concrete wall. This involved accidentally baring the cable in parts so I decided to cut it off from the highest point I could and apply new cable. To join old + new cable, I used 30 amp terminal blocks but over tightened some so the metal cracked. The cables seemed to be fixed tight so I didn't worry. Should I have?

Reply to
Brian
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15amp?

tightened some

didn't worry.

This has got to be a troll, or at least I hope so.....

Reply to
:::Jerry::::

Have you reburied these in the wall ?

Dave

Reply to
dave stanton

I've never noticed them get even slightly warm at full rated, so I would think so. If the 2 wires are both put thru full length instead of half way you get a good copper to copper connection, making the connector current rating less significant. But really you ought to use a 30A conn.

tightened some

replace it then, you cant get even a half decent clamping with broken metal. Recipe for a fry up.

NT

Reply to
bigcat

If you are going to plaster over the cable again then you need to either solder or crimp the join and not use screw terminals. Sheath the individual wires and the overall cable in heatshrink as well.

Reply to
John Rumm

OK - I've decided that the terminal blocks aren't a good enough solution so I've decided they must come out. Some were contained behind plasterboard, which has meant a messy pain in the a*** to expose them, but I guess you live and learn.

I'm going to go and buy a crimping kit but I don't fancy mucking around with heatshrink wrap (I haven't got a soldering iron and the terminal blocks I'm replacing are in awkward positions). Will good electrical tape do as good a job?

One other question - is there any harm in my using 4mm core cable in what may be a 2.5mm core radial system?

Reply to
Brian

And what about this discussion, previously held on this very forum?

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'll be honest, guys - I'm getting confused.

Here's the situation. I have some ring main cables coming out of a concrete cladded wall.

For reasons of a damp proof membrane, I had to pull the cable out from the concrete up until around 1.5 metres high.

I bared the wire in parts while doing this, so have had to replace that patch of cable.

I now need some safe and reliable method of joining the old ring main cable to new. I previously used terminal blocks but I don't think they're safe. Crimping appears to be both a dark art and dangerous. Soldering sounds like the next best option but does this simply involve a standard soldering iron

  • solder (as we use to make circuit boards)?

Help will be really appreciated here.

Reply to
Brian

solution so

plasterboard,

Put your tools down NOW and step back, you are clueless and a danger, employ an electrician before you burn your house down...

Reply to
:::Jerry::::

Only if it's 50 watts +. But the sheds sell 'instant' heat solder guns which will have power aplenty quite cheaply.

Reply to
Dave Plowman (News)

Well to quote Whitfield from his guide the the regs: "All joints must be accessible for inspection and testing unless they are buried in compound or encapsulated, are between the cold tail and element of a heater such as a pipe tracer or underfloor heating system, or are made by soldering, welding, brazing, or compression."

So that limits your choices a little. Crimps remain an allowable solution in the wiring regs, and personally I have not had any problems with crimped connections (made with a decent ratchet crimper). That does not mean however that problems do not occur though. I find that if you crimp 2.5mm T&E (I use splice connectors that are long enough to let you get in two crimps per side) you get a mechanically strong joint that can not be pulled apart, and the metal of the crimp *does* bite into, and compress the copper.

If you want to solder, then use a powerful iron with a big bit so you can heat the joint quickly. Twist the wires together first, tin the bit of the iron, apply to joint, flow solder into joint, remove solder, remove iron. Should take about 3 secs per wire. Each wire needs to be individualy sheathed, and again there needs to be an overall sheath or container of some sort.

Reply to
John Rumm

I find heatshrink is quicker and easier than tape, a very small precision blowtorch works very well for shrinking it ;-)

(Not sure on what the official line is on using tape, I have in the past used it (as I expect has everyone else ;-), but I have never really liked it!)

No electrical or regs problem using an overrated cable, however a future maintainer may make an assumption that the whole circuit is in 4mm sq and up the fuse/mcb to 30A which won't be good for the 2.5mm sections. You may also find that 4mm sq is harder to work with in the confines of back boxes etc.

Reply to
John Rumm

You can use an ordinary hot air gun for shrinking it with some care. Preferably a two heat one on low. Even an ordinary hair drier.

Reply to
Dave Plowman (News)

The really important point with soldering is the joint must be physically strong before you solder. DON'T rely on solder to provide both strength and conductivity, it wont !!.

Dave

Reply to
dave stanton

15amp?

tightened some

replace the broken connctor, wrap them in insulting tape, end of problem. The rest is, well, making work for the sake of it. Put wires full length into the conns and each one is gripped by 2 screws, very secure.

NT

Reply to
bigcat

I've just finished soldering the joints and the power is now back on (hence my computer being up and running...)

Here's what I did. Please don't say this was wrong (this is 2.5mm core by the way):

1) Stripped around 1in of wire on each cable 2) Twisted them together using pliers (the best I could - often it was the case that one wire was tightly coiled around the other) 3) Soldered them so that the solder "flowed" into the joints between the cables (visually, this was not unlike what happens when welding pipes using presoldered joints)

To be honest, the concept of soldering cables like this strikes me as odd. Despite my best intentions (and those of anybody attempting this job), there are places where the solder will be providing the conductivity. I simply can't guarantee that copper touches copper all the way through.

Reply to
Brian

[ ... ]

The best answer is to replace the whole of the run of cable which is najjered with new stuff. It's a ring main, and Therefore each individual run of cable's usually pretty short - from one socket to the next. Really, truly, the 'do it once, do it right, then forget about it for

30+ years' approach is to work out where the cable you najjered runs from, and replace the run with a new bit.

Another sensible, useful, and compliant approach is to find a place for a new socket - it's a rare room that wouldn't benefit from a new one. Put said socket on the non-najjered bit of cable, i.e. 'upstream' of the bit you did Bad Things to; run a new run from there to the Ould destination.

Either way's better than putting an unexpected, uninspectable joint somewhere in the deep middle of nowhere - it's even more confusing to future inhabitants if the sheath colour or guage of cable changes in mid-run.

Doing something else won't kill you or burn your house down unless you're truly and massively cackhanded and terminally stupid, but the pleasure of d-i-y is being able to do a *proper* job with *better* workmanship than a pro who's trading off quality against time-to-finish.

Stefek

Reply to
Stefek Zaba

I entirely agree and I would run new cable if I could. But you missed one point above - the wires are coming out of a concrete wall. I've no idea where they've come from. They might have come from the room next door or they might have come from upstairs. I haven't got a wiring diagram for this house. I don't even know if it's a radial or ring man system (the cables throughout appear to be 2.5mm so I'd guess the former).

This really is a situation where joining cables is the only sensible solution, short of rewriting the entire house.

Reply to
Brian

Whilst agreeing with all the solder/crimp responses nobody seems to have suggested the accessable option. Put a standsrd socket box into the wall at the join, then add either a socket or chocolate block and a blank cover.

Doesn't have the aesthetics but is simple to install (assuming you can cut the wall for the box!)

Mike

Reply to
mike

Did so! ;-)

Reply to
Stefek Zaba

Yeah, Sorry, Didnt spot your one 'till after I had posted.

Mike

Reply to
mike

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