Cable repair within wall

[Jupiter01]

I am helping my sister with an electric job that’s been left midway by the builder. I noticed today that a wire was taped as it entered the metal socket box from the wall. When I unwrapped the tape, a piece of the neutral fell into my hand. No attempt was made to join the cable. It was just taped to give the impression of a complete cable. It was the feed for a heat alarm.

The 1.5mm twin and earth was buried inside plaster as it travelled up the wall. There was no option to replace the cable or trace it up to the ceiling void where I could have put a joint inside a box.

I was unsure on how to approach this and in the end used a wago (wrapped in insulation tape) and chose to bury it in filler that wil be used to make this good.

Was this the right thing to do?

The rest of the damage is due to the metal box being 25mm and not being deep enough for the dimmer switches. I replaced it with a 47mm box.

 

[winston1]

No. Wagos wrapped in so called insulation tape buried in filler is not OK.

 

[winston1]

At the very minimum solder and use self amalgamating tape.

 

[sparkwright]

You could use an in-line cable crimp (a red one) and heat shrink sleeving to repair the cable, and plaster over.

You would need a proper crimping tool though, not those cheap rubbishy things, as you need to make a sound connection.

(That said, there has been some debate about whether crimps should be used on 'solid' cable, so hopefully someone can come up with reasons for and against this.)

***

This is precisely why people should use conduit or capping, and leave a little slack in the cable in the ceiling void above.

 

[JohnW2]

(That said, there has been some debate about whether crimps should be used on 'solid' cable, so hopefully someone can come up with reasons for and against this.)

Indeed. There certainly seems to be a view that crimping of solid conductors (at least, using 'single plane'/'squashing' crimping, as with all the tools that get discussed here) cannot be guaranteed to produce an electrically reliable connection.

General guidance about this seems to be hard to find. One often sees it suggested that NASA's relevant 'Workmanship Standard' prohibits the crimping of solid conductors, but I'm not sure about that, since it seems to be based on their interpretation of a (rather surprisingly) pretty ambiguous statement ....

Those who think NASA prohibits the practice presumably read that statement as:

Crimping of (solid wire) OR (component leads) OR (stranded wire that has been solder tinned) is prohibited.

.... but it could also be intended to mean ...

Crimping of (solid wire, component leads or stranded wire) that has been solder-tinned is prohibited.

... and that would mean that crimping of non-tinned solid conductors was not prohibited. Since the drawing appears to show a tinned solid conductor (certainly a tin-coloured outside but copper-coloured end), this interpretation is perhaps the more likely?

Kind Regards, John

 

[Jupiter01]

Unfortunately, I don't own a crimping or a soldering tool.
Would my situation be any different if I used PVC capping over the connector rather than bury it in filter? I am looking for alternatives to the crimping method if there are any.

Thanks for your help.

 

[ericmark]

I have used the triangular crimps on solid aluminium wires with a 3.3 kV supply many times, However buried the expansion and contraction due to temperature change is likely less than when buried in a wall. But there was really no other way to join them, I was using the official kit deigned for the cable and it was either epoxy resin lined shrink sleeve or epoxy resin filled box.

Copper cables at 150 mm² tends to be stranded, never seen solid copper, to get solid copper looking at under 4 mm² and it tends to carry a lot less current at that size.

Buried in a wall the main concern is if the wall becomes damp, and this can cause earth leakage, and in turn cause a RCD to trip, even using a box, unless the box is hermetically sealed water can end up filling the box, and finding the problem would be a nightmare, so what ever repair is used, it needs to be water proof, no regulation to state this, just common sense, an epoxy resin joint with 1.5 mm² is not really an option, so one is left with epoxy lined shrink sleeve as only official method.

However silicon sealant is good at resisting water once set and also once set will give some mechanical grip, so even in a card board box a joint filled with silicon sealant will in time set solid and make a good joint even if not strictly complying with regulations. Some times one has to use some common sense, I have needed to remove silicon sealant filled joints, and found not problems inside the joint, and a orange/red/blue/yellow pre-insulated crimp in silicon will have not movement so unlikely to every have a problem.

With a die like this it is unlikely there would be any problem, but be it a cheap pair of pliers used twice, or a set of ratchet crimp pliers, the problem with latter is they need calibrating, these are what most of us use, and here

is the adjustment so they can be calibrated, in my 50 years in the trade only GEC large steam turbines would calibrate our crimp tools, it was not permitted to use our own crimp pliers as they had three sizes of crimp, and they could not be sure it was calibrated for each of the three sizes, so we had to carry 4 sets of crimp pliers and even the crimps had to be one make as the insulation and tube thickness can vary make to make, so can only be sure crimped correctly if always using same make of crimp.

So in some ways the cheap nasty crimp pliers may be better, as they rely on the skill of the user, not being calibrated to ensure a good crimp, I personally use both skill and a ratchet crimp pliers, if I don't need to squeeze hard I know some thing is wrong, I would have loved to have seen how our crimp pliers were calibrated, but never did see how it was done.

I have never seen pliers calibrated by any other company, but the fact there is an adjustment, clearly they should be calibrated, and no point telling people to use ratchet crimp pliers unless those pliers are calibrated for the make of crimp used.

 

[sparkwright]

Unfortunately, I don't own a crimping or a soldering tool.
Would my situation be any different if I used PVC capping over the connector rather than bury it in filter? I am looking for alternatives to the crimping method if there are any.

Thanks for your help.

I can't say I like the idea of any connector buried directly in plaster or filler, and wrapping it in just ordinary tape is a no.


If i was in your situation, I wouldn't be too worried if I used a wago within some 20 or 25mm plastic oval conduit - but of course I can't tell you this as I believe Wago insist their maintenance free connectors must go in one of their own enclosures when the join is inaccessible,

It seems common sense can't be applied to much nowadays.

***

Alternatively you could flush another switch box higher up, and have a blanking plate or two switch plates one above the other, but.................... seems a bit of a faff.

 

[sparkwright]

Indeed. There certainly seems to be a view that crimping of solid conductors (at least, using 'single plane'/'squashing' crimping, as with all the tools that get discussed here) cannot be guaranteed to produce an electrically reliable connection.

General guidance about this seems to be hard to find. One often sees it suggested that NASA's relevant 'Workmanship Standard' prohibits the crimping of solid conductors, but I'm not sure about that, since it seems to be based on their interpretation of a (rather surprisingly) pretty ambiguous statement ....

View attachment 271257

Those who think NASA prohibits the practice presumably read that statement as:

Crimping of (solid wire) OR (component leads) OR (stranded wire that has been solder tinned) is prohibited.

.... but it could also be intended to mean ...

Crimping of (solid wire, component leads or stranded wire) that has been solder-tinned is prohibited.

... and that would mean that crimping of non-tinned solid conductors was not prohibited. Since the drawing appears to show a tinned solid conductor (certainly a tin-coloured outside but copper-coloured end), this interpretation is perhaps the more likely?

Kind Regards, John

Intersting.

As you indicate, the drawing do not show any wires that are NON-tinned (ie made completely of copper) - and bearing in mind virtually all fixed wiring now tends to be ALL copper and not tinned, you have to wonder.

 

[EFLImpudence]

You would need a proper crimping tool though, not those cheap rubbishy things, as you need to make a sound connection.

Exactly.

(That said, there has been some debate about whether crimps should be used on 'solid' cable, so hopefully someone can come up with reasons for and against this.)

See if you can find any crimping products that show solid cores being crimped.

 

[winston1]

Unfortunately, I don't own a crimping or a soldering tool.

Not owning the correct tools is not an excuse to dangerously bodge it. Either buy the correct tools and learn how to use them or pay someone else to do the job.

 

[Jupiter01]

Not owning the correct tools is not an excuse to dangerously bodge it. Either buy the correct tools and learn how to use them or pay someone else to do the job.

Point made!
But is crimping the only method and the crimper the only tool? I was trying to establish the alternatives. As is often the case with almost everything. And that doesn’t mean a “bodge”.

 

[JohnW2]

Intersting. .... As you indicate, the drawing do not show any wires that are NON-tinned (ie made completely of copper) - and bearing in mind virtually all fixed wiring now tends to be ALL copper and not tinned, you have to wonder.

Indeed. I must admit that, since I'd seen it said/written so often, until quite recently I had presumed that it was true that NASA prohibits the crimping of solid conductors. However, when I recently 'looked into it', all I could find was what I posted, which certainly seems to raise strong doubts as to whether the 'prohibition' relates to non-tinned solid conductors.

Kind Regards, John

 

[winston1]

Point made!
But is crimping the only method and the crimper the only tool? I was trying to establish the alternatives. As is often the case with almost everything. And that doesn’t mean a “bodge”.

As I said in post 3, solder it and cover with self amalgamating tape.
Once you own a soldering iron you will wonder how you ever managed without it. I’ve had one since I was 12 years old.

 

[plugwash]

Since all the cables seem to be coming from above I would be tempted to simply move the box up a bit.