Insulated through crimps and heat shrink - settle an argument

[adamh]

as above i've seen a few posts and from what i can make out everybody does this . I dont know the BS number but was led to believe they are a maintenance free compression joint ,
and when heatshrinking as well i would say have good protection from water ingress moisture etc.

A new lad has started at my work who says that this method of jointing cables is unacceptable when buried in walls to be plastered, had a bit of an argument over it and he has asked his tutor for l3 last night who says they can not be burried in walls etc because they are not waterproof only weatherproof as they are hermetically sealed when heat shrunk and if the wall became wet it would become live!!

I just laughed it off and said his tutor sounds like a clown i did use a different word to be honest ha and i also said what ip protection do your normal 25mm metal k/o b/boxes offer as they would be affected by the same situation. at which point he quoted two regs from the BGB i cant remember the no's but i can get them.

The gist of it was all joints need to be accessible for inspection and maintenance with the exception of 1's in MF accessories and there was something else I just said its not an accessory and it will have a bs no im sure stating it is maintenance free which i dont know.

Any help on this 1 as he said his tutor is amazing and i said i will check on a forum i use as there are people on it far more knowledgable than me ...

 

[HandySparks]

Does anyone here use soldering for joints in ordinary T&E cable?

I've used it, with adhesive lined heatshrink over each core and then over the whole joint for ELV flexible signal cables and I think it's a pretty robust and reliable jointing method.

 

[Rockingit]

Well, I know there's a soldering iron on the van. Somewhere. Might be hidden under the cobwebs along with the pyro roller.

 

[Guest55]

I think that common sense would dictate that if you sleeve a joint then cover it in wet plaster, unless you can guarantee a completely watertight seal all around, there is going to be some water seepage into the joint. This may be fine for a while, but how does anyone know whether corrosion is occurring behind the plaster and how long before it all goes wrong?

Well for a start plaster doesnt stay wet for long does it ? touch dry in a hour.
Plus its not as liquid as water anyway , rather semi solid.
And please explain how bricks corrode ?

Crimped joints embedded in a wall may officially be viewed as a bodge however i see it a good method of cable repair in a confined space.
Mr DIY drills thru cable halfway up wall - what you gonna do , chase out whole cable run ? fit JB on wall ?
Need to be sensible about this rather than quote regs numbers that dont actually prohibit their use.

 

[Guest111]

you can also get a crimp which you warm up after crimping and an adhesive flows out and seals the crimp preventing moisture ingress,got some from a mate on the railways,bit more expensive but worth it if damp is an issue.

 

[Guitarist]

Personally Biff, I fit a backbox and blanking plate if I have to. I never said that bricks corrode, but crimps that have got wet can oxidise and cause problems down the line. I'm sure we've all seen it at some point.
Each to their own though, as the old saying goes.

 

[Guest55]

Fair do's.

 

[OscarMike]

What if the cables are under a floorboard or in an cupboard for instance, So accessable. would normal insulation tape suffice

 

[stef]

It looks tatty and unprofessional, a maintenance free junction box doesn't cost an arm and a leg, it can be secured to joists, looks neat and it is safe. The thing with tape is it won't stick forever due to temperature differences, moisture and dust etc. nah, i would prefer a proper junction box.

 

[malcolmsanford]

Agree with Stef it looks unprofessional and tatty a bit of insulation tape around a joint and so therefore could be against regulation 134.1.1 but more for me would be. that it calls into doubt the mechanical strength and protection of the joint as in regulation 526.1

 

[OscarMike]

Yes i agree obviousley a jb is the better option but if space is limited And crimping is needed or several cables, is heat shrink or amalgamating tape needed with regards to bs7671

Thanks

-OM

 

[malcolmsanford]

The problem you have also is just leaving the connection loose under that accessible floor ( ??) or cupboard.

The regulations in 526.5 calls for a termination to be enclosed either by an accessory or equipment to an appropriate standard, such as a box to BS 5733 or an "enclosure" partially formed or completed with building material, which I doubt under the floor or inside a cupboard will suffice.

You then have reg 528.8 concerning in this case sheathed cable as I'm sure it will be T+E and it's termination into that joint.

 

[Amp David]

And heres me plastering 30 amp JBs into the walls on all my repair jobs:rockon:

 

[PC Electrics]

What if the cables are under a floorboard or in an cupboard for instance, So accessable. would normal insulation tape suffice

NO

Two points:
1. that black/white/red stuff you buy from the wholesalers is not insulation tape. It is PVC tape
2. PVC tape only has a simple sticky layer that remains sticky once applied. It eventually dries out and the joint comes apart. The tape also has very little mechanical strength.

The point about self amalgamating tape is that......well, the clue is in the name really! The layers, once stretched over each other properly, bond together at the molecular level (thats the amalgamating bit) and form a solid rubberised "enclosure". The tape will also stick to the sheath where it overlaps and forms a watertight bond.

Heatshrink thickens as it shrinks. Two layers of good quality heatshrink will end up thicker than the original sheath.

Both self amalg and shrink are designed and engineered to provide both high dielectric and mechanical strengths.

Denmans do a very high quality self amalgamating tape that is thick and strong (much better than the stuff from Screwfix or Toolstation)
I get my heatshrink from thesitebox.com. They do all sizes and colours and glue lined.

 

[i=p/u]

I bought heat-shrink the other day and was 2 .40 per meter ... I use crimps and either put , amalgamating tape over each joitnt or i put in choc box.

But amalgamating tape reinstates the sheath.

 

[Amp David]

This stuffs good

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