Cable failure was it wrong cable?

[ericmark]

I found the electricians rewiring mothers house about to use twin and earth on a cantenary wire to supply garage from house, I pulled them up on this and what seemed to be a tough black cable was used instead.

This was a twin core and earth with a foil touching the earth screening the cable, at the time I did not question this cable,

was brown, blue with black outer but looks similar to picture.

When the new roof was being fitted to garage the builder was making a hammering sound and with one bang the power went off, tried to reset, but tripped a B32 MCB, a RCD and a 13A fuse, tried to test with multi-meter no fault found, but replacing fuse it ruptured as soon as switched on.

Cable was replaced and all worked, but I felt the builder had done something to cause the problem. New insulation tester arrived, blue shows completely clear, but brown showing around 5 MΩ varying, but cable now disconnected, but still on the catenary wire.

The picture clearly states not suitable for 240 volt. So the big question was the electrical firm responsible for failure or builder? Can't really blame builder if the cable was wrong type and simply failed because of vibration.

I thought it was the cable for the job, but now not so sure, clearly on a canteinary wire cable will flex so neither SWA or T&E are suitable, this cable has around 7 strands in each wire, but not what I would call flex.

I can see no external damage, but since replacing it with flex has cured the problem there is something wrong with it, I have not got step ladders tall enough to cut all cable ties to get it down.

I had expected to find down to earth with insulation tester, but that was not the case. Any ideas as to what cable it is and if rated 240 volt?

 

[bernardgreen]

Looks like cable for 100 volt line speaker systems

 

[ban-all-sheds]

I wonder if they thought it was BS8436

 

[bernardgreen]

I wonder if they thought it was BS8436

BS8436 is not a catenary type cable.

AEI Cables has launched a new screened wiring cable which exceeds the requirements of BS8436 for use in walls, partitions and building voids where there is a risk of damage or penetration from nails or screws. Protec is a multi-purpose, future-proof cable ideal for industrial, commercial or domestic applications.

It has been designed by AEI Cables as a Low Smoke Zero Halogen (LSZH) screened cable which, due to its reduced electromagnetic interference, is also an ideal choice when electromagnetic compatibility (EMC) is a priority. This is of particular importance in hospitals or where IT equipment may be used.

The product exceeds the requirements of BS 8436 and satisfies the requirements of the new 17th Edition IEE Wiring Regulations. Under Chapter 52, there is reference to the specific selection of cables which are installed less than 50mm from the surface of a wall or void.

Protec has been specially designed and manufactured to satisfy these new regulations and can be easily stripped, providing reduced installation time and cost for the electrical contractor.

Typical uses for Protec are in computer rooms, hospitals and airports, and for fans and heaters, ventilation systems and air conditioning systems.

 

[ban-all-sheds]

BS8436 is not a catenary type cable.

Of course.

Thank you for that valuable input, Bernard, because it means we can discount the possibility of anybody ever using it as such, for exactly the same reasons that nobody has ever suspended twin & earth from a catenary wire.

 

[ericmark]

OK actually cable. Could not get a good picture last night. It has an area which is not perfectly round so possible the builder slipped with a hammer, But can hardly charge the builder if the wrong cable to start with.

The builder I should have realised what he is like, his name is Jerry! has damaged an array of items while doing the work, caravan mounding around tow hitch, stood on a dolls house, got grinder hot metal on freezer and camping trailer, and has helped him self to items out of my garage like cable ties which he used as if no tomorrow, he was to replace the roof on garage, he was trying top persuade me to have the work done, so he agreed to empty garage remove roof on Sunday and replace by Wednesday, but did not empty garage, removed the roof using grinder, and took nearly 4 weeks to replace the roof. He did put a tarpaulin on roof however all it did was stop it drying out again after the rain.

OK some of the delay was due to bad weather, however that made it worse, and it was not bad weather on the Wednesday when due to replace roof, he said he could not get hold down bolts, we actually found a supplier and got them for him. He is a miss measure once and cut twice guy.

Being fair finished product looks good, however when working outside on my house, (some work on mothers, some on mine and some on father-in-laws) my power also went off, the house 1979 has cables in the cavity wall, and he was doing pointing, if I find he damaged garage cable without admitting it, then I must assume he has also damaged cable in cavity wall without admitting it! I have caught him doing some things which are questionable. This is how I found a socket in the garage after he had left, I was going around trying to find out what had gone wrong, seems he wanted to help, however this socket was no where near where he was working, or myself, so it was not something I would naturally look for.

We still have not made final payment, so we are looking at what to hold back from final payment. But want to be fair never the less.

 

[ericmark]

Although black it seems this is one of the Doncaster cables firesure range. I can see Doncaster cables marked on it and firesure, however the writing is not plain enough to read the part number. However it would seem this cable was suitable for outdoor use, even if not ideal for hanging off a catenary wire. So down to builder to repair or replace not the electrical firm which is the info I needed.

 

[Cigaro]

Looks like shielded twisted pair. I use it in vehicles for reducing noise on cam and crank sensor signals. I've never seen this sort of cable used in a mains voltage installation before and I'm struggling to think why you'd want to...! Although the colours do seem to suggest it was intended for this use.

 

[RF Lighting]

It does look like an FP200 type cable. Are the live conductors insulated with a silicone type material?

 

[ban-all-sheds]

Looks like shielded twisted pair.

No it doesn't.

 

[Cigaro]

No it doesn't.

After I hit "post" I went and looked for screened mains cable, to find that it does, indeed, exist.

I'm still not sure why, though.

Same if it's fire-rated - what benefit does the screened outer section have for fire-rated cable?

 

[ban-all-sheds]

After I hit "post" I went and looked for screened mains cable, to find that it does, indeed, exist.

Screened does - it was the "twisted-pair" part that was incorrect.

I'm still not sure why, though.

With some, e.g. BS8436, it's so that anything penetrating the cable makes contact with an earthed layer first, then if it hits a live conductor the protective device will operate.

What its function is for fire-resistant cables is I don't know. My guess would be mechanical strength.

 

[Ragnar_AT]

Some hippie folks specify screened to reduce electro-magnetic fields in their homes. I believe it's also used in EMF-sensitive environments like certain medical treatment rooms and that's probably what it was designed for.

 

[ban-all-sheds]

Some hippie folks specify screened to reduce electro-magnetic fields in their homes.

There's nowt so queer as folk, as they say in some parts of the UK.