Joining Armoured Cable together.

[psd99]

Hi guys,

I got my wiring done recently and one of the circuits is dedicated to my garage which is like 25 metres away from the RCD unit.

Irritatingly The RCD for the garage trips and then it will not turn back on again causing all of the right hand side of the RCD to trip. First I thought it was rain water somewhere but...

I suspect the problem is when I was turfing my garden I remember slightly nicking the armoured cable and that might be causing the trip. I think two of the cables are touching each other and causing the trip.

So it looks like I am going to have to dig up some of my turf to get to this cable and patch the cable up.

but how exactly do I re-join armoured cable together? What type of unit/box do I need that I can keep underground permanently?

Links to products would be good or names. Thanks.

 

[Armageus]

Quick google suggests something like this:
http://www.screwfix.com/p/prysmian-puj2cc-resin-joint-kit-2-5mm-4-core-max/61439
http://www.screwfix.com/p/prysmian-puj10cc-resin-joint-10mm-4-core-max/43363

Assuming it's SWA cable.

 

[psd99]

so the problem I got right is how will I know exactly which type of cable I have?>

i.e 2.5mm 2 core or
4mm 3 core

what does the core bit mean just like live, neutral and earth?

 

[psd99]

thanks for the reply

I think I shall have to dig up the ground and work out where this cable is damaged it just has to be the problem.

what type of crimping tool would work? Same one as RJ45?

 

[Syla5]

Core is amount of cables. If its an option you could take your housing cover off your main fuse board and visually check the SWA at the point its wired in to see if its 2 core, or 3 core etc and also the diameter.

 

[psd99]

it also might also be written on the cable? so 2 core is 2 little cables and 3 core is 3?

I might need to actually join this up twice and buy additional cable as it will not be long enough to rejoin.

 

[Mercenary Keyboard Warrior]

I cant see how you can just nick armoured cable and cause that fault unless the strands are being used as an earth.
If the have nicked the outer and are earthing the strands then surely just a decent repair with waterproof tape is enough to isolate the strands

The point of armoured is that you cant simply nick the cores

 

[Gaijin]

At risk of sounding like a nag - if you nicked it whilst turfing, considering re-burying it deeper when you have a look at it. I think it's advisable to bury it at least 45-60cm down.

If it makes you feel any better, I have to do 40 metres of it over the next few weeks without the use of a digger, all in 50mm ducting.

 

[MassiveJim]

I cant see how you can just nick armoured cable and cause that fault unless the strands are being used as an earth.
If the have nicked the outer and are earthing the strands then surely just a decent repair with waterproof tape is enough to isolate the strands

The point of armoured is that you cant simply nick the cores

I did think this also, you would have had to hit it pretty hard with something with at least an edge on it to damage it.

From your post it seems as though you might not fully understand what SWA is, it (should be) a 2 or 3 core cable surrounded by a steel sheathing. So even if you slightly nic the outer sheathing the core will still be protected.

Might be a lot easier and cheaper in the long run to get a qualified spark out to locate the fault for you.

 

[Entai]

It's recommended to bury SWA at around 400mm depth and also lay marker tape above it along the whole length of run, at a depth of 250mm, so that you will always come across that first and know there is cable underneath.

Obviously you laying the cable will know where it is, but the next house owner or other tradesmen you bring in possibly will not know hence the need for marker tape.

It's not unknown to bury SWA direct, but ideally you should put it through ducting or conduit or trunking of some sort, preferably black or orange in colour. If it is buried direct, then normally there is then a requirement to surround the cable with sand filtered free of sharp stones, to around 100mm around the cable, then top soil above that and turf or whatever above that.

 

[Gaijin]

It's not unknown to bury SWA direct, but ideally you should put it through ducting or conduit or trunking of some sort, preferably black or orange in colour. If it is buried direct, then normally there is then a requirement to surround the cable with sand filtered free of sharp stones, to around 100mm around the cable, then top soil above that and turf or whatever above that.

Agreed - I bought 50 metres of red ducting today and already had bought the warning tape.

 

[JustBen]

At risk of sounding like a nag - if you nicked it whilst turfing, considering re-burying it deeper when you have a look at it. I think it's advisable to bury it at least 45-60cm down.

If it makes you feel any better, I have to do 40 metres of it over the next few weeks without the use of a digger, all in 50mm ducting.

Feel the pain, i did about 5meters digging down 2 foot without a digger and it was hard work! I put electrical cable, waste pipe and a blue water pipe into the trench.

 

[psd99]

interesting replies

what happened was I was using a sharp spade and it did nick the cable
I suspect that the wires were visible inside. I know i should have taped it at the time. I wish I had.
Everything worked fine before the turf but since then it doesn't go on or just trips randomly.

I can't work out what else the problem could be, you're probably right in asking a sparky to come out but money is tight right now.

One suggestion from my friend was to temporarily run another cable from the RCD to my garage and see if that works.

If that does work then 100% I know it is the cable but I still do not know 100% exactly WHERE the fault on the 25 metre cable is! I believe the cable is damaged very close to the garage from memory within a few metres.

 

[Beer_MonsterUK]

Just disconnect the armoured from the consumer unit and see if the RCD stays in / doesn't trip.

If it is the cable, then the only real option is a resin torpedo joint, as stated above, but it's not an easy job for a layman and it might be easier to get a man in or relay the cable.

 

[Mercenary Keyboard Warrior]

If the cable is armoured can you see if the metal sheathing has been earthed?

My suspicion is it has, and you have nicked the outer plastic and opened the now earthed metal sheathing to the elements.This just needs a waterproof repair as you haven't compromised the main cable just created a bridge between the metal sheathing and the outside world, which has probably quickly become damp and is conducting to earth.

If you have somehow managed to cut clean through the outer plastic, metal sheathing and some of the inner wires with one spade cut, which seems dubious as the point of this cable is to protect vs exactly that scenario, then IMO easier to just lay a new line time.

 

[NoobCannon]

I join swa cables every day at work.

If you trust me and provide postage ill send you a resin jointing kit we use on mains cables hey are designed to be buried in the footway

Just find the damage and cut it out. Hopefully there will be enough slack to rejoin the cores and earth bonding (armour) if not you may need to bridge joint a piece in between.

 

[rtho782]

The steel armouring of an SWA cable should be earthed anyway. However, that steel armouring going to ground should not cause the RCD to trip, as the RCD detects an imbalance in the live/neutral phases. What is happening on the earth doesn't matter, except in that current goes there when it's not going over the neutral.

For you to have nicked an actual L/N/E conductor, I wonder if you actually have NYY (non armoured, not suitable for burial) cable not SWA.

It could also be that the RCD tripping is unrelated to this cable. Heating elements for example (cookers, sandwich makers, immersion heaters) tend to cause RCDs to trip when they are close to failure, and RCDs tend to get more sensitive as they age.

RCBOs make it much easier to fault find than an RCD covering multiple circuits.

 

[Telecaster]

I find it hard to believe you've nicked an armoured core with a spade, are you sure it's armoured?

 

[psd99]

thanks for the reply guys that helps...

the RCD works for the garage today bizarrely

I find it hard to believe you've nicked an armoured core with a spade, are you sure it's armoured?

I'm pretty sure it is armoured. It is quite tough cable and black in colour

The steel armouring of an SWA cable should be earthed anyway. However, that steel armouring going to ground should not cause the RCD to trip, as the RCD detects an imbalance in the live/neutral phases. What is happening on the earth doesn't matter, except in that current goes there when it's not going over the neutral.

For you to have nicked an actual L/N/E conductor, I wonder if you actually have NYY (non armoured, not suitable for burial) cable not SWA.

It could also be that the RCD tripping is unrelated to this cable. Heating elements for example (cookers, sandwich makers, immersion heaters) tend to cause RCDs to trip when they are close to failure, and RCDs tend to get more sensitive as they age.

RCBOs make it much easier to fault find than an RCD covering multiple circuits.

I just find it strange how everything was good before I did the turfing. What is RCBO?

I join swa cables every day at work.

If you trust me and provide postage ill send you a resin jointing kit we use on mains cables hey are designed to be buried in the footway

Just disconnect the armoured from the consumer unit and see if the RCD stays in / doesn't trip.

If it is the cable, then the only real option is a resin torpedo joint, as stated above, but it's not an easy job for a layman and it might be easier to get a man in or relay the cable.

Just find the damage and cut it out. Hopefully there will be enough slack to rejoin the cores and earth bonding (armour) if not you may need to bridge joint a piece in between.

Thanks I might need two of these though? I will take you up on your kind offer very soon I guess I will PM you in trust thanks man certainly helps. Just trying to locate exactly which cable this is.

If the cable is armoured can you see if the metal sheathing has been earthed?

My suspicion is it has, and you have nicked the outer plastic and opened the now earthed metal sheathing to the elements.This just needs a waterproof repair as you haven't compromised the main cable just created a bridge between the metal sheathing and the outside world, which has probably quickly become damp and is conducting to earth.

If you have somehow managed to cut clean through the outer plastic, metal sheathing and some of the inner wires with one spade cut, which seems dubious as the point of this cable is to protect vs exactly that scenario, then IMO easier to just lay a new line time.

I will need to dig the ground up to see the cable first.. hopefully soon.

I'm hoping your suspicion is correct and I will just need some electrical tape. what do you reckon? only way of working this out is digging the ground up.

 

[psd99]

Just disconnect the armoured from the consumer unit and see if the RCD stays in / doesn't trip.

If it is the cable, then the only real option is a resin torpedo joint, as stated above, but it's not an easy job for a layman and it might be easier to get a man in or relay the cable.

but with the cable connected + the RCD switch ON for the the 'garage' switch on the RCD that does not seem to work for the whole right hand side
when I turn the garage off everything is okay.

- by removing this cable what do I prove?