Buried SWA cable fault finding

[ruston]

As the posts above , get the people in with the gear to find it. The cost will be compensated by the time you waste and end up having to get help anyway.

 

[timhoward]

Quick further thought - if recently installed it will be metal boxes both ends. To ask an obvious question, are you sure the live isn't simply resting on the box the end you aren't testing, with the SWA still glanded to the case and providing the continuity you are seeing? If so this might be a red herring.
I'd be looking first and foremost where the cable leaves the house and enters the garage - are there any joint boxes there that have water ingress.
Obviously if you completely removed the SWA, including glands both ends then this isn't a valid thought.

 

[Intoelectrics]

Quick further thought - if recently installed it will be metal boxes both ends. To ask an obvious question, are you sure the live isn't simply resting on the box the end you aren't testing, with the SWA still glanded to the case and providing the continuity you are seeing? If so this might be a red herring.
I'd be looking first and foremost where the cable leaves the house and enters the garage - are there any joint boxes there that have water ingress.
Obviously if you completely removed the SWA, including glands both ends then this isn't a valid thought.

Absolutely, you have got to completely rule out all the obvious and exposed parts first, else it could end up an unnecessary expensive repair.

 

[danielz000]

What were all the readings between cores and between cores and armour?
and end to end continuity of each core?

as it’s a 3 core, you could swap the colours and use the shorting out core as earth.

That’s only possible if only one core is damaged. And it’s not a long term solution as any moisture will eventually rot the armour away.

Thanks! Swapping cores isn't something I thought about. I believe my earth and neutral are in good condition so that might work!

Edit: I haven't checked continuity end to end as the multimeter won't reach the far. I can try connecting the other ends and doubling back though. I haven't tried resistance yet but will do asap.

 

[danielz000]

Guys loads of replies. Thank you so much. I'm going to read through them all now.

 

[danielz000]

Even if you work out how far from each end it is, and unless you know for sure it’s in a straight line and not wiggling all over the place…. You might still end up digging a 6ft wide hole looking for it.

Advise getting a professional with proper test equipment to check it. Your multimeter may not be picking up slight damage to a second core which would scupper my suggestion above.

multimeters give out roughly 9v…. Professional gear- up to 1000v

Thanks mate, I'll look about for a professional but a brief search last night didn't pick anything up. I know the exact root and depth of the cable.

 

[littlespark]

Thanks! Swapping cores isn't something I thought about. I believe my earth and neutral are in good condition so that might work!

As my further post said…. Get the cable checked by a professional with the right test equipment. There may be further damage to the cable that you’re multimeter isn’t detecting.

Make sure you identify the cables properly at each end… not just a little flag of tape that could fall off.
Might surprise a future electrician finding a brown core on the earth bar

 

[DPG]

Thanks! Swapping cores isn't something I thought about. I believe my earth and neutral are in good condition so that might work!

Edit: I haven't checked continuity end to end as the multimeter won't reach the far. I can try connecting the other ends and doubling back though. I haven't tried resistance yet but will do asap.

You definitely need to IR test the cable and see what the damage is. The other cores may be damaged also.

 

[danielz000]

Thanks everyone.

It's a long story, but in regards to the ducting, these builders were absolutely ripping the arse out of it on day rate. In the end I got so frustrated I just had to settle with a number of things I wasn't happy with including the lack of ducting.

In regards to a second hand Megger I'll look in to that if I can't find an electrician smart enough to do it.

Out of curiosity though, how would an insulation resistance test work and would it help me locate the break? Or just confirm the damage exists?

Thanks again little spark, swapping the cores isn't ideal and a repair was my favoured option but swapping cores might be a good temporary fix!

 

[DPG]

Thanks everyone.

It's a long story, but in regards to the ducting, these builders were absolutely ripping the arse out of it on day rate. In the end I got so frustrated I just had to settle with a number of things I wasn't happy with including the lack of ducting.

In regards to a second hand Megger I'll look in to that if I can't find an electrician smart enough to do it.

Out of curiosity though, how would an insulation resistance test work and would it help me locate the break? Or just confirm the damage exists?

Thanks again little spark, swapping the cores isn't ideal and a repair was my favoured option but swapping cores might be a good temporary fix!

I'd be getting the builders back and getting some of the original bill refunded. . The repair to this cable is going to cost you money - it will almost certainly need an electrician.