UK Buried SWA Troubleshooting

denny2k2 · Jun 3, 2023

Hi guys, long time lurker first time poster.

I have an SWA 3 core armoured cable buried that runs to my back garden. This originally serviced an old delapitated workshop from the previous home owner. The workshop was removed, SWA armoured cable cut and left available to be reused in the back garden or hooked up to new shed or garage.

I’ve decided to use it as a simple feed to power an outdoor double socket for occasional electrical mower/strimmer and outdoor lighting

I was always under the impression it fed straight to our main fuse box, labelled under “garage” which is RCD protected. This has always had the garage breaker off ever since the workshop was removed.

I’ve switched the fuse breaker on to test that the cable is live with a multimeter and it’s showing as dead? Other than the fuse itself, is there anything else that could cause it to be dead?

I’ve checked for any switches and there is one under the fuse box that I thought might control the feed but it’s still dead with that switched on or off.

Any help would be great!

Will provide pics below.

timhoward · Jun 3, 2023

A general point - before relying on an old underground cable being ok to use again you could do with finding a friendly sparks to do a quick insulation resistance test on it. (Your normal multimeter can't do that). That will prove beyond any doubt that the cable isn't damaged. There are also safer ways to check the cables integrity and polarity. We prefer knowing it won't go bang as opposed to hoping it doesn't go bang!
Regarding your actual question, first thing I'd do is turn off, remove the fuse, and with your multimeter set on Ohms (resistance) see if you get very low resistance when you touch either side of it. If the fuse has gone, I wouldn't just replace it in case there is a dead short somewhere underground. So we come full circle to getting it properly tested.

denny2k2 · Jun 3, 2023

timhoward said:
A general point - before relying on an old underground cable being ok to use again you could do with finding a friendly sparks to do a quick insulation resistance test on it. (Your normal multimeter can't do that). That will prove beyond any doubt that the cable isn't damaged. There are also safer ways to check the cables integrity and polarity. We prefer knowing it won't go bang as opposed to hoping it doesn't go bang!
Regarding your actual question, first thing I'd do is turn off, remove the fuse, and with your multimeter set on Ohms (resistance) see if you get very low resistance when you touch either side of it. If the fuse has gone, I wouldn't just replace it in case there is a dead short somewhere underground. So we come full circle to getting it properly tested.

That all sounds pretty wise! Think that's what I'll do then if fuse is ok.

snowhead · Jun 3, 2023

Can you see the end of the SWA at / near the main box in the house?

denny2k2 · Jun 3, 2023

snowhead said:
Can you see the end of the SWA at / near the main box in the house?

Yeah, pics below should explain the set up.

[ElectriciansForums.net] Buried SWA Troubleshooting

IMAGE 001 - Garage labeled as MCB 1.

IMAGE 002 -Wider shot of CU

IMAGE 003 -In cupboard below CU, this looks like the SWA box with warning label.

IMAGE 004 -This is what is on the other side of the wall, cable coming out is likely SWA (helpfully painted white by previous owners) which is buried.

IMAGE 005 -Finally the SWA within the back garden itself.

westward10 · Jun 3, 2023

What colour are the conductors within that black box.

loz2754 · Jun 3, 2023

The cable has more than likely been disconnected in the consumer unit for safety reasons.

denny2k2 · Jun 3, 2023

westward10 said:
What colour are the conductors within that black box.

Brown, Black and Grey (with earth sheath) and armoured to matches the SWA outside

denny2k2 · Jun 3, 2023

loz2754 said:
The cable has more than likely been disconnected in the consumer unit for safety reasons.

It's looking likely or the fuse/MCB is faulty/needs replaced

westward10 · Jun 3, 2023

You need to stop switching on the mcb to see if it is live, with the cable ends floating about it is dangerous. An electrician can easily check the mcb and carry out continuity and insulation resistance tests.

denny2k2 · Jun 3, 2023

westward10 said:
You need to stop switching on the mcb to see if it is live, with the cable ends floating about it is dangerous. An electrician can easily check the mcb and carry out continuity and insulation resistance tests.

Yep, haven’t touched anything since I realised it was dead/a fault. So kept everything off and tidied away. The cable ends are wrapped up/capped and stored away from elements.

brianmoooore · Jun 5, 2023

No one going to mention the 'C1' bell transformer?

davesparks · Jun 5, 2023

brianmoooore said:
No one going to mention the 'C1' bell transformer?

No because that's not relevant to the question and the OP clearly doesn't care about electrical safety as they have been attempting to make a bare ended cable live.