Earth connection for SWA and correct cable size?

[fuzzytrifle]

I've just had a couple of lights installed along my drive, the electrician has used 2 core 1.5mm SWA cable.

I don't really want to question the work done, but is it OK to use the armoured sleeve on the SWA cable as the earth? Previous electricians have used 3 core cable, connecting both the sleeve and one cable to the earth.

Also, is 1.5mm cable adequate? Cable length is just short of 50m, two lights fitted with 40w bulbs and no provision for extra lights is needed. The cable runs through buried conduit for the first 20m and is then clipped to the back of the top rail of a fence for the remaining 30m.

Many thanks in advance.

 

[Iggifer]

1.5mm is more than adequate, you're drawing less than half an amp.

And yes, it's perfectly acceptable (in certain situations) to only use the SWA as the earth. Using a core as a CPC is sometimes belts and braces, but with larger cables where the amount of copper is much larger than the amount of steel, it is needed. In your case, it's fine.

 

[ban-all-sheds]

clipped to the back of the top rail of a fence for the remaining 30m.

What if the fence blows down or is damaged in a storm?

And even in the absence of such gross damage, fences tend to move a bit all of the time under the pressure of normal winds - what has the electrician done to ensure that the cable won't be damaged by long-term flexing?

 

[fuzzytrifle]

clipped to the back of the top rail of a fence for the remaining 30m.

What if the fence blows down or is damaged in a storm?

Sorry, I should have mentioned that it's a 3' high field fence - three rails and 6" x 3" posts. The cable has slack at either end where it is connected to junction boxes and has plenty of clips.

Thinking that maybe I should have got him to use the existing conduit that runs the entire length of the fence, but would be a real pain to access due to a hawthorn hedge.