Swa earthing/termination

[taycast]

I have my shed connected to house by3 x 2.5 mm swa in to a 13amp fcu in house which is rcd protected at the cu. This terminates in shed to another 13 amp fcu which supplies a twin socket, and then a 3 amp fused connection unit for light ( all latter switches and boxes metal).

My only mistake is I have not earthed armour as local spark told me it wasn't needed. I have studied other posts and pics, which are v. useful.

However, I cant see a solution to my problem. I have cut armour as swa enters house, with 3core continuing in insulator to fcu in house. What box should I use to earth swa with gland on outside wall? Could I use a IP 66 junction box, terminating swa with gland/banjo or piranha nut, then 2.5mm twn & earth going through hole to fcu in house? More preferable, is there another type of box which could go on outside on house to earth armour, but leaving existing 3 core and sheath heading through wall to fcu. I know both methods will require earth conductor going from banjo/nut but what size of earth conductor, and would I connect to earth in load of fcu or elsewhere?

Thanks

 

[Adam_151]

Not really sure its right to have the cores from the SWA passing through the wall only surrounded by the bedding (I'm not sure the bedding counts as a sheath as such)

Putting that issue aside, galv conduit trouser box, one CW20S, two stuffing glands (if you one that will go small enough for something like 4/6mm earth), one lid and a gasket

 

[sparkyspike]

How have you connected the other end of the SWA to the metalclad fcu in the shed? Have you glanded it with a banjo bolted onto the box? If so, you don't need to earth the other end necessarily.

 

[taycast]

Thanks for your speedy replies. Sounds quite tricky.

At the shed, I have done the same - just cut the armour a bit short then run the 3 core and sheath into a 6 cm bit of plastic conduit to the fcu.

Other posts have mentioned earthing at supply end but it would be easier for me to wire shed end. I could lower fcu in shed to armour level to do gland etc if you guys think that is ok.

That means I would connect with banjo/ pirannah nut, then connect earth lead to earth terminal in supply in fcu?

 

[sparkyspike]

Yes, as long as the fcu is earthed between the terminal and the frontplate, you can use the fcu for the earth connection. You can use a banjo and bolt, or Orbix screw, or a pirhana nut.

What kind of earthing system do you have at the supply?

 

[taycast]

TN-C-S.

Please say if this changes things. Want to get this right, even if it means paying the pros to do it for me.

Thanks again

 

[sparkyspike]

There is only an issue if you have any structural metal, or water or gas pipes etc in the shed. Or a concrete base could be an issue.

It's all to do with exporting the earth from a TNCS system. You either insulate the earth and use a rod instead, or run a larger earth cable (usually 10mm) in order to be able to bond the shed to the MET.

 

[taycast]

None of these so sounds like I should be ok.

Thanks for all the info.