Earthing armoured on a sub-mains

[robd]

Guys, am doing a maisonette, the meter box is downstairs in the garage and the CU is approx 8 metres away so have pulled in some SWA as a sub-mains (25 mm2 3 core using one of the cores as the main earth). Have a CU that I can’t gland into, and the other end the SWA is going into the meter box. Realise that I need to bond the armoured as an exposed conductive part, any practical ideas as to how? Many thanks

 

[Sav]

Hi,
Is it a TT, TNS or TNCS system ?

Also, you will need some kind of double pole isolator from the incoming supply to your c/u ( as you now have set up a submains as you have mentioned ).

Sav

 

[robd]

TNC-S Sav

 

[robd]

Also, you will need some kind of double pole isolator from the incoming supply to your c/u ( as you now have set up a submains as you have mentioned ).

Can I not use the self connect switch (100A DP) next to the meter for that?

 

[Sintra]

Gland SWA into a metal switch fuse at supply end and earth box and armour there.

 

[Mr Mark Sparks]

gland swa into adaptable box then run earth from cu earth bar to banjo (sheath will be earthed from load end thats fine)

 

[Sintra]

Can I not use the self connect switch (100A DP) next to the meter for that?

No as that is just an isolator and does not provide overcurrent protection for the sub main.

 

[Sav]

So,
25mm tails from your incoming mains supply, into your double pole Isolator (work out fuse rating ).
Make off your swa into isolator using gland kit and earth the armoured via banjo into earthing bar in isolator. You will also need an earth from the earthing bar to go into the MET.
If your c/unit is plastic, then you can still make a 25mm hole at the bottom and again using a gland kit, earth the armoured using a banjo.

Hope this is of some help,
Best regards,
Sav

 

[Spudnik]

Not all CU's will take a 25mm SWA gland as the covers go right over and back to the wall.

If installation methods allow, split con would have saved all the hassle

 

[robd]

Possibly not that well thought through on my behalf, however tbf the CU is wall mounted on a stud wall with everything coming in from the back so not sure where I'd have got a gland in there... am a bit worried as to how much room I will be left at the meter end by the time siemans come and do their bit as to whether or not I'll get a metal DP switch fuse in there