Earthing of metal sheathing

[Top Cat]

Got a job coming up where there will be an outside meter box and new consumer unit in hallway (about 4 Mtrs). The only route i can take (and the customer wants) is to chase tails in wall up to D/B.

Was thinking of RCD protection in meter box as cables will be less than 50mm but then i wondered if you earthed the metal sheathing would that be OK to then put a KMF in meter box?

 

[Richard Burns]

Assuming you are using SWA as the tails to the CU then earthing of the armour is fine without an RCD.
Not sure about metal sheathing, what type of cable is this?

 

[Top Cat]

Assuming you are using SWA as the tails to the CU then earthing of the armour is fine without an RCD.
Not sure about metal sheathing, what type of cable is this?

25mm tails that's the "iffy" bit. Just a hypothetical question really. If the sheathing is earthed are you covered?

 

[GaryM]

Sheathing on 25mm tails? It's not April the 1st is it?

You could cover the tails with a 3mm thick metal plate which would offer mechanical protection so no RCD would be needed.

 

[Top Cat]

Sheathing on 25mm tails? It's not April the 1st is it?

You could cover the tails with a 3mm thick metal plate which would offer mechanical protection so no RCD would be needed.

As i said, only a hypothetical question. If in prescribed zones, earthed sheathing, what Reg says no?

 

[GaryM]

You lost me. Earthed sheathing? The sheathing on a PVC 'tail' is PVC!
I think you need to clarify what this sheathing is you're proposing to earth.

 

[GaryM]

Hang on, are you talking about metal capping?

If so it wouldn't comply with 522.6.6

EDIT - quoted from memory, reg number is now 522.6.101

 

[telectrix]

can you use a CATenary?

 

[Top Cat]

Hang on, are you talking about metal capping?

If so it wouldn't comply with 522.6.6

Yes metal capping.
522.6.6? Not in my BGB!

 

[GaryM]

Sorry, quoting from memory. Try 522.6.101, your solution is neither.

 

[Plonker 3]

I would imaging the only earthed sheath acceptable would be ones recognized in the BGB (eg SWA, MIMS, glav conduit trunking etc)

 

[GaryM]

522.6.101 (iv) would allow a 3mm thick steel plate covering the tails. That should be sufficient to prevent the penetration by nails and screws. Don't suggest a Paslode nail gun as that's not normally used on a domestic internal wall!

 

[Top Cat]

522.6.101(v)?

 

[telectrix]

522.6.101 (i) cable shall incorporate an earthed metallic covering. i.e the metallic covering is part of the cable, not a scrap of flimsy capping.

 

[telectrix]

522.6.101(v)?

but if not complying with 522.6.101 i,ii,iii,iv, shall have RCD - 522.6.102

here endeth the lesson.