3 phase TPN boards - earthing TT

[Jsummers923]

Hi guys, starting a new install on a job soon and having a complete mind blank. The supply at the main cut-out is a 3 phase TNCS supply. There is then a 50mm SWA running a considerable distance to a workshop where i will be installing a new TPN board as well as an earth rod to make all the workshops on a TT arrangement. From the cut-out end obviously the SWA armouring will be earthed in the switched fuse via the TNCS supply, but i want the workshops separate to this on a TT arrangement. How would you suggest i configure this in a way that the TNCS arrangement isnt continuous through to the TPN boards via the SWA armouring?

Any suggestions would be greatly appreciated.

 

[mainline]

Hi guys, starting a new install on a job son and having a complete mind blank. The supply at the main cut-out is a 3 phase TNCS supply. There is then a 50mm SWA running a considerable distance to a workshop where i will be installing a new TPN board as well as an earth rod to make all the workshops on a TT arrangement. From the cut-out end obviously the SWA armouring will be earthed in the switched fuse via the TNCS supply, but i want the workshops separate to this on a TT arrangement. How would you suggest i configure this in a way that the TNCS arrangement isnt continuous through to the TPN boards via the SWA armouring?

Any suggestions would be greatly appreciated.

A suitable stuffing gland ?

 

[westward10]

Contain in an all insulated enclosure and identify it's purpose. Don't expose the armour within and wrap in self amalgamating tape, fit terminal blocks and come out in 6181Y.

 

[timhoward]

Normally I use an intermediate plastic enclosure, terminate the SWA into it, and run the cores right through the box and use a plastic coupler to the board. Though that could get a bit fun with 4 x 50 sq mm conductors!

I wondered about 6181Y, wasn't sure you can get anything other than yellow/green in 50 sq mm.

 

[Jsummers923]

A suitable stuffing gland ?

Thanks for the reply, this did go through my head but i was second guessing as to whether I'd get called 'rough' thanks again

 

[westward10]

You can get 50.0 6181Y.

 

[Jsummers923]

Contain in an all insulated enclosure and identify it's purpose. Don't expose the armour within and wrap in self amalgamating tape, fit terminal blocks and come out in 6181Y.

Thanks for your reply mate

 

[westward10]

I wouldn't use an exposed stuffing gland too easy to undue and access the armour even if the sheath isn't removed.

 

[timhoward]

You can get 50.0 6181Y.

Ah my bad, I always get "singles" and "meter tails" backwards by number....sorry
I was briefly contemplating plastic trunking and singles before deciding the conductor size was too big for that.

 

[brianmoooore]

Does the 6181Y have to be 50mm2? I'm assuming the SWA is sized for voltage drop, since the OP says "considerable distance", rather than current carrying capacity.

 

[pc1966]

I wouldn't use an exposed stuffing gland too easy to undue and access the armour even if the sheath isn't removed.

I'm assuming the cable will have to be cleated well to hold it in place anyway, as a stuffing gland ain't going to hold it tight like a SWA gland to metal box would do?

If so the gland is really serving as an IP seal and less of a cable termination method and in which case it seems reasonable enough to take it in directly to the TPN board a few cm beyond the gland and then some self-amalgamating tape over the end of the SWA sheath and cut/snapped off armour to tidy up and avoid accidental contact. Fewer joints and not too different from a usual TN earthed board.