Terminating 50mm tails into rccb?

[wozzit99]

Hi

Due to the long length of a distribution circuit I'm installing, the cable csa is 50mm sq.
The earthing arrangement at the origin is TT.
25mm tails at the service are to be connected to a 300ma 100amp time delayed rcd then into a 100amp s/fuse ( fuses rated at 80 amp )
From the s/fuse a 50mm sq 4 core cable is going to be ran to a out building some distance away which is to supply a 4 way 3 phase dis board.
The NICEIC advised me to install a separate TT earthing arrangement at the db end.
The problem is I have to terminate 50mm sq 4 core armoured cable into an rccb. I know I have to keep the armoured insulated from the db earthing system but how am I going to connect the tails?
Are there any rccb's which will take this cable size?
It would be a hell of a lot easier to export the origin TT that way I could terminate to a isolator at the db end.

Cheers

 

[Guest123]

If you do still need to find a suitable termination, pin lugs......

 

[spark 68]

@ E54,

Connect them altogether and improve the overall TT system, using the SWA of your 50mm 4 core cable...

That is what I would have done, for the same reason, but I did not want to contradict the NIC, in case it was for a specific reason they wanted it done this way.

 

[netblindpaul]

You could use an SWA 50UP to go from 50mm sq core quite easily and really acceptably down to a 35mm sq pin.
Try here:
http://www.s-w-a.co.uk/resources/Copper_Tube_terminals/un_insulated_copper_reducing_pin.pdf

 

[netblindpaul]

Lenny,
You beat me to it a little, though I gave a part no & maker for a 50>35 reducing pin!

 

[Engineer54]

Sod the NIC, ....They do not make the rules, even though they like to THINK they can!! Ring them and ask for specific reasons Why they want to separate a TT system into 2 separate earthing systems, ....i for one would like to know that one!!!

 

[wozzit99]

Hi Engineer 54

The load is a 50kw micro generator 70amps/ phase max load, the cable is this size to keep the vault drop within the less than 1% range
There will be four inverters supplied from the sub db.


As for the Nic ,the guy did not give a clear reason about seperating the earths just said do it.

 

[Engineer54]

E54, A "TRUE" PME system...

Not with you, have i missed something somewhere??

 

[netblindpaul]

Think what PME stands for exactly...

 

[Engineer54]

Hi Engineer 54

The load is a 50kw micro generator 70amps/ phase max load, the cable is this size to keep the vault drop within the less than 1% range
There will be four inverters supplied from the sub db.


As for the Nic ,the guy did not give a clear reason about seperating the earths just said do it.

That's because there isn't a clear reason!! Different if the source supply was PME, but it isn't so don't try separating the TT system, you'll be defeating the very nature of a TT system...

 

[spark 68]

Think what PME stands for exactly...​

Protective Multiple Earthing​

 

[Engineer54]

Think what PME stands for exactly...

Protective Multiple Earthing , i know, and yes that is exactly my point!! But by just stating PME on this thread it will confuse the young or inexperienced into thinking along the lines of PME/TNC-S supplies, but that was not really what you (or i) were talking about is it??...lol!!!