3 phase supply to classroom, unsure to TT?

[Toneyz]

Is there an existing distribution board in the new building?

 

[mpoy222]

Is there an existing distribution board in the new building?

No its a new building, there was a mobile unit there a few years ago but there was just a cable left over. This building is meant to be more permenant. The cable was just disconnected in the main building DB. It runs under a playground so theres no chance of running a new one or thats the route i would have gone. I've been asked to reinstate the cable and fit a new DB plus a few sockets, lights and water heater for the toilet.

 

[Toneyz]

Ok thanks so all new wiring then.

 

[mpoy222]

Ok thanks so all new wiring then.

Yep everything in the building will be new.

 

[westward10]

So is main protective bonding required.

 

[davesparks]

Thats the one mate. The earth strap in these kits cant have the same CSA as the armour so i didnt want to use it as a main earth. Its a resin joint.

The CSA of the tinned copper braid is different to that of the armour, copper has a much higher conductivity so you need far less of it to get the same current carrying capacity.
If a correctly sized joint kit has been used then I see no reason to worry, it has been designed for this purpose.

 

[davesparks]

Thats the one mate. The earth strap in these kits cant have the same CSA as the armour so i didnt want to use it as a main earth. Its a resin joint.

The CSA of the tinned copper braid is different to that of the armour, copper has a much higher conductivity so you need far less of it to get the same current carrying capacity.
If a correctly sized joint kit has been used then I see no reason to worry, it has been designed for this purpose.

There is no seperate CPC. The SWA is earthed but i wasnt confident in using this as a main earth for the installtion of the building because of the join.

If you are concerned that there is a problem with the joint cut it out and re-joint the cable properly.