3phase supply

[badwolf]

Hi there, heres hoping i can borrow some of your time to corroborate an nic inspector's advice.

The job is to move a 3p+n supply 30m to an adjoining building through a duct in the ground. The customer needs over 70A per phase for his equipment. So coming from the existing kiosk with 3phase cutout with suppliers isolator, the nic inspector has asked for an mcb to be fitted in the kiosk, along with the existing isolator.

So this means fitting a 100A mcb and keeping the 100A isolator? is this correct, surely a 3pole switch fuse would be better?

Any ideas?, thanks.

 

[Sintra]

Re: 3phase move

He might be advising installing a 100A MCB to provide discrimination between the circuits overcurrent protection and the supply fuses.

ie. A BS 1361 100A fuse takes 5 seconds to disconnect with a fault current of 630A where a BS 60898 100A B type MCB will disconnect in 0.1 seconds with a fault current of 500A.

Hope this helps.

 

[ACDC]

Only a guess, is the equipment down stream protected by MCB`s? if so, fitting fuses upstream could possibly screw your discrimination and tripping times. (Fuse and MCB combinations are the worst).
Maybe thats why the NIC chap suggested MCB`s