On 05/03/2018 20:13, ARW wrote:
Take a 3 phase incoming supply to a main distribution DB with a C100A
rated main switch.

This DB has a C63A 3PH MCB to power DB1 that is about 15m away with some
16mm SWA.

You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Then you turn on the 20A MCBs?

So which goes first?

One of the 13A BS1362 fuses, both of the 13A BS1362 fuses, a B20A MCB
etc............?

Educated guesses welcome.

What was the PSSC at the supply end?

(although I am guessing since you asked the question probably the 63A
3ph MCB ;-)


--
Cheers,

John.

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