Jim K wrote:

ARW Wrote in message:
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.

--
Adam


The 20A MCB?
(uneducated in electricals)

Purely from domestic experience I reckon one or both B20 MCBs while the
13A fuses are in a brief molten/vaporised state. But also no expert.
It may be possible to calculate whether the C63A should trip before the
others have time to open.

--

Roger Hayter