discrimination.

[paddyc3112]

I have a 63amp mcb feeding a 60amp switch fuse which feeds a fuseboard - is this good enough discrimination??

 

[paddyc3112]

Also, do I need double pole isolation for this submain or can I do away with the switch fuse all together??

 

[Darkwood]

Cant you just fit links into the switch fuse and have the up-stream device as your sole means of overload.... and in short circuit you wont achieve any discrimination and check you time/current curves for the mcb and whatever type fitted in switchfuse to see about the overload discrimination.

 

[Darkwood]

If your sub mains has a main switch it wont require another local means of isolation, if the switch fuse is the local means for the D.B. then get some links for the isolator and turn it in to a isolation switch only.

 

[paddyc3112]

Thanks darkwood.

So I can link out in the switch fuse and do away with the fuse.

Do I still need double pole isolation for the submain or is a single pole 63amp mcb suitable??

 

[Darkwood]

Its a submain and only requires single pole isolation as from your last post i now assume its single phase..i would suggest not having it as double pole unless your isolator has early make and late break on the neutral ...although this is more crucial to 3ph systems where damaging voltages can occur if neutral makes late or breaks erly.

 

[paddyc3112]

It is a 3 phase system but the submain is only 1 phase.

Thanks got you help darkwood. Much appreciated.