In line switch fuse ???

[sparky692]

Hiya Fellas. Need some views on a up and coming job
quick scenario.. 3 phase 100amp head and supply . 9 units all slightly different but all with the same head and supply.
some have 16 or 25mm tails through a isolator to either 3 phase DBs or that plus a single phase CCU.
question is as far as the single phase ccu is concerned i think i need a 60 amp switch fuse between the head and the main switch on the ccu as its only 60/80 amp rated. also size of the tails should be 25mm minimum as its 100 amp head. Any views . switch fuse with 25mm tails or is it ok ?

 

[Knobhead]

Personally I can’t see what you’re worrying about. Are the tails over 3m? If you’re that concerned change the CU isolator to a 100A unit.

 

[Deleted member 26818]

What's the loading on the single phase CU?
If it's less than 60A, then I wouldn't worry about it.
Obviously, if it's a lot more, then you would probablly be best to as Tony suggests, uprate the main switch, and the tails.
I believe 16mm² has a CCC of 87A in free air or on perforated tray.

 

[needasparks]

Why can't you feed the single phase from the three phase db on a 63a mcb ? Or did i miss something, seems alot of work and parts to install another s/fuse.

 

[mogga]

assuming the db is within 3mtr of the cable head 25mm tails to the 3ph db then 16 or 25 from a 63a cmb to the single phased db
just watch for balancing the phases accordingly