Feeding 250 amp 3 phase board direct from buzz bar need isolatir

[Lintay]

I'm working in a warehouse and replacing the old fuse boards with a new 3 phase board.
The board will be sitting directly above the buzz bar im not sure if I need to put in an isolator in between them to isolate the 3 phase board?
Thx

 

[buzzlightyear]

pic would be nice.

 

[Lintay]

pic would be nice.

View attachment 35545

 

[Lintay]

The isolator on the left would be feeding the board but is it needed as there's an isolator feeding the buzz at thx

 

[Lintay]

Buzz bar

 

[Darkwood]

Depends on the rating of the dist-board switch disconnector, the tails you use and what fuses protect the busbar (buzz bar?).

You could always upgrade the dist' board to have a front end MCCB switch/fuse as oppose to a disconnector.

 

[Lintay]

Dist- board switch is 250amp, and the fuses which protect the busbar are 200amp.was gonna use 25 mm tails.thx

 

[buzzlightyear]

whats with the adaptable box next to the main isolator ,32 mm pvc conduit

 

[Lintay]

Lighting controls for new led lighting

 

[Lintay]

The isolator load tails will route back through the bus bar into dust-board

 

[Darkwood]

I take it your not usually doing this kid of work given the questions?, you have 2 options here, fit an mccb rated at the tails you wish to use or upgrade the tails so that they are rated to the busbar O/L protection (200amps), the latter been the cheaper but you need to check it will fit on your switchgear, if not you can parallel 2 smaller tails up.

Why do you have a 250amp disconnector in the board costing a lot more than a standed 100amp 4 pole disconnector if you only intend to use 25mm tails, what is the designed demand on the dist board?

 

[westward10]

25.0 conductors contained are not rated at 100A anyway for a triple pole supply.

 

[Lintay]

I'm usually doing domestic work but now work for a new employer. He's gave me a 100 amp isolator to feed from the bus bar to then feed the dist-board,my boss has supplied all the materials.
So if the dis-board main switch was 100amp I could connect tails direct to busbar?
Thx guys

 

[Darkwood]

25.0 conductors contained are not rated at 100A anyway for a triple pole supply.

Tri -rated?

 

[westward10]

Tri -rated?

Or BS7211.