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

[Darkwood]

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

No you won't be doing this, the bussbar chamber is not a through route for circuits be they submains or final circuits, you do not need this isolator anyway there are other options I have mentioned already, it does seem your are quite inexperienced in this area, I would suggest and judging from your questions that you bring someone in who has the experience here and work alongside so your can get the valuable experience yourself, the design is totally wrong, your unaware of the relevant regulations which will limit your options here, please take this as constructive advice, errors in this kind of work can be very costly and good, compliant design is crucial here.

 

[buzzlightyear]

can you not use the trucking for the swa cable for the led cable. or use the did board .

 

[westward10]

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

When you say isolator is it fused at 100A. If so you need at least 35.0 conductors to and from it. Have you got additional busbar clamps, I hope you are not going to pair up from existing clamps.

 

[Darkwood]

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

Im sorry to say this but seems your boss has designed this wrong too, I cannot understand why with a modern distribution board that he hasn't fitted a 100amp mccb front end device in the dist board to allow for reduced tails, all the isolator etc is extra work and wasted space, either this or we don't have the full story here, I'm still lost with the design.

PS - you will need to protect your tails for overcurrent if your not fitting 200amp rated (as stated protects the busbar) tails direct to the 250amp disconnector.

 

[Lintay]

Thx for constructive advise darkwood hence why I'm querieing the design.
So could I come straight off the bus bar into dist-board and double up the tails?or will I need to replace the main switchwith a fused switch aswell? Thx

 

[westward10]

Yes I have to agree, you need to have a chat with your boss and explain that at the moment this maybe outside the scope of your competence and you need some guidance and assistance. I think you may also need to bear in mind that he, assuming it is a he has not really thought this through. This isn't routine domestic work as you have realised and the reality from a piece of paper can be a harsh lesson.

 

[Lintay]

I mean an mccb/switch fuse thx

 

[westward10]

Thx for constructive advise darkwood hence why I'm querieing the design.
So could I come straight off the bus bar into dist-board and double up the tails?or will I need to replace the main switchwith a fused switch aswell? Thx

You can come direct from the busbar but your conductors need to be at least 95.0, have you ever worked with this size of conductor.

 

[Lintay]

Yes I have to agree, you need to have a chat with your boss and explain that at the moment this maybe outside the scope of your competence and you need some guidance and assistance. I think you may also need to bear in mind that he, assuming it is a he has not really thought this through. This isn't routine domestic work as you have realised and the reality from a piece of paper can be a harsh lesson.[/QUOTE

 

[Lintay]

If the isolator feeding the busbar has 100amp fuses in could I then feed the dist board directly with 35 mm tails and downrate the dist-board switch to a 100amp mccb.
If my boss is adamant about using the isolator I will still need to use 35 mm tails anyway is that right ?
Thx for advise

 

[Lintay]

You can come direct from the busbar but your conductors need to be at least 95.0, have you ever worked with this size of conductor.

No

 

[westward10]

Yes you could although the main switch at the board is not likely to be an mccb but an EN60947-3, 125A isolator.

 

[Lintay]

Yes you could although the main switch at the board is not likely to be an mccb but an EN60947-3, 125A isolator.

So downrate the the dist- board switch to 125. Amp?
If he's adamant about not changing the isolator or dist- board all I need to do is feed the isolator with 35 mm tails which feeds the dist- board with 35 mm tails which don't route through the bus bar chamber as long as the fuses feeding the bud ad are 100amp

 

[Darkwood]

Sorry earlier I'm sure you said the busbar was fused at 200amp, now are you saying 100amp? It changes alot of the advice or are you suggesting derating them which is unwise as it strangles the future use of the busbar plus you need to assess the demand existing.

 

[Lintay]

Sorry earlier I'm sure you said the busbar was fused at 200amp, now are you saying 100amp? It changes alot of the advice.

Yes I'm thinking now it's 100amp sorry