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.

 

[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

 

[Darkwood]

I think tbh you need to know exactly what is existing, you cannot design a system by guessing what's existing, like I said earlier, small mistakes cost big in this side of the industry.

 

[Lintay]

I think tbh you need to know exactly what is existing, you cannot design a system by guessing what's existing, like I said earlier, small mistakes cost big in this side of the industry.

If the fuses are 100amp can I feed the dist board directly with 35 mm tails thx

 

[Darkwood]

Yes but you have to look at the bigger picture here, can the fuses be uprated again ie.. is the cable big enough to do so, you want to avoid forcing limitations on future additions, they may just have 100amps because of the low demand but fitted a 200amp system for expansion, we lack the info to give you a true informed reply but your boss really should have done all this and supplied you with the correct gear to start with with which I have my doubt he has.

 

[Lintay]

Yes but you have to look at the bigger picture here, can the fuses be uprated again ie.. is the cable big enough to do so, you want to avoid forcing limitations on future additions, they may just have 100amps because of the low demand but fitted a 200amp system for expansion, we lack the info to give you a true informed reply but your boss really should have done all this and supplied you with the correct gear to start with with which I have my doubt he has.

Maybe he couldn't get a 100amp dist-board hence why he got the isolator?but then the cost in price is a huge difference?But he had said to use 25mm tails.il have to run through the design with him tomorrow,thx for the advise really appreciate it.
I only started new job last week so had to make sure I knew what I wax on about before speaking to him.thx

 

[Toneyz]

what 250A D.B. have you been provided with ?

 

[Lintay]

what 250A D.B. have you been provided with ?

Will check in the morning

 

[westward10]

Try and be open with your boss about your lack of experience with this.

 

[Lintay]

I told him first day on the job, but he was the one who designed it and ordered bits

 

[LeeH]

Tri -rated?

Probably be ok but the ratings are based on 90degC remember with tri.

 

[Darkwood]

Probably be ok but the ratings are based on 90degC remember with tri.

You raise a good point but tri rated still has a higher capacity at 70c plus we do not know the switchgear, the busbar will be ok for 90, I install this stuff all the time and you can maintain the 90c ratings if you choose the correct gear, otherwise it's pointless making it.

 

[Lintay]

what 250A D.B. have you been provided with ?

SE48B250 KQ16 TP WAY 250 type B DIST
THX

 

[Pete999]

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

Must be a loose connection if the busbar is buzzing

 

[Lintay]

If I replace the main switch which is a SE 125SW3L switch disconnector with a 125 a Mccb I can come straight of the bus bar to the dist board?

Must be a loose connection if the busbar is buzzing

lol

 

[westward10]

You are not going to be able to do that.

 

[Lintay]

You are not going to be able to do that.

Why

 

[westward10]

Main switches for those boards are 125A, 160A, 200A or 250A and none offer circuit protection they are 60947-3 switch disconnectors. Off hand I am not certain if you can get a 60947-2 which offers circuit protection, if you can it will be the higher rated devices and not 125A.

 

[Darkwood]

You have led a confusing conversation here, I was under the impression it was already kitted out with a 250amp disconnector but it sounds like you have a standard incomer.

Yes!.. these boards can be upgraded with various incoming devices, you will have to find out the lowest rated version, 100amp I think ...see here http://www2.schneider-electric.com/resources/sites/SCHNEIDER_ELECTRIC/content/live/FAQS/141000/FA141814/en_US/SE8386-RTI Catalogue_MAY_2015.pdf

If you go for the upgrade kit it will probably come complete with expansion box and you'll have to fit it all, it can be very confusing and puzzling if you have never done one as the instructions are pictorial and worse than Ikea for been easy to follow, the kit will just be as expensive as the whole board itself but your saving on tail sizes, switch fuse unit and labour so should work out better, this is the main reason I queried the original diagram you presented as you had this simple option and seems your boss is also clueless to this kind of work. Check with the wholesalers or direct with schnieder that your chosen kit is compatible with your board before getting it as there are many kits out there for there varying ranges.

 

[Lintay]

Main switches for those boards are 125A, 160A, 200A or 250A and none offer circuit protection they are 60947-3 switch disconnectors. Off hand I am not certain if you can get a 60947-2 which offers circuit protection, if you can it will be the higher rated devices and not 125A.

Boss has told me to use 35mm tails into isolator then 35 mm tails to feed the dist board and to use the 125amp switch disconnector.

 

[Lintay]

Boss has told me to use 35mm tails into isolator then 35 mm tails to feed the dist board and to use the 125amp switch disconnector.

My boss is telling me the dist- board needs an isolator before it incase someone wants to work on the board they don't need to kill the busbar

 

[westward10]

My mistake you can get 60947-2 devices, but yes you are giving conflicting information. We all get situations where we have to find a solution to a problem but we do that from experience and consulting colleagues. It is clear you don't have the experience to find that solution and you really need to sit down with your boss who hopefully will guide you or put someone with you to assist. He is being totally irresponsible if he basically shrugs shoulders and tells you to get on with it.