upgrade of a 3p board from 100a to 200a

[bahco king]

I have recently upgraded a 3p isolator from a 100a to 200a with the help of scottish power. I now need to fit a sub mains board for my mcbs does anyone know what size i need my tails to be coming from the isolator into the distrubtion board which will be located next to the 200a isolator and also should i put a 200a 3 pole breaker in my sub board.

 

[malcolmsanford]

When you say isolator I assume there are no protection devices inside it, as an isolator is just a switch, we need to know if what you have is a switch isolator or a switch fuse.

If it is an isolator then your size of tails will be governed by the protection devices in the SP head.

 

[mad house]

I think you mean your main DB from the service head via 200A isolator. then bs 7671 current caring capacity's dependant on you cable requirements will determine the size of the conductor.

 

[cliffed]

I have recently upgraded a 3p isolator from a 100a to 200a with the help of scottish power. I now need to fit a sub mains board for my mcbs does anyone know what size i need my tails to be coming from the isolator into the distrubtion board which will be located next to the 200a isolator and also should i put a 200a 3 pole breaker in my sub board.

50mm is the quick answer,but b careful ,r scottish power providing ct cabinet,norm neters may only accept 35mm

 

[bahco king]

yeah the 200a isolatar is fused i asked the scottish power guy and they have to put 70mm tails in but 50mm is sufficent. thanks for your posts

 

[Darkwood]

ERRRMMM!!! have i misread all this or is your set-up like this... Service head 3ph tailed to a 200amp fused isolator from which you want to supply a dist' board. If this is the case then how will you be tailing i.e. within trunking , clipped direct etc etc...

Firstly you would have been better just fitting a 3ph dist' board with a front end mccb 200amp rated thus omitting the need for an isolator, this would require 95mm tails if standard stranded and in trunking or 70mm clipped direct, can you pls reaon why you get 50mm?

Your method means because you have fused upstream of the tails you only need a 200amp disconnector as main switch in dist' board, but this will most likely be a much larger than normal switch thus requiring an extension box often supplied all in as a kit, do make sure you select the correct dist' board and that its internal busbars are 200amp rated.

(im on the assumption you've fitted 200amp fuses????)

 

[Darkwood]

Ps also to be noted is your supply is now twice as big so your supply earth and bonding cables will need to be re-calculated and checked for correct sizing, notably the supply type (tns, tncs) will make a big difference to requirements at these sizes.

 

[Darkwood]

50mm is the quick answer,but b careful ,r scottish power providing ct cabinet,norm neters may only accept 35mm

Most supplies over 100Amp have a ISU (Industrial Supply Unit) as by the nature of the tailing size it would require larger cables than 35mm, would be pointless having a 200amp rated meter that only allowed 35mm tails.

 

[Darkwood]

ERRRMMM!!! have i misread all this or is your set-up like this... Service head 3ph tailed to a 200amp fused isolator from which you want to supply a dist' board. If this is the case then how will you be tailing i.e. within trunking , clipped direct etc etc...

Firstly you would have been better just fitting a 3ph dist' board with a front end mccb 200amp rated thus omitting the need for an isolator, this would require 95mm tails if standard stranded and in trunking or 70mm clipped direct, can you pls reaon why you get 50mm?

Your method means because you have fused upstream of the tails you only need a 200amp disconnector as main switch in dist' board, but this will most likely be a much larger than normal switch thus requiring an extension box often supplied all in as a kit, do make sure you select the correct dist' board and that its internal busbars are 200amp rated.

(im on the assumption you've fitted 200amp fuses????)

You can get around this if you've already fitted 50mm by de-rating fuses to 160amps if tails are clipped direct?

 

[i=p/u]

how many amps can a normal 3 pase board give out? or what is the limit..#

im not too clued up on this but any jobs ive been on and there a 3phase board theres 3x100A service head fuses

 

[Darkwood]

how many amps can a normal 3 pase board give out? or what is the limit..#

im not too clued up on this but any jobs ive been on and there a 3phase board theres 3x100A service head fuses

Hard to define the word normal but most recognised brands can be bought with a 100amp or 125amp main switch disconnector, but some brands can be upgraded to 200/250amp with a adaption kit with replaces the incoming arrangement of the board usually with a extension box to fit under board.
Higher rated boards are available but usually have to be specified during purchase i think 630,800,1200amps etc all tend to be mccb enclosures so not your norm' but will accept mccb of any ratings your familiar with.

 

[i=p/u]

but 125A isnt that much extra for the need for an extra 2 phases, or isit just specified as there will be 3 phase equipment.


so say l1 l2 l3 all 25mm csa does that not mean they can have a 300A mainswitch.. and in a three phase piece of equipment will the load be shared equally??

<< probably talking bull but..

 

[Darkwood]

but 125A isnt that much extra for the need for an extra 2 phases, or isit just specified as there will be 3 phase equipment.


so say l1 l2 l3 all 25mm csa does that not mean they can have a 300A mainswitch.. and in a three phase piece of equipment will the load be shared equally??

<< probably talking bull but..

The reasons behind why hes putting the 3ph board in hasnt been disclosed by OP but it could be that a 3ph machine might be on the cards etc...
a three phase 100amp supply only requires a switch disconnector rated at 100amp as its 100amps per phase each through their own seperate channel on the 3ph switch, they in effect can utilise up to 300amps of single phase loading or 100amps 3phase loading and/or a mixture, a three phase supply allows for balancing of 1ph loads across the 3ph board which will effectively reduce the neutral current the better its balanced, this will translate into cheaper electricity bills this is the main reason larger intalls have 3ph supplies irrespective of the need to connect a machine etc that uses 3ph.

 

[JD6400]

Just installed a panel board on Thursday for a new supply on one of this years grain stores it's a 400a head that will be down rated to 200a SSE have supplied the speck for it and it states they want 70mm tails ( If I can work out how I will post a link to the said speck sheet . )
Anyway we will see if it's right , they are out at 8am tomorrow to connect up ?!

 

[i=p/u]

well if your 200A is within 3m then 70mm tails seems ok . and what do i know

 

[JD6400]

It seems that the forum has a limit of 2mb per upload and the one from SSE is nearly 8mb , so with my limited knowledge of puters I am stuffed !:banghead:

 

[Knobhead]

Just post a link to the SSE document.

Or if you’ve scanned it, re-scan at a lower resolutioin.

 

[JD6400]

Just post a link to the SSE document.

Thanks Tony , but that would need more than the totally illiterate and basic understanding of these bloody machines that I currently pocess !
I can just manage to forward the email on that had the attachment on it !:willy_nilly:

 

[Knobhead]

See the PM I've sent you.

EDIT

will send another PM with my e-mail add, pass the mail on to me and I'll sort it.

 

[JD6400]

Thanks Tony , have sent it to you .
I hope you got it and have not ballsed that up as well ?!!!:thinking:

 

[Knobhead]

I can’t find the source file from it to give a link. Best bet is to ask the guy that sent it to you, it isn’t a controlled copy that should be no problem.

If you read through it does give all answers you need. Most importantly the space required and conductor sizes.

I can create a link but it would open my e-mail to abuse and I won’t do that.

 

[JD6400]

Tony , that first bit might as well be in Swahili !!!
Will try and see if it is possible but the old boy that sent that was not over impressed that i asked for it in the first place ?
Thanks anyway !