# Sizing Branch Circuit



## k_buz (Mar 12, 2012)

I'd use 1/0, but that is coming from an employee who doesn't pay the bills.


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## nolabama (Oct 3, 2007)

one ought


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## MDShunk (Jan 7, 2007)

It's the difference between 3% drop and 4% drop. To make that decision, I'd probably see what amount of drop you're working with already. You might already be served with slightly over 208, so you don't really have to concern yourself with VD.


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## nolabama (Oct 3, 2007)

MDShunk said:


> It's the difference between 3% drop and 4% drop. To make that decision, I'd probably see what amount of drop you're working with already. You might already be served with slightly over 208, so you don't really have to concern yourself with VD.


spoken like someone that buys the wire:thumbsup:


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## MDShunk (Jan 7, 2007)

nolabama said:


> spoken like someone that buys the wire:thumbsup:


The reality is that many (perhaps most) of these RTU's are marked with a very wide tolerable voltage range. It's very normal to see the dataplate say "200-230 volts".

So, to sum up, check the voltage you already have at the MDP, and check the dataplate or cut sheet of the RTU.


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## dronai (Apr 11, 2011)

1.732*12.9*200*125/133100 = 4.19

cmil for 2/0 133100


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## kaboler (Dec 1, 2010)

Does he make mention of voltage? I don't understand MCA and MCOP.

Hope it's 277/480.

Do you guys in the USA get 347/600 yet? I've heard you don't have it. Or it's really rare.


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## GEORGE D (Apr 2, 2009)

kaboler said:


> Does he make mention of voltage? I don't understand MCA and MCOP.
> 
> Hope it's 277/480.
> 
> Do you guys in the USA get 347/600 yet? I've heard you don't have it. Or it's really rare.


Minimum Circuit Ampacity, Max Overcurrent Protection. Also its 120/208 volt system.


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## GEORGE D (Apr 2, 2009)

MDShunk said:


> The reality is that many (perhaps most) of these RTU's are marked with a very wide tolerable voltage range. It's very normal to see the dataplate say "200-230 volts".
> 
> So, to sum up, check the voltage you already have at the MDP, and check the dataplate or cut sheet of the RTU.


Unfortunately this job is 2 hours out so I can't just go check available voltage. The price difference in wire and conduit will be somewhere around $1000.


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## local134gt (Dec 24, 2008)

GEORGE D said:


> Unfortunately this job is 2 hours out so I can't just go check available voltage. The price difference in wire and conduit will be somewhere around $1000.


If it's not worth your time to go check the voltage, it certainly wouldn't be worth your time to have the wrong materials show up when your ready to work. :thumbsup:


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## GEORGE D (Apr 2, 2009)

local134gt said:


> If it's not worth your time to go check the voltage, it certainly wouldn't be worth your time to have the wrong materials show up when your ready to work. :thumbsup:


No doubt about that! I went ahead and submitted for 1/0.


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