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#98759 - 06/05/06 07:03 PM conductor size  
prodieseldog  Offline
Member
Joined: Jun 2006
Posts: 13
deltona, florida, united state...
I AM ABOUT TO BEGIN A PROJECT AT A PRO SPORTS FACILITY IN WHICH I AM REQUIRED TO INSTALL A STEP DOWN TRANSFORMERFROM 480/277 TO 120/208 TO OPERATE A LED VIDEO BOARD THE LOAD IS 250AMPS WHAT IS THE PROPER FORMULA THAT I NEED TO USE TO OBTAIN THE CORRECT SIZE CONDUCTOR ON THE LINE SIDE OF THE TRANSFORMER. ALSO WHAT IS THE PROPER WAY TO GROUND THIS SYSTEM. KEEP IN MIND THIS IS A THREE CONDUCTOR TO A FOUR CONDUCTOR SYSTEM


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#98760 - 06/05/06 07:48 PM Re: conductor size  
Dnkldorf  Offline
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Joined: Dec 2004
Posts: 1,064
nowhere usa
First, pls turn them caps off...it makes it hard to read your post,

Tell us how you plan on doing this, with your results, and we can help you from there, you have to do some work...

Hint..conductor size is found in 310.16..

But we need to know termination ratings, VD calc(if applicable),what size transformer..ect.


#98761 - 06/05/06 08:13 PM Re: conductor size  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,260
Fullerton, CA USA
There are too many variables that need to be answered before anyone can give you any help here.
Anyone that would give you an answer without more info would not be doing you any good.

Does the board take 250 Amps of 120/208 3ph power?
What do you plan on using as the grounding electrode?
BTW, You will be transforming 480V power, not 480/277V


#98762 - 06/05/06 08:24 PM Re: conductor size  
prodieseldog  Offline
Member
Joined: Jun 2006
Posts: 13
deltona, florida, united state...
i will be using a kva 100 transformer, and it is 3ph power, as far as the ground electrode i plan to use a copper five eighths ground rod grounded by a 2/0 bare copper conductor this would be grounded at the base of the concrete to the transformer


#98763 - 06/05/06 08:27 PM Re: conductor size  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Other hint: All of Art. 450, Location selection and tempature of that location are key, as you will be putting a large heater in it...
250.30, and everywhere that leads you.... Same with all of 310.

Sorry the questions are just so broad....


Mark Heller
"Well - I oughta....." -Jackie Gleason

#98764 - 06/05/06 08:28 PM Re: conductor size  
prodieseldog  Offline
Member
Joined: Jun 2006
Posts: 13
deltona, florida, united state...
and it is my understaning that in this system my ocpb have 125% rating as maximum load which would be 250amps with a winding change of 0.0057 i come up with a 1/0


#98765 - 06/05/06 08:31 PM Re: conductor size  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
All other voltages in the building must be bonded to make ONE SYSTEM in terms of grounding, you may already have an electrode to go to?


For the sake of discussion here's 250.30

[This message has been edited by e57 (edited 06-05-2006).]


Mark Heller
"Well - I oughta....." -Jackie Gleason

#98766 - 06/05/06 08:34 PM Re: conductor size  
prodieseldog  Offline
Member
Joined: Jun 2006
Posts: 13
deltona, florida, united state...
the location is in a room that is approximately 45x72x30 this room has louvers at the top of the structure and also has a stair case with an open entry way at all times there are also three 2hp fan motors located at the top opposite side of louvers so as far as the temp it will maintain atemp slightly greater than the outside temp


#98767 - 06/05/06 08:41 PM Re: conductor size  
prodieseldog  Offline
Member
Joined: Jun 2006
Posts: 13
deltona, florida, united state...
sorry i failed to mention that this location for the transformer is located over 150 feet above the main distribution and currently at this time there is only a small amount of power up there you know the basics


#98768 - 06/05/06 08:51 PM Re: conductor size  
prodieseldog  Offline
Member
Joined: Jun 2006
Posts: 13
deltona, florida, united state...
310.16 so are you saying that i should use a 4/0 on the 480 side of the voltage?


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