Max. Ckt. Breaker Load

[wilsonv]

We are going to install a new sports lights system on an existing ballfield. The existing A/C Panel is a 480, 3ph, 225A. The new load is 160A and after appling the continuous operation factor is 200A (160*1.25).
1. Can I use the existing A/C Panel?
2. It is right that the breakers can be loaded up to a maximum of 80% of his rating? If this is correct, I need help to find were is this rule described.
Thanks.

 

[rbulsara]

wilsonv:

I would agree with your interpretation, if the load is indeed non-continuous, that is it will not last for 3 hours or more.

But if you are saying its sports lights, chances are that they will stay lit for more than 3 hrs.

Other important issue you want to consider is the harmonics, HID lights have quiet a bit harmonics and I have seen 200A breaker tripping on 175A of currents due to harmonics. So besides the strict interpretation of Code, design wisely. Rememner that Code is only there for minimium safety measures, it does not care if your lights go out in the middle of a game.

 

[wilsonv]

rbulsbara:

Yes, lights will be treated as a continuous load. The actual total load will be 157A. Applying the continuous operation factor the calculated load is 197A. The main breaker on the existing panel is 225A. It should work with no problems.
My doubt was appling the 80% rule. I was thinking that a 225A can be loaded up to 180A (the 80% of 225). I was double derating the breaker, applying the 125% factor and limiting the breaker to an 80% use.

Thanks everybody for your help on this "simple..." matter.

 

[alehman]

I agree with this conclusion.

Sorry for the confusing NEC reference in my earlier post. That was based on the 1999 code. In 2002, the 80% rule has been removed completely from the panelboard section and remains in articles 210, 215, 220 and 230 where it is stated as "125 percent of continuous load plus 100 percent of noncontinuous load...". It actually is somewhat simpler than 1999.