Re: help with a lighting calculation
I recommend dealing with one load/topic at a time. line_noise's reply suggestion above about "getting data for the actual ballast in use" is correct and safer for your calculation. This Electrical Rating information is available as per 410-35 (b). Your calculation process is correct but use the actual electrical rating information in your calculation to come up with the potential load. So with this said your lighting potential load will be more than 281 amperes and your service for the lighting alone will be at least a 300A circuit fed with 350 MCM cu minimum, don't forget to account for voltage drop.
Follow 220-10 to help calculate the additional loads for the correct service. If you can get accurate data from your client you may consider using "actual maximum demand figures to determine the existing load" as per 220-35, watch out for this method because if your client has not been operating all the circuits like they really want due to breakers tripping you could be using wrong data. This 220-35 in your case is probably unsafe to use, you just need to add the additional loads to the lighting load and the total will tell you what size service they need. The numbers don't lie you have to serve the load potential.
Hope this helps
