I would use a basic demand of 30 Watts per sq. meter. To that I would add any highlight lighting for individual exhibits.
This is for the calculation of the ampacity of service conductors and feeders.
I would ask the local inspector to agree with these figures.
30 Watts per sq. meter is based on the Canadian code requirements for Stores, Restaurants and Theatres.
Bill
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"Why not the best?"
Jimmy Carter