I can't see where the unbalance would occur.
My worry has always been that every bedroom in a home would end up on one 20a AFCI. Using the 3va/sq.ft rule you could have 800 sq/ft of bedrooms on one circuit.
The US NEC requires that the load be balanced so you have to evenly proportion the square footage over the Lighting and appliance branch circuits that are the result of the square footage computation. In other words if two thirds of the square footage is bedrooms then two thirds of the required L&A circuits must be used to serve them. If you install more L&A circuits than the code requires you still have to evenly proportion the square footage or the outlets over those circuits.
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Tom H
