I know that we cannot share the neutral or ungrounded wire for AFCI. Which mean no multi circuit wiring, otherwise we will need a 2 pole AFCI. BUT what about wiring the lights and receptacles under the same circuit? Will that cause the AFCI to trip? Will that cause the unbalance in neutral?

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

Tom I have heard that from other people and I have also heard that is not the case.

I really do not know the answer, where does the NEC spell this out?

Bob

If someone is building to minimum code why would you expect the rest of the general lighting circuits to work out to much less than 3va per foot? 800 sq/ft is a lot of "bedroom" in a 1600 sq/ft house.

Now isn't the 3va/sqft deal for calculation, not connection?

The circuit needs to be sized for what it is connected to....

Balance is not required, but strongly implied that some idea of balance on the connection is what they're looking for right?

Anyway, rknikko, I have had problems with AFCI's on certain types of loads. Dimmed LV lighting, flouresant lighting, and a flat screen monitor. If this type items have problems on a 2-wire circuit, why bother trying to chance it with a 3-wire?

I beleive 210-11(B) talks about this.

Yeah, was going to mention it, but started ww3 before on it....