Hi,

If a furnace air handler install manual says it requires 200 square inches "free area opening", what does that mean? I assume it means the minimum duct size, incoming AND outgoing, is 200 square inches? And it would need to be 200 square inches until it branches?

Any thoughts on where to find basic information like this? Seems my google muscles are weak.

I don't have a HVAC guy I trust yet, so want to educate myself to ask better questions, rather than relying on a salesman's assurances that it'll work.

Thanks!