How critical is is that the indor and outdoor coils be sized...

[Larry Cameo]

How critical is is that the indor and outdoor coils be sized exactly the same?

Also, if adding AC to an existing newer (<10 years old) mid or high efficiency gas furnace, will the blower need to be changed to a two speed unit?

Thanks!

[CurtisC]

Its pretty important, but depends. Certain units can be mixed and matched. This typically will decrease the efficiency of the unit though. You need to check with the manufacture.