Sorry to bust open this topic again. I have a few questions about the space pak or unico systems.

1. I notice with both brands there is a single return duct. Is it possible to go with 2 returns to get better air movement, filtration? I see they have a 4' max length of return duct in the space pak manual.

2. Can this system be used as a sort of HRV in the winter with an outside air intake? Thinking using hydronic coil to temper outside air.

3. The manual shows minimum outlets for given size units (7 per ton space pak) is there a maximum? What CFM are you looking for at the outlets?

4. Having a little trouble understanding the high velocity concept, when the air handler moves lower volumes of air compared to a standard air handler.Is it more the design of the air handler, or the duct work design that gives it the higher velocity? If it is the duct design, what would happen if a standard air handler was given the same sort of duct design?

I have radiant heat so this would be used for AC only unless an HRV type setup would be feasible. My reason for leaning towards the high velocity systems is due to the duct design.