[malfist]

Both should go outside. One should take in outside air to blow over the coils and the other to return that air back outside with the extra heat from inside. All movement of inside air should be over the other side of the condenser and not go outside or come from outside

[philwelch]

Yes this is how it is installed. You can see a drawing on page 13 of the PDF.

A dual hose model is still less efficient than a window unit, but it’s an improvement over a single hose design.