Why does the 2000U need intake air from outside?
And why doesn't this system provide fresh air ventilation?
The answer to the first question is counter-intuitive, air conditioners create a lot of heat! They actually remove the heat from your space and reject or exhaust it outside. That's why temporary or portable AC units in the home are usually connected directly to a window. Rather than have your 2000U Under-bench unit hanging out the window, you have the vent holes cut into your vehicle/property. One gets rid of the heat from your space (the Hot side exhaust vent). The other, (the intake vent) sucks in fresh air to help keep your air conditioner breathing. Without access to fresh ambient air, your air conditioning unit might overheat or fail to meet your needs and you'd have to blow that hot air back into your now nicely cooled space!
For the second question, it's a matter of air conditioner design. Keeping the inside air and outside air separate is an important part of meeting performance expectations. If we designed the 2000U to provide fresh air ventilation, the increased complexity would be seen in the cost as well as more holes cut in your vehicle/property.
If you're still considering models, the new V3 Rooftop model is the only one in our line which offers fresh air ventilation! With a built exhaust fan and advanced, air distribution box with motorized vanes to help stir up stagnant air.