As a follow up to my previous post, this is described in the graphic
at the website:
With a single hose unit, the unit draws air from the room to cool the
the compressor and condenser coil. It then expels this hot air through
the exhaust. Since this will create negative air pressure in the room,
the room will suck air into the room from any source that it can get
it from, most likely that leaky window where the hose goes out.
Now you've got outside air, at say 80 - 90 degrees, inside the room
that you have to cool off.
If you suck the exterior air in through the intake hose and exhaust it
right back out via the exhaust hose, there is no negative pressure and
the unit doesn't have to try and cool off any sucked in air.
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