[ecomodded]

Hey Dend I was not thinking about the stack effect but can see how this plays a role. Mixing the air temperatures differences via a return duct or equivalent would help to elevate the pressure differences.

I gave up the hope of heating with the single hose set up , its negative pressure was MUCH stronger then I was lead to believe by the online quoted numbers.

I was reading the portable ac would exhaust 1/3 its front sides output our the rear that was wrong it turned out it expels 240 CFM out both the vents. making for much too strong negative pressure to allow heat to warm the upstairs.

I tried it out on two days it did nothing but super heat the downstairs room room to 35c

The intake hoses in the photo are strung out the window the unit breaths 100% outside air now. It no longer creates negative pressure.

Its basically acts as a non inverter mini split at this point with me controlling its on / off cycles via a timer.

to be clear this unit uses two fans one for the front heat and one for the exhaust so the two air streams never meet.