I’ve installed a handful of mini splits now, primarily in historic homes which have no usable duct work.  Since they’re also being used to heat these homes in midwest winter, over-sizing is basically inevitable.  (note: the argument could be made to right size these units and install supplemental resistance heat, but for the purposes of this question, we’re talking about existing work).

My question is – I’ll be installing the supply from the dehumidifier at the top of the stairwell.  A mini split head already exists at the top of this stairwell.  I’m going back and forth on whether the supply should be place BELOW or ABOVE the head.  I’m concerned that if it’s placed below, the cold air will take the dry air down the stairwell before it’s able to blend with the existing upstairs air.