Air Conditioning Setup

Air conditioning will be provided via a swappable seat module, located behind the driver seat.
  In winter it is a seat + storage box. In summer, it is swapped for a seat + AC box.

The user priorites for AC were simple:
  • All day use in 110°F / 45°C weather, only using PV solar (600W max) - missed that goal, see the "Cabinet and Results" post below
  • No loss of interior space in the non-summer seasons
  • No loss of ceiling head space
  • Easily repairable / replaceable by future owners
The design priorities were a bit trickier:
  • Dirt cheap
  • No thermal leaks in winter
  • No element exposed to harsh road conditions under the chassis
  • High-ish efficiency (ex: no single hose unit)
  • Easy and toolless removal between seasons
  • Marginal weight penalty
The cost & weight & removal requirements ruled out mini splits and ceiling devices, while the summer use profile & weight constraints ruled out systems based on circulating water.
 
In the end, the venerable Frigidaire 5000 BTU window mounted unit was procured. At 12x16x15.25" it is very small and can easily fit in a seat box.
FYI: got several questions about availability of this unit, so here are a few model numbers it's sold under, as of 2025: GE AHEC05AC ($175) AWAS05BWA ($150), Frigidaire FFRA051WAE ($130), Amazon Basic MWHUK-05CMN8-BCK0 ($120), Midea, Senville, etc.

It supposedly consumes only 450W (not true, see next "Results" post...) but should still be powerful enough to cool down such a small, well insulated, van space. Should it require replacement years down the road it, or a copycat, will still likely be available. And, cherry on the croissant, the $153 price (Aug'21) was unbeatable 😍
 
An airbox, mounted in the van's wall cavity, provides ambient air from outside and channels the hot air out:
 
A couple of coats of exterior rated polyurethane were applied to the inside of the air box. This will reduce humidity absorption by the wood, as condensation is unavoidable in this application. 
 
Oblong holes were drilled with hole saws in the cavity's floor to accomodate 3x4" downspout pipes:
 
A temporary dam was set up around the holes in the floor. Liquid caulk was then generously poured, sealing all the gaps around the pipes.
 
Finally, the pipes exit through the skirt under the chassis. Hot exhaust on the right, intake on the left (barely showing in the leftmost skirt hole):
 
A 4" drain pipe, held up with 2 aluminum strips bent like collars, redirects the hot exhaust to the back, away from the intake. Both vents will later be fitted with screens to prevent intrusion from bugs.
 
Now, the choice of a window unit came with a catch: its hot side does not have 2 well defined air In & air Out hose stubs. Instead, the openings are spread across the unit's back and sides, and need to be collected to mate with the airbox. And that, van enthusiasts, will be the job of the seat box. In the next post... 
 

  Update Spring'25   The inlet and outlet were completely redone to provide way more airflow ! Details in the next post below.

  
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