Update Spring'25 The inlet and outlet were completely redone to provide way more airflow ! Details at the end.
With the in-wall airbox done, the cabinet holding the A/C could now be designed to tightly couple with the airbox.
As condensation builds
up during use, water can start dripping if it overflows the pan built
into the bottom of the A/C unit. As that unit's pan does not have a drip pickup nipple,
there was no convenient way to catch overspilling water and route it
out the van. So the base of the enclosure (pic above) serves as a backup
water catch pan. It received 4 coats of exterior polyurethane.
There
is no specific hot side intake on this A/C unit, as it draws air from louvers
on both its top and sides. So most of the enclosure serve as a
distributing space for the air coming from the airbox's intake to reach
the louvers:
The white strips in the pic above are weatherstrips that tighly seal off the A/C unit's sides.
To hold the A/C unit firmly pressed against the weatherstrips in the back of the enclosure, ear tabs were installed on the unit's cover (pic above). Long wood keys are then inserted, exerting pressure:
More weatherstripping later... and voila, time to test that puppy:
Well, it did not go too well... The temp in the van dropped 7°F / 4°C in a few minutes, but crept back up over the next 10'. The cold side was blowing warm-ish air. Time to investigate...
The exhaust pipe under the van was blowing hot air, hard. However, the intake pipe was no showing much suction. Finally, opening the enclosure lid did bring the cold side back down to cool temps. So, suspicion confirmed: no matter the application it is always much harder to suck than to blow ! 😂
Since the airbox's 3 foot long 3x4 intake pipe is too restrictive for this A/C unit, the intake fan had to get help drawing in air from outside. Enter the cavalery: 4 high pressure high speed 12V 0.8A 80x80x38 server fans that together can push 300CFM...
As they need to automatically start when the air conditioning is on, I tapped into the 110V line going to the thermostat to power a 12V adapter that feeds the fans:
18AWG yellow wires were spliced in:
Since the A/C unit's selector switch is rated for 25A, way beyond that
unit's specs, it should have no problem with an add'l ~50W max load.
This powers an AC/DC adapter with adjustable output voltage, to fine tune the fans' speed. No need for 300CFM or ear bleeding noise levels...
Seems to work, road tests necessary...
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Update Spring'25 Well, road tests in 90oF (33oC) showed pretty poor results, with only a few degrees of effective cooling. Due to the too-restrictive 3x4" downspouts used for the hot air inlet and exhaust.
So the 4 high pressure fans from the inlet box were ditched, and a hole in the floor now serves as a massive outside-air inlet opening. And the hot-exhaust air outlet box in the wall now exits air throuth all the holes that were previously drilled at the bottom of the wall cavities:
A
large opening was cut in the bottom of the cabinet, matching the shape
of the new floor air inlet.
This completely defeats the initial
water-catching design of the cabinet's bottom, but so far all the
condensed water has been caught by the AC unit's bottom pan.
No overflow, even when driving, even though we can hear the fan slosh the
water around during startup. Granted that I have traveled only in low
humidity states so far: CO, MN, UT, WY. Planning to install a small drain pipe
that simply hangs down through the floor inlet.
Now, to avoid road mud and crud intrusion, deflecting protection baffles were made out of a 3/32" thick aluminum sheet, and secured with rivet nuts in existing or new holes. The large distance between their respective mouths helps reduce air recirculation between the inlet and the hot exhaust air:
Also, since the bottom holes in the wall cavities open down into pretty much the whole length of the outside wall skirt under the van, some hot exhaust air exits around the inlet, not good. So the small holes were plugged, and expanding foam was squirted at the bottom of the driver seat's pillar:
Time to reinstall the A/C unit:
Finally, the unit now efficiently cools the van down to 74oF (24oC) in 90-96oF (35oC) weather. Tested for 5 weeks this summer in Wyoming, Montana and Utah.
The cardboard piece in the pic above is a cold air up-kicker, to avoid recirculation between the ambient inlet and cold exhaust. It kicks the cold air up toward the ceiling and the back of the van. That made a big difference. Can even feel a light cool breeze when in bed now 😍 Made out of improvised cardoard and duct tape, but planning to design a proper 3D printed vane one day.
One issue that crept up is road dust. Despite the outside-air inlet baffle opening toward the rear of the van, and despite the window screen, a lot of dirt still makes it into the A/C unit when on dirt roads. Looking into adapting a house air filter to the inlet.
Unexpectedly, the unit consumes 700W, as measured with the Victron inverter, not the 450W advertised. On a sunny day, running A/C the whole afternoon+evening takes more than the 600W solar array provides, so about half of the 10KWh battery's capacity is consumed. Solar charging in the morning is critical.
Man, that took a while to make work... Lesson: let your A/C air circuits breathe, a lot !
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