Formica wrote:I am going to be using a small window AC unit in a trailer while on playa this year. I am concerned about the amount of dust that'll get into it, and how to reduce or prevent this.
My first idea is to build a trapezoidal intake which goes on the front of the unit, and has a HEPA furnace filter at the front. The objective is to make sure that the unit can draw enough air, and to keep the filter away from the intake, since said intake is also the primary heat exchanger for the unit. Still, I'm concerned about making the fan work too hard, and about heat build up potentially causing a fire hazard or damaging the compressor if the heat exchanger can't radiate as well as it should.
Anyone have advice on the topic? I've seen plenty of AC units on-playa that are running unfiltered, but I shudder to think about what one good dust storm could do to the interior of the unit if all that alkaline dust gets inside...
Can you explain that?
I don't know if this can be done, but a hepa filter would not be the way.
All filters gain higher efficacy and lower flow as they collect dirt.
If you compare filters, the difference in flow between a 95% filter and a 99-99.9% (hepa) unit is dramatic.
That flow won't get better.
A true hepa filter capable of flowing enough air would be quite large.
These are typically units cased in steel with many folds, and about two feet deep.
They are actually quite reasonable in cost, as they are widely used, and can last forever with prefiltering.
They are incorporated into central air units usually.
Another factor is radiant heat reflection and insulation, which can be caused just from close proximity to the unit.
A simple mesh screen, as on a flywire door, restricts air flow about 50%, so square footage must be increased accordingly.
I would suggest that the most open material you can get away with, would be the filter material to use.
Perhaps the open weave fibreglas filters that do virtually nothing in normal use, would work, or open cell foam?
A filter like this would need attention as it would become restrictive quickly, just as any prefilter will, on a proper filter.
Perhaps a different approach, similar to the intakes used on vehicles designed for unpaved countries and on some usa cars, with an articulated intake to trap dust by gravity, or prevent it being drawn in?
Larger units, as they used to be designed, had a slower fan and wouldn't be so prone to collect dust, I would think.
Even large louvres might allow dust to drop out for the most part.
We have a shop here that custom makes them, and very cheaply too.
A cover that curves down would have a similar effect.
If you aren't working within the design capacity of the ac unit, you may need to add a fan or fans to it.
Ac units are always most efficient with the fan on high.
You would want to always use a filtered unit on high.
I'm not saying this is a good idea, or practical.
Just some suggestions.
I think I would use a mesh filter only, like the very fine mesh used in well pump filters, or several layers of a more open mesh.
Perhaps different materials could be used under that for catching dust, even open weave cotton?