Well I don't want to speak too soon but I did successfully run my nozzles w/ 30 psi air pressure and they were producing a very fine mist (although whenever the air flow stopped, a trickle of solution continued to pour out of the nozzles when gravity fed, I guess this is just a function of leftover pressure from gravity/venturi effect, maybe siphon fed makes more sense...). And this is my first attempt at any sort of aeroponics rig so as far as the plumbing is concerned, the setup was not too bad. In fact, I've got much fewer fittings/nozzles to worry about, lower pressure all around so I can opt for cheaper components, and my air compressor has a pressure switch, outlet pressure regulator, and built in safety valves. Each
nozzle+
adapter+
solenoid came out to $80 and 1 of these air atomized nozzles should be capable of replacing 4-8 hydraulic cloudtop/biocontrol/etc. All in all it doesn't seem that much more expensive than an equivalent hydraulic setup, and I like working with lower pressures and larger pressure differentials (much happier with 130psi -> 30 psi vs. 130psi->100psi). There just doesn't seem to be as much [mis]information out there compared to hydraulic HP aero.
It's not without its set of problems though -- the air
compressor I have is loud as hell, but I was willing to make that compromise if it was good quality and capable of handling my system... and under $300. Also the compressor is configured such that when it's on, it runs until max/default pressure is achieved (145-150psi), safety valves blow slightly and pressure is stabilized, then it kicks on again as soon as the pressure dips at all. Ideally I would like a cut in pressure of 40psi if I'm running my regulated air pressure at 30psi, but I'm not sure how to achieve this. I'm guessing I can buy an external pressure switch for the system, but then I imagine I would have to somehow bypass whatever internal pressure switch on the compressor? Or I can just let it kick on every time the unregulated pressure drops a few psi. The HD employee I spoke with said that these compressors were designed to 1) operate at or near "max" pressure and 2) cycle on frequently, even though there is plenty of stored energy/pressure in the tanks. Just sharing some of air compressor concerns if anybody has any input, I think I had a pretty good understanding of diaphragm pumps and the entire hydraulic schematic but it's tough to find good info on air compressors and how to regulate all their internal components.