Any condensate drain can clog. Happens on residential too. Has happened with the Lounge unit. Dust is part of it, but you’ll never stop dust completely. The important part is being able to vacuum out the condensate lines and clear them. This won’t drain any condensate that has already overflowed a stuck drain, draining the overflow pan is a separate step.
Vacuuming the lines clean is not possible with the “common rail” where all 4 port onto a single line that passes each unit, that crap drain was here when we moved in. If you put a vacuum on the common drain tube, it’s going to pull air through the other 3 drains that are clear and will never draw enough vacuum to suck the muck past the p-trap on the clogged line.
Each unit must have its own line, and not meet up until at person-height with ports you can disconnect and hook up a shop vac to. Then you can suction individual lines clean any time you need. Ultimately these lines all just go to the building sewer. Thus the need for a p-trap on each unit. Note vacuuming will deprime the p-traps, so that’s a thing.
Algae is a part of it too, it’s supposed to be algae growing on dust making it clump together more. Typically we throw anti-algae tablets inside the units. Trying to bleach out the lines isn’t all that helpful by itself, though. Also, the way the drains are ported right now, it doesn’t have access to do that. We need to replumb it so we can keep the drains clean.
Plus, the rise/run of the current drain is far below guidelines. Needs more slope. But that’s not where our clogs actually occur.
Better filtering is good for other reasons, but this drain setup just has to be fixed. Even if we had the best filters possible, you can still have a mess of problems with that common drain.
The units DO have a low voltage float switch that shuts off the compressor (not the fan) if the overflow pan is full of water. The pan should never see any water under normal conditions, it only overflows once the condensate drain is already clogged, and will stay clogged if you just drain the pan, and will immediately start to overflow again. Don’t try to add a second drain to the overflow pan or anything, that’s just not a solution.