Thanks.
The house has 2 "zones", really just one full heating/AC system for upstairs and one for downstairs. They are both completely contained in the attic except for the AC heat exchangers (condensers?) and pumps outside on the ground. There is a laundry room upstairs (I prefer downstairs but that's how they do it in vegas) that would make the water, drain, and electrical connections very easy, but I'm not sure it would be within the 20 ft max distance from the hot/cold box in the attic where the individual ducts branch out from. The attic space would have a place to wire it in and I could route the drain to the AC condensation drip pan which dumps out at ground level outside so I'd have elec and drain, but I'm not sure there is an easy place to tap into the water lines up there.
I'm going to have an HVAC/plumbing installer come out to look at it and make his recommendations. There are some decent evap units that just need the filter thingy replaced every few months, and those supposedly use a lot less electricity than the steam ones. Some of the evap ones are sold with blowers so they can work even when the main heater/ac blower is not running, but obviously that would cost more and be one more thing to break.
The water here is pretty hard so an RO setup would be a good idea, except that that's one more thing to have to maintain and crawling up in the attic is a pain in the butt. It's just a trap door in the ceiling above a hallway, no built-in ladder or stairs. I'd like to limit my trips up there to once or twice a year, at most, so less routine maintenance is a good thing.
I am thinking of only putting one on the upstairs system, since the downstairs floor plan is completely open except for one small den/office and a bathroom. So running just through the upstairs vents ought to work for the whole house.
