re: Paging HVAC guys...Do you think this product works?

There is a big difference between the outside unit getting wet every so often from rain vs. being saturated with tap water 24/7.

I am sure the filtration helps but the dissolved salts in the water (what causes hard water deposits/stains) will build up over time and clog the condenser. Unless it's an RO filter the water isn't really clean enough for this application in the long term. I also think it would shorten the life of the cabinet components over time. You'll find newer outdoor units are designed with louvers so the coils stay pretty dry in most average rainfall.

Commercial systems bathed in water constantly (cooling towers, etc.) have a full time water treatment system and are monitored for the water quality.