The concept is sound in terms of reducing energy useage but the drawback has always been that tap water contains minerals that will cause scale and corrosion on the condenser fins resulting in lower equipment life. The company says it has developed a special filter to prevent this. Their explanation sound like complete bullshit.
All new window air conditioners I've seen are now designed so that condensate from the evaporator coil drains to the bottom of the condenser coil where the hot refrigerant is cooled and re-evaporates the condensate. That saves energy and eliminates the unsightly dripping from the air conditioner. Condensate does not contain dissolved minerals but there is still some degree of corrosion that occurs with time. I don't think most window units are designed to last more than three or four years.
Mildew, mold, mosquitoes in the dropped water or wet surfaces under the unit, dirt collecting? Plus the minerals mentioned above.
I'm very, very suspicious of anything "wet" regularly going across my A/C condenser's nice clean heat exchanger plates.
The only advantage of this would be the increased heat transfer by water droplets evaporating as they go across the HX surface. Which is an advantage of course, but I'm not convinced its practical in the real world.
willards, moisture in the air doesn't have minerals like water from a tap.
I've seen plenty of AC condensors where the home owner complains that the system doesn't keep up like it uise to. Go outside and look at the condenser and the beautiful white arc across the unit from where the sprinkler system is spraying water on it. The mineral build up is restrict air flow and lowering the heat transfer rate.
In humid Houston, the condensed water is sent to a sanitary drain with a p trap. Then there is an emergency overflow that dumps the condensed water to the ground outside. WHY the emergency system? because in a few months the drain system is clogged with slime mold. Diligent home owners pour bleach down the drain every few months.
On two story homes, the AC units are in the attic. The emergency drain drips from under an eve of the roof. The amount of water dripping during emergency draining is 5 to 7 gallons per day on a 3 ton AC.
Air conditioner evaporators/heaters can also pick up harmful vapors from household chemicals. Mfgr's of high efficiency (condensing) heating equipment have had to go to exotic tubing such as SeaCure or equivalent to withstand the attack of NH3, Cl2 and other nasties coming right out of the washing machine and utility room cubbard. Those compounds would be downright harmful to most condenser tubing.
I once tried to recover condensate in an industrial application thinking that it was just good "distilled" water, right? This was in a wood dryer that had a refrigeration dehumidifier and had lots of available condensate. Turns out that that particular atmosphere was full of what ever it was that it took to make tannic acid and it tore up what ever it was that the condensate was collected for use in. Sorry but I can't remember any more details than that but I DO remember the takeaway that evaporator condensate isn't always that pure.
I could very easily pipe mine (I live in Houston and I would question dcasto's 5-7 GPD and think like it is more like 5-7 GPH.) from the evaporator (second story attic) to the condenser (outside on the ground) but after getting burned at the wood plant, I never have.
I have gone out on some VERY hot summer days when the unit was just laboring along and struggling to keep up and hosed it down with a garden hose for a few minutes. Not too many minerals get deposited with that limited use.
And I have on a couple of occasions when relays or capacitors on the fan motor (or the fan motor itself on one occasion) went out on a weekend (when else would it go out?) put a garden sprinkler right inside the unit and let it sprinkle directly on the tubing all weekend until I could go out on Monday and buy the necessary part (that wasn't in Houston, but in a small town where the side walks were rolled up on Friday afternoon before moving here) and fix it.
Some of the old ,window shaker, air conditioners built in the 70s had a slinger ring on the condenser fan, that picked up water from the drain pan and threw it over the condenser coil. They also seemed to suffer from rotted coils. Coincidence?
B.E.
Evaporative cooling is always a thermodynamically good idea. Practically, the issues above concerning scale and corrosion need to be considered and can turn a good idea into a nightmare.
I live in the southwest and have a whole-house forced air evaporative cooling system. It uses around 200 W to cool the house to about 20F below ambient. During the drought that sort of ended a couple of years ago one of the brain trust legislators suggested that they outlaw evaporative coolers to "save water". Someone pointed out to him that generating the electricity used to air condition a house (I think the air conditioning load was around 14 kW but I'm not certain) evaporates around 30 gallons/kW or 370 gallons per day as opposed to an evaporative cooler directly evaporating 1-5 gallons/day.
