MMT,
Thanks for the advice about measuring electricity. Since that is what I want to reduce, that is what I should measure. I don't have a loop ammeter, but I do have a house KW meter. It will "tare", so I can set it for base load and then do my AC tests. There will still be variability, so the clamp meter will be better. I'll see if I can get one for a reasonable price. I am able to do some rough calculation of ambient air temperature, coil temperature, and air output temperature as well as register temperature with my IR thermometer and regular thermometer, so that will provide some information about what is going on in the system.
There is a lot of discussion of this idea over at
hvac-talk.com with most of the guys poo-pooing the idea as too complicated, too many problems, too much room for end user error, etc. My feeling is that they are a rather unimaginative lot, but most people don't want imaginative from their HVAC tech.
I have looked more into the mineral content of my water. According to the water company, our water has dissolved solids at a rate of 40 ppm. Rainwater has less than half that, about 17 ppm. However, the rates of problematic dissolved minerals are much closer to rainwater: Ca 6.7 ppm (5.5 ppm for rainwater) and Mg 0.98 ppm (0.74 for rainwater). Still, I assume that sedimentation will eventually be a problem, so I get back to only running it in the hottest temperatures. I will test it in the high 80s or low 90s, but don't plan on running it all of the time.
Thanks for pointing out the increased capacity issue. I have a 2 ton system and a very small house. The unit was likely oversized to begin with and after air sealing and adding more insulation it is definitely oversized. I need to model with HEED or something similar to get a more accurate idea of needed sizing. The HVAC-talk.com guys were saying that most systems are set to run optimally between 90* and 95* F, so I plan on only using it only when temperatures are above that. What do you think?
As I have gone on with this project, I came to similar conclusions as you to set up a partial swamp cooler around the condenser. I was concerned about airflow and I think your solution to cover only part of the condenser is an elegant one. If I were installing a new system I would try to go this route. It would make a lot of sense in a hot, dry climate. According to
this study on the CoolNSave, most of the cooling effect comes from water evaporating off of the coil, not from pre-cooling the air. However, a swamp cooler-AC would probably do nearly as good a job only cooling the air instead of coating the coils. Gary's suggestion to use rainwater is duly noted.
Now from theory to practice...
I couldn't find misters at the hardware store, so I ordered five 0.8 gph misters from an irrigation supply company. I won't be able to test the system until these arrive. However, I did some basic tests with the mist attachment to my garden hose to get an idea of spray patterns. It looks like the mister works best when pointed up parallel to the coils. Most of the mist is pulled in by the fan, but a portion collects on the cage around the coils. There is no water vapor coming out of the stack, so all of it either evaporates in the warm air, collects on the coils and drips down, or overshoots and is carried off by the wind. I will use four misters, one per side, and move the valve to the back of the condenser. Hot weather has returned (105* F today), so the misters can't come soon enough!
I'll keep everyone updated and I look forward to more from MMT.
-Ben