Home made swamp cooler for about $115.
Summer is coming and I need an additional swamp cooler for the warm greenhouse which on a 95F day tops way over 100F. I decided to build my own, here are the components needed:
1) Attic exhaust fan, HD $70
2) 110V to 24V transformer, Grainger $15
3) Electric (24V) sprinkler system valve HD $15
4) 3 Misting nozzles Charley's Greenhouse $15
5) Plywood, 2 x 4s and some PVC pipe
The attic fan has a thermostat. Electricity comes from the source to the thermostat which I set at 85F. From the thermostat it goes to the fan, I spliced into that line and sent one leg to the 110V/24V transformer. From there it goes to the 24V valve which in turn feeds the 3 misting nozzles. A rectangular box is built out of plywood and 2 x 4s, open at both ends. The exhaust fan sits in one end blowing air into the 2' x 2' x 4' box. Air comes from the outside of the greenhouse. The misting nozzles are on the inside just next to the fan. The other end of the box opens inside the greenhouse. The roof of the box slants down a little.
The thermostat needs to sit inside the greenhouse. That's the temperature we want to control. You can see that the line from the thermostat to the fan is only about 1' long. I'll cut that and make it 10' long as I want the thermostat to sit in the middle of the greenhouse close to the roof. That's where it gets the hottest. When it reaches 85F (inside the GH, not outside in the backyard) the fan goes on and the valve opens up to city water which feeds the nozzles. Moist cool air rushes into the greenhouse. The entire contraption sits on the ground and the roof slants down so that any unevaporated water ends up in the gravel instead of causing a grey film on the leaves.
The nozzles will clog with calcium and need to be cleaned every 6 month or so depending on the hardness of your water. They need to be placed in an accessible location with unions so the can be removed for cleaning.
Joe Parker from the Pleurothallis Alliance in San Francisco showed me the one he built, I built one last year for the cold greenhouse which works beautifully. Instead of buying a swamp cooler, I decided to build another one of these things, much cheaper and works just as well.
Here is a picture of the components, except the wood and the PVC pipe. You can follow the flow of electricity from the extreme right of the picture to it's targets. The only other thing missing is the motivation to slap it all together. Maybe that will come later today ----- or tomorrow ----- or the next day. Right now, a glass of wine, some cheese and catching some rays is in order. Its nice to be retired.