Evaporative cooler


Is there any way to modify the code for an evaporative cooler? The components that would need to be controlled are the water pump, high speed fan (when setpoint is ~ 5 degrees F above setpoint), and low speed fan (when at or ~ 2 degrees F above setpoint). Can only run one speed at a time. I’m an HVAC tech and very familiar with the wiring aspect but lacking on the programming side. There’s no need for heat control, cooling only.


Welcome to the club @mstudent We are swamped right now with the production of the units sold during our crowdfunding campaign and we cannot help very much atm. What I can say though is that the units available in the next ~45 days will have Heating/Cooling option and 2-stage support which I believe is what you need. Not sure if the 2 thresholds (2 and 5 degrees) will be the same but maybe we can make this a variable from the GUI.
Have you built your HestiaPi yourself?


I’m in process of it right now. We live in New Mexico, in higher elevations (6300’/1920 meters), and it is very dry so traditional A/C does not work well without dehumidifying the air further. I haven’t gone into the code yet, maybe I can gain some insight by looking into it.


Does evaporative cooling run on a different wire? Can it be ran on the same wire as the cooling or does it have a different run cycle? Curious because I don’t live in an area where these humidifiers are typically installed in air handling ducts.

If you do need to run the cooling and humidifier on different wires then I know openhab can be configured to support it if you replace the heating configuration and reuse the gpio pin from the heating but it would require quite a bit of reconfiguring.

I’ve switched over to iothermostat (I didn’t need openhab’s additional features) otherwise I’d offer to help. :slightly_frowning_face:


Thanks for the response. The way evaporative coolers work is by starting a circulating pump which wets the media, then brings on a fan which pushes fresh, humidified air into the house actually cooling it. I have no need for heating control (radiant floor heating) as they are two totally separate systems. Right now I’m using a nest with Y for the pump, and G for the fan. The nest doesn’t pre-wet the media before it brings on the fan, so I end up with a lot of dust in the house until the media is wet, nor does it control the second speed of the fan. What I’d really like is on a call for cooling, to bring on the pump for 2 minutes to pre-wet the media, then however close to setpoint the temperature is, bring on either high or low speed fan. I wish I could work on it more than I’ve been able to, but wife doesn’t like me sitting in front of the computer quite that much.


The hardware version ONE can surely support that. The software needs a minor tweak to use

  • the first stage heating for first stage cooling
  • the second stage heating for second stage cooling
  • add the (variable) 2 minute delay to the fan

Both hardware and software will be available first on the crowdfunding page. The shortly after the software will be released on GitHub.