It might be my inept ability to search but I created an app that solves a couple of issues for me around my dehumidifier. I took a look at the app in the ST Public repository/store (Smart Humidifier) with the thought that I could just reverse it for dehumidification but it’s wicked old and only so-so at what it does. But, it did give some inspiration.
Anyhow, the Smart Dehumidifier Control, which is a very simple (maybe even crude!) app, allows you to control a dehumidifier using an external humidity sensor and a smart plug of some sort. It also gives you (push and/or SMS) alerts if the dehumidifier is running for longer than a desired number of hours. From experience, this is always how dehumidifiers seem to fail (evaporator dies and the thing just runs and ices up) and you might not notice unless you’re there and looking at it. The other thing that it does do is give you the option to define a “setpoint band” which allows the humidity to overshoot before the dehumidifier turns on and once it is on, it will dehumidify to an equally lower humidity. This allows for fluctuation in the humidity, which easily happens, and you get longer periods of off. In theory I think that will save energy.
For my personal setup, I use the following devices:
- Humidity Sensor: Halo Smart Smoke Detector from Halo Labs (already installed, great location, hardwired, seems very accurate) - https://community.smartthings.com/t/halo-smart-smoke-detector
- Smart Plug: Zooz ZEN15 Smart Plug from @TheSmartestHouse (also nicely reports the power usage and cost which I love but don’t exploit in this app) - https://community.smartthings.com/t/release-zooz-power-switch-zooz-smart-plug
The “tricky” part about this is the humidity sensor reporting. Depending on the sensor it might not report changes very frequently or it could blast out a lot of noise (aka same readings). The Halo is a bit chatty but it seems to only report a change in humidity when there actually is a change. So, fairly responsive but not annoying. I can only guess that some of the battery powered sensors, you might have fewer reports in an effort to save battery but that too could be an issue. So far for me the Halo has been working in this “unintended purpose”.
Almost goes without saying but this app depends on your dehumidifier to be able to run continuously (i.e. have a drain) and be able to restart from power off. For those that are worried about turning on and off the power on the dehumidifier, don’t. It won’t shorten the life. I’ve been controlling window A/Cs this way using solid-state relays for 20 years (up until recently, now with ST!) without issues.
Desired Humidity Setpoint: %RH that you want to target, defaults to 50% which is a good place to start
Also allow an overshoot of +/-: %RH that you want to allow above/below the setpoint before it turns on/off, defaults to 0% and can be up to 25%. 5% is a good place to start and if combined with the default setpoint of 50% would establish a 45%-55% band. Also helps to alleviate excessive switching since the %RH can fluctuate quickly.
Require a minimum off cycle time of this many minutes: A setting that allows you to not turn on the dehumidifier too soon. Most dehumidifiers have sensors in them to not run the compressor blindly but this ensures a minimum amount of off time. The default is 0 but 5 minutes is probably adequate if you need the feature. A dehumidifier that has this protection built in will typically run the fan for a period of time when powering up (very typical unless the dehumidifier is old).
Continuous Runtime Notifications: Here you set the desired notifications for a push or push+SMS. It’s also where you set the runtime threshold “Maximum Runtime (Hours)” which defaults to 0 (no notifications ever) and up to 48 hours. This will depend on how long you expect the dehumidifier to cycle. I think something like 2 or 4 hours is probably a good place to start but it really depends on the dehumidifier and the space it runs in.
Pause dehumidification while any of these doors or windows are open: Allows the dehumidifier to pause its operation while any door or window equipped with a contact (open/close) sensor is open so as to not waste electricity dehumidifying the earth. Also allows you to specify a maximum time for the door/window to be opened before pausing so as to not trigger during routine use. Allows you to monitor any number of doors or windows and won’t resume until all are closed again.
- There is no “user” logging of routine operations in the Messages tab of the ST phone app but if you enable the alert (see above) you’ll get the push message which also will be logged there. The default push message is basically:
Warning: Dehumidifier has run continuously for more than 2 hours. Humidity is 62%
- There is plenty of debug logging that the app does and you can see from the Groovy IDE. Messages include the current %RH changes that are reported to the app and if the dehumidifier is on, and for how long, or off and when it is turned off how long it ran for. A typical message (one of them anyway) is:
humidity is above 45% +/-5%, humidifier has been running for 107 minutes
I’m still debugging but it seems pretty stable so here’s the current code. Any comments are of course welcome!