Using Dewpoint to control AC units

Configuration
1

I have a few temperature sensors and all of them measure relative humidity as well as the current temperature.

Given you have temp and relative humidity, it is possible to google for the formula to calculate the Dewpoint.

I am wondering about updating my the sensor feed for my Generic Thermostat so that instead of using the current temperature it uses the Dewpoint.

Has anyone else used Dewpoint to control AC - how did it work out for you / were there any issues to be aware of?

In case it’s relevant, outside humidity can range from 50-80% depending on time of year.

2

A quick update, I created a template sensor to calculate the Dewpoint from the temperature and relative humidity, then hooked it up to the AC, here is a graph of how it worked (most of the time set to 13 C Dewpoint):

Cooling
Cooling2682×1786 178 KB

I have found it a bit harder to tune the cooling when using Dewpoint for the following reasons:

  • Humidity appears to be more of a trailing indicator than temperature - after the AC turns off the Humidity continues to drop and vice versa.
  • I am using an Broadlink RM4 Mini for doing the temp/humidity sensing and its only polling once per minute.
  • Frankly I don’t know what 13 C Dewpoint feels like, note the true temperature appears to be holding around 23 C.
  • The metric isn’t precise because different combinations of temp and humidity can create the same Dewpoint.

I am going to play with it a bit more and literally see how it “feels” at different Dewpoints.