Target Humidity

Bringing my HVAC humidifier into Indigo and thought that others would find this script segment helpful. I am basing target humidity on data published by Trane, which suggests the following (fans of the metric system will have to convert the formula to fit):

Code: Select all

Outdoor Temp      Indoor Humidity
+40°F               45%
+30°F               40%
+20°F               35%
+10°F               30%
  0°F               25%
-10°F               20%
-20°F               15%


The 10° range between temperatures means that the outside temperature of 39° will call for 40% humidity (even though you'd want closer to 45%.) Since the relationship between temperature and humidity is linear (and because I can't leave well enough alone), I came up with the formula:

Code: Select all

   targetHumidity = 45 - ((40 - currentTemp) / 2)

So I run this every 15 minutes:

Code: Select all

currentTemp = float(indigo.devices[12345678].states["temp"]) # "OUTSIDE TEMPERATURE"

# not more than 45% humidity
if currentTemp >= 40:
   indigo.variable.updateValue(12345678, '45')
   
# not less than 15% humidity
elif currentTemp < -20:
   indigo.variable.updateValue(12345678, '15')

# temperature is between -20 and 40
else:
   targetHumidity = 45 - ((40 - currentTemp) / 2)
   targetHumidityRnd= round(targetHumidity)
   targetHumidityInt= int(targetHumidityRnd)
   targetHumidityStr = str(targetHumidityInt)
   indigo.variable.updateValue(12345678, targetHumidityStr)


[EDIT} Takes out an unnecessary python variable.

[matt (support)]

Great tip, thanks for sharing Dave.