I've noticed it over the years in various living quarters: an inside A/C temperature setting that's appropriate and comfortable for a given outside temperature is quite unbearable when the outside temperature changes (to result in a different number of A/C runs).
One may think this due to the positioning of the thermostat, but I think the problem is elsewhere — humidity.
As such, I'm curious why is it so common that air conditioning control units only have a thermostat, which so often requires such frequent adjusting when the outside temperature changes? Wouldn't it make more sense to have some sort of a humidistat instead, which would be set at a given point, and would, supposedly, require no further adjustment?
Is there any solution to this effect?
Maybe a control unit that lets you set a cooling value based on humidex, instead of °C / °F? I'd much rather set my HVAC to 27 humidex for the whole cooling season, than keep adjusting it between 21°C and 27°C, up and down, all the time.
Best Answer
I can think of several reasons.
A thermostat is a reliable, proven, simple, and inexpensive device which works well enough in most cases.
A humidistat and its derivatives rely on a comparatively expensive relative humidity sensor plus some finicky electronics. A thermostat would still be necessary to prevent potentially dangerous results, like shutting off when the humidity is below 75% but it is still 40°C/104°F (admittedly unlikely), but also the humidity threshold may not be satisfied until the temperature is 5°C/41°F. Not so good for many living things.
Humidistat technology of old has a limited range, limited responsiveness, and a short lifetime of it being accurate. Stable and reliable sensors have been around only since the 1990s.
In short, it is reasonable to expect new devices to commonly incorporate this functionality. As manufacturing volume increases, it reduces the price and consumers expect more.