Smart thermostat
Another major feature of smart thermostats is their ability to connect to the internet. Smart thermostats are designed with a WiFi module that allows the thermostat to connect to the users home or office network and interface with a web portal or smartphone application, allowing users to control the unit remotely. The WiFi feature also has the ability to send reports on energy usage and HVAC system performance via the web portal, informing the user on their energy efficiency and how it compares to other smart thermostat users. It also alerts users when a problem arises with their HVAC system or when it is time for equipment maintenance. The thermostat also uses the WiFi connection to display current weather conditions and the weather forecast.
Thermostat
Depending on what is being controlled, a forced-air air conditioning thermostat generally has an external switch for heat/off/cool, and another on/auto to turn the blower fan on constantly or only when heating and cooling are running. Four wires come to the centrally-located thermostat from the main heating/cooling unit (usually located in a closet, basement, or occasionally in the attic): One wire, usually red, supplies 24 volts AC power to the thermostat, while the other three supply control signals from the thermostat, usually white for heat, yellow for cooling, and green to turn on the blower fan. The power is supplied by a transformer, and when the thermostat makes contact between the 24 volt power and one or two of the other wires, a relay back at the heating/cooling unit activates the corresponding heat/fan/cool function of the unit(s).