Kung Fu Maintenance discusses the role of transformers, the fan relay control center, and a little bit about thermostats.
OK. This part here is your transformer and your fan relay. The transformer transforms the power that comes in from the 110 outlet down here. It transforms it into 16 to 24 volts 29 volts some where in there for your thermostat to run. That way your thermostat runs at a lower voltage and is a bit safer for you to operate.
Usually your thermostat is located in a central area such as a hallway that gets an even amount of the distribution of air or heat. That way it gets a good sample of what is in the dwelling whether a house a business or what not.
The settings on your thermostat tell the system what to do whether to turn the heater on. You know to open the zone valve for the heat and turn the fan blower on. Or whether to turn the fan blower on as well as send the signal to the contactor for the split system to engage the 220 power that’s there for the condensor to run.