Any central heating system needs a few basic components to operate. It must have a heat source and some kind of fuel or energy to power it. There must also be a distribution system to move heated (or cooled) air throughout the house, and a way to control the system—typically one or more thermostats.
Beyond this, different types of system may require devices to control the heat flow and the distribution of heat to individual rooms or zones in the house. Hydronic systems require various pumps and devices to control the amount of air dissolved in the system’s fluid and a means to control the pressure of the water that’s delivered into the system from a municipal water system or well.