Final answer:
The most common pump in hydronic heating systems is the circulator pump, designed to move water through the system, which is heated externally.
Step-by-step explanation:
The most common type of pump used for hydronic heating systems is the circulator pump. These pumps are specifically designed to move hot water through the network of pipes in a hydronic heating system, ensuring an even distribution of heat throughout the space. Unlike heat pumps, which transfer thermal energy from a cold environment to a hotter one, circulator pumps do not actively heat the water; instead, they rely on an external heat source, such as a boiler, to provide the heated water that they then circulate.