Air source heat pumps (ASHPs) have enormous potential for promotion and application in China due to their excellent efficiency and economic viability. However, the application of large-capacity units or clusters are plagued by severe issues such as noise and vibration, poor heating stability during defrosting, and efficiency degradation under part-load operation. To address these challenges, this paper proposes a novel form of distributed small-capacity ASHP system for centralized heating in residential buildings and conducts field tests on two systems in a community in Zhengzhou. The heating performance of the system form and the influence of heat source configurations were analyzed during a typical week, including system efficiency and defrosting behavior. Then the long-term energy consumption performance of different control modes was compared during an 81-day testing period. As the results show, the system form could achieve the higher efficiency and show the better heating reliability when defrosting is frequency during high-humidity conditions. For the case systems, when the rated capacity increased by 19%, the System COP (SCOP) increased 6.2% in the typical week and increased 7.66% in the mid-to-late testing period, showing the significant impact of configuration. Regarding to defrosting performance, the cycle could be extended and the degree of frosting would be decreased by operating at the efficiency status. The sudden supply water temperature drops could be limited at lower than 2 °C when the simultaneous defrosting ratio is less than 15%. Of course, cluster defrosting should not exhibit high concentration and decentralized defrosting is necessary for stable heating.