The summary of this report is shown as follows.
These studies aim at development of a low flow circulation (LF) ground source heat pump (GSHP) multi-split system in order to reduce energy consumption of circulation pumps in the GSHP system. This system applies low flow circulation system in primary side and multi-split system in secondary side. This paper contributes Part 1 in the series of these studies. First, the system concept and development planning are introduced. Then verification test of operation reliability of a water source multi-split heat pump were carried out in the manufacturing factory. As the result, the authors confirmed heating operation reliability of the heat pump even on conditions of inlet temperature of 10°C and low flow circulation in primary side of 30 L/min. In addition, field test apparatus of the LF-GSHP system were constructed to investigate the optimum circulation flow rate of the LF-GSHP system and demonstrate the effect of reduction of circulation pumps' electric power consumption. When the cooling output is around 14 kW, the maximum SCOP of 5.31 is obtained on the condition that the flow rate is 30 L/min. On the other hand, the flow rate condition of 96 L/min provides the highest SCOP value of 3.78 in case where the cooling output is around 24-28 kW. These suggest that variable water volume (VWV) control of the circulation pump can reduce circulation pumps' electric power consumption the most.