Performance test for an air conditioning system using thermal storage tank as a heat source was carried out. Refrigerant pump and water cooled heat exchanger were equipped in this system and refrigerant flow direction had been reversed comparing to normal vapor compression cycle. In the test, the suggested system was worked well as an air conditioner. And optimal refrigerant charging amount was found to be 7 kg in this system. The energy efficiency ratio(EER) of the system was varied with the condensing temperature determined by thermal storage tank. More than 10.0 of EER value was easily obtained in this system when cooling water temperature from thermal storage tank was sustained below 8℃.