By installing the additional condenser on the existing air-conditioning machine for R22, a more effective heat pump system could be operated with R134a. This heat pump system could also be operated at high and low ambient temperature. It was proved that COP was improved by 10% when operating with R134a and that the air-conditioning machine could be operated when the temperature exceeding 50℃. It was also shown to be able to prevent frost on the outdoor unit for heating operation.
