We removed a couple of tired old Welstar split AC systems, more than 15 years old, they were noisy and were not putting out much heat due to low refrigerant(gas) charge. As both used the now defunct R22 refrigerant. It was decided to replace them with a pair of Mitsubishi Electric Inverter units.These latest systems from Mitsubishi use the newly introduced R32 enviromentally friendly refrigerant. They are not only very quiet in operation but incredibly efficient. A pleasure to install.