Designed and manufactured at Mitsubishi Heavy Industries specialist research laboratories, the PFD flow divider now enables all indoor units to be integrated into an air conditioning network, to switch from cooling mode to heating mode, or vice versa, while the whole system remains operational, thus preventing costly power on and power off cycles. In case of conversion from cooling mode to heating mode and vice versa, by simply combining the indoor unit and the PFD box, the sound level is reduced, thanks to the shutdown of the compressor which, however, does not lead to any reduction in capacity. The risk of refrigerant leaks is reduced by changing the welding method between the refrigerant piping and the PFD box.