Samsung Mode Control Units (MCU) are available in 1-port, 2-port, 4-port and 6-port versions. Indoor units connected to a 3-pipe heat recovery outdoor unit can operate independently on heating or cooling mode. There is a serial port on the 4-port and 6-port MCU allowing mains pipe-work to pipe directly through the MCU without the need for Y joints. MCU requires a 230V supply. No drain required