MC-PB Multicluster Piggyback Board for Sunny Island Inverters and Multicluster Box The SMA MC-PB multicluster piggyback board is designed to retrofit the Sunny Island inverters for communications capability with the multicluster box. Utilizing a controller area network (CAN) and RS485 this card enables communication between the main cluster and extension clusters. It also allows the Sunny Island inverters to communicate with other SMA inverters and communications devices. The MC-PB is compatible with the SI4545-US-10, SI5048-US, and the SI6048-US-10. The MC-PB kit enables the setup of the multicluster communication and of the RS485 communication. The multicluster communication is established between the master of the main cluster and the master of the extension cluster via CAN. Via RS485 the Sunny Island can communicate with SMA communication products and SMA inverters.