The CS series of condensing units for boats provides heating and cooling in a highly efficient package. The hermetically sealed, highly efficient compressor reduces amp draw while pressure switches, thermal-overload, and start components provide constant system protection and proper operation. In addition, the expansion device and check-valve assemblies control load balancing during operation. The copper-encased cupronickel condenser coils are highly resistant to corrosion caused by continuous seawater flow. The electrical box can be mounted remotely. It has a moisture-resistant design with a corrosion-resistant enclosure. CS Digital (CSD) units include the Passport I/O circuit board.