The AK-PC 781 multifunctional pack controller makes it easy to set up energy-efficient capacity control of refrigeration compressors and condensers with modular hardware and flexible software that extends as system requirements grow or change. It is easy to configure inputs and outputs for sensors, switches, and relays with a modular controller that can change as needs change — plus provide oil management, heat recovery, and CO2 gas pressure control. The AK-PC 781 capacity controller ensures precise and stable suction and condensing pressure regulation for a variety of applications and refrigerants. Modules snap onto a common platform to accommodate digital and analog inputs and outputs for compressors, condensers, gas coolers, fans, expansion valves, sensors, switches, and alarms. Capacity control is available for up to eight compressors, with three unloaders for each compressor. Functions include speed control of one or two compressors, handling up to six safety inputs per compressor, optional capacity limitation to minimize peak energy consumption, capacity control for up to eight fans, and coordinating cascade controllers for medium- and low-temperature operation. Advanced module features support heat recovery for hot tap water production and general heat recovery in transcritical CO2 booster systems.