A liquid submersion cooling system that is suitable for cooling a number of electronic devices in parallel using a plurality of cases connected to a rack system. The system cools heat-generating components in server computers and other devices that use electronic, heat-generating components and are connected in parallel systems. The system includes a housing having an interior space, a dielectric cooling liquid in the interior space, a heat-generating electronic component disposed within the space and submerged in the dielectric cooling liquid. The rack system contains a manifold system to engage and allow liquid transfer for multiple cases and IO connectors to engage electrically with multiple cases/electronic devices. The rack system can be connected to a pump system for pumping the liquid into and out of the rack, to and from external heat exchangers, heat pumps, or other thermal dissipation/recovery devices.