If your system needs the default state to be closed (on), you'll probably have to use a board with mechanical relays, and use the Normally Closed terminal blocks. This way your state in 'On' even if the Phidget is not powered or plugged in. If you need to use SSRs for some reason (longevity, PWM, etc.), you probably need to rethink your system.
At present the system is using two KTA323's for controlling power to subsystems.
As the project is a sustainable solar powered unmanned surface vessel we cannot afford the power used by coil relays.
The solid state relays would be ideal if they could maintain their on/off state while the process controlling them needed a restart or had a forced restart.