Class I. The device is grounded. Any electrical faults, internal or external, or caused by the load, are cleared via the grounding circuit.
Class II. The device is not connected to a protective conductor. User is protected by reinforced insulation around the live parts (an insulating case and no contact with live parts, i.e. plastic buttons, moulded connections, etc.) or double insulation.
Class III. The device may be connected only to SELV (safety extra-low voltage) circuits.
The PowerPact circuit breakers are class II devices (front) and may be installed through the door in class II switchboards (standards IEC 61140 and IEC 60664-1), without reducing insulation, even with a rotary handle or motor mechanism module.