From which breaker in a 3Ø panelboard will there be 208 volts to ground when powered by a 3Ø transformer supplying 120/240 volts?

In a 3-phase panelboard powered by a 3-phase transformer that supplies 120/240 volts, the voltage characteristics depend on the phase arrangement of the panelboard and how the breakers are installed.

In a standard 3-phase panelboard, the configuration typically allows for access to two types of voltages: line-to-line and line-to-ground. For a 120/240 volt service, the line-to-ground voltages are typically 120 volts corresponding to the phases attached to a neutral and 240 volts across two phases.

To obtain 208 volts to ground from this panelboard, we must look for a specific configuration of the various phases. In a 3-phase system with a typical 120/240 transformer, the remote phase with respect to the neutral (ground) yields 208 volts when appropriately derived from two of the 120-volt service lines (where the "high leg" or unused phase allows the calculation to come out to 208 volts).

The breaker in space 10 is associated with the correct configuration of phases, allowing the potential difference between the chosen phase and the ground to yield 208 volts. Since the panelboard is fed from a 3-phase transformer, the position in space 10 correlates with