Hi Marcus, for those P42s equipped with dual heat pumps, like ours, it is set up for 60 amps of AC power. The shore power plug beneath the coaming step closest to the rail provides 30 amps to both A and B sides. That way only one 30 amp cord is needed to operate all systems on the boat. The other plug closest to the cockpit provides a second 30 amp cord for those who want 60 amps of power. This plug, as I recall, supplies power only to the heat pumps.
With both heat pumps running (25 amps), hot water heater (10 amps), microwave (10 amps), entertainment system (8 amps), misc. (5 amps), this beast can become quite the power hog. I've never used both cords. I manage power consumption to 30 amps, which works out quite well. That is also why Hunter equipped our boat with an 8KW Onan Genset for those who need power while away from shore. The slide that blocks your choice between shore power and Genset serves to protect against a power conflict.
Pity the electrical engineer who designed this sophisticated system, which works very well. Certainly away over my head. The wire work behind the main panel was done very professionally; clean, organized and well done.