Hi Wallace, as you are only using the fridge, the water pump, and presumably the cabin lights, as all these come off the 12 volt circuits, it is unlikely that any of them will be causing the problem. Essentially the shore current, whether it be 220 volts or 110 volts, will go only to the mains distribution circuits onboard, i.e. to your mains power sockets, to the mains side of the calorifier used for heating the water, or to the battery charger. If your circuit breaker is continually tripping, the fault has to be within the mains circuits only. On my B36, the calorifier can be isolated as it is only plugged in to a mains type power socket located just forward of the calorifier, so it is easy to unplug. Once unplugged it will then be possible to see if your circuit breaker continues to trip. By disconnecting each of the mains circuits you should be able to determine which of them is faulty. Good luck, and be careful to unplug your shore power before you do anything. If you are not comfortable working with mains circuits get an electrician in to do the job for you.
