for shore power you need to switch (3) contacts/poles
you need (9) conections
3 NC 3 NO and 3 common
WHY ?
because you must also switch the ground
why
because the shore power side has ground and neutral bonded together st the shore power service entrance
if you don't break the ground, you actually have a continuation of the shore neutral into the RV on the ground wire, while powering the RV from the inverter
i would not risk an inverter/shore short, or an imbalance on the shore loads causing a hot neutral
Transfer switches .. swtich ALL (3) wires on 30amp, all (4) on 50amp
