I have preparation for an AC connection with 3-phase 220V 3X16A breaker. I want to install a 220V 1-phase unit, which also needs a 16A breaker. The physical connection has screw-on terminals, so there is no worry about plug compatibility.
I have spoken to 3 electricians: one says that I need only change the 3-phase breaker to 3 separate 1-phase breakers, and leave the 2 additional phases disconnected and unused in the AC connection. The other two electricians say that there is no problem leaving the 3-phase breaker and just leaving the unused phases disconnected. All of them agree that there is no worry about the shared neutral of the connections, and say there is no need to re-wire the neutral.
Should I listen to the majority? I tend to trust them more since they are basically telling me that they don't have to work (do nothing = no get paid), so I'm more suspicious of a guy telling me I need to pay him to do the needed changes.
I'm asking both in terms of code-correctness and more importantly, safety for myself, the AC unit and the house (electrocution is bad, blown AC unit is bad, fire is bad).
Edit: to clarify, mains voltage in Israel (where I live) is 220V. Most older homes have 1-phase 40A (or even 25A) breakers, and new homes (like my own) have 3-phase 3X25A breakers. The main usage for the 3-phase is AC units and electric cooktops and ovens. The rest of the electrical wiring in the house is distributed across the three phases to even out the load.