If the wiring does not appear to be correct then the wiring should be traced out and identified and corrections made as needed. It should be taped another color if the circuit is 240v so that someone doesnt mistake the white wire as a neutral.
Color Coding Electrical Wires And Terminal Screws
Black tape on white wire. Even red tape would work good for that. Sometimes youll find a white wire with a piece of black electrical tape wrapped around it. By convention that means the wire is hot. However those same 220 volt appliances can be wired with a black and white wire where the white wire had been marked with black or red tape at both the appliance and in the main panel to indicate. The ground wire is for safety. The white wire goes to the white metal screws on an electrical outlet.
Same in a junction box where you have several black wires and one white under a wire nut i never wondered if that white was grounded or not first thing that comes to mind whether it is. The ground wire goes to the green screw. White wires with black or red tape. White wires are often used for switching however the white wire should then be identified with black electrical tape or a permanent marker. You are allowed to use the white wire to carry power only for purposes of switching and only if the white conductor is part of a multi conductor cable. A white tape band indicates that the wire is a neutral black or red tape indicates hot and green means ground.
Not trying to be sarcastic but think about this why would you put black tape on a white wire if it were 120v. I have also seen neutral conductors that were nicked and repaired with black tape i suppose that is a violation better make that repair with white tape. The idea is to mark the white wire of a cable as an ungrounded hot conductor. Neutral wires grounded conductors should be white. You must however use the black wire as the return path from the switch to the light so the black from the light fixture connects to the black from the cable used for the switch. Home science math history literature technology.
When you connect an outlet or light switch the black wire goes to the brass screws. The white wire is supposed to be identified with black tape to show that it is a current carrying wire but in a lot of cases this does not get done. Hot when a white wire is augmented with a red or black color marking this often indicates that it is being used as a hot wire rather than a neutral wire. Typically this is indicated with a band of black or red electrical tape but other colors may be used wrapped around the wires insulation. Hi greg from what you have described the existing switch is a three way switch. If you have a ground wire its green or bare.