The question is irrelevant if you don't include the amperage.
240
The key parameter in sizing wire is the current requirement. Once you know that you can look up value in a wire gauge table. The length of the run is important for longer runs because of the resistance of the wire itself. Aluminum wire requires a larger diameter than copper for the same current. Once you calculate the wire size you can then size the conduit.
You size wire by the current. Various insulations are rated for voltage, temperature and the medium where the wire will be run.
Depends on the size of the circuit which you did not list.
Presuming that you would like the least expensive installation, the following is calculated on overhead aluminum wire. The wire size needed to hold the voltage drop to 3% would be 3/0 MCM. If the installation could be run on 240 volts then the wire size can be reduced to #2.
you must run the proper size wire based on the ampacity needed, wire must have four conductors including the gound
I would use AWG # 4 copper.
A #10 copper conductor will limit the voltage drop to 3% or less when supplying 21 amps for 150 feet on a 240 volt system.
240
The key parameter in sizing wire is the current requirement. Once you know that you can look up value in a wire gauge table. The length of the run is important for longer runs because of the resistance of the wire itself. Aluminum wire requires a larger diameter than copper for the same current. Once you calculate the wire size you can then size the conduit.
You can't. The 120 volt GFCI is probably just a 2-wire (hot, neutral and ground) You would have to run a new 3-wire (2 hots, neutral and ground). The two hots are how you get the 240 volts (120+120=240). Also you must make sure the wire is gauged properly. #10 wire for 30 amps, #12 wire for 20 amps, etc.
It won't run.
Yes, if the motor is rated 240 volts 3 phase.There is such a thing as 240 volt 3 phase power.However if you are asking if you can use 240 volts single phase on a three phase motor, then the answer is no.
You size wire by the current. Various insulations are rated for voltage, temperature and the medium where the wire will be run.
Depends on the size of the circuit which you did not list.
yes 240volts is 240 volts
Presuming that you would like the least expensive installation, the following is calculated on overhead aluminum wire. The wire size needed to hold the voltage drop to 3% would be 3/0 MCM. If the installation could be run on 240 volts then the wire size can be reduced to #2.