A 2/0 copper conductor will limit the voltage drop to 3% or less when supplying 125 amps for 230 feet on a 240 volt system.
Need the voltage to make this calculation.
NEC 310.16
#1 THHN Copper
Wire is not sized by voltage. It is sized by current measured in amps. Some common copper wire sizes and their current capacities are: 15 amps -- 14 gauge wire 20 amps -- 12 gauge wire 30 amps -- 10 gauge wire 40 amps -- 8 gauge wire
You need a 3 conductor #10 cable. A #10 wire is rated at 30 amps.
You should never try to use more than 15 amps through a 14 gauge wire.
70 amps.
You are probably thinking about 1/0 wire (1 ought wire). In copper it is rated at 175 amps and in aluminum 125 amps.
3/0 gauge
The guage of wire for 20 amps is #12 copper.
The amps that a four gauge wire will handle will depend with the thickness of the wire. If the wire is thin, the four gauge will handle 95 amps.
Wire is not sized by voltage. It is sized by current measured in amps. Some common copper wire sizes and their current capacities are: 15 amps -- 14 gauge wire 20 amps -- 12 gauge wire 30 amps -- 10 gauge wire 40 amps -- 8 gauge wire
AWG # 14 is the smallest wire you can install in a home and it can only be used in living areas. It will carry 15 amps.
You need a 3 conductor #10 cable. A #10 wire is rated at 30 amps.
At the service entrance you will need AWG 1/0 gauge.
As a service entrance wire you need AWG # 3/0 gauge copper.
140 AMPS
You should never try to use more than 15 amps through a 14 gauge wire.
A #6 copper wire with an insulation factor of 75 and 90 degrees C is rated at 65 amps.
Sorry, there is no such wire size as "30 gauge" in the AWG (American Wire Gauge) system. For the ampacity rating of all standard conductor sizes, go to Table 310-16 of the National Electric Code. If you mean what wire size will carry 30 amps then a #10 copper wire insulation rating of 90 degree C is rated at 30 amps.