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Different calculators all seem to give me different results. And What am I supposed to put for Voltage for the standard 240 V North American Power? in NA power one wire is 240 volts relative to the second wire, but only 120 volts relative to neutral.
I have 4-4-4 Aluminum Underground Direct Burial with an Ampacity of 125 amps.
I want to use it to move standard 240 V power about 150-180 feet away.
I cannot figure out the maximum amperage.
The only time you're allowed to use 3-wire for 120/240V is on the service entrance -- that's from the utility drop, through your electric meter, to the very first disconnect switch or breaker.
Beyond that, you must assign 1 wire to safety ground. With 4-4-4, that leaves only 2 wires, so you'll either have 120V only, or 240V only (no neutral).
If you run in 240v only mode, then at wire redline (65A) you'll have 4.5% voltage drop. That's "not great, not terrible" - I wouldn't sweat it. In the US you are not required to sweat it.
In Canada, you are required to limit to 3.75% voltage drop (literally: 3% drop at 80% ampacity, but, same thing). That calls for a 55A circuit (3% happens at 44A).
If you run in 120V mode, then you'll be at the horns of a decision. You can run 65A of draw at an alarming 9% voltage drop.... or you can run proportionally less amperage at proportionally less voltage drop.
Canada rules would limit the circuit to 25A. Ouch.
In your case, voltage drop is insigificant for 240V power over a mere 180' of distance, but you are limited to a 70A breaker (65A actual ampacity) on 4AWG Al by the NEC Table 310.16 ampacity chart, assuming your terminations are rated for 75°C. (The 125A number you gave for the cable is likely only for electrical utility use.)
