A #6 aluminium conductor with an insulation factor of 90 degrees C is rated for 55 amps.
Copper is preferable to aluminum and the size of wire should be the same or the next size down if copper is used.
#1 copper thhn
Awg #6
enameled round aluminum wire enameled flat aluminum wire enameled square aluminum wire
Today the only use of aluminum wire is in service entrances and underground feeds where the larger sizes are needed. By using aluminum the overall project wire costs are kept to a minimum even with the bigger size needed over copper. Wiring branch circuit in aluminum has not been vogue for many years now.
Wire size is rated by Amperes of current. You did not mention the wire size of the aluminum wire, so there is no way to answer your question. The voltage rating is more a rating of how good the insulation around the wire is.
Copper is preferable to aluminum and the size of wire should be the same or the next size down if copper is used.
Don't use aluminum wire inside the house.
Awg #6
#1 copper thhn
250 MCM aluminum minimum
enameled round aluminum wire enameled flat aluminum wire enameled square aluminum wire
A 100 amp service requires that you use AWG 4 copper wire or AWG 2 aluminum wire.
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.
Today the only use of aluminum wire is in service entrances and underground feeds where the larger sizes are needed. By using aluminum the overall project wire costs are kept to a minimum even with the bigger size needed over copper. Wiring branch circuit in aluminum has not been vogue for many years now.
AWG # 6 copper or AWG # 4 aluminum
300 kcmil @ 75°