It says 10 AWG (American Wire Gauge) for the 36,000 BTU unit, which is the one in your link. 10 AWG is heavier than 12 AWG. Get the 10 AWG and get a cable for 230v installations - 12/2 is usually for 110v installations.
Cable for a 230v system is usually a 10/3, not a 10/2.OK thanks...when you say
do you mean get that in addition to the 10 AWG ?