My boss and I have taken odds on this topic. The difference of opiion is wheather a 50amp Spilt system Air-conditioner can be wired with the conductors being Alum #6 XHHW. It is my belive that due to 110.14(C)(1)(a)(2) we must use a larger wire #4. But he feels that the fact that the conductor rateing of #6 xhhw falling in the 75c column @50 amps is sufficiant. Any advice would help on the topic.