8.300-1(b) says demand for a range is 8 kw plus 40% of the rating over 12 kw. 8000 plus 2000 or 10,000 watts which is 41.5 amps non- continuous load per 8-200(3) So the number 8 is good for 45 amps and the breaker should be 60amps. Your local inspector may permit the 50 amp breaker but the rating is required for the 52 amps IE 41.5 X 1.25 = 51.8 amp breaker size. The domestic range cord supplied with most 12 to 14 KW ranges have a number 8 conductors with a 10 neutral. I don't know what these cords are actually rated for. I imagine the 50 amp cord is #6 with a full sized neutral and costs 5 times as much. The same range if it could be used in a commercial install (most are not rated for continuous use) would need 70 amp wire on a 90amp breaker. I don't think I have ever seen a domestic range at 17 KW.
