[Jon Stratis]

Per Table 4-1 under R18, it's not clear if a fan is considered a custom circuit or a motor (please check that table to ensure the fan is, in fact, legal).

R55 part D states "Fans may be attached to motor controllers and may be powered from the power input terminals.". As those motor controller input terminals are correctly connected to the PDP terminals, this ruling would imply that connecting fans to the terminals is legal. I'm not aware of any rule that would make it illegal. As a historical note, this hasn't always been in the rules. A long, long time ago it wasn't strictly legal to hook fans up to the inputs of the speed controllers they were on, and the ONLY way to do it was to go through a dedicated 20A breaker (you could have multiple fans per breaker).

For what it's worth, my team has legal fans cooling our compressor hooked up to a 20A breaker.