I am not aware of any CODE requirement to use a 'starter' anywhere. Perhaps we need to clear up our terms a bit.
A 'starter' is defined as a contactor with the addition of motor overLOAD protection. This is not to be confused with other functions that packaged starters commonly perform in addition to those first two.
The NEC provides, in various places, for there to be a disconnecting means. If a 'starter' contains a disconnecting means, it is called a 'combination starter.' These days, thats what most of us really mean when we say 'starter.' Keep in mind that, if used as a disconnect, the starter needs to open ALL the 'hot' wires (many starterrs within HVAC equipment don't do this).
OverLOAD protection is not required by the NEC; overCURRENT protection is. While in many cases the two functions are served by the same fuse or circuit breaker, in a starter a different element is used. The 'heaters' in a starter are absolutely useless in protecting the motor from, say, a shorted winding; their response is far too slow. The 'heaters' are very good, however, at protecting the motor from being asked to do more than it is expected to do. That is, they'll limit the time a 1hp motor will be allowed to provide 1.1hp of work. Fuses and circuit breakers would trip on the start-up current if they were set this close to the capacity of the motor.
