I think the confusion is about a $50 motor protected by $150 of overload devices.
Thermal protection doesn't meet the requirements of 28-302(b) for overload protection unless it is responsive to motor temperature and motor current. I'm not sure that it is.
28-308(c) provides that "a motor constructed so that it cannot be overloaded" does not need overload protection. An example would be a bathroom exhaust fan that has such high resistance that when it stalls, it doesn't draw much current. Low current motors tend to be like that.
I apply that rule so that I don't have to install overload protection on furnace motors. I've seen many thermally protected furnace motors stall and trip the thermal protection. The windings remain intact.
Apply the rule differently and we'll be putting overload protection on bathroom exhaust fans, furnaces, air exchangers, air conditioners, etc.
