For a roof HVAC unit, the mechanical guy wants a separate 120V circuit for a DDC (control) unit. The DDC will be mounted inside the HVAC enclosure. They wanted to keep it on and not run it through the unit disconnect. Article 440 states that the compressor and controls get disconnected from the circuit conductors. If you have run into this, have you used an auxilary switch with the 480V disconnect, a separate disconnect switch, or do as they want?