Does a Mini Split Indoor Head Need Its Own Disconnect?
For a standard mini split where the outdoor condensing unit is the only thing connected to the branch circuit and the indoor head is fed from the outdoor unit by interconnecting conductors, the disconnecting means at the outdoor unit is the required disconnect. The indoor head does not need one of its own. Where the head is separately powered from a branch circuit of its own, it does.
What 440.14 actually requires
Section 440.14 requires a disconnecting means to be located within sight from and readily accessible from the air conditioning or refrigerating equipment. Within sight is defined in Article 100 as visible and not more than 15 meters, or 50 feet, distant from the other. The disconnect may be installed on or within the equipment but shall not be located on panels designed to allow access to the equipment or obscure the equipment nameplate.
The equipment being served in a typical mini split is the outdoor unit, because that is where the compressor and the branch circuit connection live. Article 440 applies to equipment with hermetic refrigerant motor compressors. The indoor head on a single zone system contains a blower motor and control electronics powered through the interconnecting cable from the outdoor unit, so it is not separately supplied and is not the point where the branch circuit lands.
That said, plenty of inspectors and plenty of manufacturers want a means of disconnection at the head for service, particularly on multi zone systems and on ducted concealed units in attics. Check the installation instructions, which are enforceable under 110.3(B). If the manufacturer calls for a service switch at the head, install one.
When the head does need its own disconnect
Three cases turn a nice to have into a requirement. First, if the indoor unit is fed by its own branch circuit from the panel, it is separately supplied equipment and needs a disconnect within sight under 440.14, or under 422.31(B) if it is treated as an appliance rated over 300 volt amperes. Second, if the head is a ducted air handler with electric resistance heat, it is a separate load with its own overcurrent protection and needs its own means. Third, on many multi zone systems the indoor units are powered from the branch circuit rather than through the outdoor unit, depending on the manufacturer wiring diagram, which puts you back in case one.
Section 422.31(B) also covers the general case for permanently connected appliances over 300 volt amperes: the branch circuit switch or circuit breaker may serve as the disconnecting means where it is within sight from the appliance or capable of being individually locked in the open position under 422.31(C), and the lock provision must remain in place with or without the lock installed per 110.25.
Two more items that come up on mini split inspections. Section 440.14 does not permit the disconnect to be mounted on the removable service panel of the unit, so that pull out disconnect needs to go on the wall or the mounting bracket, not on the condenser cover. And 210.63(A) requires a 125 volt service receptacle within 25 feet of the outdoor unit, GFCI protected per 210.8(E), which is the item most often missed on a mini split final.