The National Electric Code (NEC) Section 422.30 requires "permanently connected appliances" to have "lockable" disconnects, so that power can be reliably cut to the appliance when it is serviced. Here is an example of a lockable circuit breaker for a built-in oven:
This seems like a great fail-safe to prevent someone from flipping a circuit breaker on while someone else is in contact with a conductor on the circuit. My question is: Why are lockable disconnects only required for hard-wired appliances?
The picture here shows a 240V 40A circuit, but the NEC rule applies to any appliance rated over 300VA, so such locks also appear on 120V 15A breakers for hard-wired appliances. But anyone working on a simple wall outlet or light switch could be exposed to at least 1800VA if the circuit breaker were unexpectedly turned on. So why does the NEC only mandate locks on some appliance circuits, and not all circuit breakers? Do appliances pose a different and greater hazard than other hot conductors?
Best Answer
Because if they plug in, you can just unplug them :)
The purpose of disconnects, whether this type or those in fluorescent lights, is to allow you to unhook it when hardwiring.
The purpose is for lockout/tagout
This is why Code requires a disconnect switch within line-of-sight of the equipment in question. That is true in all instances; mainly this is applicable to industrial.
If a line-of-sight disconnect is not practicable, then Code is allowing a lockout/tagout device in its stead.