Disconnect location for detached buildings
A detached garage, ADU or other building fed from another building needs a disconnect for its supply. It must be readily accessible, inside or outside, nearest where the conductors enter. Older code books numbered this rule 225.32.
What the code requires
Every building or structure supplied by a feeder or branch circuit from elsewhere needs a means to disconnect all ungrounded (hot) conductors that supply it or pass through it (225.31(A)).
Under 225.31(B), that disconnect may be inside or outside the building it serves, or where the conductors pass through. Either way it must be readily accessible and located nearest the point where the conductors enter.
Conductors the code treats as outside a building count as outside here too (230.6). Examples include conductors under at least 2 in. of concrete beneath the building, or in a raceway encased in at least 2 in. of concrete or brick.
No more than six switches or breakers may serve as the disconnect (225.33), and they must be grouped and marked (225.34). This rule was numbered 225.32 in older editions; in the 2023 NEC it is 225.31(B).
On the job
- A disconnect placed deep inside the outbuilding, rather than nearest where the conductors enter, is a common correction.
- A feeder-supplied ADU or house also needs the 225.41 outdoor emergency disconnect, marked with white letters at least ½ in. high on a red background.
- Plans or correction notices that cite 225.32 are using the older numbering. The 2023 reference is 225.31(B).
Exceptions that matter
- Under single management, with documented safe switching procedures and monitoring by qualified persons, the disconnect may be located elsewhere on the premises.
- Buildings or structures that qualify under 685.1 (integrated electrical systems) may also have the disconnect located elsewhere on the premises.
- Towers or poles used as lighting standards, and poles supporting signs installed under 600.1, may also have the disconnect located elsewhere on the premises.
Related sections
- NEC 225.30: One supply per outbuilding: garages, ADUs and shops
- NEC 225.33
- NEC 225.34
- NEC 225.41
- NEC 230.6
- NEC 110.29
- NEC 250.32: Grounding at detached garages, ADUs and outbuildings
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