Gabinetes, Cajas de Corte y Bases de Medidor

El Artículo 312 rige la caja metálica o no metálica que aloja un tablero, desconectador o medidor. Fija cuánto espacio de curvatura necesita un conductor donde entra a una terminal, qué tan profundo debe ser el gabinete, qué tan ajustado puede quedar contra una pared combustible, y la exigencia de tapar los orificios sin usar para que el gabinete quede íntegro.

Gran parte trata sobre la curva. Un conductor grande forzado en poco espacio agrieta su aislamiento en la terminal, justo donde se concentran el calor y la corriente. Las tablas de espacio de curvatura traducen el calibre del conductor directamente en dimensiones mínimas del gabinete.

When it applies

This covers the enclosures that house panelboards and disconnects — cabinets, cutout boxes and meter socket enclosures. It sets how the box mounts relative to a finished wall, the bending and gutter space conductors need inside, and the rule that every unused opening gets closed.

Common mistakes

• Setting a flush panel too far back so the front sits below a combustible wall surface it should be flush with or ahead of.
• Cramming large conductors into a shallow enclosure and violating the required deflection space at the terminals.
• Leaving knockouts open, which lets in fingers, rodents and debris and breaks the enclosure rating.

In the field

I check my wire-bending space before I ever mount the can. Feeders that fight the box do not seat cleanly on the lugs, and a loose lug in a tight enclosure is the kind of connection that comes back as a burned panel.