Chapter 3 of the NEC contains articles addressing specific wiring methods. These are clustered into sequences by wiring method type. There’s a sequence for cable types (Articles 320–340) followed by a sequence for conduit types (Articles 342–356). The first article on cable types is for armored cable (Type AC).
As its name implies, armored cable has a metal armor [320.2]. And it’s flexible—a feature that is both its strength and its weakness. Generally, you should run conduit or tubing rather than armored cable unless you need the flexibility.
However (depending upon the situation), the fact that armored cable is an assembly can reduce overall installation costs. But consider this carefully; it’s not always the case. It’s probably not the case where you have additional labor and materials costs of protecting the armored cable from damage where exposed.
You can’t use armored cable where it’s subject to dampness or physical damage [320.12]. Where flexibility is needed for:
- Applications exposing it to physical damage, you must add protection against physical damage.
- Damp applications, you’ll have to use a different wiring method that isn’t quite as strong. A good alternative is running conductors through Liquidtight Flexible Nonmetallic Conduit [Article 356].
Its flexibility makes armored cable ideal for connections to vibrating equipment (e.g., motors). Its armor makes it ideal for connections where you can’t use flexible cord (e.g., lights in ceiling spaces). Both features are why it’s ideal for protecting conductors in cable trays.
Source: Mark Lamendola | Mindconnection