Chapter 3 of the NEC contains articles addressing specific wiring methods. These are clustered into sequences by wiring method type. Thereís a sequence for cable types (Articles 320Ė340) followed by a sequence for conduit types (Articles 342Ė356). 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 itís flexibleóa 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; itís not always the case. Itís probably not the case where you have additional labor and materials costs of protecting the armored cable from damage where exposed.
You canít use armored cable where itís 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, youíll have to use a different wiring method that isnít 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 canít use flexible cord (e.g., lights in ceiling spaces). Both features are why itís ideal for protecting conductors in cable trays.
Source: Mark Lamendola |†Mindconnection