Topic 1 of 5
Cable types
Choosing the right cable depends on where it's going, what it's feeding, and what it might be exposed to: heat, damage, water or fire.
| Cable | What it's like | Typical use |
|---|---|---|
| Flat twin and earth (6242Y) | Line and neutral cores with a bare CPC, in a flat PVC sheath | Most domestic sockets and lighting, clipped or in walls |
| Three core and earth (6243Y) | Three insulated cores plus a bare CPC | Two-way lighting switching |
| Single-core (6491X) | One insulated conductor, no sheath | Must be inside conduit or trunking |
| Steel wire armoured (SWA) | Insulated cores, bedding, steel wire armour and an outer sheath | Underground, outdoors, supplies to outbuildings, industrial work |
| Mineral insulated (MICC) | Copper conductors in compressed mineral powder inside a copper sheath | High temperatures and fire alarm or emergency circuits |
| Fire-resistant soft-skin (such as FP200) | Fire-resistant insulation with a screen and sheath | Fire alarms and emergency lighting |
| Flexible cord (flex) | Stranded cores so it bends without breaking | Connecting appliances and pendants |
| Data cable (Cat 6 and similar) | Twisted pairs | Networks; kept apart from mains cables |
Parts of a cable
- Conductor: usually copper. Solid for small sizes, stranded for flexibility and bigger sizes.
- Insulation: stops current leaking between conductors. Thermoplastic (PVC) is rated to 70 °C. Thermosetting (XLPE) is rated to 90 °C.
- Sheath: protects the insulation from damage.
- Armour: steel wire that protects against mechanical damage, and can act as the CPC if it's large enough.
Exam tip: the bare CPC in twin and earth must be covered with green-and-yellow sleeving wherever it's exposed at a termination.
Try it: Cable size calculator
Mini test
6 questions. Pick an answer to see if you're right and why.