Electrical wires and cables are used to carry electrical current but are two different things. A wire is whole in itself and is made of a single conductor and a cable is a bundle of multiple wires inside a common sheathing.
Electrical cables and wires are categorised on the basis of different factors including label information, colour and applications. Let us see what all factors are important.
Wire gauge determines the right size of the wire. 10, 12 and 14 are the common wire sizes – a higher number means a smaller wire size and also determines the amount of power it carries.
Wire & Cable Labelling
The labelling of cables provides a lot of information related to the insulation types, the gauge of wires and number of wires.
- 14-2G: Contains 2 insulated wires and 1 ground wire; the individual wire is 14-gauge.
- 14-3G: Contains 3 insulated wires and 1 ground wire; individual wires are 14-gauge.
- 12-2 w/G: Contains 2 insulated wires with 1 ground wire; individual wires are 12-gauge.
- 12-3 w/G: Contains 3 insulated wires with 1 ground wire; individual wires are 12-gauge.
- 600 V: Commonly used NM cable for home wiring. It is rated for a maximum of 600 volts.
- TYPE NM-B: NM stands for Non-metallic. Commonly used cable for wiring appliances and devices in the home. It is a non-metallic sheathed cable of type-B.
For insulation or the plastic coating around the conducting wires, some common labels are THHN, THW, THWN and XHHN. Here,
- T – Thermoplastic Insulation
- H – Heat Resistance
- HH – High Heat Resistance
- W – Suitable for wet locations
- X – Synthetic polymer that is flame-resistant
- N – Nylon coating, resisting to damage by oil or gas
- White: Always neutral.
- Black: Hotwire, for switches or outlets.
- Green and Bare Copper: Only for grounding.
- Blue and Yellow: Hotwires, pulled in conduit. Blue for 3-4 way switch application, and yellow for switch legs to control fan, lights etc.
- Red: Hotwire, for switch legs. Also for connecting wire between 2 hardwired smoke detectors.
Types of Wires
1. Triplex Wires
Used between the power pole and weather heads in single-phase service drop conductors. These wires are made of 2 insulated aluminium wires which wrapped with a bare wire which act as a common neutral. The neutral is of a smaller gauge.
2. Panel Feed Wires
Black insulated THHN, these are mainly used to power the junction box & the circuit breaker panels. Should be rated for 25% more than the actual load.
3. Main Feeder Wires
Made with stranded or solid THHN, these wires connect the service weather head to the house.
4. Single Strand Wires
THHN wire, each wire is separate and multiple wires can be drawn together from a pipe. Most commonly used for layouts that use pipes to accommodate wires.
5. Non-Metallic Sheathed Wires
Also, know as Romex, these wires are used mostly in homes. It has 2-3 conductors, each with a bare ground wire and plastic insulation. It is relatively cheaper.
In the case of electrical wires and cables installation, safety is the most important factor.