1. Types of Cables

2. Three Wiring Systems
Three systems of wiring used in most installations: 1.) Non-metallic sheathed cable 2.) Armored cable 3.) Conduit

3. Non-Metallic Sheathed Cable
Copper or aluminum wires covered with paper and vinyl for insulation and protection
Some non-metallic sheathed cable are waterproof and suitable for burial in soil

4. Armored Cable
Consists of a flexible metal sheath with individual wires inside
The wires are insulated with vinyl and wrapped in paper for protection
Armored cable provides good protection against mechanical damage
It is fairly easy to install in narrow and irregular building sections
Does have a tendency to rust and develop short circuits which makes it unsuitable for use in damp areas

5. Conduit Tubing that contains individual insulated wires
1/2”, ¾”, 1” or larger in diameter
May be rigid or bendable
Available in metal or plastic

6. Electrical Metallic Tube (EMT)
Special benders permit shaping EMT in bends of up to 90 degrees
Couplings and connectors are used to assemble conduit and attach
Waterproof plastic fittings provide waterproof seals where needed for metal conduit
Conduit systems are used to provide the most common protection for wiring and are required for most commercial jobs

7. Wire Type and Size
Individual wires within cable or conduit may be aluminum or copper
Smaller sizes include No.14 wire for 15amp circuits, No 12 for 20amp circuits, and No. 10 for 30amp 120 volt circuits
Ampere ratings apply to copper wire
For aluminum, it is necessary to use one wire size larger than is specified for copper wire
Wire size is designated by gauge or AWG (American Wire Gauge)
The lower the gauge number, the larger the wire size

8. Strands
Strands are placed together to form bundles for wire sizes No.8 and larger in order to improve flexibility and conductivity
Electricity is carried on the outer surfaces of wire
Stranded wire has more total surface area than solid wire of equal diameter and carries more current
Either solid wire or stranded wire may be placed in cables or conduits

9. Voltage Drop Refers to a loss of voltage as it travels along a wire
Causes lights to dim, heaters to put out less heat, and motors to put out less power and to overheat
The larger the wire, the less problem there is with voltage drop for a given amount of current
Longer wire = greater problems

10. Wire Identification Outer covering Individual wire covering
Cable construction
Number of wires
All of these items determine where a cable can be used

11. Wire Identification Cont’d
Wire type is stamped on the outer surface of the wire or cable or cable covering
*Common types of wire & cable:
Type T – for use in dry locations
Type TW – for use in dry or wet locations
Type THHN – for use in dry locations with high temperature
Type THW and THWN – for use in wet locations with high temperature
Type XHHW – for high moisture and heat resistance
Type UF – for direct burial in soil but not concrete

12. Wire Identification Cont’d
Individual wires are color coded to help identify their function in the circuit
Black wires, red wires, and blue wires are positive (hot) wires
Carries current to appliances
White wires = neutral wires
Carries current from appliance back to the source
Green wires and bare wires are used to ground all metal boxes and appliances in the circuit

13. Nonmetallic Sheathed Cables
12-2: two strands of No.12 wire, one black and one white
12-2w/g: two strands of No. 12 wire plus a ground wire (w/g means “with ground”), one black, one white, and one green or bare
12-3: three strands of No.12 wire, probably, one black, one red or blue, and one white
12-3w/g: same as 12-3 cable with the addition of a green or bare wire for grounding the circuit