Conductors and Wiring Accessories

Chapter 2

CONDUCTORS AND INSULATORS

Electric conductors are materials used to carry or allow the flow of electric current. Insulators on the other hand, are those that resist the flow of electric current.

The following are some materials considered as good electric conductors:

1. silver
2. copper
3. aluminum
4. nickel
5. brass
6. zinc
7. platinum
8. iron
9. lead
10. tin

The following are good insulating materials:

1. rubber
2. porcelain
3. varnish
4. slate
5. glass
6. mica
7. latex
8. asbestos
9. thermoplastic
10. paper
11. oil
12. wax

Wires – are those electrical conductors which are 8 sq. mm. (AWG No. 8) or smaller.

Cables -  are those which are larger than the wires.

Wires and Cable are either:

• Stranded – consisting of groups of wires twisted to form a metallic string.
• Solid – consisting of only one wire.

Chord -  is an insulated stranded wire

 

AMPACITY OF ELECTRICAL CONDUCTORS

Ampacity is defined as the ability of the wire or conductor to carry current without overheating.

The table below can be helpful in determining the ampacity of the wire. Since TW wire is most commonly used, the same will be presented.

Table 1. Allowable Ampacities of Insulated Copper Conductors

                          SIZE OF WIRE

sq. mm.	dia. (mm.)	AWG	ampacity
2.0	1.6	14	15 A
3.5	2.0	12	20 A
5.5	2.6	10	30 A
8.0	3.2	8	40 A
14.0		6	55 A
22.0		4	70 A
30.0		3	90 A
38.0		2	100 A
50.0		1	120 A

 

RACEWAYS

Raceways are wiring accessories or channels designed for holding wires or cables which are either made of metal or plastics.

 

CONDUITS

Conduit pipes are the most common electrical raceway used in all types of construction.

According to the type of materials used, conduit may be classified into:

• Metallic such as steel pipes, and aluminum
• Non-metallic such as plastic and the like

According to its make, conduits may be classified as:

• Rigid metal
• Flexible metal
• Rigid non-metal
• Flexible non-metal

The purpose of Electrical Conduits are:

1. To provide a means for running wires from one point to another.
2. To physically protect the wires.
3. To provide a grounded enclosure.
4. To protect the surroundings against the effect of fault in the wiring.
5. To protect the wiring system from the damage by the building and the occupants.
6. To protect the building and the occupants from damage by electric system.

Table 2. Maximum Number of Wires in a Conduit

                              :                   Number of Wires in One Conduit (mm)

Size of Wires	1	2	3	4	5	6	7	8	9
14	13	13	13	20	20	25	26	27	28
12	13	13	20	20	20	25	25	25	32
10	13	20	20	25	25	25	32	32	32
8	13	20	25	25	25	32	32	32	32
6	13	25	32	31	38	38	50	50	50
5	20	32	32	31	38	50	50	50	50
4	20	32	32	38	50	50	50	50	63
3	20	32	32	38	50	50	50	63	63
2	20	32	38	38	50	50	63	63	63
1	20	38	38	50	50	63	63	75	75

 

OUTLETS

An outlets  is a point in a wiring system at which current is taken to supply utilization equipment. In simple terms, as outlets is any point that supplies as electric load.

Kinds of Outlets:

1. Convenience outlets -  A device which by insertion in a receptacle establishes connection between the conductor of the flexible cord and the conductor connected permanently to the receptacle.
2. Lighting outlet – is an outlet intended for direct connection to lamp holder, a lighting fixture or a pendant cord terminating in a lamp holder.

SWITCHES

Switches are classified into:

1. General use switch – is intended to use in the general distribution and branch circuit which is rated in amperes. It is capable of interrupting the rated current at a rated voltage.
2. General use snap switch -  is a form of general use switch usually installed in flush device boxes or an outlet box cover.

 

Next: Chapter 3: The Branch Circuit