Wire, cable and conduit.
Wires, cables and cords are the means for bringing electricity to its point of use. Wire refers to a single conductor. Cable is two or more separately insulated conductors in a single covering used in permanent installations. Cord refers to the portable conductors that carry electricity from outlet to appliance.
Minimum electrical needs in a home are 150-200 amperes and 125V. General-purpose 15- and 20-amp circuits will handle lamps, radios and TV sets and outlets for small appliances drawing no more than a total of 1,875 watts for a 15-amp fuse or 2,500 watts for a 20-amp fuse at one time. A 20-amp circuit is required to serve appliances in the kitchen because of the load density.
There is often confusion about which colors are used for hot, neutral and ground wires. The ungrounded conductor, or hot wire, can be any color other than white, gray or green. Although the hot wire is typically black, there are exceptions. The grounded conductor or neutral wire is green, green with one or more strips, or bare.
Wire is rated by its resistance to the flow of electricity passing through it.
* Copper or tinned copper is the most common conductor in home wiring because it has minimum resistance at reasonable cost. Aluminum is occasionally used, but because of its higher resistance, it is usually restricted to high-voltage lines where weight is more important than bulk. It is rarely used in ordinary home wiring.
* The diameter of wire is directly proportional to the amount of current it will carry. Larger wire carries more current. If toe much current is forced through the wire, it will overheat and blow a fuse or trip a circuit breaker.
* Wire is grouped by gauge number, running from 0000 to No. 40. The smaller the number, the thicker the wire. For home use, the most common gauges are between 10 and 20. No. 12 wire is recommended for general home use. Wire is also characterized by letters that correspond to the insulation type and electrical capacity.
Cable refers to a collection of two or more strands of wire or conductors. Cable constitutes the bulk of the wiring sold in electrical departments. Cable is classified according to the number of wires it contains and their size or gauge.
* Electricity entering the house must form a circuit by returning to the point of entry to be connected to a ground. Consequently, all cables are made of at least two conductors, a "hot" line to carry the current to the appliance and a "neutral" line to complete the loop.
* All cables are marked with a series of letters followed by a number, a dash and another number. The letters indicate the type of insulation (cord, wire and insulation). The first number indicates the resistance of the wires in the cable, and the number following the dash indicates the number of individual conductors in the cable.
* If the designator "G" follows the series, it means that the cable is also equipped with a non-current-carrying ground wire. Hence, the designator USE 12-3/G indicates an underground cable containing three separately insulated wires capable of carrying 20 amps of current plus a grounding wire.
* The most common jackets sold in the U.S. are NM-B (Non-Metallic Building Indoor), UF-B (Underground Feed) and BX, which is flexible metallic cable.
Two-conductor cable has one black wire and one white wire. The black wire is always the "hot" wire and must be fused. The white is always neutral and must never be fused. When current bridges the gap from the 110V hot wire to the neutral, it results in a 110V input to the appliance.
Three-conductor cable contains a red wire in addition to black and white. The black and red wires are "hot," carrying 110V each, and both must be fused. The white remains neutral.
Bridging either 110V wire to the neutral wire produces 110V. Bridging both 110V wires results in 220V. This three-wire circuit is increasingly common in home wiring; it accommodates major 220V appliances, such as ranges and air conditioners.
Both two- and three-conductor cables can carry grounding wires, which provide a path of least resistance from the frame or case of an appliance to the ground to guard against electric shocks.
The electric motor in a refrigerator, for instance, might develop a current leak to the frame of the appliance. A person touching the refrigerator could create a path for the current to pass to the ground. Consequently, he would receive a shock.
A grounding wire, attached to the frame of the refrigerator and directly to the ground, would provide a lower resistance path than the person. The electricity could then pass safely to the ground.
The National Electrical Code (NEC) was changed in 1996 to require a separate ground wire for certain appliances to ground their frames. If your customers are wiring for 120/240V or 120/208V ranges, wall-mounted ovens, counter-mounted stoves or clothes dryers, they need the separate ground wire.
Thermostat cables are used in low-voltage control, alarm and communication systems. Most common types are braided, twisted and plastic-jacketed types.
All three use solid copper conductors and are twisted and insulated with plastic.
* Twisted cable, which has no outer braid, is used in doorbells, burglar alarms, intercom telephones and public address systems.
* Braided cable is covered with cotton braid and is used primarily in thermostat controls and other low-voltage, remote control circuits.
* Plastic-jacketed cable is also used in similar low-voltage applications.
* Although thermostat cable is low voltage, it carries a UL-listing for being flame-retardant since it is installed in the wall. Wiring used in security alarm and smoke detection systems must be UL-listed.
* Thin-wall conduit, also known as EMT (electric metallic tubing), comes in inside diameters of 1/2" to 4"; 1/2" is most common. Do not use underground. Steel pipe is used to carry house wiring in places where it is exposed.
* Heavy-wall conduit, also known as rigid conduit, comes in the same sizes as EMT but has thicker walls. It has threaded ends for connections and is used for carrying wire outdoors and underground.
* Plastic conduit is easy to use inside and outside. It is best for burying underground as it will not corrode with water.
1. Single-Contact Bayonet Incandescent Base
2. Candelabra Incandescent Base
3. Double-Contact Bayonet Incandescent Base
4. Intermediate Incandescent Base
5. Medium Incandescent Base
6. Medium Skirted Incandescent Base
7. Three-Contact Medium Incandescent Base
8. Mogul Incandescent Base
9. Three-Contact Mogul Incandescent Base
10. Circline Florescent Base
11. Medium Bi-Pin Fluorescent Base
12. Four-Pin Fluorescent Base
13. Recessed D.C. Fluorescent Base
14. Two-Pin Single-End Fluorescent Base
15. Four-Pin Single-End Fluorescent Base
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|Title Annotation:||Electrical Supplies|
|Date:||Aug 1, 2006|
|Previous Article:||Miscellaneous electrical.|