ARC--BUILDING-UTILITIES-2-PART-2 (1).pdf
- 1. ARC 101 BUILDING UTILITIES 2 – ELECTRICAL, ELECTRONICS, AND MECHANICAL SYSTEMS PREPARED BY: AR. J.I.S.B (PART 2)
- 2. “Energy can neither be created nor destroyed – only converted from one form of energy to another.” - JULIUS ROBERT MAYER
- 3. 1. Resistance Resistance is a measure of the opposition to current flow in an electrical circuit. Resistance is measured in ohms, symbolized by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm (1784-1854), a German physicist who studied the relationship between voltage, current and resistance. He is credited for formulating Ohm's Law. Resistance measurements are normally taken to indicate the condition of a component or a circuit. The higher the resistance, the lower the current flow. If abnormally high, one possible cause (among many) could be damaged conductors due to burning or corrosion. All conductors give off some degree of heat, so overheating is an issue often associated with resistance. The lower the resistance, the higher the current flow. Possible causes: insulators damaged by moisture or overheating.
- 4. 2. Electrical conductors and insulator What are Conductors? The materials or substances that allow electricity to flow through them are conductors. Also, conductors allow heat to be transmitted through them. The examples of conductors are metals, the human body, Earth and animals. The human body is a strong conductor. It, therefore, offers a resistance-free route from a current- carrying wire through the body for the current to flow. Conductors have free electrons on their surface that allow the easy passage of current. This is the reason that electricity transmits freely through the conductors. Applications of Conductors In certain aspects, conductors are very useful. They have many real-life applications. For example, • To check the temperature of a body, mercury is a common material in the thermometer. • Aluminum finds use in the manufacture of foils for food preservation. It is also used in cooking vessels as it is a good conductor of electricity and heat. • Iron is a common material used to conduct heat in vehicle engine manufacturing. The iron plate is composed of steel to briskly absorb heat. • In car radiators, conductors find their use in the eradication of heat away from the engine.
- 5. What are Insulators? The materials or substances that resist or don't allow the current to pass through them are insulators. They are, in general, solid in nature. Often, in a number of systems, insulators are used as they do not allow heat to flow. The resistivity is the property which makes insulators different from conductors. Some good examples of insulators are wood, fabric, glass, mica, and quartz. Insulators provide protection against fire, sound, and, of course, electricity transmission. In addition, insulators have no free electrons at all. This is the predominant explanation of why they don't conduct electricity. Examples of Insulators • As it has the highest resistivity, glass is the strongest insulator. • Plastic is a good insulator and is used to manufacture a variety of products. • A common material used in the manufacture of types, fire-resistant clothing, and slippers is rubber. This is because it is an insulator.
- 6. Cable and wire insulation prevents the wire’s current from coming into contact with other conductors, it preserves the wire material against environmental threats and resists electrical leakage.
- 7. 3. Insulated copper conductors – wires and cables What is meant by insulated copper wire? The wire which is made of copper, and it can insulate electric current is said to be insulated copper wire. It is used in the construction of transformers, inductors, motors, speakers, hard disk head actuators, electromagnets etc. Copper wire used in an electromagnet is insulated with a coating of non- conductive insulation like plastic or enamel which is to prevent from the charging of wires. Insulated copper wire and insulated copper cable are among the most common sources for scrap copper. Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor. Copper is the electrical conductor in many categories of electrical wiring. Copper wire is used in power generation, power transmission, power distribution, telecommunications, electronics circuitry, and countless types of electrical equipment. Copper and its alloys are also used to make electrical contacts. Electrical wiring in buildings is the most important market for the copper industry. Roughly half of all copper mined is used to manufacture electrical wire and cable conductors.
- 8. 4. Wiring methods – cable wiring methods, raceway methods Cable Wiring Methods The utility company provides electricity to power homes and businesses. In order to get the electricity into the building, the connection must be taken from the main switchboard into the home. Various types of loads run through this main switchboard and different types of wirings are used. These can be applied for residential, commercial and industrial purposes. Cleat Wiring Here, PVC insulated cables are used. They are fastened to the wall using porcelain, wood or plastic cleats which are installed at intervals. This type of wiring is relatively inexpensive but is also best for temporary applications and is not suitable for home electrical wiring. It is rarely used in modern times.
- 9. Casing and Capping Wiring The cable runs through a wood casing that has parallel grooves that appear at regular intervals along it. The casing is fixed to ceilings or walls with screws. It is then covered with a cap so that the wires are protected. This system is also relatively inexpensive but there is a high risk of short circuits that can result in fire hazards.
- 10. Batten Wiring Batten wiring is one of the basic wiring methods that is used today. In batten wiring, insulated wires are run through the straight teak (teak wood, incredible durability and water resistance.) wooden battens. These are fixed on ceilings or walls with plugs or screws. The cables are fitted onto the battens with tinned brass link clips that are fastened on with rust resistant nails. This is a simple and efficient form of wiring that is mainly used for indoor installations.
- 11. Conduit Wiring Conduit wiring uses PVC cables that are threaded through PVC or steel conduit pipes. If the pipes run on the surface of the walls and ceilings, it’s called surface conduit wiring. If it runs inside the surface of the walls and covered with plastering, it’s called concealed conduit wiring. Surface conduit wiring is used in industrial applications to connect heavy motors. Concealed wiring is used in residential applications and is the most popular of the basic wiring methods for residential use because it is safer and aesthetically pleasing. SURFACE METAL CONDUIT SURFACE PVC CONDUIT CONCEALEDFLEXIBLE CONDUIT
- 12. Raceway methods Raceways have an important job in electrical systems. A raceway is an enclosed channel that forms a physical pathway for electrical wiring. Raceways protect the inner workings (wires and cables) from heat, corrosion, humidity, water, and other kinds of threats. Raceways are installed according to the National Electrical Code (NEC) which protects people and property from electrical hazards. There are three types of common raceways, including galvanized steel (both flexible and rigid), non-metallic conduit or PVC (both flexible and rigid), and flexible metal conduits. • Galvanized Steel – This is used primarily in industrial and commercial to protect wires in corrosive environments. • Non-Metallic Conduit (PVC) – This type of conduit is used most often in homes as well as underground. It is non-conductive and water-resistant. • Flexible Metal Conduit (FMC) – This type of conduit is ideal for wiring that has to turn or curve and is good for areas that have a lot of vibration because it keeps wires safe even with movement. However, this is not a good option for a corrosive environment Flexible Metal Conduit (FMC) Non-Metallic Conduit (PVC) Galvanized Steel
- 13. 5. Switches A Switch is a device which is designed to interrupt the current flow in a circuit. In simple words, a Switch can make or break an electrical circuit. Every electrical and electronics application uses at least one switch to perform ON and OFF operation of the device. In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts is touching current can pass between them, while when the contacts are separated no current can flow. Switches are made in many different configurations; they may have multiple sets of contacts controlled by the same knob or actuator, and the contacts may operate simultaneously, sequentially, or alternately. A switch may be operated manually, for example, a light switch or a keyboard button, or may function as a sensing element to sense the position of a machine part, liquid level, pressure, or temperature, such as a thermostat. Many specialized forms exist, such as the (a)Toggle switch – An electric switch operated by means of a projecting lever that is moved up and down. Toggle switches are best used for changing the state of system functionalities and preferences.
- 14. (b) Rotary switch – Is a switch operated by rotation. These are often chosen when more than 2 positions are needed, such as a three-speed fan or a CB radio with multiple” frequencies of reception or “channel”. (c) Mercury switch – An electric switch in which the circuit is made by mercury flowing into a gap when the device tilts. They can be use for example in vehicle, security, vending machines (with tilt, vibration alarm), bimetal thermometers, bombs, construction machines or stair machines. (d) Push-button – A push button switch is a mechanical device used to control an electrical circuit in which the operator manually presses a button to actuate an internal switch mechanism.
- 15. (e) Reversing switch – An electric switch that has four terminals capable of being connected in pairs in two different ways so as to reverse the direction of current flow. (f) Relay switch – Relays area electrically operated switches that open and close the circuits by receiving electrical signals from outside sources. (g) Circuit breaker or safety switch– A safety switch quickly turns off the electricity supply if an electrical fault is detected.