Transcript Electrical Principles and Wiring Materials

Electrical Principles and
Wiring Materials
OBJECTIVES
AM16.01 Define common electrical terms.
2. AM16.02 Compute electrical energy use and
cost.
3. AM16.03 Investigate safe practices involving
electricity. .
4. AM17.01 Describe materials used in electric
wiring.
5. AM17.02 Explain the procedure for installing
switches, making common splices, and
doing other electrical wiring tasks.
1.
I. Principles of Electricity
A. Electricity is a form of energy that can
produce light, heat, magnetism,
chemical changes
B. Resistance: tendency of a material to
prevent electrical flow
C. Conductor: if electricity flows easily
D. Insulator: material that provides great
resistance
II. TERMS
A. Amperes: measure of the rate of flow
of electricity in a conductor (gallons/min)
B. Volts: measure of electrical pressure (PSI)
C. Watts: measure of the amount of energy or
work that can be done
D. Ohms: measure of electrical resistance
to flow
III. Ohm’s Law
A. Ohm = R (resistance)
B. Volts = E (pressure)
C. Amps = I (rate of flow)
D. Ohm’s Law: E = IR or I=E/R or R=E/I
IV. Electrical Safety
A. Two most dangerous things about ElectricityShock and Fire
B. Never disconnect any safety device
C. Don’t touch electrical items with wet hands or
feet (sweat)
D. Don’t remove ground plug prong
E. Use GFI in wet areas-Ground Fault Interrupter
F. Discontinue use of extension cord that feels warm
G. Don’t put extension cords under carpet
V. Electrical Safety
A. Install wiring according to NEC- National
Electrical Code
B. Blown fuse or breaker, determine cause
C. Don’t replace fuse with larger fuse
D. Don’t leave heat producing appliances
unattended
E. Heaters & lamps away from combustibles
F. Don’t remove back of TV (30,000v when off)
G. Electric motors lubricated, free of grease
etc.
Electrical Safety
H. Keep appliances dry
I. Don’t use damaged switches, outlets,
fixtures, extension cords
J. Follow manufacturer’s instructions for
installation and use of electrical
equipment
VI. Service Entrance
Power from Electric company
1. Jones-Onslow
2. Progress Energy
B. Transformer: drops volts from
25,000 volts to 240 volts
C. Service drop: wires etc from
transformer to house
D. Entrance head: weather-proof at
house
E. Meter: $$$
F. Service Entrance Panel (SEP): box
with fuses or breakers
A.
VII. Branch Circuits
Usually begin at Service Entrance
Panel (SEP)
B.
1. Protection devices- stop current
flow when max. amps are
exceeded
a. Fuses- metal strips
1). Cartridge
2). Screw in
2. Circuit breakers-reset
B. Branch out all over house
C. Size of circuit
1. Only 1 motor
2. Series of outlets
3. Series of lights
D. Use correct size wire and fuse or
breaker
A.
VIII. Types of Cable
A. Nonmetallic sheathed cableROMEX: copper or aluminum
wire covered with paper,
rubber, or vinyl for insulation
B. Armored cable: flexible metal
sheath with individual wires
inside. Wires are insulated
C. Conduit: tubing with
individually insulated wires
IX. Wire Identification
A. Type based on :
1. Outer cable (more than one wire)
covering- underground
2. Individual wire covering
a. Plastics
3. Size of wire- 1st #=gauge 2nd = #
of conductors
a. 12-2 has two strands of
No. 12 wire (black &
white)
1). 12-2 w / g same, with
one green or bare
b. 12-3 has three strands of
No. 12 (black, red, white)
1). 12-3 w/g same, with
green or bare
4. Number of wires- 12-2
B. Wire type stamped on outer surface
C. Wire Color codes
1. Black- load carrier
a. Wire carries current to
appliance
2. White- neutral
a. Wires carry current from
appliance back to
source
3. Green- ground
a. Ground all metal boxes and
appliances
4. Red- load- traveler in 3-way
switches
X. Wire Type and Size
A. Copper or aluminum
1. Aluminum use one size larger
2. Does not handle heat
B. Sizes
1. Lower gauge number = larger wire
2. No 14 (14 gauge) = 15 amp circuits
(125V)
3. No 12 = 20 amps (240 V)
4. No 10 = 30 amps
5. No 8 and larger use bundles of wires
6. Current travels on outer surface of wire,
so a bundle of smaller wires can carry more
C. Wire types (places in house ? )
1. Type T - dry locations
2. Type TW - dry or wet
3. THHN - dry, high temps
4. THW and THWN - wet, high temps
5. XHHW - high moisture & heat resistance
6. UF - direct burial in soil but not concrete
XI. Voltage Drop
A. Loss of voltage as it travels along a
wire
1. Lights dim, motors overheat
B. Larger wires have less voltage drop for
a given amount of current
C. Longer wire = greater problem
D. Must increase wire size as distance
increases
XII. Electric Meter-measures
electricity used
A. Watts: measure of the amount of energy or
work that can be done
B. Watt-hour = use of 1 watt for one hour
1. 100 watt light bulb for 1 hour - 100 watt-hours
C. Kilowatt = 1000 watts
1. Kilowatt-hours: how electricity is sold
2. Kilowatt-hour = 1000 watts for one hour
XIII. Calculating electrical use
A. Watts=Volts x Amps
1. Problem=What is the watt rating of a 20 amp
saw in a 220 V circuit ?
2. Solution= Watts = Volts x Amps
Watts= 220 Volts x 20 Amps= 4400
B. Watt- hours = (V x A) x hours of use
1. Problem = How many watts will an electric motor
that requires 7.5 amps of electricity, and is on a
120 V circuit for 10 hours?
2. Solution Watt- hours = V x A x hours of use
Watt-hours= 120 V x 7.5 A x 10 Hrs= 9000
C. Kilowatt- hours= watts/1000 x hours of use
1. Problem- An Ag. Shop has 5- 200 watt
lights, a 600 watt saw and a 100 watt
fan that were used for 5 Hrs. How many
kilowatts were used.
2. Solution- Kilowatt-hours= watts/1000 x hrs used
KWH= (5x200 watts) + 600 watts +100 watts x 5 = 8.5
1000 watts/Kilowatt
D. Cost = KILOWATT-HOURS x Cost / kilowatt –hr.
1. . Problem = If the local rate for electricity is
$ .12 per KWH, how much should the
electric bill be for 100 KWH ?
a). Solution- Cost = KWH x Cost/KWH
Cost = 100 KWH x $ .12/KWH=$ 12.00