Electrical Wiring and Electrical Energy
consumption
Lecture 7
U.S. Consumer Product Safety Commission Has Found:
Electrical Fires – Majority Caused by Aging Wiring and Misuse of Surge Protectors
In the U.S. Over 750 People Are Killed Every Year by Electrical Fires
Extension Cords - Leading Cause of Home Electrical Fires in the U.S.
– An Extension Cord Related Fire Occurs Every 6 Minutes
Replace Damaged Electrical Cords
Do Not Run Electrical Cords Through Doorways and Under Carpets
Avoid Overloading Electrical Outlets
If Switches/Outlets Feel Warm – Contact service ASAP
Appliances, Extension Cords, Power Strips,– Certified By an Independent Testing Laboratory,
Use Ground-Fault Circuit Interrupter (GFCI) Plugs Around Water
Test the GFCI Plug Every Month
Power/Extension Cord Safety
Never Remove the Ground Pin (3rd Prong) to Fit into a Two-Prong Outlet
Extension Cords: Use On a Temporary Basis – Not Intended for Use as Permanent Wiring
Never Plug Power Strip into Another Power Strip
Never Overload the Capacity of the power strip
Electrical Wiring – Basic Concepts
NEVER work on a live circuit it can be dangerous.
In every junction box there is generally only one hot wire bringing power into the box.
Separate all the wires
first so none touch each other.
Installing home-electrical-wiring
for breakers and fuses inside a
breaker box
How to Determine the Capacity of a Power Cord or Power Strip
Assume V = 125 V
Total Watts Should Not Exceed 80% (0.80) of the Rated Capacity
Example – Surge Protector Rated at 15 Amps 15 Amps X 125 Watts/Amp = 1875 Watts
1875 Watts X 0.80 = 1500 Watts Capacity of the Surge Protector Multiple Items Plugged into a 15 Amp Surge Protector:
Computer – 2 amps = 250 Watts Monitor – 1.2 amps = 150 Watts Coffee Maker – 650 Watts
Laser Printer
Idle – 2 amps = 250 Watts
Printing – 9.4 amps = 1175 watts
Example of Items Plugged into a 15 Amp Surge Protector (Continued)
Total Wattage While Printer is Idle:
250 (Computer) + 150 (Monitor) + 650 (Coffee Maker) + 250 (Printer in Idle) = 1300 Watts
Total Wattage While Printer is Printing:
250 (Computer) + 150 (Monitor) + 650 (Coffee Maker) + 1175 (Printer Printing) = 2225 Watts
While Printing, the 1500 Watt Surge Protector Capacity is
Exceeded! – Plug the Printer into a Separate Surge Protector & a Different Duplex Plug
It is
criticalthe circuit breaker that protects a circuit be of the right amps rating for the size of the wire.
Most circuits in your home are 15 amp and 20 amp, but no matter what, it is again
CRITICAL that breaker rating be appropriate for the wire rating.
If the breaker rating is too low, the breaker will trip before the wire capacity is close to being reached.
If the breaker rating is too high, the wire can get too hot and potentially start a fire.
Mapping Electrical Circuits in Your
Home
Efficiency
A lamp uses 100 Joules of electrical energy each second.
Efficiency is the % transferred as useful energy
Useful = the type the device was designed to produce
Efficiency Useful energy output Total energy input
= X 100 for %
Energy wasted = Total energy input - Useful energy output
Efficiency
A lamp uses 100 Joules of electrical energy each second.
It transfers this into
1.
80 Joules of heat
2.
20 Joules of light
The lamp has an efficiency of 20%
The Total wasted energy = 80 Joules
Electrical energy
consumption
Note: the units of energy not the Joule KWH : kilowatt-Hour
How much does it cost to run a 60W lamp for 20 hours?
First you must convert W into kW by dividing by 1000
1.
60 W = 60/1 OOOkW = 0.06
2.
kWh used = 0. 06 x 20 = 1.2 kWh
3.
Cost = 1 .2 x 5 = 6.0 halalah
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Q. Calculate the total energy used for 30 days in (KWH) and the total monthly bill if the following office devices