benkidd_practicalelectricity

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Practical Electricity

A Brief Overview of Basic Electricity, Safety,Electrical Design & Work

Benjamin W. Kidd

[email protected] 9, 2008

Presented especially for the UVA Chapter

of Engineering Students without Borders


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Todays Goals

Provide you a basic understandingof

How electricity works

How touse it practically How to stay safe


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Local Tradesmen

Hire them!

Oftenwhat they lack in

theoretical understandingthey make up for in

experience

They knowwhere toget stuff

They need the money

Building relationships


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What is Electricity?

The transferofenergy via the

coordinated movement ofelectrons

within a conducting medium


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Fundamentals ofElectricity

Voltage Electrical Pressure, higher the voltage,the greater the potential todowork.

Voltage Across

Current Literally the numberofelectrons thatpass through a given point in a wire over a givenperiodof time. 1 Ampere = 6.28 x 1018 electrons persecond.

Current Through

Resistance Measure of the property ofamaterials opposition to current.

Resistance Of

Load Something that uses electricity


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Insulators & Conductors

Insulator a material that does not allow thefree flowofelectrons through it. Glass

Porcelain

Rubber

Plastic

Pure Water

Conductor a material that allows electricity

toflowfreely through it Metals (Copper, Iron, Aluminum, Gold, etc)

Water (non-distilled)


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Power & Energy

PowerAn instantaneous measure of

energy, or measure of the mechanical

output ofa system. (Watts, HP)

Energy the aggregationofpower

usage over time. (Joules, kW-Hr)


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A Simple Circuit

Circuit The circular path that electricity

takes from source to load and back

again.


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Series & Parallel Circuits

Series Circuit Parallel Circuit


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Essential Equations

Ohms Law

The Power Law

RIV v!R

VI !

I

VR !

R

VRIIVP

22

!!v!

Measure Symbol Unit Abbreviation

Voltage V Volts V

Current I Amperes A

Resistance R Ohms

Power P Watts W


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Safety The Anatomy ofA Shock

1. Muscle Contraction

Can prevent victim from being able to let

goofsource ofshock

Can cause fibrillations ofthe heart muscle

2. Burns

Same as regular burns

Usually in two places (entry & exit)


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Safety The Anatomy ofA Shock

Note the path ofElectricity through the

body


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Safety Prevention & Protection

Turnoffthe power

Water is ourworst enemy! NEVERWORKAROUNDLIVE WIRING WHENWATERIS

PRESENT! Wear Appropriate Dress

Clothing

Gloves

Shoes Safety Glasses

As little as 5mA (0.005A) can be lethal!


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Safety First Aid

1. Stop the Shock! Donot touch the person

Get them away from the source of the shock

using a non-conductive object, Or Turnoffthe electricity

2. AdministerFirst Aid Ifnot breathing/no pulse, AdministerCPR

Use an AED Treat for Burns (Entry & Exit)

Treat forshock


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Safe Wiring Practice

Helps buildings stay

safe

Helps people stay safe

We strive create

electrical installations

that are not only safe

and effective by

themselves, but also

installations that

promote safe practices

by the users


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Safe Wiring PracticesNeatness Counts


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Safe Wiring Practices

Securing & ProtectingCables

Making tight wiring connections

Workingneatly Labeling yourwork

Leaving room forfuture work

FollowingCode Requirements


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Why is goodwiringDesign &

Practice important?

Podowon Church Firehttp://www.nbc4.com/slideshow/news/9543771/detail.html

Montclair Water Fatalities

June 6, 2001 - Residence, TimberRidge Dr., Dumfries, VA, Lake

Montclair. Two young boys enteredwaternear pontoon boat.

Battery chargers (2) connected to modified extension cordfrom

house. Electric shock drowning cause ofenergized hull not

reported.(http://qualitymarineservices.net/Electric%20Shock%20Drowning

%20Incident%20List.doc)


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North AmericanWiringCodes &

Conventions

National Electric Code (NFPA)

Americans with Disabilities Act (ADA)

International Residential Code (IRC)


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WiringColorCoding

120/240VACColorCoding

Black (HOT 120V)

Red (HOT 120V)

White (NEUTRAL Grounded)

Greenor Bare (GROUND Grounding)

12/24/48VDCColorCoding

Red (Positive) Black (Negative Ground)

Bare (Earth Ground)


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Electricity Around the World

http://www.kropla.com/electric2.htm

Different Voltages

Different Plugs & Receptacles 50Hz vs. 60Hz

Power Quality Issues


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Electricity Around the World


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Power Quality

Voltage Regulation

Frequency Regulation

Power Outages

Brownouts


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PowerDistribution Grid

HighVoltage The higher the voltage,

the lower the I2RLosses

AlternatingCu

rrent

Easy tostep-upfor transmissionorstep-down foruse

using transformers


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PowerDistribution


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What is RMS?

Root MeanSquare (RMS) is the equivalent DC

voltage that would provide the same power to a

given load as an alternating current (AC) signal.

For sinusoidal signals, the peak voltage is given bythe equation:

RMSPEAKVV v! 2


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Residential PowerDistribution


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Typical Residential 1P Circuit-Breaker Panel

Panel Schedule

MainCircuitBreaker

Single-PoleCircuit Breaker

Double-Pole

Circuit Breaker

Knock-out


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Grounding

Grounding is electrically and physically

connecting a portionofa circuit to the

earths crust

Provides a common reference for

voltages (0V)


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Grounding inHomes


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Grounding inHomes

SilverScrew

Neutral

(White Wire)

Brass Screw

Hot

(Blackor Red Wire)

GreenScrew

Ground

(Green or Bare Wire)


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Understanding the Safety Ground


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GroundFault Circuit Interrupters

Also known as GFI(GroundFaultInterrupters)

Required by code inall wet locations

Measures currentgoingout andcoming in and turnspoweroff if there is >

5mA Difference


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SizingConductors Properly

Current Rating Wire must be sizedaccording to how much current it will berequired to carry. The size (known as

gauge) can be pickedusing an ampacitytable.

Voltage Rating The insulationon thewire determines how many volts it cansafely carry. Check the manufacturersdata if indoubt.


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Photo-Voltaic Panels

Basic Components

Basic Connection

Considerations whenusing PV systems

UVA SolarHouse Crozet, Virginia ecoMOD 2 House Gautier, Mississippi


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Basic Solar PowerSystem


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Solar PowerSystem with Inverters


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GridConnectedSystem

ForResidential Energy Production

Only practical inNet Meter localities

where utility companies are required tobuy back power produced by consumer

Only provides powerduringdaylight

hours (no storage)

Not suitable for applications where there

is NO GRID!


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GridConnectedSystem


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Design

Draw a floor plan

Knowwhat appliances & equipment will

be used & where DoLoadCalculations

Determine numberofcircuits, wire sizes,

& circuit connections


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DrawingSymbols


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ecoMOD 1 Design Example


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Panel Schedules


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LoadCalculations


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Wire Gauge Table

Wire size

AWG

Diameter

(inches)

Ohm's per100ft

(@ 68)

Safe Current

(Amperes)

12 0.080 0.16 20

14 0.064 0.25 15

16 0.051 0.40 1018 0.040 0.64 8

20 0.032 1.02 5

22 0.025 1.61 4

24 0.020 2.57 3

26 0.016 4.08 2

28 0.013 6.49 1.5

30 0.010 10.30 1.3

AWG AmericanWire Gauge


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Circuit Protection

Fuses Made up ofa thinfilament wire inside a glass orceramic casing. When the currentbecomes too high, the filamentwire melts, opening the circuit.

Response time can be very fast(microseconds).

Circuit Breaker Uses anelectromagnet or bi-metallic stripto pull a switch openwhen too

much current flows.R

esponsetime is typically slow(milliseconds).

Eitherform ofcircuit protectionmust be placedIn Series in serieswith the load towork.

Fuses(From www.radioshack.com)

Circuit Breakers

(F

rom www.lowes.com & www.oselectronics.com)


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SizingFuses & Circuit Breakers

Fuses should be sized

between 125% and 250% of

the rated load

Circuit Breakers should besized at approximately 125%

ofthe rated load

On 120VAC systems, the

fuse shouldALWAYS protect

the Hot wire


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ElectricianTools Whats inMy

Tool Pouch

Chisel

Linesmen Plier

Wire

Strippers

Needle Nose

Pliers

Diagonal

Cutters

Tape MeasureElectrical Tape

Hammer

Level

Drywall Saw

Phillips SD

Flat-headSD

Small Flat-HeadSquare Drive SD

Scissors

Utility Knife

Adjustable Wrench

Voltage Sensor

Pencils

Cat


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Todays Activity


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Lots ofHelpful Books


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References & FurtherReading

http://www.kropla.com/electric2.htm

www.people.virginia.edu/~bwk7j

JeffYagos site

NEC 2005

DEWALT Electrical Professional Reference -

2008 Code by Paul Rosenburg

http://qualitymarineservices.net/Electric%20Shock%20Drowning%20Incident%20List.doc

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