Electrical Safety

Introduction Electricity is essential to modern life Some employees work with electricity directly Some indirectly Electricity is a serious workplace hazard Electricity can be productive and safe

Agenda Vocabulary Misconceptions and myths about electricity Electrical shock and other injuries Electrical hazards Electrical safety for maintenance and custodial employees Electrical safety for offices and classrooms

Vocabulary Voltage Low voltage High voltage Current Resistance Conductor Insulator Ohm’s law

Voltage Electromotive force Electrical potential energy –“Pressure” Measured in volts (V)

Low Voltage Electrical installations and electrical equipment operating or intended to operate on systems of 600 volts, nominal, or less. All work performed directly on or in proximity to such electrical installations, equipment, or systems.

High Voltage Electrical installations and electrical equipment operating or intended to operate on systems of more than 600 volts. All work performed directly on or in proximity to such electrical installations, equipment, or systems. Beyond the scope of this training.

Current The continuous movement of electrons past a given point Measured in amperes (amps) (A) –Sometimes the symbol “I” is used

Resistance Opposition to the movement of electrons Resistance is used for direct current Measured in ohms (Ω) “Impedance” is the proper term for alternating current –“Resistance” is commonly used

Conductor A person who collects tickets on trains A person who leads a orchestra, band, or choir

Conductor A substance or thing that allows electricity (or heat) to flow by passing energy from particle to particle Silver, copper, gold, aluminum

Insulator A barrier that wraps conductive materials to protective against electric shock A material with little or no conductive properties –High resistance Glass, rubber, mica, and some plastics

Ohm’s Law R = V / A One volt will cause a current of one ampere to flow through a conductor having the resistance of one ohm V = A * R

Ohm’s Law V (Volts) A (Amps) R (Ohms)

Electrical Misconceptions Electricity tends to go to ground –After it reaches ground, it disappears Ground serves as just one of the electrical loops that misdirected current can use to get back to the grounded power source

Misconception #2 If an electrical appliance or tool falls into a sink or tub of water, the item will short and trip the circuit breaker This may not happen because the sink or tub may be non-conductive and therefore not part of the loop to ground

Misconception #3 AC reverse polarity is not hazardous Many tools have switches in only one of the two conductors serving the item The switch is supposed to be on the “hot” conductor supplying he power

Myths About Electricity Electricity takes the path of least resistance Current will take any conductive paths, high or low resistance, in order to return to the source that provides it power Small amounts of current will flow through paths of high resistance

Myth #2 Double insulated power tools are doubly safe and will always provide safety Double insulated power tools can be hazardous if dropped into water Electrical current can flow out of the power tool into the water

Myth #3 It takes high voltage to kill; 120 volts AC is not dangerous Current is the culprit that kills Voltage is a factor in determining how much current will flow

Electrical Shock A sudden and accidental stimulation of the body’s nervous system by an electrical current Current will flow through the body when it becomes part of an electrical circuit

Electrical Shock Dynamics CurrentEffect 3+ mAShock 10+ mAMuscular contractions 30+ mARespiratory paralysis 50+ mAHeart paralysis (can be fatal) 100+ mAVentricular fibrillation (usually fatal) 200+ mAHeart clamps tight mATissue and organs burn

Other Injuries Burns Falls Injuries when machinery starts suddenly

Electrical Burns Current passing through tissue generates extreme heat Skin damage at entry and exit Internal tissue damage Result from arcs or flashes Thermal burns from overheated wires or equipment or fires

Falls Initiated by a shock Muscles contract involuntarily Worker can lose balance and fall

Machinery Injuries Unexpected activation Shock Pinch Crush Shear

Electrical Hazards Bare conductors Insulation failure Equipment failure Static electricity Heating and overheating Electrical explosions

Bare Conductors Live overhead wires most common Working on rooftops Repair of electrical systems Capacitors

Insulation Failure Heat and elevated temperatures Moisture and humidity Mechanical damage Rodents, fungi Chemical incompatibility

Equipment Failure Older portable tools Energized housing Broken connections Wrongly replaced internal wiring Lack of grounding plug

Static Electricity Occurs when two different materials contact and then separate High voltage, low current Flammable liquids Lightning

Heating and Overheating Use of electricity results in heat Can cause accidental fires Burns out equipment –Equipment failure and ignition Hot surfaces

Electrical Explosions Rapid overheating from overcurrents Caused by short circuits, power surges, or lightning Heated contaminants in oil-filled breakers or transformers Capacitors subject to wrong polarity

Safety for Maintenance and Custodial Employees Qualified electrical workers Engineered protection Safety considerations Safe practices Lockout/tagout Personal protective equipment (PPE)

Qualified Electrical Workers A person, designated by the district, who by reason of experience or instruction has demonstrated familiarity with the operation to be performed and the hazards involved

Engineered Protection Insulation Grounding Circuit breakers Fuses Ground-fault circuit interrupters

Insulation Parts of electrical equipment coated with a low-conductive material Rubber mats to stand on Rubber gloves Insulated shoes

Grounding Protects from shock Safeguards against fire Protects against damage to electrical equipment

System Grounding One conductor of the circuit is intentionally connected to earth Protects against high voltage contact Stabilizes voltage in a system

Equipment Grounding Equipment grounded by a permanent and continuous connection or bond Provides a path for dangerous fault current to return to system ground Enables protective devices to operate

Circuit Breakers Guard against overloads of current Ensure current flow does not produce heat that causes temperature to rise to dangerous levels Break the current path Thermal Magnetic

Fuses Guard against overloads of current Ensure current flow does not produce heat that causes temperature to rise to dangerous levels Break the current path Melt when current exceeds a designated value

Ground-Fault Circuit Interrupters Fast-acting electrical device sensitive to very low levels of current imbalance due to flow to ground Reduces duration of a shock Not an overcurrent device like a circuit breaker or fuse

Types of GFCI Circuit-breaker type Receptacle type Permanently mounted type Portable type Cord connected type

Circuit-Breaker Type A direct replacement for a standard circuit breaker Installed in a panelboard Includes the functions of a standard circuit breaker Can protect an entire branch circuit with multiple outlets

Receptacle Type A direct replacement for a standard receptacle Protects one or more receptacle outlets Protects additional non-GFCI type receptacles connected “down stream” Very popular because of low cost

Permanently Mounted Type Mounted in an enclosure Designed to be permanently wired to the supply Frequently used around large commercial swimming pools or similar wet areas

Portable Type Designed to plug into existing non-GFCI protected outlets Contain one or more receptacle outlets protected by the GFCI module Easily transported from one location to another Approved for outdoor use –Some are listed as rainproof

Cord Connected Type Consists of an attachment plug which incorporates the GFCI module Protects the cord and any equipment attached to the cord Plug has non-standard appearance and is equipped with test and reset buttons

Safety Considerations Plan every job Consider what could go wrong Use proper tools –Procedures, drawings and related documents Isolate equipment from energy sources Identify hazards that may be present

Safety Considerations Isolate hazards Test every circuit, every conductor, every time before touching Use PPE, when necessary Do you have the skills, knowledge, tools, and experience to perform this work safely?

Safe Practices Qualified and authorized electrical technician Voltages and frequency should be identified so that proper precautions can be implemented Ratings of overcurrent protection chould be checked to determine adequate protection

Safe Practices Work on de-energized systems –Use buddy system for energized systems Never touch a bare conductor until a system has been de-energized and verified Enclose and lock all exposed conductors All removed grounding cables should be replaced as soon as possible

Safe Practices Cords should be inspected before using Repair or replace if defective All tools, equipment, and extension cords should be grounded Use nonconductive tape measures near energized equipment

Safe Practices Avoid working on electrical circuits or equipment while clothing and/or shoes are wet Wet floor areas should be covered by dry wood or rubber matting Remove rings, watches, keys, and other metal items before beginning work

Safe Practices Plug power equipment into wall receptacles with power switches in the off position Unplug equipment by grasping the plug Check receptacles for missing or damaged parts

Personal Protective Equipment Insulating gloves Insulating blankets Insulating sleeves Floor covering Safety helmets

Safety in Offices and Classrooms Outlets Cords Machinery

Outlets Do not overload outlets by using extension devices to increase the number of outlets at that socket

Cords Keep cables, cords, and plugs clean and in good repair Protect cords that cross aisles and walkways Extension cords are for temporary use only Extension cords must be 16 gauge or larger

Extension Cords Extension cords should not: –Be affixed to structures –Extend through walls, ceilings, and/or floors –Be placed under doors or floor coverings –Be subjected to physical or environmental damage

Multi-Outlet Strips Multi-outlet strips and surge protectors are not considered extension cords One multi-outlet strip should not be plugged into another

Machinery Report damaged or defective equipment –Request repair or replacement Unplug defective equipment Carry equipment by the base –Never by the cord Do not touch grounded metal parts

Summary Work environments depend on electricity Electrical hazards are in all environments Electrical safety requires effort