1

Electrical Safety

2

Electrical Hazards & OSHA

� 29 CFR 1910.303(b)(1) requires:

� “Electrical equipment shall be free from recognized hazards that are likely to cause death or serious physical harm to employees”

� Michigan has adapted the appropriate OSHA regulations

3

Electrocution� Each year, ~9% of fatalities in American

workforce is by electrocution while working around electricity.

� Workplace electrocution hazards:

� Broken light bulb

� Frayed cords

� Exposed wires

� Water around electrical equipment

� Crowded outlets

4

Voltage Voltage: amount of electrical force (electromotive

force) to move electricity between 2 points

This is difference of electron and proton potential.

Measurement between 2 points can be between “hot” and neutral, or between other charged items

Voltage measured in volts

5

VOLTS

VOLTS

RMS

One Cycle

Hot

Neutral

6

Resistance Resistance: measure of opposition of flow of

current (opposite of conduction)

Measured in Ohms (Voltage/Current)

Similar to friction

Caused by nature of material or work done

Example: A toaster wires get hot due to resistance.

Safe Electrical Work Practices� Checked for frayed cords

� Wear correct PPE

� Use correct tools

� Turn off unused machines

� Use non-conducting ladders

� No water around electrical equipment

� Grounding

7

8

Current Current: amount of electricity that flows in a

circuit

Measured in amperes (Amps)

Milliamp = 1/1000 of amp

9

Current� There are 2 different types of current:

AC- Alternating current (outlets)DC- Direct current (batteries)

10

V fib means heart loses meaningful pumping action, thus causing death in a short period of time.

This happens when a small current passes either (a) from head to foot, or (b) from hand to foot and thru the heart.

Ventricular Fibrillation

~100 milliamperes can cause VF

Current between 70-200 milliamperes, if passed through heart, can cause ventricular fibrillation.

11

Grounding Ground: Process of achieving earth neutral

Common (wired) return path for electrical circuit to ground

12

GFCI� Ground Fault Circuit Interrupter

Prevents electrocution by detecting a ground fault and opening circuit (so our body doesn’t become part of circuit)

A type of undercurrent Use: kitchen, bathroom, basement, garage,

outside, laundry roomActivates at 5-1 mA and 1/25 of second

13

GCFI-Receptacle

14

Grounded Equipment� Never use a plug with a missing ground

prong.

� Always check before plugging into a receptacle.

15

Overcurrent� Overcurrent - extra amount of current that

passes through a circuit

� Overcurrent protection device opens the circuit (electricity won’t flow)

� These devices are circuit breakers or fuses.

16

Short Circuit

� A short circuit is when there is a direct contact between “hot” and “neutral”.

17

Static Electricity� Static electricity - buildup of difference of

potential (electric charge) between materials

� E- move from one object to another when surfaces come into contact (friction)

� Can ignite vapors

Positive

Negative

18

Extension Cords� Extension cords cannot be used:

As a substitute for fixed wiring Running through holes Running through doorways, windows,

etc. Behind walls, ceiling, or floorsShould contain warning labels & rating info (&

only be used temporarily)

Polarized Plugs

� One prong slightly wider so can only be inserted one way

� Allows live and neutral connection safety

19