Electrical Safety

1. Electrical Safety For Qualified Electrical Workers

2. Electrical Hazards

3. SHOCK. Electric shock occurs when the human body becomes part of the path through which current flows. • The direct result can be electrocution. • The indirect result can be injury resulting from a fall or movement into machinery because of a shock

4. BURNS. Burns can result when a person touches electrical wiring or equipment that is energized. • ARC-BLAST. Arc-blasts occur from high- amperage currents arcing through the air. This can be caused by accidental contact with energized components or equipment failure.

5. ARC-BLAST. The three primary hazards associated with an arc-blast are: • Thermal radiation. • Pressure Wave. • Projectiles. • EXPLOSIONS. Explosions occur when electricity provides a source of ignition for an explosive mixture in the atmosphere.

6. FIRES. Electricity is one of the most common causes of fires both in the home and in the workplace. Defective or misused electrical equipment is a major cause.

7. EFFECTS ON THE HUMAN BODY Factors: • Current and Voltage • Resistance • Path through body • Duration of shock

8. Effects of AC Electricity • More than 3 mA- Painful shock- cause indirect accident • More than 10 mA- Muscle contraction – “No Let Go” danger • More than 30 mA- Lung paralysis, usually temporary

9. Effects of AC Electricity • More than 50 mA- Ventricular fibrillation, usually fatal • 100 mA to 4 A- Certain ventricular fibrillation, fatal • Over 4 A- Heart paralysis, severe burns

10. Electrical Equipment

11. Examination of equipment • Electrical equipment must be free of recognized hazards that are likely to cause death or serious physical harm to employees.

12. Examination of equipment Safety of equipment must be determined using the following considerations: • Suitability for installation and use • Mechanical strength and durability • Electrical insulation • Heating effects under conditions of use

13. Examination of equipment Safety of equipment must be determined using the following considerations: • Arcing effects • Classification by type, size, voltage, current capacity and specific use • Other factors

14. Splices Conductors must be spliced with: • Splicing devices suitable for the use • Brazing, welding or soldering (with a mechanically and electrically secure joint before soldering & then soldered)

15. Splices • All splices and joints and the free ends of conductors must be covered with an insulation equivalent to that of the conductors or with an insulating device suitable for the purpose.

16. Marking Electrical equipment may not be used unless the manufacturer’s name, trademark or other identification is on the equipment. Other markings must be provided giving voltage, current, wattage, or other ratings as necessary. Markings must be durable enough to withstand the environment.

17. Identification • Each disconnecting means must be legibly marked to indicate its purpose, unless located and arranged so that its purpose is evident. • These markings must be durable enough to withstand their environment.

18. 600 volts, nominal, or less • Working space about electrical equipment. • This section refers to a person qualified to work on electrical equipment, usually an electrician.

19. Working clearances • Except as required or permitted, the dimension of the working space in front of live parts (600 volts or less) and likely to require examination, adjustment, servicing, or maintenance must be at least three feet. • The workspace in front of electrical equipment must not be less than 30 inches wide. • Working spaces may not be used for storage.

20. 600 Volts or less Guarding of live parts operating at 50 Volts or more. • The purpose of this requirement is to protect any person who is in the vicinity of electrical equipment against accidental contact, not just electricians.

21. 600 Volts or less Guarding of live parts. Guard against accidental contact by: • Location accessible only to qualified persons • Permanent, substantial partitions or screens

22. 600 Volts or less Guarding of live parts. Guard against accidental contact by: Location on a suitable elevated balcony or platformElevation of 8 feet or more above the floor or other working surface

23. 600 Volts or less Guarding of live parts. • In locations where electrical equipment would be exposed to physical damage, enclosures or guardians must be so arranged and of such strength as to prevent such damage.

24. Over 600 Volts Workspace around equipment. • Sufficient space must be provided and maintained around electrical equipment to permit ready and safe operation and maintenance.

25. Work Area Illumination(Over 600 Volts) • Adequate illumination must be provided for all working spaces around electrical equipment. • The lights and switches must be arranged so that persons making repairs or turning on lights wont contact live ports.

26. Elevation of unguarded live parts • Unguarded live parts above working space must be maintained at elevations not less than specified in Table S-3 of the OSHA Standard. • The minimum is 8 feet.

27. Grounded and grounding conductors The grounded conductor is an energized circuit conductor that is connected to earth through the system ground. It is commonly referred to as the neutral.

28. Grounded and grounding conductors The equipment grounding conductor is not an energized conductor under normal conditions. It is energized only if there is a leak or fault in the normal current path and directs current back to the source.

29. Grounded and grounding conductors The National Electric Code requires that: • The grounded conductor (neutral) be continuous white or natural gray. • The equipment grounding conductor be green, green with yellow stripes or bare.

30. Polarity of connections No grounded conductor may be attached to any terminal or lead so as to reverse designated polarity. Reversed polarity is a condition when neutral conductor is incorrectly connected to the “hot” terminal of a plug, receptacle or other connector.

31. Overcurrent protection600 Volts or less Conductors and equipment must be protected from overcurrent conditions. Fuses and circuit breakers are designed to disconnect a circuit from its supply source when a maximum allowable heat is reached. Overcurrent devices must be readily accessible but not located where they will be exposed to physical damage or in the vicinity of easily ignitable material.

32. Grounding Paths The path to ground from circuits, equipment, and enclosures must be permanent and continuous

33. Grounding Tools Tools likely to be used in wet and conductive locations need not be grounded if supplied through an isolating transformer with an ungrounded secondary of not over 50 volts.

34. Double Insulation Listed or labeled portable tools and appliances protected by an approved system of double insulation, or its equivalent, need not be grounded. However, they must be distinctively marked.

35. Electrical ToolsDouble Insulated • They work with GFCIs • Casing must be labeled • Tool must be inspected • Extension cord must be three-prong

36. Wiring methods. General requirements. No wiring system of any type shall be in ducts used to transport dust, loose stock or flammable vapors, or used for vapor removal or ventilation of commercial-type cooking equipment.

37. Temporary Wiring Temporary electrical power and lighting wiring may be of a class less than would be required for a permanent installation. Permitted for 600 volts or less. During and for remodeling, maintenance repair, or demolition or similar activities.

38. Temporary Wiring Uses permitted for over 600 volts only during tests, experiments and emergencies.

39. Lighting Lamps for general illumination must be protected from accidental contact or breakage. Protection can be provided by an elevation of 7 feet or by a suitable fixture with a guard.

40. Conductors entering boxes, cabinets, or fittings. • Conductors entering boxes, cabinets, or fittings must be protected from abrasion. • Unused openings in cabinets, boxes, and fittings must be effectively closed.

41. Electrical box covers • All pull boxes, junction boxes, and fittings must be provided with approved covers. • Metal covers must be grounded. • Outlet boxes must have a cover or a faceplate. • Outlet box covers with holes for flexible cords must bushings or smooth, well- rounded surfaces.

42. Switchboards & Panels • Panels must be mounted in approved cabinets or boxes and must be dead front. • Others are accessible only to qualified persons.

43. Flexible Cords & Cables

44. Flexible cords & cables. Allowed uses: • Pendants • Wiring fixtures • Portable lamps or appliances • Elevator cables • Wiring cranes or hoists

45. Flexible cords & cables. Allowed uses: • Connect stationary equipment to facilitate frequent interchange • Prevent transmission of noise or vibration • For removal for maintenance/repair

46. Flexible Cords Flexible cords and cables must be protected from accidental damage.Sharp corners or projections must be avoided. Protection must be provided when passing through doorways or other pinch points.

47. Flexible cords & cables. May not be used: • As a substitute for the fixed wiring of a structure. • Where run through holes in walls, ceilings or floors.

48. Flexible cords & cables. May not be used: • Where run through doorways, windows, or similar openings • Where attached to building surfaces • Where concealed behind building walls, ceilings, or floors.

49. Flexible cords and cables. Flexible cords must be used only in continuous lengths without splice or tap. Hard service flex cords, No. 12 or larger, may be repaired if spliced so that the splice retains the insulation, outer sheath properties, and usage characteristics of the original cord.

50. Flexible cords and cables. Flexible cords must be connected to devices and fittings so that strain relief is provided which will prevent pull off from being directly transmitted to joints or terminal screws.