1. Office of Safety & Health Consultation presents
Electrical in Construction
Notes:

2. Objectives In this course, we will discuss the following:
Common electrical hazards
Standards relating to those hazards
Electrical equipment defects/hazards
Tools/techniques used in identifying hazards
Notes:

3. 29 CFR 1926 - Subpart K 1926.400 – Introduction
– Applicability
– General requirements
– Wiring design and protection
– Wiring methods, components, and equipment
– Specific purpose equipment and installations
– Hazardous (classified) locations
– Special systems
, 417, 431, 432, 441 – Safety-related practices and maintenance
Definitions
Notes:

4. Common Electrical Hazards
Electric shock/electrocution occurs, when current flows through the body damaging the body.
Electrical burns are caused by arc blast or hot conductors.
Indirect falls from ladders, scaffolds or other walking and working surfaces.
Notes:

5. Common Electrical Hazards
Explosions can be caused when electricity provides a source of ignition for an explosive mixture in the atmosphere.
Fires are caused by overloading a circuit or appliance or by current flowing through
high resistance due to faulty
wiring, setting fire to insulation
and surrounding materials.
Notes:

6. General Requirements
Notes:
(a)

7. General Requirements
Electrical equipment must be free from recognized hazards that can cause death or serious physical harm to employees
Suitability for installation
Mechanical strength and
durability
Electrical insulation
Heating effects under
condition of use
Arcing effects
Classification by type, size, voltage,
current capacity, specific use
Notes:
(b)(1)

8. General Requirements
Listed, labeled, or certified equipment must be installed and used in accordance with instructions included in the listing, labeling or certification
Notes:
(b)(2)

9. Nationally Recognized Testing Laboratories
Canadian Standards Association (CSA International)
Communication Certification Laboratory, Inc. (CCL)
Curtis-Straus LLC (CSL)
FM Approvals LLC (FM)
Intertek Testing Services NA, Inc. (ITSNA)
MET Laboratories, Inc. (MET)
NSF International (NSF)
National Technical Systems, Inc. (NTS)
SGS U.S. Testing Company, Inc. (SGSUS)
Southwest Research Institute (SWRI)
TUV SUD America, Inc. (TUVAM)
TUV SUD Product Services GmbH (TUVPSG)
TUV Rheinland of North America, Inc. (TUV)
Underwriters laboratory Inc. (UL)
Wyle Laboratories, Inc. (WL)
Notes:
NRTL’s are recognized by OSHA.

10. Box Not Approved as a Pendant
Notes:

11. General Requirements
Equipment shall be installed and used in accordance with instructions.
Notes:
(b)(2)

12. Used in Accordance With Instructions
Notes:

13. General Requirements Splices Splicing devices suitable for use
Welding/brazing/soldering
Mechanically/electrically secure before soldering
Covered with insulation equivalent to that of the conductors
Insulating device suitable for purpose
Notes:
(e)

14. General Requirements
Each service, feeder, and branch circuit, at its disconnecting means or over current device, shall be legibly marked to indicate its purpose.
Notes:
(h)

15. General Requirements
Live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by cabinets or other forms of enclosures, or by another suitable method.
Notes:
(i)

16. Wiring Design and Protection
Polarity of connections
No grounded conductor may be attached to any terminal or lead so as to reverse designated polarity
Correct Polarity
Hot
Neutral
Ground
Hot
Notes:
Neutral
Ground
Reversed Polarity
(a)(2)

17. Wiring Design and Protection
Employer shall use either ground fault circuit interrupters, or
An assured equipment grounding conductor program to protect employees
Notes:
(b)(1)(i)

18. Wiring Design and Protection
Portable generators need not be grounded if:
Supplies only equipment
mounted on the generator
and/or cord and plug
equipment is plugged into
receptacle mounted on the
generator
Noncurrent-carrying metal
parts of equipment and
grounding conductor
terminals of the receptacle
are bonded to generator frame
Notes:
(f)(3)

19. Wiring Design and Protection
Vehicle-mounted generators; vehicle frame may serve as system grounding if:
The frame of the generator
is bonded to the vehicle
frame and ….
Generator supplies only
equipment located on the
vehicle and/or equipment
plugged into the generator
and ….
Notes:
(f)(3)

20. Wiring Design and Protection
The noncurrent-carrying metal parts of equipment and grounding conductor terminals of the receptacles are bonded to the generator frame, and ….
The system complies with all other provisions of this section.
Notes:
(f)(3) 20

21. Wiring Design and Protection
The path to ground from circuits, equipment, enclosures must be permanent and continuous.
Notes:
(f)(6)

22. Wiring Design and Protection
Equipment connected by cord and plug
Noncurrent-carrying metal parts which may become energized must be grounded
Notes:
(f)(7)(iv)

23. Wiring Design and Protection
Equipment connected by cord and plug must be grounded, if:
In a hazardous location
Operated at over 150 V to
ground
Except guarded motors and
appliances permanently insulated
from ground
Hand held motor-operated tools
Equipment used in wet and/or
conductive locations
Portable hand lamps
Notes:
(f)(7)(iv)

24. Wiring Design and Protection
Flexible cords and cables must be protected from damage.
Notes:
(a)(2)(ii)(I)

25. Wiring Design and Protection
Extension cord sets used with portable electric tools and appliances must be of three-wire type and must be designed for hard or extra-hard usage.
Notes:
(a)(2)(ii)(J)

26. Wiring Design and Protection
Conductors entering boxes, cabinets, or fittings must be protected from abrasion.
Notes:
(b)(1)

27. American Wire Gauge
Notes:
Note: The larger the gauge number, the smaller the wire.

28. Wire Rating #10 AWG 30 amps 28 amps #12 AWG 25 amps 23 amps 20 amps
Wire Size:
Handles up to:
Allowable
ampacities:
Unless permitted
in NEC 240.4(E-G):
#10 AWG
30 amps
28 amps
#12 AWG
25 amps
23 amps
20 amps
#14 AWG
17 amps
15 amps
#16 AWG
18 amps
8 amps
Notes:
Reference: American Wire Gauge (AWG): Source NIOSH (Electrical Safety, Safety and Health for Electrical Trades, Student Manual – Revised Edition; pg. 41)

29. Safety factor of 20% Tool Estimated Watts Amperage Used Receptacle25 40
Maximum Amperage Load
(less 20%)
Jig Saw
300
2.5 (*5.0 motor startup) 20 32
Table Saw
1800 15
7 ¼” Circular Saw
1200 10
Chop Saw
1550 13
Total Usage
4850
43 (* includes startup)
Notes:
NFPA 70, National Electrical Code, 2011 Edition [see Article (A)(1);

30. Wiring Design and Protection
Notes:
(b)(1)

31. Wiring Design and Protection
Unused openings in cabinets, boxes and fittings must be effectively closed.
Notes:
(b)(1)

32. Wiring Design and Protection
All pull boxes, junction boxes, and fittings must be provided with a cover.
If metal covers are used, they must be grounded.
Notes:
(b)(2)

33. Wiring Design and Protection
Flexible cords and cables must be suitable for conditions of use and location.
Notes:
(g)(1)

34. Wiring Design and Protection
Permitted uses of flexible cords and cables
Pendants
Fixture wiring
Portable lamps and
appliances
Elevators cables, cranes,
and hoists
Stationary equipment
Frequent interchange
Appliances – to permit removal
for maintenance and repair
Notes:
(g)(1)

35. Wiring Design and Protection
Prohibited uses of flexible cords and cables
As substitute for fixed wiring of structure
Run through holes in walls, ceilings or floors
Run through doors, windows or similar openings
Attached to building surfaces
Concealed behind building walls, ceilings, or floors
Notes:
(g)(1)(iii)

36. Flexible Cord Run Above Ceiling
Notes:

37. Wiring Design and Protection
Flexible cords shall be connected to devices and fittings so that strain relief is provided.
Will prevent pull from being directly transmitted to joints or terminal screws
Notes:
(g)(2)(iv)

38. Wiring Design and Protection
Notes:

39. Safety-Related Work Practices
Employer must not permit an employee to work in such proximity to any part of an electric power circuit.
If employee could
contact the power
circuit, it must be
de-energized or
guarded.
Notes:
(a)(1)

40. Safety-Related Work Practices
Working spaces, walkways, and similar locations shall be kept clear of cords so as not to create a hazard to employees.
Notes:
(b)(2) 40

41. Safety-Related Work Practices
Worn or frayed electric cords must not be used.
Extension cords shall not be stapled, hung from nails or suspended by wire.
Notes:
(e)

42. Tools for Identifying Hazards
An electrical receptacle voltage tester with GFCI tester.
Line voltage probes
Notes: 42

43. Summary In this course, we discussed: Common electrical hazards
Standards relating to those hazards
Electrical equipment defects/hazards
Tools/techniques used in identifying hazards
Notes:

44. Recognize Any Hazard(s)?
Construction Focus Four: Electrocution - Hazard Recognition
Recognize Any Hazard(s)?
Notes:

45. Construction Focus Four: Electrocution - Hazard Recognition
Yes
No employer shall permit a worker to work in such proximity to any part of an electric power circuit that the worker could contact the electric power circuit in the course of work
Notes:

46. Recognize Any Hazard(s)?
Notes:

47. Construction Focus Four: Electrocution - Hazard Recognition
Yes
Notes:
Crossing electrical line must be supported, protected or removed to safeguard workers

48. Recognize Any Hazard(s)?
Construction Focus Four: Electrocution - Hazard Recognition
Recognize Any Hazard(s)?
Notes:

49. Construction Focus Four: Electrocution - Hazard Recognition
Yes
Spliced electrical extension cords. Extension cords should be marked DO NOT USE. Also, bad housekeeping, trip hazard and unprotected hole in photograph

50. Recognize Any Hazard(s)?
Construction Focus Four: Electrocution - Hazard Recognition
Recognize Any Hazard(s)?

51. Construction Focus Four: Electrocution - Hazard Recognition
YES
1. No GFCI
2. System not grounded
3. Openings where conductors entered not closed
4. No cover on boxes
5. Panel boards were not dead front
Notes:

52. Recognize Any Hazard(s)?
Construction Focus Four: Electrocution - Hazard Recognition
Recognize Any Hazard(s)?
Notes:

53. Construction Focus Four: Electrocution - Hazard Recognition
YES
Electric drill flexible cord was spliced to a non-flexible conductor with damaged insulation
Notes:

54. Recognize Any Hazard(s)?
Notes:

55. Yes
Notes:
Scaffold was erected 4 ½ feet from 7.2 kV power lines

56. Recognize Any Hazard(s)?
Construction Focus Four: Electrocution - Hazard Recognition
Recognize Any Hazard(s)?
Notes:

57. Construction Focus Four: Electrocution - Hazard Recognition
YES
Continuous path to ground not maintained; multiple cords used for fixed equipment
Notes:

58. Recognize Any Hazard(s)?
Construction Focus Four: Electrocution - Hazard Recognition
Recognize Any Hazard(s)?
Notes:

59. Construction Focus Four: Electrocution - Hazard Recognition
YES
Employer was operating a stand fan without grounding protection
Notes:

60. Recognize Any Hazard(s)?
Notes:

61. Construction Focus Four: Electrocution - Hazard Recognition
Yes
Conductors entering boxes, cabinets, or fittings shall be protected from abrasion.
Openings through which conductors enter shall be effectively closed
Notes:

62. Recognize Any Hazard(s)?
Notes:

63. Construction Focus Four: Electrocution - Hazard Recognition
Yes
Flexible cords and cables may pass through doorways or other pinch points, if protection is provided to avoid damage
Notes:

64. Your Questions?
Notes: