Electrical Safety

Use of equipment

    • Portable equipment shall be handled in a manner which will not cause damage
    • Flexible electric cords connected to equipment may not be used for raising or lowering the equipment
    • Flexible cords may not be fastened with staples or otherwise hung in such a fashion as could damage the outer jacket or insulation

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    • Portable cord and plug connected equipment and flexible cord sets (extension cords) visually inspected before use for external defects (such as loose parts, or damage to outer jacket or insulation) and for evidence of possible internal damage (pinched or crushed outer jacket)
    • Extension cords which remain connected once they are put in place and are not exposed to damage need not be visually inspected until they are relocated
    • A flexible cord used with grounding type equipment shall contain an equipment grounding conductor
    • Attachment plugs and receptacles may not be connected or altered in a manner which would prevent proper continuity of the equipment grounding conductor at the point where plugs are attached to receptacles

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    Use

    Only qualified persons may perform testing work on electric circuits or equipment

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    Use of equipment

    • (c)(2)”Visual inspection.” Test instruments and equipment and all associated test leads, cables, power cords, probes, and connectors shall be visually inspected for external defects and damage before the equipment is used.
    • If there is a defect or evidence of damage that might expose an employee to injury, the defective or damaged item shall be removed from service, and no employee may use it until repairs and tests necessary to render the equipment safe have been made.

    Safeguards for personnel protection

    • (a)(1)Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed

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    • (a)(1)(ii)Protective equipment shall be maintained in a safe, reliable condition and shall be periodically inspected or tested, as required by 1910.137 *

     

    • (a)(2)(i)When working near exposed energized conductors or circuit parts, each imageemployee shall use insulated tools or handling equipment if the tools or handling equipment might make contact with such conductors or parts

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    (b)The following alerting techniques shall be used to warn and protect employees from hazards which could cause injury due to electric shock, burns, or failure of electric equipment parts:

    • Safety signs and tags
    • Barricades
    • Attendants

    (b)(1)Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards which may endanger them, image

    (b)(2)Barricades shall be used in conjunction with safety signs where it is necessary to prevent or limit employee access to work areas exposing employees to uninsulated energized conductors or circuit parts

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    • If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant shall be stationed to warn and protect employees

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    Work Shouldn’t be…

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    Shocking!


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Safety related Work Practices

Scope

Covers:

  • Qualified persons (those who have training in avoiding the electrical hazards
  • Unqualified persons (those with little or no such training)

Working on or near the following:

  • Premises wiring
  • Wiring for connection to supply
  • Other wiring

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Training

Scope:

  • The training requirements contained in this section apply to employees who face a risk of electric shock that is not reduced to a safe level by the electrical installation requirements of 1910.303 through 1910.308
  • Employees shall be trained in and familiar with the safety-related work practices required by 1910.331 through 1910.335 that pertain to their respective job assignments

Footnote to Table S-4

(1) Workers in these groups do not need to be trained if their work or the work of those they supervise does not bring them or their employees close enough to exposed parts of electric circuits operating at 50 volts or more to ground for a hazard to exist.

Training

(b)(3) Qualified persons: (i.e. those permitted to work on or near exposed energized parts) shall, at a minimum, be trained in and familiar with the following:

(i) The skills and techniques necessary to distinguish exposed live parts from other parts of electric equipment

(ii) The skills and techniques necessary to determine the nominal voltage of exposed live parts

(iii) The clearance distances specified in 1910.333(c)

Deenergized parts

Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them:

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  • Unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible
  • Live parts that operate at less than 50 volts to ground need not be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs

Working on or near exposed deenergized parts

(1) Conductors and parts of electric equipment that have been deenergized but have not been locked out or tagged in accordance with paragraph (b) of this section shall be treated as energized parts

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Illumination

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  • Employees may not enter spaces containing exposed energized parts, unless illumination is provided that enables the employees to perform the work safely
  • Employees may not reach blindly into areas which may contain energized parts.

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Portable ladders

  • Portable ladders shall have nonconductive siderails if they are used where the employee or the ladder could contact exposed energized parts

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Conductive apparel

  • Conductive articles of jewelry and clothing (such a watch bands, bracelets, rings, key chains, necklaces, etc…) may not be worn if they might contact exposed energized parts
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1910.305 (g)(1) Use of Flexible Cords & Cables

Flexible cords and shall be approved and suitable for conditions of use and location*

* The OSHA electric standard (1910.305) lists specific situations in which flexible cords may be used

1910.305 (g)(1)(iii) Prohibited uses of flexible cords

Except for the previously listed exemptions, flexible cords may not be used for:

(A) As a substitute for fixed wiring of the structure;

(B) Where run through holes in walls, ceilings, or floors;

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(C) Where run through doorways, windows, etc..

Judgment of application

  • There are usually citations when the usage is obviously not temporary; and,
  • When the cord is extended to some distant outlet in order to avoid providing a fixed outlet where needed

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Identification, Splices and Terminations

  • Flexible cords shall only be used in continuous lengths, no taps or splices

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Identification, Splices and Terminations

  • Flexible cords shall be connected to devices and fittings so that strain relief is provided which will prevent pull from being directly transmitted to joints or terminal screws

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1910.305 (g)(2)(ii)

  • Flexible cords shall be used only in continuous lengths without splice or tap.
  • Hard service flexible 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 cord being spliced.

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1910.305 (b) Conductors Entering Boxes, Cabinets or Fittings

    • Conductors can be damaged if they rub against the sharp edges of cabinets, boxes, or fittings
    • Where they enter they must be protected by some type of clamp or rubber grommet
    • The device used must close the hole through which the conductor passes as well as provide protection from abrasion

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    • If the conductor is in a conduit and the conduit fits tightly in the opening, additional sealing is not required
    • The knockouts in cabinets, boxes, and fittings should be removed only if conductors are to be run through them
    • Open knockouts and other holes must be closed

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    • All pull boxes, junction boxes and fittings must be provided with approved covers
    • If covers are metal they must be grounded.
    • Each outlet box must have a cover, faceplate or fixture canopy

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    1910.305(e) Enclosures for damp or wet locations

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    • Cabinets, cutouts boxes, fittings, and panelboards shall be weatherproof
    • Switches, circuit breakers, and switchboards shall be in weather proof enclosures

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Testing GFCI’s

    • GFCI’s are complex mechanisms, they must be tested on a regular basis
    • Installation must be correct according to the listing & labeling requirements or the GFCI will not protect as designed
    • For permanently mounted types, once a month testing is recommended
    • Portable GFCI’s should be tested before each use!
    • GFCI’s have a test-circuit which imposes an artificial ground fault when the test button is pushed

    Wiring methods, components, and equipment for general use

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    1910.305(a)(1)(ii) Wiring in ducts

    • No wiring systems of any type shall be installed in ducts used to transport dust, loose stock or flammable vapors

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    1910.305(a)(2) Temporary wiring

    • (iii)(F) Lamps for general illumination shall be protected from accidental contact or breakage
    • Protection shall be provided by elevation of at least 7 feet from normal working surface or by a suitable fixture or lampholder with a guard

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    • (iii)(G) Flexible cords and cables shall be protected from accidental damage
    • Sharp corners and projections shall be avoided.
    • Where passing through doorways or other pinch points, flexible cords and cables shall be provided with protection to avoid damage

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    1910.305(a)(2)(iii)(G) Flexible Cords

    • Where passing through doorways or other pinch points, flexible cords and cables shall be provided with protection to avoid damage

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1910. 304 (f) Grounding

The path to ground from circuits, equipment, and enclosures shall be permanent and continuous

Grounding

There are two kinds of grounding:

  1. Electrical circuit or system grounding
  2. Electrical equipment grounding
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Electrical System Grounding

  • One conductor of the circuit is intentionally grounded to earth
  • Protects circuit from lightning, or other high voltage contact

Equipment Grounding

  • All metal frames & enclosures of equipment are grounded by a permanent connection or bond

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  • The equipment grounding conductor provides a path for dangerous fault current to return to the system ground at the supply source should a fault occur


Grounding Equipment Connected by Cord and Plug

  • Exposed non-current carrying metal parts of cord and plug connected equipment which may become energized shall be grounded
  • If in a hazardous location
  • If operated at over 150 volts

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Note that properly bonded conduit and associated metal enclosures can also serve as a grounding conductor.


Ground fault circuit interrupters (GFCI’s)

  • A GFCI is not an overcurrent device like a fuse or circuit breaker
  • GFCI’s are designed to sense an imbalance in current flow over the normal path
  • GFCI contains a special sensor that monitors the strength of the magnetic field around each wire in the circuit when current is flowing
  • The field is proportional to the amount of current flow

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  • If the current flowing in the black (ungrounded) wire is within 5 milliampers of the current flowing in the white (grounded) all the current will flow in the normal path
  • If the current flow differs by more than 5mA +/- 1mA, the GFCI will quickly open the circuit

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Summary of Intent of 1910.304

Polarity of connections

Improper connection of these conductors (‘hot and neutral’) is most prevalent on smaller branch circuits:

  • Standard 120 volt receptacle outlets
  • Cord-and plug-connected equipment

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Reversed Polarity

Reversed polarity is a condition when the grounded conductor (neutral) is incorrectly connected to the ungrounded (hot) terminal of a plug, receptacle, or other type of conductor


Normal Wiring

1910.304(a)(2)
Reverse Polarity

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1910. 304(b) Branch circuits

1. Reserved
2. Outlet devices. Outlet devices shall have an ampere rating not less than the load to be served

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1910. 304 (d)(1) Disconnecting means

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  • General. Means shall be provided to disconnect all conductors in a building or other structure from the service-entrance conductors.
  • The disconnecting means shall plainly indicate whether it is in the open or closed position and shall be installed at a readily accessible location nearest the point of entrance of the service-entrance conductors.


1910. 304 (d)(2) Services over 600 volts, nominal

(i) Guarded to make them accessible only to qualified persons
(ii) Signs warning of high voltage shall be posted where other than qualified employees might come in contact with live parts

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1910. 304 (e)(1)(vi) Circuit breakers

  • Circuit breakers shall clearly indicate whether they are in the open (off) or closed (on) position

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1910.304 Wiring Design and Protection

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1910.304 Wiring Design and Protection

1910.304(a)(1) Identification of Conductors

  • A conductor used as a grounded conductor shall be identifiable and distinguishable from all other conductors.
  • A conductor used as an equipment grounding conductor shall be identifiable and distinguishable from all other conductors

Identification of Conductors

  • Grounded conductor and equipment grounding conductors marked or color coated
  • So that employees can i.d. and tell apart
  • Grounded conductor is an energized circuit (conductor that is connected to earth through the system ground) Commonly referred to as the neutral)

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Grounding Conductors

  • Equipment grounding conductor acts as a safeguard against insulation failure or faults in the other circuit conductors
  • Not an energized conductor under normal conditions.
  • Energized if a leak or fault in the normal current path
  • Directs current back to the source
  • Enabling fuses or circuit breakers to operate

Identification of Conductors

Grounded conductor i.d. and distinguished from other conductors w/ white or gray image

Equipment grounding conductor i.d. and distinguished w/ green, green w/ yellow stripes, or bare

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1910.304(a) Use and identification of grounded and grounding conductors

  • (2) No grounded conductor may be attached to any terminal or lead so as to reverse polarity
  • (3) A grounding terminal on a receptacle, cord connector, or plug may not be used for purposes other than grounding

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Guarding live parts – 1910.303

Guarding live parts – 1910.303

(g)(2)(i) or other forms of approved enclosures, or by any of the following means:

  • (A) By location in a room, vault, accessible only to qualified persons
  • (B) By permanent, substantial partitions or screens
  • (C) By location on a suitable balcony or platform as to exclude unqualified persons
  • (D) By elevation of 8 feet or more above the floor or other working surface

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(2)(iii) Entrances to rooms and other guarded locations containing exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter

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    1910.303(h)(3)(ii) Illumination

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    • Adequate illumination for all working spaces about electric equipment
    • The lighting outlets arranged that persons changing lamps or making repairs on the lighting system will not be endangered by live parts or other equipment

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