ES&H Manual



6200 Appendix T4

General Electrical Safety Guidelines



1.0            Purpose


This appendix provides an overview of general electrical safe work practices to be used by everyone at Jefferson Lab.  These practices include: power cords, ground-fault circuit interrupter (GFCI), wall/blind penetration, portable and vehicle-mounted generators, portable and vehicle-mounted engine driven welding machines.  It is recognized that increased awareness of these practices helps maintain an electrically safe work environment. 


2.0            Scope


This appendix describes the electrical safe work practices used during daily operations at Jefferson Lab.  This guidance does not take the place of “common sense” or the need for work planning, control, and authorization.  Electrical work determined to have a Risk Code>2, by a Task Hazard Analysis, requires a work control document.


This appendix is written in coordination with to ES&H Manual Chapter 6200 Jefferson Lab Electrical Safety Program.


3.0            Responsibilities

NOTE:     Management authority may be delegated at the discretion of the responsible manager.


3.1              Everyone at Jefferson Lab

·         Perform work using electrical safe work practices.

·         Report electrical safety hazards to your Supervisor/Subcontracting Officer’s Technical Representative /Sponsor.

·         Submit a Facilities Management Work Request if new, repair, or maintenance electrical work is needed (including installation of electrical outlets).

·         Report cases of electric shock to Jefferson Lab Occupational Medicine Department (x7539)


3.2              Qualified Electrical Worker

·         Provide electrical repair or installations upon request and supervisor approval.

·         Build, repair, and test power cords in accordance with Section 4.1 Power Cords.


3.3              Supervisor/Subcontracting Officer’s Technical Representative (SOTR)/Sponsor

·         Ensure compliance with safe electrical work practices.

·         Report electrical safety hazards to the appropriate authority.


4.0            Electrical Safe Work Practices


4.1              Power Cords

Power cords connect devices to power sources.  They include extension cords, power strips, uninterruptible power supplies (UPS), and small appliances.  Everyone at Jefferson Lab performs the following activities:

·         Check cords for external defects prior to use and periodically over its lifetime.

·         Discard those that are damaged.  (Permanently disable the power source, by removing the cord end(s), prior to disposal.)

·         Turned device(s) “off” before connecting or disconnecting power source.

·         Keep cords out of the line of traffic.  If unavoidable, use cord covers to prevent trip hazards and physical damage.

·         Avoid “daisy-chaining” power cords, one into another.

·         Ensure that cords have adequate air circulation when in use.

·         Fully insert all prongs into an outlet.

·         Grasp or pull the plug, not the cord, to remove it from an outlet.


4.1.1        Build

Only Jefferson Lab qualified electrical workers are authorized to field-assemble power cords for specific use(s).


4.1.2        Repair

Only Jefferson Lab qualified electrical workers are authorized to repair power cords.  The following criteria are used:

·         Determine whether repair is feasible/cost-effective.  If not, properly dispose of the item.

·         Cords and ends are replaced with parts of equal or greater quality.

·         Electrical tape is never used to cover or repair damage to the outer jacket insulation.

·         Repairs are checked to ensure conductors are connected to their proper terminal and for electrical continuity.


Nicks and abrasions, which do not penetrate completely through the outer jacket, are not considered a safety concern.  Repair or replacement of the extension cord would not be required.


4.1.3        Types              Extension Cords

Extension cords are used to deliver power to a desired location on a temporary basis. 

·         Use as a temporary power supply (less than 90 days).

·         Unplug, coil, and store out of the line of traffic when not in use.              Power Strips

Power strips, including strip plugs and surge suppressors, are used to provide power to multiple electronic devices at one time.  Use the following safety guidelines:

·         Check the wattage rating to ensure compatibility with all devices connected to avoid overload.

·         Do not plug one power strip into another.              Uninterruptible Power Supply (UPS)

UPS is a battery backup unit that supplies power when there is a sag in the normal 120 VAC power.  These units have a potential for shock; even when the power cord is disconnected from the wall outlet, due to stored energy.  Use the following safety guidelines:

·         Determination of Replacement – Contact the Computer Center (x7155) if assistance is needed to determine whether to replace the batteries or the unit.  (If battery replacement is feasible, the work is to be done by a qualified electrical worker.)

·         Purchase – through Jefferson Lab’s WebStock system.

·         Disposal – Use Jefferson Lab’s Property Movement, Disposal or Transfer System.

Step 1         Click on “Submit disposal/excess of "administrative" property not on your inventory

Step 2         Complete the “Property to be excessed” Form to generate a work order for the UPS to be picked up for disposal.


4.2              Ground-Fault Circuit Interrupter (GFCI)

GFCI is a device intended for the protection of personnel.  It de-energize a circuit, or portion thereof, within an established period of time when current to ground exceeds approximately 6mA.  A GFCI is required:

·         Per the National Electrical Code.  They are installed in all new construction and renovation projects as required.

·         Where 125-volt single-phase; and 15- and 20-ampere receptacles are installed (i.e., bathrooms, kitchens, rooftops, outdoors, and within six feet of the outside edge of a sink).

·         For all receptacle outlets (including extension cords, and temporary wiring used to supply power to equipment during construction, remodeling, maintenance, repair, or demolition of buildings, structures, or equipment, or similar activities.)

·         For use with:

o   Cord-and-plugged vending machines (installed after 1/1/2005).

o   Electric drinking fountains (installed after 1/1/2008).

o   Portable generators – for all 125-volt single-phase 15-, 20-, and 30-ampere receptacles that are in use by personnel.

·         When supplying temporary power, with the use of extension cords, in a damp or wet location.

·         When supplying temporary power for Jefferson Lab sponsored events – for all 125-volt single-phase 15-, 20-, and 30-ampere receptacles that are in use by personnel.


4.2.1        Testing GFCI

Jefferson Lab recommends that GFCI receptacles be tested in accordance with manufacturer’s recommendations, periodically, and before using a device after an extended period of time.


4.2.2        Types of GFCIs              Receptacle:  A GFCI receptacle is used in place of a standard outlet (see Figure 1.  GFCI Receptacle).  These are generally found near water sources (e.g., kitchens, bathrooms, etc.).


Figure 1.  GFCI Receptacle

gfci receptacle1gfci receptacle2              Portable:  A portable GFCI is used to provide temporary power from an unprotected outlet.  They are tested prior to each use (see Figure 2.  Portable GFCIs).


Figure 2.  Portable GFCIs

Portable GFCI              Circuit Breaker:  A GFCI circuit breaker controls an entire circuit on the main panel board.  In the event of a ground fault, short circuit, or overload the breaker trips and shuts off electricity to circuit.  Only those persons who have been trained by a qualified electrical worker are authorized to reset GFCI circuit breakers.  Contact Facilities Management (x7400) for assistance if electricity is interrupted to your work area.        Switching (resetting) circuit breakers

Only those persons who have been trained by a qualified electrical worker for the specific area, or equipment, are authorized to turn on/off or reset a circuit breaker.


Exception: During an emergency anyone at Jefferson Lab may turn on/off or reset a circuit breaker or disconnect switch as long as doing so does not put them at risk.


4.3              Wall/Blind Penetration

Jefferson Lab buildings have electrical conduit, piping, and data/communications cable within their walls and imbedded in floor slabs.  It also has an extensive buried utility system on-site.  Any work requiring penetration into walls, a floor, or soil, requires a Facilities Management’s Excavations and Blind Penetrations into Walls & Floors.  Submit a Facilities Management Work Request to ensure compliance with this requirement.


4.4              Portable and Vehicle-Mounted Generators

GFCI protection is required for all 125 volt, single phase, 15-, 20-, and 30- ampere receptacles on portable and vehicle-mounted generators.  All other receptacle types require either GFCI protection or follow the National Electrical Code Equipment Grounding Conductor Program.


NOTE: The rules for grounding depend on the specific use and design of the auxiliary power generator. Therefore, if available, always refer to the manufacturers’ operation manual for further instructions.


4.4.1        Portable Generators

Jefferson Lab does not require the frame of a portable generator to be connected to a grounding electrode (e.g. ground rod) if the system, supplied by the generator, complies with the following conditions:


·         It is mounted on the generator.




·         Is connected (cord-and-plug) through receptacle(s) mounted on the generator.




·         The non-current-carrying metal parts of equipment, and the equipment grounding conductor terminals of the receptacles, are bonded to the generator frame.


4.4.2        Vehicle-Mounted Generators

Jefferson Lab does not require the frame of a vehicle to be connected to a grounding electrode (e.g. ground rod) for a system supplied by the generator if the following three conditions are satisfied:


·         The frame of the generator is bonded to the vehicle frame.




·         The generator only supplies power to equipment mounted on the generator, or vehicle, and/or cord-and-plug-connected equipment through receptacles mounted on the generator, or the vehicle.




·         The non-current-carrying metal parts of equipment, and the equipment grounding conductor terminals of the receptacles, are bonded to the generator frame.


NOTE: If a portable generator is being used as a separately derived system (e.g. as a temporary electrical service to a building), or if the load is hard wired (not cord-and-plug-connected) to the internal terminals of the generator, then a grounding electrode conductor is required and shall be sized and installed per the National Electrical Code (NFPA 70).


4.5              Portable and Vehicle-Mounted Engine Driven Welding Machines

Portable and vehicle-mounted engine driven welding generators often have the capability to supply auxiliary power.  When this type of equipment is being used to supply electrical power only, it must abide by the same requirements as a portable or vehicle-mounted generator (see 4.4. Portable and Vehicle-Mounted Generators). 


When a portable or vehicle-mounted engine driven welding machine is being used for welding purposes (with or without cord-and-plug-connected power), then Jefferson Lab does not require the frame to be connected to a grounding electrode conductor (e.g. ground rod).


5.0            References


·         National Fire Protection Association (NFPA) Code 70E Electrical Safety Requirement for Employee Workplace

·         Institute of Electrical and Electronic Engineers (IEEE)

·         Underwriters Laboratories (UL)


6.0            Revision Summary


Revision 1.1 – 11/19/10 – Added general electrical safe work practices for portable and vehicle-mounted generators per Todd Kujawa.

Revision 1 – 05/10/10 – Updated to reflect current laboratory operations.













ESH&Q Division

Todd Kujawa






This document is controlled as an on line file.  It may be printed but the print copy is not a controlled document.  It is the user’s responsibility to ensure that the document is the same revision as the current on line file.  This copy was printed on 5/8/2013.