11.D Grounding.
11.D.01 All electrical circuits, equipment and enclosures must be grounded in accordance with the NEC and the NESC to provide a permanent, continuous and effective path to ground unless otherwise noted in this manual.
Electrodes of rod or pipe, practical, must be embedded below permanent moisture levels.
- A ground must be provided for non-current carrying metallic parts of equipment such as generators (per NEC 250.34, portable and vehicle-mounted generators are exempt from grounding provided conditions if Section 11.D.01.b and c are met), non-engine driven electrically powered arc welders, light plants, switches, motor controller cases, fuse boxes, distribution cabinets, frames, non-current carrying rails used for travel and motors of electrically operated cranes, electric elevators, metal frames of non-electric elevators to which electric conductors are attached, other electric equipment, and metal enclosures around electric equipment.
- Portable Generators. Portable describes equipment that is easily carried by personnel from one location to another. The frame of a portable generator is not required to be grounded and may serve as the grounding electrode for a system supplied by the generator under the following conditions:
- (1) The generator supplies ONLY equipment mounted on the generator, cord-and-plug- connected equipment through receptacles mounted on the generator, or both; and
- (2) The non-current-carrying metal parts of the equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.
- Vehicle-Mounted Generators. The frame of a vehicle need not be grounded and may serve as the grounding electrode for a system supplied by a generator located on the vehicle under the following conditions:
- (1) The frame of the generator is bonded to the vehicle frame;
- (2) The generator supplies only equipment located on the vehicle or cord-and-plug- connected equipment through receptacles mounted on the vehicle;
- (3) The non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame; and
- (4) The system complies with provisions of Section 11.D.01.
- A system conductor that is required to be grounded (per NEC 250.34) must be bonded to the generator frame where the generator is a component of a separately derived system.
- Portable and semi-portable electrical tools and equipment must be grounded by a multi-conductor cord having an identified grounding conductor and a multi-contact polarized plug and receptacle.
- Floodlights, light plants and work lights must be grounded.
- Tools protected by an approved system of double insulation, or its equivalent, need not be grounded. Double-insulated tools must be distinctly marked and listed by a nationally-recognized testing laboratory.
- A grounding terminal or grounding type device on a receptacle, cord connector, or attachment plug may not be used for purposes other than grounding.
11.D.02 Grounding Rod and Pipe Electrodes.
- Electrodes of rod or pipe must be free from non-conducting coatings and, if practicable, must be embedded below permanent moisture levels.
- Grounding rods and pipe electrodes must be in unbroken 8 ft (2.4 m) lengths and driven to full depth. Where rock bottom is encountered, the electrode must be driven at an angle not to exceed 45º from the vertical or must be buried in a trench that is at least 2.5 ft (0.7 m) deep.
- A single electrode that does not have a resistance to ground of 25 ohms or less, must be augmented by one additional electrode spaced no closer than 6 ft (1.8 m) to the first electrode.
- Electrodes or rods of iron or steel must be at least 5/8 in (15 mm) diameter. Nonferrous rods, or their equivalent, must be listed by a nationally-recognized testing laboratory and must be at least 1/2 in (12 mm) diameter.
- Electrodes or pipe or conduit must be at least 3/4 in (21 mm) trade size. Pipes and conduit of iron or steel must have the outer surface galvanized or otherwise metal-coated for corrosion control.
- Grounding electrode systems of permanent facilities must be in accordance with NEC 250.
11.D.03 Conductors used for bonding or grounding stationary and movable equipment must be of ample size to carry the anticipated current.
- When attaching bonding and grounding clamps or clips, a secure and positive metal- to-metal contact must be made.
- The ground end must be attached first. The equipment end must be attached and removed by insulated tools or other suitable devices.
- When removing grounds, the grounding device must be removed from the line or equipment first, using insulated tools or other suitable devices.
- Bonding and grounding attachments must be made before systems are activated and must not be broken until after systems are de-activated.
- A designated grounding conductor must not be used as a current carrying conductor.
11.D.04 Grounding circuits must be checked to ensure that the circuit between the ground and a grounded power conductor has a resistance low enough to permit sufficient current flow to allow the fuse or circuit breaker to interrupt the current.
GFCI and grounding.
11.D.05 Ground-Fault Circuit-Interrupter (GFCI) Protection For Personnel. All receptacle outlets (125-volt, 15-, 20-, 30-amperage and greater) that provide temporary electrical power during construction, remodeling, maintenance, repair, or demolition must have ground-fault circuit-interrupter (GFCI) protection for personnel. > See NEC, Article 590.6 and 29 CFR 1926.404(b); See also paragraph g below.
- GFCI protection must be provided on all circuits serving portable electric hand tools or semi-portable electric power tools (such as block/brick saws, table saws, air compressors, welding machines, and drill presses).
- The GFCI device must be calibrated to trip within the threshold values of 5 ma +/- 1 ma as specified in UL Standard 943. GFCI devices must be tested before initial use and before use after modification.
- Receptacle outlets that are not part of the permanent wiring of the building or structure must be GFCI protected by one of the following means:
- (1) A receptacle outlet with integral GFCI protection;
- (2) A standard receptacle outlet connected downstream of a receptacle outlet with integral GFCI protection; or
- (3) Receptacles protected by a GFCI-type circuit breaker.
- Receptacle outlets that are part of the permanent wiring of the building or structure and are used for temporary electric power, (including portable generators) must use a portable GFCI if the receptacle outlets are not already GFCI protected. The portable GFCI must be as near as practicable to the receptacle outlet.
- Exception: In industrial facilities only, where conditions of maintenance and supervision ensure that only qualified personnel are involved, an Assured Equipment
- Grounding Conductor Program (AEGCP), see also Appendix E, must be permitted for only those receptacle outlets used to supply equipment that would create a greater hazard if power was interrupted or having a design that is not compatible with GFCI protection.
- Electric tool circuits that are hard-wired directly to an electrical source of power must be protected by a GFCI circuit-breaker type.
- GFCIs must be installed in accordance with the NEC. The permanent wiring must consist of electrical circuits grounded in accordance with the NEC.
- GFCIs may be sensitive to some equipment (such as concrete vibrators), or unavailable for the voltage and current rating. In these instances, an AEGCP in accordance with Appendix E is acceptable in lieu of GFCIs if the exception is documented on an AHA and contains the following:
- (1) The conditions, or need, for the exception; and
- (2) Implementation of the requirements of the AEGCP;
- (3) The request for the exception, the AHA, and the AEGCP must be submitted and accepted by the GDA prior to implementing the program.
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11-4. How far must grounding rods and pipe electrodes be driven into the ground?
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