DIVISION 26 ELECTRICAL
SECTION 26 05 26 GROUNDING AND BONDING FOR ELECTRICAL SYSTEMS
PART 1 - GENERAL
0.1 RELATED DOCUMENTS
A. Drawings and general provisions of the Contract, including General and Supplemental Conditions and Division 01 Specification Sections, apply to this Section.
0.2 SUMMARY
A. This Section includes methods and materials for grounding systems and equipment.
0.3 SUBMITTALS
A. Product Data: For each type of product indicated.
B. Other Informational Submittals: Plans showing dimensioned as-built locations of grounding features specified in Part 3 "Field Quality Control" Article, including the following:
1. Ground rods. 2. Grounding arrangements and connections for separately derived systems. 3. Grounding for sensitive electronic equipment.
C. Qualification Data: For testing agency and testing agency's field supervisor.
D. Field quality-control test reports.
E. Operation and Maintenance Data: For grounding to include the following in emergency, operation, and maintenance manuals:
1. Instructions for periodic testing and inspection of grounding features at grounding connections for separately derived systems based on NFPA 70B.
a. Tests shall be to determine if ground resistance or impedance values remain within specified maximums, and instructions shall recommend corrective action if they do not. b. Include recommended testing intervals.
0.4 QUALITY ASSURANCE
A. Testing Agency Qualifications: An agent with the experience and capability to conduct the testing indicated, that is a member company of the International Electrical Testing Association or is a nationally recognized testing laboratory (NRTL) as defined by OSHA in 29 CFR 1910.7, and that is acceptable to authorities having jurisdiction.
B. All electrical equipment shall be grounded as per the National Electrical Code Article 250 and all other applicable Articles.
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C. Electrical Components, Devices, and Accessories: Listed and labeled as defined in NFPA 70, Article 100, by a testing agency acceptable to authorities having jurisdiction, and marked for intended use.
D. Comply with UL 467 for grounding and bonding materials and equipment.
0.5 DESCRIPTION
A. The grounding electrode shall consist of each of the following:
1. A metal underground water pipe in direct contact with the earth for 10 feet or more. 2. The metal frame of the building where effectively grounded. 3. An electrode encased by at least 2 inches of concrete located near the bottom of a concrete foundation or footing that is in direct contact with the earth.
In addition to, or if none of the above systems for electrodes is available, then the following electrodes shall be used:
1. Other local metal underground systems or structures. 4. Rod and pipe electrodes at least 10 feet in length. 5. Plate electrodes which expose at least 2 square feet surface to exterior soil.
PART 2 - PRODUCTS
0.1 CONDUCTORS
A. Insulated Conductors: Copper wire or cable insulated for 600 V unless otherwise required by applicable Code or authorities having jurisdiction.
B. Bare Copper Conductors:
1. Solid Conductors: ASTM B3. 2. Stranded Conductors: ASTM B8.
C. Bare Grounding Conductor
1. No. 4 AWG minimum, soft-drawn copper.
D. Grounding Bus: Rectangular bars of annealed copper, .25 x 4 in cross section, unless otherwise indicated; with insulators.
E. All grounding electrode conductors and all bare or insulated bonding conductors shall be copper (CU) only-NO EXCEPTIONS.
0.2 CONNECTORS
A. Listed and labeled by a nationally recognized testing laboratory acceptable to authorities having jurisdiction for applications in which used, and for specific types, sizes, and combinations of conductors and other items connected.
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B. Bolted Connectors for Conductors and Pipes: Copper or copper alloy, bolted pressure-type, with at least two bolts.
1. Pipe Connectors: Clamp type, sized for pipe.
C. Welded Connectors: Exothermic-welding kits of types recommended by kit manufacturer for materials being joined and installation conditions.
0.3 GROUNDING ELECTRODES
A. Ground Rods: Copper-clad steel; 3/4 inch by 10 feet in diameter.
PART 3 - EXECUTION
0.1 TEMPORARY GROUNDING
A. Install ground rods at the distribution panel and elsewhere as required; to provide adequate grounding for neutral conductor of the wiring system, metal enclosures, and portable power tools. Drive additional rods until satisfactory low ground resistance is obtained. A separate grounding conductor paralleling the receptacle circuits may be installed in lieu of ground rods at each point of utilization. Temporary grounding to comply with latest requirements of OSHA.
0.2 APPLICATIONS
A. Conductors: Install stranded conductors for No. 12 AWG and larger, unless otherwise indicated.
B. Underground Grounding Conductors: Install bare copper conductor, size as shown on single line diagram.
1. Bury at least 36 inches below grade or as detailed.
C. Isolated Grounding Conductors: Green-colored insulation with continuous yellow stripe. On feeders with isolated ground, identify grounding conductor where visible to normal inspection, with alternating bands of green and yellow tape, with at least three bands of green and two bands of yellow.
D. Conductor Terminations and Connections:
1. Pipe and Equipment Grounding Conductor Terminations: Bolted connectors. 2. Underground Connections: Welded connectors except at test wells and as otherwise indicated. 3. Connections to Ground Rods at Test Wells: Bolted connectors. 4. Connections to Structural Steel: Welded connectors.
E. Install insulated equipment grounding conductors with all feeders and branch circuits.
F. Install insulated equipment grounding conductors with the following items, in addition to those required by NFPA 70:
1. Feeders and branch circuits.
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2. Lighting circuits. 3. Receptacle circuits. 4. Single-phase motor and appliance branch circuits. 5. Three-phase motor and appliance branch circuits.
0.3 INSTALLATION
A. Grounding Conductors: Route along shortest and straightest paths possible, unless otherwise indicated or required by Code. Avoid obstructing access or placing conductors where they may be subjected to strain, impact, or damage. Ground conductors shall be identified by green insulation or by painting green at all accessible locations and shall be connected with approved connectors and terminators to boxes, devices, equipment, etc., and to ground bars in panels.
B. Ground Rods: Drive rods until tops are 2 inches below finished floor or final grade, unless otherwise indicated.
1. Interconnect ground rods with grounding electrode conductor below grade and as otherwise indicated. Make connections without exposing steel or damaging coating, if any. 2. For grounding electrode system, install at least three rods spaced at least one-rod length from each other and located at least the same distance from other grounding electrodes, and connect to the service grounding electrode conductor.
C. Bonding Straps and Jumpers: Install in locations accessible for inspection and maintenance, except where routed through short lengths of conduit.
1. Bonding to Structure: Bond straps directly to basic structure, taking care not to penetrate any adjacent parts. 2. Bonding to Equipment Mounted on Vibration Isolation Hangers and Supports: Install so vibration is not transmitted to rigidly mounted equipment. 3. Use exothermic-welded connectors for outdoor locations, but if a disconnect-type connection is required, use a bolted clamp.
D. Grounding and Bonding for Piping:
1. Metal Water Service Pipe: Install insulated copper grounding conductors, in conduit, from building's main service equipment, or grounding bus, to main metal water service entrances to building. Connect grounding conductors to main metal water service pipes, using a bolted clamp connector or by bolting a lug-type connector to a pipe flange, using one of the lug bolts of the flange. Where a dielectric main water fitting is installed, connect grounding conductor on street side of fitting. Bond metal grounding conductor conduit or sleeve to conductor at each end. 2. Water Meter Piping: Use braided-type bonding jumpers to electrically bypass water meters. Connect to pipe with a bolted connector. 3. Bond each aboveground portion of gas piping system downstream from equipment shutoff valve. 4. In all flexible conduit. 5. Between receptacles and their metallic outlet boxes. Exception: Receptacles UL listed as self-grounding. 6. Between grounded power outlets and their metallic outlet boxes. 7. Between loosely joined sections of metallic raceway such as at expansion fittings. 8. Between the service equipment neutral bus and ground bus. 9. Between other interior metallic piping systems and the service equipment ground bus.
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10. Between the service equipment ground bus and the metallic building structure, if such is present. 11. Between communications system enclosures, conduits and protector grounding studs and the main service equipment grounding electrode conductor. 12. Between service equipment ground bus and the metallic conduit system. 13. All exterior exposed metallic conduit installed as riser's up utility drop pole shall be grounded. 14. All exposed metallic surfaces of underground junction boxes shall be bonded to the equipment grounding conductor installed with circuit conductors. Size as per 250-122 for largest branch circuit conductor within box. 15. Bonding jumpers installed around unions, valves, water meters and other points where a water-piping-system electrode might be opened, shall have enough slack to permit removal of part.
E. Bonding Interior Metal Ducts: Bond metal air ducts to equipment grounding conductors of associated fans, blowers, electric heaters, and air cleaners. Install bonding jumper to bond across flexible duct connections to achieve continuity.
F. Grounding for Steel Building Structure: Install a driven ground rod at base of each corner column and at intermediate exterior columns at distances not more than 60 feet apart.
G. An equipment grounding conductor shall be included with all circuit conductors over 100 volts. Size the insulated grounding conductor in accordance with NEC Article 250.122 and Table 250.122 except not smaller than No. 12 AWG for all power and lighting circuits and No. 14 AWG for control circuits. The branch circuit or feeder conduit shall not be considered as the sole means of grounding – No exceptions.
H. Cord connected appliance frames shall be grounded to the conduit system and wired grounding system, where applicable, thru a green grounding conductor in the cord.
I. The system ground is the intentional grounding of the neutral to hold all exposed metal enclosures at ground potential and to limit the voltage that can be impressed upon the electrical system due to lightning or other high voltage surges. The ground system consists of:
1. The grounding electrode conductor, minimum size per NEC Article 250.66 and Table 250.66, shall be run from ground bar in the main service entrance equipment to the street side of the water meter on the building water service. 2. A bonding jumper, of the same size, shall be used around the water meter and associated dielectric fittings, valves and service unions. Bond dielectric connections in the cold water piping system. 3. The grounding electrode conductor shall be connected to the neutral in only two locations - on the supply side of the service disconnect means per NEC 250.24, and on separately derived systems per NEC 250.30. Because the ground is lost through the transformer, it must be reestablished by use of a grounding conductor, minimum size per NEC Table 250.66, which connects the transformer secondary neutral point to the interior cold water system and to the service entrance grounding electrical connection. 4. A grounding conductor shall be installed in each non-metallic PVC conduit. 5. The neutral of the service entrance shall be bonded to the enclosure by a main bonding jumper minimum size as per NEC Table 250.66. The neutral of the transformer of a separately derived system shall also be bonded by a main bonding jumper, minimum size per NEC Table 250.66, to the transformer enclosure. These jumpers may be omitted if the equipment is supplied with manufacturer's bonds in accordance with NEMA and UL standards. The service entrance conduits shall be bonded to the switchgear structure. 6. Other than the above two exceptions, neutral connections and assemblies shall be insulated from metal enclosures.
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J. The building neutral shall be identified throughout with white conductors.
K. All non-metallic conduit and all surface metal raceway shall include a properly sized, insulated, and properly identified copper grounding conductor.
1. In the event that circuits from more than one panelboard or from more than one source are included in the same raceway, a grounding conductor from each panelboard or source shall be included.
a. Surface metal raceway shall be bonded to all grounding conductors.
L. Grounding conductors shall be included inside the raceway enclosing the circuit to which they are related.
1. Solitary grounding conductors, if placed in conduit, shall be installed PVC conduit.
0.4 FIELD QUALITY CONTROL
A. Testing Agency: Engage a qualified testing and inspecting agent to perform the following field tests and inspections and prepare test reports:
B. Perform the following tests and inspections and prepare test reports:
1. After installing grounding system but before permanent electrical circuits have been energized, test for compliance with requirements. 2. Inspect all ground connections for continuity and tight electrical and mechanical connections. 3. Test completed grounding system at each location where a maximum ground-resistance level is specified, at service disconnect enclosure grounding terminal, and at individual ground rods. Make tests at ground rods before any conductors are connected.
a. Measure ground resistance not less than two full days after last trace of precipitation and without soil being moistened by any means other than natural drainage or seepage and without chemical treatment or other artificial means of reducing natural ground resistance. b. Perform tests by fall-of-potential method according to IEEE 81.
4. Prepare dimensioned Drawings locating each test well, ground rod and ground-rod assembly, and other grounding electrodes. Identify each by letter in alphabetical order, and key to the record of tests and observations. Include the number of rods driven and their depth at each location, and include observations of weather and other phenomena that may affect test results. Describe measures taken to improve test results.
C. Grounding system will be considered defective if it does not pass tests and inspections.
D. Prepare test and inspection reports.
E. Report measured ground resistances.
F. Maximum permissible ground grid resistance is 5 ohms.
G. If ground grid resistance is not achieved, add an additional rod at a minimum distance at least as far away as the 1st ground rod is long.
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H. Excessive Ground Resistance: If resistance to ground exceeds specified values, notify Architect-Engineer promptly and include recommendations to reduce ground resistance.
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