260526.pdf

DCFT #082207

Hanson #03S1408GGB

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GROUNDING AND BONDING

FOR ELECTRICAL SYSTEMS

DIVISION 26- ELECTRICAL

SECTION 260526 – GROUNDING AND BONDING

FOR ELECTRICAL SYSTEMS

PART 1 - GENERAL

1.1 RELATED DOCUMENTS

A. Drawings and general provisions of the Contract, including General and Supplementary Conditions and Division 01 Specification Sections, apply to this Section.

1.2 SUMMARY

A. This Section includes methods and materials for grounding systems and equipment.

1.3 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 ground rings 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.

1.4 QUALITY ASSURANCE

A. Testing Agency Qualifications: An independent agency, with the experience and capability to conduct the testing indicated, that is a member company of the International Electrical Testing

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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:

1. Testing Agency's Field Supervisor: Person currently certified by the International Electrical Testing Association to supervise on-site testing specified in Part 3.

B. 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.

C. Comply with UL 467 for grounding and bonding materials and equipment.

1.5 SYSTEM DESCRIPTION

A. Grounding electrical service neutral at service entrance equipment to metal underground water pipe, metal frame of building and grounding rod.

B. Ground each separately derived system neutral to structural member of building or by using a separate ground rod.

C. Ground raceways and electrical equipment; use double locknuts at all panels; use bonding jumpers where conduits are installed in concentric knockouts. Ground panels, switches, motor frames, motor starters fixtures, and outlets with separate ground conductor in conduit system.

D. Bond together system neutrals, service entrance enclosures, exposed non-current carrying metal parts of electrical equipment, metal raceway systems, grounding conductor in raceways and cables, receptacle ground terminals, building structural steel and plumbing systems.

PART 2 - PRODUCTS

2.1 CONDUCTORS

A. Materials used for grounding conductors shall be in accordance with NEC Article 250-62.

B. Insulated Conductors: Copper wire or cable insulated for 600-Volt unless otherwise required by applicable Code or authorities having jurisdiction. Equipment grounding conductors shall be 600-Volt, same type as phase conductors, green in color.

C. Bare Copper Conductors:

1. Solid Conductors: ASTM B 3.

2. Stranded Conductors: ASTM B 8.

3. Tinned Conductors: ASTM B 33.

4. Bonding Cable: 28 kcmil, 14 strands of No. 17 AWG conductor, 1/4 in. (6.4 mm) in diameter.

5. Bonding Conductor: No. 4 or No. 6 AWG, stranded conductor.

6. Grounding Electrode Conductor: bare stranded annealed copper.

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D. Grounding Bars: Rectangular bars of annealed copper, 1/4 by 2 in. (6.4 mm x 50 mm) in cross section, unless otherwise indicated; with insulators.

2.2 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.

B. Bolted Connectors for Conductors and Pipes: Copper or copper alloy, bolted pressure-type, with at least two (2) 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. Connections shall include ground wire to ground rod, ground wire to ground wire, and ground wire to steel column.

2.3 GROUNDING ELECTRODES

A. Ground Rods: Copper-clad steel; 3/4 in. (19 mm) by10 ft (3,050 mm) in diameter, UL listed with minimum 10 mil. copper coating.

PART 3 - EXECUTION

3.1 APPLICATIONS

A. Conductors: Install solid conductor for No. 8 AWG and smaller, and stranded conductors for No. 6 AWG and larger, unless otherwise indicated.

B. Underground Grounding Conductors: Install barecopper conductor, No. 2/0 AWG minimum:

1. Bury at least 24 in. (600 mm) below grade.

C. Grounding Bus: Install in electrical and telephone equipment rooms, in rooms housing service equipment, and elsewhere as indicated:

1. Install bus on insulated spacers 1 in. (25 mm), minimum, from wall 6 in. (150 mm) above finished floor, unless otherwise indicated.

2. Where indicated on both sides of doorways, route bus up to top of door frame, across top of doorway, down to specified height above floor, and connect to horizontal bus.

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.

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3. Connections to Ground Rods at Test Wells: Bolted connectors.

4. Connections to Structural Steel: Welded connectors.

3.2 GROUNDING UNDERGROUND DISTRIBUTION SYSTEM COMPONENTS

A. Comply with IEEE C2 grounding requirements.

B. Pad-Mounted Transformers and Switches: Install minimum two (2) ground rods and ground ring around the pad. Ground pad-mounted equipment and noncurrent-carrying metal items associated with substations by connecting them to underground cable and grounding electrodes.

Install tinned-copper conductor not less than No. 2 AWG for ground ring and for taps to equipment grounding terminals. Bury ground ring not less than 6 in. (150 mm) from the foundation.

3.3 EQUIPMENT GROUNDING

A. Install insulated equipment grounding conductors with all feeders and branch circuits.

B. Install insulated equipment grounding conductors with the following items, in addition to those required by NFPA 70:

1. Feeders and branch circuits.

2. Lighting circuits.

3. Receptacle circuits.

4. Single-phase motor and appliance branch circuits.

5. Three (3) phase motor and appliance branch circuits.

6. Flexible raceway runs.

C. Air-Duct Equipment Circuits: Install insulated equipment grounding conductor to duct-mounted electrical devices operating at 120-Volt and more, including air cleaners, heaters, dampers, humidifiers, and other duct electrical equipment. Bond conductor to each unit and to air duct and connected metallic piping.

D. Signal and Communication Equipment: For telephone, alarm, voice and data, and other communication equipment, provide No. 4 AWG minimum insulated grounding conductor in raceway from grounding electrode system to each service location, terminal cabinet, wiring closet, and central equipment location:

1. Service and Central Equipment Locations and Wiring Closets: Terminate grounding conductor on a 1/4 by 2 by 12 in. (6.4 mm x 50 mm x 300 mm) grounding bus.

2. Terminal Cabinets: Terminate grounding conductor on cabinet grounding terminal.

E. Metal Poles Supporting Outdoor Lighting Fixtures: Install grounding electrode and a separate insulated equipment grounding conductor in addition to grounding conductor installed with branch-circuit conductors.

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3.4 INSTALLATION

A. The Contractor shall furnish and install all grounding shown on the plans and/or as may be necessary or required to make a complete grounding system as required by the latest National Electrical Code (NFPA 70) in force. The reliability of the grounding system is dependent on careful, proper installation and choice of materials. Improper preparation of surfaces to be joined to make an electrical path, loose joints or corrosion can introduce impedance that will seriously impair the ability of the ground path to protect personnel and equipment and to absorb transients that can cause noise in communications circuits.

B. 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.

C. Ground Rods: Drive rods until tops are 2 in. (50 mm) below finished floor or 24 in. (600 mm) below 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 and one-half-rod (1 1/2) length from each other and located at least the same distance from other grounding electrodes, and connect to the service grounding electrode conductor.

D. Bonding Straps and Jumpers: Install in locations accessible for inspection and maintenance, except where routed through short lengths of conduit:

1. Bond all grounding systems together.

2. Bonding to Structure: Bond straps directly to basic structure, taking care not to penetrate any adjacent parts.

3. Bonding to Equipment Mounted on Vibration Isolation Hangers and Supports: Install so vibration is not transmitted to rigidly mounted equipment.

4. Use exothermic-welded connectors for outdoor locations, but if a disconnect-type connection is required, use a bolted clamp.

E. 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.

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F. 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.

G. 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 ft (18,300 mm) apart. Bond structural steel system to electrical ground system.

H. All bolted or mechanical connections shall be coated with a corrosion preventative compound before joining, Dearborn Chemical Company “No-Oxide A” compound or equal.

I. Metallic surfaces to be joined shall be prepared by the removal of all non-conductive material, per 2005 National Electrical Code Article 250-12. All copper bus bars must be cleaned prior to making connections to remove surface oxidation.

J. Raceway fittings shall be made up tight to provide a permanent low impedance path for all circuits.

K. All connections between the different types of grounding conductors above grade shall be made using UL-listed double compression crimp type connectors or UL-listed bolted ground connectors. For ground connections to enclosures, cases and frames of electrical equipment not supplied with ground lugs the Contractor shall drill required holes for mounting a bolted ground connector. All bolted ground connectors shall be Burndy, Thomas and Betts, or equal. Tighten connections to comply with tightening torques in UL Standard 486A to assure permanent and effective grounding.

L. All metal equipment enclosures, conduits, cabinets, boxes, receptacles, motors, etc. shall be bonded to the respective grounding system. Provide grounding bushings at all conduits entering service entrance equipment (meter bases, service disconnects, service panelboards, etc.) and distribution panels or load centers and ground wire from bushing to ground bus in the respective service entrance equipment or distribution panel.

M. The equipment ground wire from equipment shall not be smaller than allowed by 2005 NEC Table 250-122 “Minimum Size Conductors or Grounding Raceway and Equipment.” When conductors are adjusted in size to compensate for voltage drop, equipment-grounding conductors shall be adjusted proportionately according to circular mil area. All equipment ground wires shall be copper either bare or insulated green in color. Where the equipment grounding conductors are insulated, they shall be identified by the color green and shall be the same insulation type as the phase conductors.

N. Do not use grounded current return conductors (neutral) for equipment grounding. Connect common system grounded conductor (neutral) to ground at the supply side of the service disconnect unit only.

O. Bond the main electrical service neutral to ground at the main service disconnect. Bond the service neutral to ground at one location only per the National Electrical Code. A grounding connection shall not be made to any neutral circuit conductor on the load side of the service disconnecting means, except as permitted by 2005 NEC 250-24.

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P. The secondary neutral of all transformers (separately derived system transformers) shall be grounded in accordance with National Electrical Code. The respective grounding electrode conductor shall be connected to the neutral point of the transformer between the transformer and the output disconnect means. Size of the grounding electrode conductor shall be in accordance with 2005 NEC Article 250-66 and Table 250-66 unless shown larger on the drawings. A bond shall be provided between the neutral and transformer case, or other metal that is part of the AC equipment grounding system, so as to complete a circuit for fault current to the transformer winding from the AC equipment grounding system. Size of the neutral bonding conductor shall be in accordance with 2005 NEC Article 250-102.

Q. All exterior metal conduit, where not electrically continuous because of non-metallic junction boxes, etc., shall be bonded to all other metal conduit in the respective duct run, and at each end, with a copper bonding jumper sized in conformance with 1999 NEC 250-102. Where metal conduits terminate in an enclosure (such as a motor control center, switchboard, etc) where there is not electrical continuity with the conduit and the respective enclosure, provide a bonding jumper from the respective enclosure ground bus to the conduit sized per 2005 NEC 250-102.

R. It is the intent of this specification that all motor frames, pump bases electrical equipment enclosures, panel housings, conduits, boxes, etc. have a continuous copper wire ground connection and shall be positively bonded to the respective grounding system. Conduit connectors will not be considered as adequate grounding.

S. Provide a positive ground bond for all outlet boxes, electrical equipment enclosures, grounding receptacles, toggle switches, etc. install a grounding conductor in all wire and cable raceways.

Ground conductor to have 600-Volt insulation and be identified by a continuous green color coating. They shall be used solely for grounding purposes and be entirely separate form white grounded neutral conductor, except at supply side of service disconnecting means, where grounding and neutral systems are to be connected to service ground.

T. Provide all boxes for proposed outlets, switches, circuit breakers, etc. with grounding screws.

Provide all panelboard, switchgear, etc., enclosures with grounding bars with individual screws, lugs, clamps, etc., for each of the grounding conductors that enter their respective enclosures.

U. Each and all grounded cased and metal parts associated with electrical equipment shall be tested for continuity of connection with ground bus system by Contractor in presence of Contracting Officer.

V. All connections between the different types of grounding conductors above grade shall be made using bolted ground connectors. Ground lugs shall be provided in all enclosures and wiring termination junction boxes. Equipment grounds and grounding conductor shall be connected to these ground lugs. For ground connections to enclosures, cases and frames of electrical equipment not supplied with ground lugs the Contractor shall drill required holes for mounting a bolted ground connector. All bolted ground connectors shall be Burndy, or equal.

W. Provide grounding bushings at all conduits entering Service Entrance Disconnect Enclosure and bare ground wire from bushing to ground bus in the Service Entrance Disconnect Enclosure.

X. Bond all noncurrent-carrying parts of equipment to ground system.

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Y. Install grounding electrode conductors and separate ground conductors in Schedule 40 conduit or exposed where acceptable to local codes. Where grounding electrode conductors or individual ground conductors are run in PVC conduit, Do Not completely encircle conduit with ferrous and/or magnetic materials. Use non-metallic reinforced fiberglass strut support. Where metal conduit clamps are installed, use nylon bolts, nuts, washers and spacers to interrupt a complete metallic path from encircling the conduit.

Z. Where motors are connected to conduit system with flexible conduit section, install grounding conductor in flexible section.

AA. Provide ground rod at each exterior pole light fixture and connect to base of pole.

3.5 FIELD QUALITY CONTROL

A. 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. 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 (2) 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.

3. Prepare dimensioned drawings locating each, 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.

B. Report measured ground resistances that exceed the following values:

1. Power and Lighting Equipment or System with Capacity 500 kVA and Less: 10 ohms.

2. Power and Lighting Equipment or System with Capacity 500 to 1000 kVA: 5 ohms.

C. Excessive Ground Resistance: If resistance to ground exceeds specified values, notify Contracting Officer promptly and include recommendations to reduce ground resistance.

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