Attachment 3 - 260525 GROUNDING-BONDING-ELEC-SYSTEMS JAN19.pdf

JUBA ELECTRICAL UPGRADE DEVELOPMENT July 13, 2020

JUBA SOUTH SUDAN Issued for Bid

GROUNDING AND BONDING SECTION 260525 - 1

SECTION 260525 - GROUNDING AND BONDING FOR ELECTRICAL SYSTEMS

PART 1 - GENERAL

1.1 SUMMARY

A. This Section includes grounding of electrical systems and equipment. Grounding requirements specified in this Section may be supplemented by special requirements of systems described in other Sections.

B. Related Sections include the following:

1. Section 076205 “Sheet Metal Flashing and Trim.”

2. Section 263105 “Solar Photovoltaic Systems.”

3. Section 264115 “Lightning Protection System.”

4. Section 270526 “Grounding and Bonding for Communications Systems.”

5. Section 331112 “Site Water Distribution Piping” for water service and water meter piping.

6. Section 337105 "Underground Ducts and Raceways" for ground test wells.

1.2 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 Article on FIELD QUALITY CONTROL, including the following:

1. Test wells.

2. Ground rods.

3. Ground rings.

4. Grounding arrangements and connections for separately derived systems.

5. 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: Include the following in operation and maintenance manuals:

1. Instructions for periodic testing and inspection of grounding features at test wells 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.

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1.3 QUALITY ASSURANCE

A. Grounding & Lightning Protection System. The system shall meet the requirements as listed on the plan drawings for UL 96.

B. Testing Agency Qualifications: Testing agency as defined by OSHA in 29 CFR 1910.7 or a member company of the InterNational Electrical Testing Association (NETA) and that is acceptable to Contracting Officer based upon input from OBO/PDCS/DE/EE.

1. Testing Agency's Field Supervisor: Person currently certified by NETA to supervise on-site testing specified in Article on FIELD QUALITY CONTROL.

C. Comply with UL 467.

D. Comply with the OBO Electrical Code (NFPA 70, “National Electrical Code” as amended by

OBO).

1. Electrical Components, Devices, and Accessories: Listed and labeled in accordance with

Chapter 1 of the OBO Electrical Code by testing agency acceptable to Contracting

Officer/COR based upon input from OBO/PDCS/DE/EE, and marked for intended use.

E. For overhead-line construction and medium-voltage underground construction, comply with

IEEE C2.

F. Comply with NFPA 780 “ Standard for the Installation of Lightning Protection Systems.”

G. Comply with UL 96 when interconnecting with lightning protection system; see Section

264115 “Lightning Protection System.”

PART 2 - PRODUCTS

2.1 GROUNDING CONDUCTORS

A. For insulated copper conductors, comply with Section 260518 "Low-Voltage Electrical Power

Conductors and Cables."

B. Equipment Grounding Conductors: Insulated with green-colored insulation.

C. Isolated Ground Conductors: Insulated with green-colored insulation with yellow stripe. On feeders with isolated ground, use colored tape, alternating bands of green and yellow tape to provide a minimum of three bands of green and two bands of yellow.

D. Grounding Electrode Conductors: Stranded copper cable.

E. Underground Conductors: Bare copper, tinned, stranded, unless otherwise indicated.

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F. Bare Copper Conductors: Comply with the following:

1. Solid Conductors: ASTM B 3.

2. Assembly of Stranded Conductors: ASTM B 8.

3. Tinned Conductors: ASTM B 33.

G. Copper Bonding Conductors: As follows:

1. Bonding Cable: 95 mm2 copper conductor.

2. Bonding Conductor: 25 mm2 or 16 mm2, stranded copper conductor.

3. Bonding Jumper: Bare copper tape, braided bare copper conductors, terminated with copper ferrules; 42 mm wide and 1.5 mm thick.

4. Tinned Bonding Jumper: Tinned-copper tape, braided copper conductors, terminated with copper ferrules; 42 mm wide and 1.5 mm thick.

H. Grounding Bus: Bare, annealed copper bars of rectangular cross section 6 x 50 mm, with insulators as shown on drawings.

2.2 CONNECTOR PRODUCTS

A. Comply with IEEE 837 and UL 467; listed for use for specific types, sizes, and combinations of conductors and connected items.

B. Welded Connectors: Exothermic-welded type, in kit form, and selected per manufacturer's written instructions.

2.3 GROUNDING ELECTRODES

A. Ground Rods: Copper-clad steel.

B. Ground Rods

1. Size: 20 mm diameter by 3000 mm long.

C. Test Wells: Provide handholes as specified in Section 337105 "Underground Ducts and

Raceways."

PART 3 - EXECUTION

3.1 APPLICATION

A. In raceways, use insulated equipment-grounding conductors.

B. Connections: Connections shall be made by one of the following methods:

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1. Exothermic-Welded Connections: Use for connections to structural steel and for underground connections, except those at test wells.

2. Irreversible Mechanical Connections (IMC): Use for any connections. Mechanical connection shall be made by specialized tool for irreversible mechanical connections which shall apply permanent marking to connector to identify that connection was made.

C. Equipment Grounding Conductor Terminations: Exothermic or irreversible Mechanical connection.

D. Ground Rod Clamps at Test Wells: Use bolted pressure clamps with at least two bolts.

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

1. Use insulated spacer; space 25 mm from wall and support from wall 150 mm above finished floor, unless otherwise indicated.

2. At doors, route the bus up to the top of the doorframe, across the top of the doorway, and down to the specified height above the floor.

F. Underground Grounding Conductors: Use bare-copper conductor, 95 mm2 minimum. Bury at least 450 mm below grade or bury 300 mm above duct bank when installed as part of the duct bank.

G. Conductor Terminations and Connections:

1. Pipe and Equipment Grounding Conductor Terminations: Bolted connectors.

2. Underground Connections: Welded connectors or IMC, 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.

3.2 EQUIPMENT GROUNDING CONDUCTORS

A. Comply with Article 250 of the OBO Electrical Code for types, sizes, and quantities of equipment grounding conductors, unless more restrictive specific types, larger sizes, or more conductors are indicated on Drawings.

B. Install equipment grounding conductors in all feeders and circuits.

C. Install insulated equipment grounding conductor with circuit conductors for the following items, in addition to those required by the OBO Electrical Code:

1. Feeders and branch circuits.

2. Lighting circuits.

3. Receptacle circuits.

4. Single-phase motor and appliance branch circuits.

5. Three-phase motor and appliance branch circuits.

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6. Flexible raceway runs.

7. Armored and metal-clad cable runs.

8. X-Ray equipment circuits

9. Computer outlet circuits

D. Busway Supply Circuits: Install insulated equipment grounding conductor from the grounding bus in the switchgear, switchboard, or distribution panel to equipment grounding bar terminal on busway.

E. Isolated Grounding Receptacle Circuits: Install an insulated equipment grounding conductor connected to the receptacle grounding terminal. Isolate grounding conductor from raceway and from panelboard grounding terminals. Terminate at equipment grounding conductor terminal of the applicable derived system or service, unless otherwise indicated.

F. Isolated Equipment Enclosure Circuits: For designated equipment supplied by a branch circuit or feeder, isolate equipment enclosure from supply raceway with a nonmetallic raceway fitting listed for the purpose. Install fitting where raceway enters enclosure, and install a separate equipment grounding conductor. Isolate equipment grounding conductor from raceway and from panelboard grounding terminals. Terminate at equipment grounding conductor terminal of the applicable derived system or service, unless otherwise indicated.

G. Nonmetallic Raceways: Install an equipment grounding conductor in nonmetallic raceways unless they are designated for communications cables.

H. Air-Duct Equipment Circuits: Install an equipment grounding conductor to duct-mounted electrical devices operating at 220 V or higher, including air cleaners and heaters. Bond conductor to each unit and to air duct.

I. Water Heater, Heat-Tracing, and Antifrost Heating Cables: Install a separate equipment grounding conductor to each electric water heater, heat-tracing, and antifrost heating cable.

Bond conductor to heater units, piping, connected equipment, and components.

J. Signal and Communication Systems: For alarm, voice, data, and other communication systems, provide insulated grounding conductor in raceway from grounding electrode system to each service location, terminal cabinet, telecommunications rooms, and central equipment location.

1. Service and Central Equipment Locations and Wiring Closets: Terminate grounding conductor on a 6.0 mm thick by 50 mm high by 300 mm long grounding bus.

2. Terminal Cabinets: Terminate grounding conductor on cabinet grounding bus bar/terminal.

K. Metal Poles Supporting Outdoor Lighting Fixtures: Provide a grounding electrode in addition to installing a separate equipment grounding conductor with supply branch-circuit conductors.

L. Common Ground Bonding with Lightning Protection System: Bond electrical power system ground directly to lightning protection system grounding conductor at closest point to electrical service grounding electrode. Use bonding conductor sized the same as power system grounding electrode conductor, and install in conduit. See Section 264115 “Lightning

Protection System.”

M. Photovoltaic Systems: For system grounding connection, use of fine stranded grounding conductor is not permitted; refer to Section 263105 “Solar Photovoltaic Systems.”

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3.3 COUNTERPOISE

A. Ground the steel framework of the building with a driven ground rod at the base of every corner column and at intermediate exterior columns at distances not more than 18 m apart. Provide a grounding conductor (counterpoise), electrically connected to each ground rod and to each steel column, extending around the perimeter of the building. Use tinned-copper conductor not less than 95 mm2 for counterpoise and for tap to building steel. Bury counterpoise not less than 450 mm below grade and 600 mm from building foundation.

3.4 INSTALLATION

A. Ground Rods: [Install ground rods as indicated on the drawings.] [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.]

1. Drive ground rods until tops are 300 mm below finished floor or final grade, unless otherwise indicated.

2. Interconnect ground rods with grounding electrode conductors. Use exothermic welds, except at test wells and as otherwise indicated. Make connections without exposing steel or damaging copper coating.

B. Grounding Conductors: Route along shortest and straightest paths possible, unless otherwise indicated. Avoid obstructing access or placing conductors where they may be subjected to strain, impact, or damage.

C. Bonding Straps and Jumpers: Install so vibration by equipment mounted on vibration isolation hangers and supports is not transmitted to rigidly mounted equipment. Use exothermic-welded connectors or IMC for outdoor locations, unless a disconnect-type connection is required; then, use a bolted clamp. Bond straps directly to the basic structure taking care not to penetrate any adjacent parts. Install straps only in locations accessible for maintenance.

D. Metal Water Service Pipe: Provide insulated copper grounding conductors, in conduit, from building's main service equipment, or grounding bus, to main metal water service entrances to building; see Section 331112 “Site Water Distribution Piping.” Connect grounding conductors to main metal water service pipes by grounding clamp connectors. Where a dielectric main water fitting is installed, connect grounding conductor to street side of fitting. Bond metal grounding conductor conduit or sleeve to conductor at each end.

E. Water Meter Piping: Use braided-type bonding jumpers to electrically bypass water meters.

Connect to pipe with grounding clamp connectors. See Section 331112 “Site Water

Distribution Piping.”

F. Bond roof metal materials to equipment grounding conductors or lightning protection system;

see Section 076205 “Sheet Metal Flashing and Trim.”

G. Bond interior metal piping systems and metal air ducts to equipment grounding conductors of associated pumps, fans, blowers, electric heaters, and air cleaners. Use braided-type bonding straps.

H. Bond each aboveground portion of gas piping system upstream from equipment shutoff valve.

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I. Install one test well for each service at the ground rod electrically closest to the service entrance. Set top of well flush with finished grade or floor.

J. [Under Ground (Concrete-Encased Grounding Electrode): Fabricate according to the

OBO Electrical Code using a minimum of 6.0 m of bare copper conductor not smaller than 25 mm2. If concrete foundation is less than 6.0 m long, coil excess conductor within the base of the foundation. Bond grounding conductor to reinforcing steel in at least four locations and to anchor bolts. Extend grounding conductor below grade and connect to building grounding grid or to a grounding electrode external to concrete.]

3.5 CONNECTIONS

A. General: Make connections so galvanic action or electrolysis possibility is minimized. Select connectors, connection hardware, conductors, and connection methods so metals in direct contact will be galvanically compatible.

1. Use electroplated or hot-tin-coated materials to ensure high conductivity and to make contact points closer to order of galvanic series.

2. Make connections with clean, bare metal at points of contact.

3. Make aluminum-to-steel connections with bi-metal stainless-steel separators and mechanical clamps approved for application.

4. Make aluminum-to-galvanized steel connections with bi-metal tin-plated copper jumpers and mechanical clamps approved for application.

5. Coat and seal connections having dissimilar metals with inert material to prevent future penetration of moisture to contact surfaces.

B. Exothermic-Welded Connections: Comply with manufacturer's written instructions. Welds that are puffed up or that show convex surface indicating improper cleaning are not acceptable.

C. Irreversible Mechanical Connection (IMC): Use hydraulic compression tools to provide correct circumferential pressure for compression connectors. Use tools and dies recommended by connector manufacturer. Provide embossing die code or other standard method to make visible indication that each connector has been adequately compressed on grounding conductor.

D. Equipment Grounding Conductor Terminations: For 10 mm2 and larger, use pressure-type grounding lugs. 10 mm2 and smaller grounding conductors may be terminated with winged pressure-type connectors.

E. Noncontact Metal Raceway Terminations: If metallic raceways terminate at metal housings without mechanical and electrical connection to housing, terminate each conduit with a grounding bushing. Connect grounding bushings with a bare grounding conductor to grounding bus or terminal in housing. Bond electrically noncontinuous conduits at entrances and exits with grounding bushings and bare grounding conductors, unless otherwise indicated.

F. Connections at Test Wells: Use compression-type connectors on conductors and make bolted-and clamped-type connections between conductors and ground rods.

G. Tighten screws and bolts for grounding and bonding connectors and terminals according to manufacturer's published torque-tightening values. If manufacturer's torque values are not indicated, use those specified in UL 486A.

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H. Moisture Protection: If insulated grounding conductors are connected to ground rods or grounding buses, insulate entire area of connection and seal against moisture penetration of insulation and cable.

3.6 UNDERGROUND DISTRIBUTION SYSTEM GROUNDING

A. Duct Banks: Install grounding conductor with at least 50 percent ampacity of largest phase conductor in duct bank. See Section 337105 “Underground Ducts and Raceways.”

B. Manholes and Handholes: Install a driven ground rod close to wall and set rod depth so

100 mm will extend above finished floor. If necessary, install ground rod before manhole is placed and provide a 70 mm2 bare, tinned-copper conductor from ground rod into manhole through a waterproof sleeve in manhole wall. Protect ground rods passing through concrete floor with a double wrapping of pressure-sensitive tape or heat-shrunk insulating sleeve from

50 mm above to 150 mm below concrete. Seal floor opening with waterproof, nonshrink grout.

C. Connections to Manhole Components: Connect exposed-metal parts, such as inserts, cable racks, pulling irons, ladders, and cable shields within each manhole or handhole, to ground rod or grounding conductor. Make connections with 25 mm2 minimum, stranded, hard-drawn copper conductor. Train conductors level or plumb around corners and fasten to manhole walls. Connect to cable armor and cable shields as recommended by manufacturer of splicing and termination kits.

D. Pad-Mounted Transformers and Switches: Install two ground rods and counterpoise circling pad. Ground pad-mounted equipment and noncurrent-carrying metal items associated with substations by connecting them to underground cable and grounding electrodes. Use tinned-copper conductor not less than 35 mm2 for counterpoise and for taps to equipment ground pad.

Bury counterpoise not less than 600 mm below grade and 150 mm from the foundation.

3.7 FIELD QUALITY CONTROL

A. Testing: Engage a qualified testing agency to perform the following field quality-control testing:

B. Testing: Perform the following field quality-control testing:

1. After installing grounding system but before permanent electrical circuitry has been energized, test for compliance with requirements.

2. Test completed grounding system at each building electric service entrance, electric/telecom rooms, generator system, buildings and lightning protection system where a maximum ground-resistance level is specified, at service disconnect enclosure grounding terminal, and at ground test wells. Tests at each ground rod before any conductors are connected are not required if a clamp-on ground tester is used. Measure ground resistance not less than two full days after the last trace of precipitation, and without the 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. Perform tests, by the fall-of-potential method according to IEEE 81.

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3. Provide 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. Maximum value of acceptable system ground resistance is 10 ohms.

4. Excessive Ground Resistance: If resistance to ground exceeds specified values, drive additional ground rods until resistance meets specified values.

END OF SECTION 260525