28 05 26.00 40 GROUNDING AND BONDING FOR ELECTRONIC SAFETY A.doc

SECTION 28 05 26.00 40

GROUNDING AND BONDING FOR ELECTRONIC SAFETY AND SECURITY

PART 1 GENERAL

1.1 REFERENCES

1.1.1 The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by the basic designation only. Unless other wise noted, the latest published version and/or revision shall be used.

1.1.1.1 AMERICAN WELDING SOCIETY (AWS)

a. AWS A5.8 Specification for Filler Metals for Brazing and Braze Welding

1.1.1.2 ASTM INTERNATIONAL (ASTM)

a. ASTM B 3 Standard Specification for Soft or Annealed Copper Wire

1.1.1.3 INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS (IEEE)

a. IEEE Std 81 Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Ground System (Part 1)Normal Measurements

1.1.1.4 NATIONAL FIRE PROTECTION ASSOCIATION (NFPA)

a. NFPA 70 National Electrical Code

1.1.1.5 U.S. DEPARTMENT OF DEFENSE (DOD)

a. MIL-STD-889 (Rev B, Notice 3) Dissimilar Metals

1.1.1.6 UNDERWRITERS LABORATORIES (UL)

a. UL 467 Standard for Grounding and Bonding Equipment

1.2 GENERAL REQUIREMENTS

1.2.1 Section 26 00 00.00 20 Basic Electrical Materials and Methods applies to work specified in this section.

1.3 SUBMITTALS

1.3.1 Government approval may be required on any of the following items. Items requiring submittals will be listed on the Submittal Register. Provide copies of all submittals per the requirements in Section 01 33 00, Submittal Procedures, or as listed on the Submittal Register.

1.3.1.1 SD-01 Preconstruction Submittals

a. Material, equipment, and fixture lists shall be submitted for Grounding Systems including manufacturer's style or catalog numbers, specification and drawing reference numbers, warranty information, and fabrication site information.

1.3.1.2 SD-02 Shop Drawings

a. Record Drawings shall be submitted in accordance with paragraph entitled, "Drawings," of this section.

1.3.1.3 SD-03 Product Data

1.3.1.4 Equipment and performance data shall be submitted for the following items including life, test, system functional flows, safety features, and mechanical automated details.

a. Manufacturer's catalog data shall also be submitted for the following items:

(1) Ground Rods

(2) Ground Wires

(3) Connectors and Fasteners

(4) Bonding

1.3.1.5 SD-06 Test Reports

a. Test Reports shall be submitted for the following tests on grounding systems in accordance with the paragraph entitled, "Field Tests," of this section. Report shall include certified record of ground-resistance tests on each driven ground rod, ground rod assembly, and other grounding electrodes. Record shall include the number of rods driven and their depth at each location to meet the required resistance-to-ground measurements specified. A statement shall be included describing the condition of the soil at the time of measurement.

(1) Bond Resistance Test

(2) Ground Resistance Tests

(3) Ground Isolation Test

(4) Continuity Isolation Test

1.3.1.6 SD-08 Manufacturer's Instructions

a. Manufacturer's instructions shall be submitted for the Grounding Systems including special provisions required to install equipment components and system packages. Special notices shall detail impedances, hazards and safety precautions.

1.4 DRAWINGS

1.4.1 Record Drawings shall indicate the location of ground rods, mats, grids, building ground bus, supplementary grounding electrodes, steel building columns, and other metal structures connected to the grounding system.

1.4.2 Location of each ground rod and ground-rod assembly and other grounding electrodes shall be identified by letter in alphabetical order and keyed to the record of ground-resistance tests.

PART 2 PRODUCTS

2.1 GROUND RODS

2.1.1 Ground rods shall be copper-clad steel rods not less than 3/4 inch in diameter and not less than 10-feet long per section. Ground rods shall be clean and smooth and have a cone-shaped point on the first section and shall be die-stamped near the top with the name or trademark of the manufacturer and the length of the rod in feet.

2.2 GROUND WIRES

2.2.1 Ground and bond wires for substations, main panels and distribution points, and ground rod connections shall be annealed bare copper conforming to ASTM B 3, stranded, with 98 percent conductivity. Wire size shall be in accordance with the grounding requirements of NFPA 70.

2.2.2 Ground wires for equipment receptacles for noncurrent carrying hardware, installed in conduit shall be soft drawn copper, in accordance with ASTM B 3, stranded, with green insulation. Wire size shall be as noted.

2.3 CONNECTORS AND FASTENERS

2.3.1 Grounding and bonding fasteners and connectors shall conform to the requirements of UL 467.

2.3.2 Grounding and bonding fasteners shall be copper or bronze as applicable.

2.3.3 Bonding straps and jumpers shall be copper and shall have a cross-sectional area of not less than No. 6 AWG. Bonding straps and jumpers for shock-mounted devices with joints shall be made of woven-wire braid flexible stranded wire.

PART 3 EXECUTION

3.1 BONDING AND GROUNDING

3.1.1 Bonding and grounding requirements shall be in accordance with NFPA 70.

3.2 GROUNDING ELECTRODES

3.2.1 Grounding electrodes shall include ground rods installed expressly for grounding systems.

3.2.2 Minimum ground rod section shall be 10 feet. Sections shall be threaded together and exothermically fusion welded.

3.2.3 Ground rods shall be installed so that the top of the rod is not less than 6 inches below finished grade or flush with grade when installed in an inspection well.

3.3 GROUND GRIDS

3.3.1 Ground grids shall consist of a series of ground rods installed with interconnecting grounding conductors between ground rods. Ground rods shall be spaced as noted.

3.3.2 Ground grid shall be buried not less than 18 inches below the finish grade. Grounding conductors shall be not less than No. 4/0 AWG and shall be exothermically fusion welded together at crossover points and to ground rods.

3.4 BUILDING GROUNDS

3.4.1 Steel framework of the building shall be grounded with a driven ground rod at the base of every corner column and intermediate exterior columns at distances not greater than 60-feet apart. Grounding conductor shall be electrically connected to each ground rod and to each steel column and shall extend around the perimeter of the building. Grounding-conductor loop around the perimeter of the building shall be not less than No. 4/0 AWG. Tap connections from the ground loop to the building steel shall be not less than 4/0 AWG.

3.4.2 Building ground shall be buried not less than 18 inches below grade and 5 feet from the building foundation. Interconnecting grounding conductor between ground grid and building grounds shall be not less than No. 4/0 AWG.

3.5 EQUIPMENT GROUNDING

3.5.1 Metallic raceway systems shall have electrical continuity with equipment individually and directly connected to the building ground, independent of the raceway system.

3.5.2 Enclosures for panelboards shall be individually and directly connected to the building ground. Grounding conductor shall be not less than indicated and shall be connected from the building ground to a copper ground-bus terminal strip located in each panelboard.

3.5.3 Polarized receptacles, lighting fixtures, and equipment enclosures shall be grounded with an identified (green color) insulated conductor, not smaller than No. 12 AWG, connected to the branch circuit ground-bus terminal strip. Ground-bus terminal strip in each panelboard enclosure shall be isolated and independent of the system neutral terminal strip.

3.5.4 Indoor substations, transformers, switchboard frames, switchgear assemblies, motors, motor control centers, air compressors, air handlers, refrigerated air dryers, generators, frames and tracks of cranes, shall be individually and directly connected and grounded to the building ground. Current-carrying capacity of the grounding conductor shall be the same as the current-carrying capacity of the power conductors for circuits utilizing power lines size No. 2 AWG and smaller. For circuits with power wiring larger than No. 2 AWG, the grounding conductor shall be in accordance with NFPA 70, except that the grounding conductor shall be not smaller than No. 2 AWG.

3.5.5 Noncurrent carrying metallic parts of electrical equipment, including metallic cable sheaths, conduit, raceways, and electrical structural members, shall be bonded together and connected to the ground grid or ground connection rods.

3.5.6 Secure ground systems shall be installed for power and instrumentation. Each system shall be independently connected to the building counterpoise as shown.

3.5.7 Secure ground systems shall consist of unspliced ground wires in individual welded or epoxied conduit runs from the secure area to the building counterpoise. Welding and epoxying shall conform to Section 26 27 26.00 40 Wiring Devices.

3.6 GROUNDING CONNECTIONS

3.6.1 Ground connections shall be bonded connections in accordance with paragraph entitled, "Bonding."

3.6.2 Ground connections that are buried or in inaccessible locations shall be welded.

3.6.3 Connections in accessible locations shall be bolted. Connections to steel building columns in accessible locations shall be cast-copper-alloy clamp lugs exothermically fusion-welded to the structure.

3.6.4 Ground connection surfaces shall be cleaned and greased and foreign matter removed. Clad material shall not be penetrated in the cleaning process. Connection shall be made between like metals where possible. Where dissimilar metals are welded, brazed, or clamped, the weld kit manufacturer's instructions shall be followed. Connections between dissimilar metals shall not produce galvanic action in accordance with MIL-STD-889.

3.7 BONDING

3.7.1 Type of Bonds

3.7.1.1 Bonding of metal surfaces shall be accomplished by welding or clamping.

3.7.1.2 Welding

a. Welding shall be by the exothermic process. Welding procedure shall include the proper mold and powder charge and shall conform to the manufacturer's recommendations.

b. Welding processes shall be of the exothermic fusion type that will make a connection without corroding or loosening. Process shall join all strands and shall not cause the parts to be damaged or weakened. Completed connection or joint shall be equal or larger in size than the conductors joined and shall have the same current-carrying capacity as the largest conductor. Buried ground connections shall be painted with a bitumastic paint.

3.7.1.3 Clamping

a. In external locations, clamping shall be used only where a disconnect type of connection is required. Connection device may utilize spring-loaded jaws or threaded fasteners. Device shall be constructed such that positive contact pressure shall be maintained at all times. Machine bolts with spring-type lockwashers shall be used.

3.7.2 Cleaning of Bonding Surfaces

a. Surfaces that comprise the bond shall be thoroughly cleaned before joining. An appropriate abrasive shall be applied with a gentle and uniform pressure to ensure a smooth and uniform surface. Excessive metal shall not be removed from the surface. Clad metals shall be cleaned in such a manner that the cladding material is not penetrated by the cleaning process. Bare metal shall then be cleaned with an appropriate solvent to remove any grease, oil, dirt, corrosion preventives, and other contaminants. Bond to the cleaned area shall be made within one hour after cleaning. Joint shall be sealed and the exposed surfaces refinished within two hours of exposure to prevent oxidation. When additional time is required, a corrosion preventive compound shall be applied until the area can be refinished.

3.7.3 Bonding Straps and Jumpers

3.7.3.1 Jumpers shall be installed such that the vibration by the shock-mounted device shall not change its electrical characteristics.

3.7.3.2 Bonds shall be welded for outdoor locations unless a disconnect type of connection is required. When a disconnect is required, clamping with bolts shall be used. A tooth-type lockwasher shall be inserted between the strap and metallic member for each bolt.

3.7.3.3 Straps shall be bonded directly to the basic structure and shall not penetrate any adjacent parts. Straps shall be installed in an area that is accessible for maintenance.

3.7.3.4 Single straps shall be used for the bonds and shall be installed such that they will not restrict movement of structural members. Two or more straps shall not be connected in series.

3.7.3.5 Straps shall be installed such that they will not weaken structural members to which they are attached.

3.7.4 Equipment and Enclosure Bonding

3.7.4.1 Each metallic enclosure and all electrical equipment shall be bonded to ground. At least one copper connection shall be made from the system ground point to one or more enclosures in the area such that all enclosures and equipment provide a low-impedance path to ground when properly bonded together.

3.7.5 Bonding of Conduit and Raceway Systems

3.7.5.1 Bond all metal conduit, fittings, junction boxes, outlet boxes, armored and metal sheathed cable, and other raceways. Care shall be taken to ensure adequate electrical contact at the joints and terminations.

3.7.5.2 Rigid Metal Conduit and Terminations

a. Threaded connections must be wrench-tight and there shall be no exposed threads. All ends of the conduit shall be reamed to remove burrs and rough edges. Conduits entering boxes and enclosures shall be bonded to the box with locknuts and grounding-type bushings. Locknuts that gouge into the metal box when tightened are not acceptable.

b. Conduit systems that are interrupted by PVC dielectric links shall be bonded separately on either side of the link. Dielectric link shall not be jumpered.

3.7.5.3 Flexible Metal Conduit

a. Flexible conduit shall have an integral grounding conductor.

3.7.6 Cable Tray Bonding

3.7.6.1 Cable tray sections shall be bonded together. Cable tray sections in tandem assembly shall be considered as having electrical continuity when these sections are bonded with the appropriate bolts. Bond straps shall be installed across expansion joints. Cable trays shall be bonded to the building ground system.

3.7.7 Protection of Finished Bonds

3.7.7.1 Finished bonds shall be protected by painting to match the original finish after the bond is made.

3.8 FIELD TESTS

3.8.1 The following tests shall be performed by the Contractor in the presence of the Contracting Officer.

3.8.1.1 Bond Resistance Test

a. Resistance of any bond connection shall not exceed 0.5 milliohm. Bonds that exceed this resistance shall be reworked by the Contractor at no additional cost to the Government.

3.8.1.2 Ground Resistance Tests

a. Grounding systems shall be tested for ground resistance. Total resistance from any point on the ground network to the building counterpoise shall not exceed 50 milliohms.

b. Ground resistance and counterpoise tests shall be made during dry weather, and no sooner than 48 hours after rainfall. Tests shall be conducted using the ratio method that measures the ratio of the resistance to earth of an auxiliary test electrode to the series resistance of the electrode under test and a second auxiliary electrode. Measurements shall be performed in accordance with IEEE Std 81.

c. Indicating instrument shall be self-contained and shall include a direct-current generator, synchronized current and potential reversers, crossed-current and potential coils, direct-reading ohmmeter, series resistors, and range-selector switch. Direct-reading ohmmeter shall be calibrated for ranges of 0 to 20 ohms and 0 to 200 ohms.

d. Auxiliary grounding electrodes shall be placed in accordance with instrument manufacturer's recommendations but not less than 20 feet apart, in accordance with IEEE Std 81.

3.8.1.3 Ground Isolation Test

a. Ground systems shall be tested for isolation from other ground systems.

3.8.1.4 Continuity Isolation Test

a. Continuity test shall be performed on all power receptacles to ensure that the ground terminals are properly grounded to the facility ground system.

END OF SECTION 28 05 26.00 40

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28 05 26.00 40-1 03/16/10