16450 GROUNDING ************************************************************************************************************* SPECIFIER: CSI MasterFormat 2004 number: 26 05 26 An optional keynote to the Drawings follows major product titles, for A/Es using National CAD Standard. ************************************************************************************************************* PART 1 GENERAL 1.1 SUMMARY A. Related Work: 1. 16120 - Wire and Cable. 2. 16425 Switch Board. 3. 16112 Conduits, Fittings and Supports. 4. 16470 Panelboards. 5. 16460 - Dry Type Transformers 1.2 SYSTEM DESCRIPTION A. All materials shall be tested and listed by an OSHA approved Nationally Recognized Testing Laboratory (NRTL). 1.3 SUBMITTALS A. Submit manufacturer's literature giving materials, finishes, accessories, and installations where required. B. Ground resistance tests. 1.4 QUALITY ASSURANCE A. Regulatory Requirements: Install a complete grounding system installation shall comply with Article 250 NFPA 70 Latest Edition of the National Electrical Code-(NEC). B. Coordination: Arrange with Plumbing Contractor to have the main metallic water line accessible for ground connection at point entrance to the building. The metallic water line shall be buried and have at least 20 feet in contact with earth. C. Maximum resistance to ground shall not exceed 5 ohms. Provide written report of acceptance test and performance verification to the A/E and M-DCPS. 1.5 SUBMITTALS A. Submit shop drawings and product data under provisions of Sections 01330, Submittals. 1.6 TESTS A. Submit under provisions of Section 01452, Testing and Inspecting Services. Project No. SPECIFICATION GUIDELINES 16450-1
B. Measure ground grid resistance with a Megger ground resistance tester, and install additional ground rods and conductors as required until resistance to ground does not exceed 5 ohms. 1. Testing and recording of results shall be by the Electrical Contractor in the presence of the A/E or his authorized agent. 2. Conduct test after the complete system has been fully grounded and under provisions of the latest editions of the N.E.C. and I.E.E.E. standard 142 recommended practice. PART 2 PRODUCTS 2.1 EQUIPMENT A. Grounding System. 1. Grounding system shall comply with ANSI C33.8, IEEE-81. 2. The electrical system and equipment shall be grounded according to the requirements of the NEC and as specified herewith. 3. The grounding conductor shall be an insulated copper wire of size indicated on drawings and following requirement of the NEC. 4. Where not indicated, the conductor shall be according to the requirements of the NEC except that minimum size shall be No.8 copper for system ground. 5. Inaccessible connections shall be made with the exothermic welding process using equipment manufactured by Burndy or Erico Products. 6. Accessible connections shall be made with multiple bolt silicon bronze connectors specifically designed and accepted for the connection to be made. 7. Connectors shall be as manufactured by Burndy or O.Z. Electric. 8. Grounding jumpers shall be provided across metal parts separated by nonconducting materials, such as conduits with expansion joints or when joined, so there is a high resistance at the joint connections. 9. Grounding electrical conductors shall not be buried directly in concrete. Provide a conduit sleeve where each cable passes through concrete. If buried in earth, they shall be tinned. 10. Grounding for the lightning protection system shall be as specified under "LIGHTNING PROTECTION SYSTEM" and as shown on the drawings. Lightning protection system shall be connected to the building grounding system as required by NEC article 250. 11. Refer to electrical drawings for additional grounding requirements. B. Grounding Source: 1. Grounding electrical system shall comply with NEC Article 250. All the grounding electrodes shall be bonded together. 2. Ground sources shall be connected to the 4" wide x 1/4" thick of necessary length (length to be determined by the number of ground terminals to be connected to the bus). Ground copper bus shall be mounted on insulating standoff on the switchgear room wall. Ground bus shall be complete with lugs for connecting grounding cables. Maximum resistance to ground shall be limited to 5 ohms. Additional ground rods shall be driven if required to maintain this level. 3. Maximum ground resistance to each of individual rods shall be 25 ohms or less. Project No. SPECIFICATION GUIDELINES 16450-2
4. Submit test results to the A/E and M-DCPS for acceptance indicating that these values have been met, using the fall of potential method as directed in IEEE latest Standards. C. System Grounds: Neutral bus and ground bus in switchgear shall be connected by means of an accepted bus link. D. Ground Rods: Copper clad steel not less than 3/4" in diameter, 10 feet long, driven full length into the earth. E. Cold Water Pipe: 1. Connection to cold water pipe shall be made by a suitable ground clamp. 2. If flanged pipes are encountered, connections shall be made with the lug bolted to the street side of the flange connection. F. Parts to be Grounded: Switchgear frame, panelboard frames, fittings, fixtures and devices, cable sheaths, neutral of transformers, boxes and raceways, motor frames, outdoor lighting poles, emergency generator set, non-current carrying parts of appliances and devices, and all other parts and equipment as required by NEC. Neutral wire shall never be used as grounding means. G. Conductor: Grounding cable shall be green insulated copper stranded cable, soft drawn or annealed, sized as indicated on drawings, from the main switchboard to each panel, power outlet, or load, except as specified for lighting branch circuits. PART 3 EXECUTION 3.1 POWER SYSTEM GROUNDING A. Supplement the grounded neutral of the secondary distribution system by an equipment grounding system. Arrange the equipment grounding system so that all non-current carrying items in close proximity with electrical circuits are maintained continuously at ground potential and provided with a low impedance path for ground fault currents. The system shall comply with the National Electric Code Article 250, modified as indicated and as specified. B. The basic grounding system utilize reinforcing bars in the footings of the building supplemented by two (2) ground rods in the Main Electrical Room and a connection to a cold water pipe, where required to meet the test requirements specified. C. Provide a green insulated copper ground conductor, in conduit, as shown to the main metallic water service entrance and connect to the supply side of same by means of ground clamps. The conduit shall be bonded to the ground conductor at each end. The use of PVC conduit for the green insulated copper ground conductor is acceptable only within the Main Electrical Room. D. Low voltage system neutrals: grounded at the related transformers to the feeder ground and to the nearest cold water line all in accordance with the National Electric Code requirements in Article 250. Project No. SPECIFICATION GUIDELINES 16450-3
3.2 COMMUNICATION GROUNDING A. Voice/Data: 1. Provide one (1) #6 from main ground bus to ground bus on telephone equipment board. B. Fire Alarm and Detection: 2. Provide equipment ground through entire system. C. Television Distribution System: D. Public Address System: 3.3 INSTALLATION A. Install grounding system as shown on drawings and as required by the latest edition of the NEC Article 250. B. Connections to equipment, bus, or conduit shall be made with approved type of solderless connector and shall be thoroughly cleaned and made bright before connection is made to insure metal contact. C. Connections inaccessible after completion of project shall be made by exothermic weld process. D. The grounding medium for lighting branch circuits shall be the conduit system. 1. Ground the lighting fixture by means of a conductor between the outlet box and the fixture. 2. Locknut connections to cabinets, pullboxes, junction boxes, etc., shall be drawn up sufficiently tight to enssure a continuous metal-to-metal bond, where a separate ground conductor is not provided. 3. Where GFCI type receptacles are indicated, provide a separate ground conductor directly from the panelboard. E. Bond conduits stubbing under switchboard, motor control center, and similar locations using bonding bushings. F. Do not use flexible conduit as a grounding medium. Provide a bonding wire in flexible conduits and connect to the boxes at each end in an approved manner. Bonding conductor in flexible conduit runs to connect low voltage control and monitoring devices is not required. G. Unless otherwise indicated, provide an equipment grounding conductor in each feeder conductor. For parallel runs, provide a ground conductor in each parallel conduit run. Project No. SPECIFICATION GUIDELINES 16450-4
H. Bond to ground all metal underground pull box covers. I. End-to-End Luminaires: continuously bonded. J. Grounding contacts of receptacles shall be connected to a system-grounding conductor (not the system neutral) by a stranded copper wire not smaller than #12 AWG. The resistance between the contacts and solid earth ground shall not exceed 3 ohms. K. Bond all metal parts. Make equipment and bus connections with suitable lugs or clamps. Cadweld all wire-to-ground rod joints. Cadweld all wire-to-wire joints #1/0 AWG or larger. L. Bond all conduits stubbing under switchboards, transformer and similar locations using bonding bushings. M. Provide a bond wire in all flexible metal conduits and connect to the boxes at each end in an approved manner. N. Use PVC for outdoor applications for sleeving grounding electrode conductors, except that where sleeves are subject to damage, use rigid metal conduit bonded at both ends. O. The TV antenna ground wire shall be connected to the main grounding system. P. Paint buried joints with red glyptal. Q. Ground all transformer secondaries under provisions of NEC-250 unless shown otherwise on the drawings. R. Light Poles: Provide a ground rod driven near pole bases and cadweld a #8 wire to the top of the rod and extend the wire to a grounding lug in the base and bond to all metal parts. END OF SECTION Project No. SPECIFICATION GUIDELINES 16450 5