HomeMy WebLinkAbout071 260526A - Grounding and Bonding for Electrical SystemsWegmans Food Markets GROUNDING AND BONDING Section 260526
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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.
B. Refer to Contract Drawings E101 and E102A.
1.2 SUMMARY
A. Section includes grounding and bonding systems and equipment.
B. Section includes grounding and bonding systems and equipment, plus the following special
applications:
1. Underground distribution grounding.
1.3 ACTION SUBMITTALS
A. Product Data: For each type of product indicated.
B. Ground grid test report and listing of test equipment used.
C. Chemical grounding system.
1.4 CLOSEOUT SUBMITTALS
A. Operation and Maintenance Data: For grounding to include in emergency, operation, and
maintenance manuals.
1. In addition to items specified in Section 017823 "Operation and Maintenance Data,"
include the following:
a. Plans showing as-built, dimensioned locations of grounding features specified in
"Field Quality Control" Article, including the following:
1) Test wells.
2) Ground rods.
3) Ground rings.
4) Grounding arrangements and connections for separately derived systems.
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1.5 DESCRIPTION OF ITEM
A. Grounding and grounding circuitry shall equal or exceed the requirements of NEC, latest issue,
Article 250 and, in the event of a conflict or discrepancy with NEC Article 250, the more
stringent requirement shall apply.
B. Raceway system which includes metal conduit, wireways, pullboxes, junction boxes, bus ducts,
built-up enclosures, enclosures, motor frames, etc. shall be made to form a continuous,
conducting permanent ground circuit of the lowest practical impedance to enhance the safe
conduction of ground fault currents and to prevent objectionable differences in voltage between
metal non-load current carrying parts of the electrical system.
1.6 DEFINITIONS
A. Earth: Absolute ground, a theoretical location of zero electrical potential.
B. Ground: A made conducting connection to earth by employing such devices as a driven metal
rod, a metallic water pipe, etc., or any multiple and/or combination of these devices, and the
conductors which may interconnect any of the foregoing.
C. System Ground: A low impedance made conducting ground plane or system, with a conducting
connection to ground, established for the benefit of a particular electrical system or related
systems.
PART 2 - PRODUCTS
2.1 SYSTEM DESCRIPTION
A. Electrical Components, Devices, and Accessories: Listed and labeled as defined in NFPA 70, by
a qualified testing agency, and marked for intended location and application.
B. Comply with UL 467 for grounding and bonding materials and equipment.
2.2 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. Stranded Conductors: ASTM B 8.
2. Bonding Conductor: No. 4 or No. 6 AWG, stranded conductor.
C. Grounding Bus: Predrilled rectangular bars of annealed copper, 1/4 by 4 inches in cross section,
with 9/32-inch holes spaced 1-1/8 inches apart. Stand-off insulators for mounting shall comply
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with UL 891 for use in switchboards, 600 V and shall be Lexan or PVC, impulse tested at
5000 V.
D. Exposed grounding conductors such as bars, straps, cables, flexible jumpers, braids, shunts, etc.,
shall be bare copper unless otherwise called for.
E. Cable size shall be as required by NEC Code, Section 250, stranded, soft drawn or soft
annealed, unless otherwise called for.
F. Provide cable insulation type and color as called for.
G. Make: Same make as for 600-volt conductors.
2.3 GROUND RODS
A. 5/8” x 10” copperweld, copperclad ground rod.
2.4 CONNECTORS AND HARDWARE
A. Listed and labeled by an NRTL acceptable to authorities having jurisdiction for applications in
which used and for specific types, sizes, and combinations of conductors and other items
connected.
B. Welded Connectors: Exothermic-welding kits of types recommended by kit manufacturer for
materials being joined and installation conditions.
C. Bus-Bar Connectors: Mechanical type, cast silicon bronze, solderless compression-type wire
terminals, and long-barrel, two-bolt connection to ground bus bar.
D. Provide mechanical connectors and clamps made of silicone bronze.
E. Provide silicon bronze alloy hardware.
F. Cable-to-Cable Connectors: Compression type, copper or copper alloy.
G. Cable Tray Ground Clamp: Mechanical type, zinc-plated malleable iron.
H. Conduit Hubs: Mechanical type, terminal with threaded hub.
I. Ground Rod Clamps: Mechanical type, copper or copper alloy, terminal with hex head bolt.
J. Service Post Connectors: Mechanical type, bronze alloy terminal, in short- and long-stud
lengths, capable of single and double conductor connections.
K. Water Pipe Clamps:
1. U-bolt type with malleable-iron clamp and copper ground connector.
L. Connectors and Hardware Manufacturers:
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1. Anderson
2. Burndy
3. Penn-Union
4. Thomas & Betts
M. Molded Fusion Weld Manufacturers:
1. Cadweld
2. Metalweld
3. Thermoweld
2.5 CHEMICAL GROUNDING SYSTEM
A. U.L. Listing: 467J, ANSI 633.8.
B. Shaft configuration: L-shaped with 20’ horizontal length.
C. Material: Type K copper, 0.084 wall thickness.
D. Construction: Hollow tube, chemical filled (non-hazardous).
E. Ground Wire Termination: #4/0 exothermically welded to tube.
F. Minimum Life: 25 years.
G. Accessories
1. Concrete protective box with grated cover.
2. Bentonite natural clay backfill.
H. Make
1. Lyncole XIT Grounding.
2. Altec Terradyne.
PART 3 - EXECUTION
3.1 INSTALLATION – GENERAL
A. Do not install bare copper bars, cables, or fittings in cinder fill or cover with soil containing
cinders or other corrosive material.
B. Install cables with enough slack to prevent breaking stresses.
C. Protect grounding conductors subject to mechanical damage by rigid steel conduit or other
suitable steel guards.
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D. Where rigid steel protects ground cable, permanently and effectively ground steel conduit to
enclosure at each end of its length.
E. Where grounding conductors pass through floor slabs, walls, etc., and are not encased in metal
conduit, provide fiber or PVC nonmetallic conduit sleeve.
F. The length, number, spacing, and location of ground rods shall be as called for.
G. The depth to which ground rods are driven shall be as called for or to refusal.
H. Connections to water pipes, including water meter or other similar device bypass connections,
shall be made only after the surface of the pipe at the point of connection has been thoroughly
cleaned and brightened and, immediately prior to actually making the connection, the contact
surfaces are to be coated with Vasoline or "NO-OX-ID-A Special".
I. 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
bonding so vibration is not transmitted to rigidly mounted equipment.
J. 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;
use a bolted clamp connector or bolt a lug-type connector to a pipe flange by 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.
K. All equipment ground bus, ground pads, frames, enclosures, etc. shall have surfaces at point of
connection thoroughly cleaned and brightened just prior to actually making the connection.
Touch-up damaged painted surfaces.
L. Splices in wire or cable grounding conductors are prohibited.
3.2 INSTALLATION - RACEWAY SYSTEMS
A. All metal supports, cable trays, messenger cables, frames, brackets, braces, etc. for the raceway
system, panels, switches, boxes, starters, controls, etc., which are not rigidly secured to and in
contact with the raceway system, or which are subject to vibration and loosening, shall be
bonded to the raceway system, the size of the bonding conductor in accordance with NEC Table
250-95.
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B. Termination of rigid conduit at all boxes, cabinets, and enclosures shall be made up tightly with
a double locknut arrangement and a bushing. Bushings shall be of the insulated type where
required by NEC.
C. Conduit which runs to or from all boxes, cabinets, or enclosures having concentric or eccentric
knockouts which partially perforate the metal around the conduit and hence impair the
continuity of system ground circuits shall be provided with bonding jumpers sized in
accordance with NEC Table 250-95 connected between a grounding type bushing/locknut on
the conduit and a ground bus or stud inside the box, cabinet, or enclosure and attached thereto.
D. Conduit expansion joints and telescoping sections of metal raceways shall be provided with
bonding jumpers sized in accordance with NEC Table 250-122.
E. Where flexible metallic conduit and/or liquid tight conduit is used, a bonding jumper shall be
provided, sized in accordance with NEC Table 250-122.
F. All nonmetallic runs of conduit and/or raceway shall be provided with a system ground
conductor sized according to Table 250-122.
G. Where conduit enters or leaves any electrical enclosure with removable coverplates, provide
conduit grounding bushings and bonding jumpers sized in accordance with NEC Table 250-122
between the grounding bushings and the enclosure rigid frame or ground bus.
H. The ground conductors contained in the interstices of interlocked armor cable shall be
connected to ground at every splice and termination point.
3.3 INSTALLATION - ATTACHMENT TO STRUCTURE STEEL
A. Location of attachment bonds of ground conductors shall be at points not subject to mechanical
damage but, if possible, where accessible for inspection.
B. Attach by molded fusion welding process.
C. Where welding is prohibited, attach by bolting, 7/16 in. hole in steel, 3/8 in. silicon bronze bolt,
bolt end peened, steel surface bright and flat prior to bolting, just prior to bolting contact
surfaces lightly coated with Vasoline or "NO-OX-ID-A Special".
3.4 INSTALLATION - GROUND GRID
A. Located as shown on Contract Drawings with top of rod 24 in. below finished grade elevation.
B. Connecting cables as called for.
C. Connect cables 24 in below finished grade as called for.
D. Size #4/0 tails for connections to each equipment ground bus or ground pads.
E. Size #4/0 circuitry between ground grid and street side of nearest metallic cold water main.
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F. Size #4/0 circuits between ground grid and building steel.
G. Unless otherwise called for, make below grade connections by molded fusion welding process,
and molds shall be new and unused at start of Work and shall be replaced when worn or broken.
Crossover molds is prohibited.
H. Where connecting cables or tails from ground grid are insulated, provide solder block by filling
conductor interstices with solder and then seal to end of insulation to prevent water from
following conductor interstices, and seal between insulated conductor and sleeve at point of
conductor entry through building wall or slab to prevent water entry.
I. Required ground grid resistance to earth shall be 5 ohms maximum.
J. Measure, record, and submit value of ground grid resistance to earth, measured before any
connections to equipment, water mains, building steel, metallic objects, or any other grounding
materials are made.
K. Measure, record, and submit value of ground grid resistance to earth, measured after all
connections have been made.
L. Use Biddle ground field earth resistance tester. Submit details of test equipment and procedures
used.
3.5 INSTALLATION - SECONDARY ELECTRICAL SYSTEMS
A. The neutral conductor of each and every low voltage, single and/or polyphase, system or
distribution system, except special isolated double insulated systems, shall be solidly connected
at one point only, preferable at the transformer neutral bushing, or at the main secondary
switchgear; to system ground and shall be sized for current carrying capacity, not to be less than
the following, which are listed in preferential order:
1. As shown or specified.
2. As required by NEC, latest issue, Table 250-122.
3. Not less than 25% of the transformer full load current or main protective device rating,
whichever is greater, based on NEMA standard bus size.
B. Provide equipment grounding conductor, green colored insulation, with phase conductors, to
primary side of all transformers rated 600 volts or less circuited to case and secondary neutral
bushing, to heating equipment, and to all convenience outlets. Insulation shall be same type as
phase conductors.
C. Transformer secondary neutral bushings are also to be circuited to nearest metallic water pipe,
building steel, or ground rod.
D. Equipment grounding conductors, where called for, shall extend from the point of termination
back to the ground bus of the serving panelboard, switchboard, transformer, or switchgear.
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3.6 CHEMICAL GROUNDING SYSTEMS
A. Core bore hole at location shown on plans.
B. Install per manufacturer’s recommendations.
C. Test in accordance with this specifications procedures.
3.7 GROUNDING BUS
A. Grounding Bus: Install in electrical equipment rooms, in rooms housing service equipment, and
elsewhere as indicated.
1. Install bus horizontally, on insulated spacers 2 inches minimum from wall, 6 inches
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, and down; connect to horizontal bus.
3.8 TESTING
A. Tests and Inspections:
1. After installing grounding system but before permanent electrical circuits have been
energized, and before backfilling test for compliance with requirements.
2. Inspect physical and mechanical condition. Verify tightness of accessible, bolted,
electrical connections with a calibrated torque wrench according to manufacturer's
written instructions.
3. Test completed grounding system at each location where a maximum ground-resistance
level is specified, at service disconnect enclosure grounding terminal, at ground test
wells. Make tests at ground rods before any conductors are connected.
a. Measure ground resistance no fewer 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 with a moving auxiliary electrode in
accordance with IEEE Standard 142 and reviewed/approved by the Engineer.
Sufficient test points shall be taken for accurate resistance value. Provide tabulated
test results indicating distance between rods and resistance readings on a plotted
graph.
4. Conduit systems shall be checked for “grounds” at convenient points such as outlets
which are located near plumbing systems or building structural steel.
5. All ground rods shall be tested for grounding resistance before any grounding conductors
are connected.
6. The “service ground” point shall be tested for ground resistance.
7. Demonstrate that derived grounds at transformer secondaries are “grounded”.
8. Check system neutrals and equipment grounding conductors separately for opens, shorts,
and unintentional grounds before interconnection to the grounding system.
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9. Test each ground electrode system separately prior to connection to the system or main
building ground bar. Test each system ground electrode system a second time after
backfilling has occurred and all final connections (building steel, water service, etc.) have
been made.
10. 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.
B. Grounding system will be considered defective if it does not pass tests and inspections.
C. Prepare test and inspection reports including soil type, date, time meter manufacturer/model
number, person performing the test, test witnesses and most recent rainfall shall be noted in test
submittal.
D. Report measured ground resistances that exceed the following values:
1. Power and Lighting Equipment or System with Capacity of 500 kVA and Less: 10 ohms.
2. Power and Lighting Equipment or System with Capacity of 500 to 1000 kVA: 5 ohms.
3. Power and Lighting Equipment or System with Capacity More Than 1000 kVA: 3 ohms.
4. Power Distribution Units or Panelboards Serving Electronic Equipment: 3 ohm(s).
5. Substations and Pad-Mounted Equipment: 5 ohms.
E. Excessive Ground Resistance: If resistance to ground exceeds specified values, notify Owner
promptly and include recommendations to reduce ground resistance.
END OF SECTION 260526