26 05 26 - Grounding.pdf

26 05 26 – GROUNDING

Herbert, Rowland & Grubic, Inc. 26 05 26 - 1 000483.0450

SECTION 26 05 26 – GROUNDING

PART 1 - GENERAL

1.1 SECTION INCLUDES

A. Grounding

1. Items to be grounded include all new work of this Contract, but not be limited to metallic water services, equipment housings, motor frames, metal raceways, grounding terminals of outlets, outdoor lighting fixtures, footing rebar, duct banks, manholes, pull boxes, and transformer secondary neutrals. In addition to the NEC requirements and the above, the following, where a part of this Project, shall be permanently and effectively grounded:

a. All structural metals.

b. All metallic panels and conduit.

c. Motor frames 10 HP and larger.

d. All metallic equipment bases.

e. Metallic handrailing and walkways.

f. Metallic portions of heating, ventilating, and air conditioning equipment.

2. Take special precautions to ground all equipment in strict accordance with the NEC and as otherwise noted in these specifications.

1.2 RELATED SECTIONS

A. Division 26

1.3 REFERENCES

A. All materials and installations shall be in accordance with the latest revisions of the following:

1. National Electric Code

2. Underwriters Laboratories, Inc.

1.4 SUBMITTALS

A. Provide submittals and samples in accordance with Section 26 05 00 – Electrical General.

Herbert, Rowland & Grubic, Inc. 26 05 26 - 2 000483.0450

B. Shop drawing shall be submitted for only the electrode system and conductors used in connection with the grounding system.

C. Submit an 18-inch sample of the ground system tin-plated conductor and other samples as may be requested by the Engineer.

D. Certified test reports of grounding system resistance per Section 26 08 00 – Electrical Field Acceptance Tests.

PART 2 - MATERIALS

2.1 ELECTRODES

A. Driven Ground Rods - 3/4-inch diameter x 10 feet long (minimum) steel core copper jacketed. Rods shall be manufactured by Copperweld Steel Company, Thompson Lightning Protection, Inc., or equal.

B. Ground Plates - 1/4-inch x 24-inch x 24-inch square copper plates.

C. Drilled Ground Rods

1. Drilled ground rods shall be a system consisting of 20 foot straight drilled holes containing salt filled copper tubes. The tubes shall be filled with a combination of NaCL and CaCL salts. All electrical connections at the ground rods shall be made via exothermic welding. All cables shall be tin-plated copper. Backfill material shall be composed of hydrous aluminum silicate. Drilling is typically done by a water well driller as a sub to the Contractor.

2. Drilled system shall be UL listed.

3. System access from grade shall incorporate the use of a concrete or polyplastic box for protection with a steel cover. Box shall be installed flush with finish grade. Use concrete when rods are installed in drives or walkways.

4. Manufacturers

a. Superior Grounding Systems, 1-800-747-7925

b. XIT Grounding System, (213) 320-8000

c. Or equal

5. Guarantee - Contractor and grounding system installer shall jointly guarantee the grounding system for two years.

2.2 CONDUCTOR

A. Ground Conductor (Above Grade) - Type XHHW insulated wire in conduit or other raceway. Color code insulation per NEC.

B. Ground System Conductor (Buried) - Soft drawn of soft annealed stranded copper, tinned bare stranded conductor. Note: This type conductor is not always readily available, and long lead times should be anticipated. For conductors run from inside of building to ground system conductor, also, use tinned bare stranded copper.

Herbert, Rowland & Grubic, Inc. 26 05 26 - 3 000483.0450

C. Equipment Bonding Conductor - For sizes 8 AWG and smaller, solid ASTM B-1. For sizes 6 AWG and larger, stranded ASTM B-8, bare copper.

2.3 CONNECTORS

A. Compression-Type Fittings

1. Construction - Two bolts and a minimum of 1-1/2 inches in length.

2. Manufacturers

a. Thomas & Betts.

b. Burndy Corporation.

c. ILSCO.

d. Or equal.

B. Welded Connection

1. Construction - Molded fusion-welding process.

2. Manufacturers

a. Cadweld.

b. Thermoweld.

c. ILSCO.

d. Or equal.

C. Mechanical Connection

1. Construction - Mechanical lugs securely fastened using silicon bronze hardware.

2. Manufacturers

a. Thomas & Betts

b. Burndy Corporation

c. Or equal.

PART 3 - EXECUTION

3.1 GROUND SYSTEM DESCRIPTION

A. Install ground system or grid as shown on the Contract Drawings. Install such that tops of ground rods are 12 inches below grade. Depth of the conductor system is to be 30 inches minimum with a length as shown on the Drawings. Thermoweld rods to copper grounding conductor.

B. When driven rods are specified and cannot be driven due to boulders or rock formations, this specification will allow the NEC 250.53G guidelines for the angled ground rods, but not the horizontal rod, and where shown, to install grounding plates below groundwater level or a minimum of 6 feet below finished grade.

C. Final resistance to ground of completed ground system shall be a maximum of 5 ohms in accordance with Section 26 08 00 – Electrical Field Acceptance Tests. If tests indicate

Herbert, Rowland & Grubic, Inc. 26 05 26 - 4 000483.0450 higher than 5 ohms resistance, then the Contractor shall install additional rods or plates at no additional cost to Owner to lower the resistance to below 5 ohms.

3.2 CONNECTIONS

A. Buried Connections - Made with thermal welded fittings specially made for grounding system or compression fitting for buried pipe/plate bonding.

B. Exposed Connections - Made with grounding system compression-type fittings.

C. Connections to Metal - Make all connections to water pipes, steel surfaces, etc., using mechanical connectors.

D. Thoroughly clean all surfaces to bright bare metal to accept ground connections.

3.3 GROUNDING ELECTRODE CONDUCTOR

A. Services - As shown on the Drawings and as required by the NEC.

3.4 MAIN SERVICE GROUNDS

A. Bond ground system securely to:

1. Building water service. (If available and if metallic water pipe is used and is of sufficient conductive length to ensure continuity, provide jumpers around meters or other removable devices as required.) See Contract Drawings for conductor size and pipe location.

2. Building structural steel (if available), including canopy, roof and hoist supports.

One No. 6 minimum two places, opposite corners of building. Buildings over 60 feet in length No. 6 ground at each corner.

3. One No. 6 to foundation (footing) steel reinforcing (20-foot minimum length 1/2-inch rebar).

4. Connect two grounding electrode conductors in conduit to facility grounding grid or system.

3.5 BUILDING GROUND CONNECTION

A. Connection from main ground to building systems shall be as specified herein as shown and as required. Positively connect equipment housings and conduit system to main service ground, only at main service ground bar.

3.6 INDIVIDUAL GROUNDS

A. If individual equipment or individual building grounds are made, separate grounding conductors (in earth where possible) shall connect these grounds to main service ground. (This requirement applies only within each system of subsystem fed from a distribution transformer.) Intent is that main ground shall be at the main or incoming power source and not at utilization point unless positively connected to same.

Herbert, Rowland & Grubic, Inc. 26 05 26 - 5 000483.0450

3.7 INTERIOR CONDUIT AND RACEWAY SYSTEM

A. Electrical integrity of conduit system shall be maintained throughout. Provide bonding jumpers at fittings as required; jumpers shall be no longer than required. Provide a separate ground wire in all conduit systems.

3.8 EXTERIOR CONDUIT AND RACEWAY SYSTEM

A. Provide separate ground wire for all conduit systems leaving the building interior. Size per NEC 250-122 in NEC or as shown.

B. Exterior grounding system to be installed in Schedule 80 PVC conduit.

3.9 FEEDERS

A. Include an insulated grounding conductor, sized per NEC 250-66, in each conduit, sized for total feeder cross-sectional area. Bond all served equipment frames, enclosures, ground bars, etc., to this conductor. Make all conductor terminations and connections using compression lugs or fittings designed and UL labeled for the purposes.

3.10 SEPARATE GROUND

A. Basic intent of grounding specification is that grounding conductor be completely separate from system neutral and connect neutral to ground at the main service grounding point only. Run separate insulated (green) grounding conductors from all grounding points independently back to main service ground. Where ground passes through panels and disconnects, ground lugs shall be brazed or bolted to panel or disconnect housings with neutral bus or lug isolated from same. Ground all metallic conduits at each panel. Clean paint from metal to accept ground lugs.

3.11 METALLIC, NON-CURRENT CARRYING ENCLOSURE

A. Connect to ground bar at load center supplying same through conduit system using proper fittings at junction boxes, expansion joints, and between ground bushings on each conduit within all sheet metal enclosures.

3.12 SHIELDED CABLE

A. Shielding to be continuous and grounded at one point only unless otherwise required by equipment manufacturer's recommendations.

3.13 CONDUIT SEALS

A. Where non-metallic conduits protecting grounding conductors enter the building from the exterior, provide watertight wall seals on each conduit and a sealing bushing on the enclosed conductor. Sealing bushings on all conduits penetrating the floor. Make bonding jumper connection to metallic conduit, where equipped with sealing bushings, Herbert, Rowland & Grubic, Inc. 26 05 26 - 6 000483.0450 with water pipe ground connections of proper size. Seal watertight the inside of all conduits entering the building below grade.

3.14 GROUND CONDUIT LABELS

A. Label all service, equipment frame or motor grounding conduits containing only grounding conductors - "(Fill In Name) ground." Label to identify item being grounded.

3.15 INDEPENDENT GROUND SYSTEMS

A. The grounding system described here shall be independent from the lightning protection ground system. However, both systems, when available, shall be bonded together.

3.16 INDIVIDUAL MOTOR CONNECTION

A. Make connections from frames of motors 50 HP and larger directly to the exterior/buried ground system. Motors up to this HP shall be connected to the circuit or raceway grounding system. Where motor is separate from and not mounted on a major equipment frame, bond frame to motor ground. Size of ground shall be per 250-122 for the motor overcurrent device.

3.17 MAJOR EQUIPMENT FRAMES AND TANKS

A. Make connection from major equipment frames, i.e., but not limited to, dewatering equipment, mechanical screens or grit equipment, and tanks directly to the exterior/buried ground system via a #6 ground. Conductor shall be installed in conduit the full length from the grounded item to outside below grade.

3.18 CONCRETE MANHOLES AND HANDHOLES

A. Provide one 3/4-inch diameter by 10-foot long driven ground rod or ground plate in or at each manhole and handhole. Provide plates as shown or where ground rod cannot be driven full depth (also see paragraph 3.01.B herein).

B. Provide No. 6 ground conductor from ground rod to all metallic parts including cable racks and manhole frame.

C. Bond ductbank grounds to manhole and handhole ground rod or plate.

3.19 DUCTBANK GROUND CONDUCTOR

A. Bond ductbank ground conductor to the new building ground system.

B. Bond ductbank grounds to manhole and handhole ground rod or plates.

3.20 METAL STAIRS AND GUARDRAILS (HANDRAILING)

Herbert, Rowland & Grubic, Inc. 26 05 26 - 7 000483.0450

A. Provide a No. 6 ground conductor to each stair.

B. Provide a No. 6 bonding jumper between sections of guardrails including stair guardrails.

3.21 EXTERIOR LIGHT POLES

A. Provide a No. 6 ground conductor from ground rod to light pole and a No. 6 bonding jumper to conduits.

3.22 FENCES

A. Provide a No. 2 ground conductor from grounding system to fence.

END OF SECTION 26 05 26