36C25622R0030 Spec 260526 v2 (updated 071322).doc

SECTION 26 05 26

GROUNDING and bonding for electrical systems

PART 1 ‑ GENERAL

1.1 DESCRIPTION

A.

This section specifies general grounding and bonding requirements of electrical installations for personnel safety and to provide a low impedance path for possible ground fault currents.

B.

“Grounding electrode system” refers to all electrodes required by NEC, as well as including made, supplementary, lightning protection system and telecommunications system grounding electrodes.

C.

The terms “connect” and “bond” is used interchangeably in this specification and has the same meaning.

1.2 RELATED WORK

N/A

1.3 SUBMITTALS

A.

Submit in accordance with Section 16050, BASIC METHODS AND REQUIREMENTS (ELECTRICAL).

B.

Shop Drawings:

1.

Sufficient information, clearly presented, shall be included to determine compliance with drawings and specifications.

2.

Include the location of system grounding electrode connections and the routing of aboveground and underground grounding electrode conductors.

C.

Test Reports: Provide certified test reports of ground resistance.

D.

Certifications: Two weeks prior to final inspection, submit four copies of the following to the Project Engineer:

1.

Certification that the materials and installation is in accordance with the drawings and specifications.

2.

Certification, by the Contractor, that the complete installation has been properly installed and tested.

1.4 APPLICABLE PUBLICATIONS

Publications listed below (including amendments, addenda, revisions, supplements, and errata) form a part of this specification to the extent referenced. Publications are referenced in the text by the basic designation only.

A.

National Fire Protection Association (NFPA):

70‑2002 National Electrical Code (NEC)

99‑2002 Health Care Facilities

B.

Underwriters Laboratories, Inc. (UL):

44‑1999 Thermoset‑Insulated Wires and Cables

83‑1998 Thermoplastic‑Insulated Wires and Cables

467‑1993 Grounding and Bonding Equipment

486A-2000 Wire Connectors and Soldering Lugs for Use With Copper Conductors

C.

American Society for Testing and Materials (ASTM):

B1-2001 Standard Specification for Hard-Drawn Copper Wire

B8-1999 Standard Specification for Concentric-Lay-Stranded Copper Conductors, Hard, Medium-Hard, or Soft

D.

Institute of Electrical and Electronics Engineers, Inc. (IEEE):

81-1983 IEEE Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Ground System

PART 2 ‑ PRODUCTS

2.1 GROUNDING AND BONDING CONDUCTORS

A.

Equipment grounding conductors shall be UL 83 insulated stranded copper, except that sizes No. 10 AWG and smaller shall be solid copper. Insulation color shall be continuous green for all equipment grounding conductors, except that wire sizes No. 4 AWG and larger shall be permitted to be identified per NEC.

B.

Bonding conductors shall be ASTM B8 bare stranded copper, except that sizes No. 10 AWG and smaller shall be ASTM B1 solid bare copper wire.

C.

Isolated Power System: Type XHHW-2 insulation with a dielectric constant of 3.5 or less.

D.

Conductor sizes shall not be less than what is shown on the drawings and not less than required by the NEC, whichever is greater.

2.2 GROUND RODS

A.

Copperclad steel, 19 mm (3/4‑inch) diameter by 3000 mm (10 feet) long, conforming to UL 467.

B.

Quantity of rods shall be as required to obtain the specified ground resistance.

2.3 SPLICES AND TERMINATION COMPONENTS

Components shall meet or exceed UL 467 and be clearly marked with the manufacturer, catalog number, and permitted conductor size(s).

PART 3 ‑ EXECUTION

3.1 GENERAL

A.

Ground in accordance with the NEC, as shown on drawings, and as hereinafter specified.

B.

System Grounding:

1.

Secondary service neutrals: Ground at the supply side of the secondary disconnecting means and at the related transformers.

2.

Separately derived systems (transformers downstream from the service entrance): Ground the secondary neutral.

3.

Isolation transformers and isolated power systems shall not be system grounded.

C.

Equipment Grounding: Metallic structures (including ductwork and building steel), enclosures, raceways, junction boxes, outlet boxes, cabinets, machine frames, and other conductive items in close proximity with electrical circuits shall be bonded and grounded.

3.2 INACCESSIBLE GROUNDING CONNECTIONS

Make grounding connections which are buried or otherwise normally inaccessible (except connections for which periodic testing access is required) by exothermic weld.

3.3 MEDIUM-VOLTAGE EQUIPMENT AND CIRCUITS

3.4 SECONDARY EQUIPMENT AND CIRCUITS

A.

Main Bonding Jumper: Bond the secondary service neutral to the ground bus in the service equipment.

B.

Metallic Piping, Building Steel, and Supplemental Electrode(s):

1.

Provide a grounding electrode conductor sized per NEC between the service equipment ground bus and all metallic water and gas pipe systems, building steel, and supplemental or made electrodes. Jumper insulating joints in the metallic piping. All connections to electrodes shall be made with fittings that conform to UL 467.

2.

Provide a supplemental ground electrode and bond to the grounding electrode system.

C.

Service Disconnect (Separate Individual Enclosure): Provide a ground bar bolted to the enclosure with lugs for connecting the various grounding conductors.

D.

Conduit Systems:

1.

Ground all metallic conduit systems. All metallic conduit systems shall contain an equipment grounding conductor.

2.

Non‑metallic conduit systems shall contain an equipment grounding conductor, except that non-metallic feeder conduits which carry a grounded conductor from exterior transformers to interior or building-mounted service entrance equipment need not contain an equipment grounding conductor.

3.

Conduit containing only a grounding conductor, and which is provided for mechanical protection of the conductor, shall be bonded to that conductor at the entrance and exit from the conduit.

E.

Feeders and Branch Circuits: Install equipment grounding conductors with all feeders and power and lighting branch circuits.

F.

Boxes, Cabinets, Enclosures, and Panel boards:

1.

Bond the equipment grounding conductor to each pull box, junction box, outlet box, device box, cabinets, and other enclosures through which the conductor passes (except for special grounding systems for intensive care units and other critical units shown).

2.

Provide lugs in each box and enclosure for equipment grounding conductor termination.

3.

Provide ground bars in panel boards, bolted to the housing, with sufficient lugs to terminate the equipment grounding conductors.

G.

Motors and Starters: Provide lugs in motor terminal box and starter housing or motor control center compartment to terminate equipment grounding conductors.

H.

Receptacles shall not be grounded through their mounting screws. Ground with a jumper from the receptacle green ground terminal to the device box ground screw and the branch circuit equipment grounding conductor.

I.

Ground lighting fixtures to the equipment grounding conductor of the wiring system when the green ground is provided; otherwise, ground the fixtures through the conduit systems. Fixtures connected with flexible conduit shall have a green ground wire included with the power wires from the fixture through the flexible conduit to the first outlet box.

J.

Fixed electrical appliances and equipment shall be provided with a ground lug for termination of the equipment grounding conductor.

K.

Raised Floors: Provide bonding of all raised floor components.

L.

Panel board Bonding: The equipment grounding terminal buses of the normal and essential branch circuit panel boards serving the same individual patient vicinity shall be bonded together with an insulated continuous copper conductor not less than No. 10 AWG. These conductors shall be installed in rigid metal conduit.

3.5 CONDUCTIVE PIPING

A.

Bond all conductive piping systems, interior and exterior, to the building to the grounding electrode system. Bonding connections shall be made as close as practical to the equipment ground bus.

3.6 LIGHTNING PROTECTION SYSTEM

3.7 TELECOMMUNICATIONS SYSTEM

Bond telecommunications system grounding equipment to the electrical grounding electrode system.

3.8 GROUND RESISTANCE

A.

Grounding system resistance to ground shall not exceed 5 ohms. Make necessary modifications or additions to the grounding electrode system for compliance without additional cost to the Government. Final tests shall assure that this requirement is met.

B.

Resistance of the grounding electrode system shall be measured using a four-terminal fall-of-potential method as defined in IEEE Standard 81. Ground resistance measurements shall be made before the electrical distribution system is energized and shall be made in normally dry conditions not less than 48 hours after the last rainfall. Resistance measurements of separate grounding electrode systems shall be made before the systems are bonded together below grade. The combined resistance of separate systems may be used to meet the required resistance, but the specified number of electrodes must still be provided.

C.

Services at power company interface points shall comply with the power company ground resistance requirements.

D.

Below-grade connections shall be visually inspected by the Project Engineer prior to backfilling. The Contractor shall notify the Project Engineer 24 hours before the connections are ready for inspection.

3.9 GROUND ROD INSTALLATION

A.

Drive each rod vertically in the earth, not less than 3000 mm (10 feet) in depth.

B.

Where permanently concealed ground connections are required, make the connections by the exothermic process to form solid metal joints. Make accessible ground connections with mechanical pressure type ground connectors.

C.

Where rock prevents the driving of vertical ground rods, install angled ground rods or grounding electrodes in horizontal trenches to achieve the specified resistance.

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