APPENDIX -D-
GROUNDING GUIDELINES FOR ELECTRIC MEASURES
Table of Contents INTRODUCTION ................................................................................................................................ 1 DWELLING ELECTRICAL HAZARDS.............................................................................................. 1 INSTALLATION OF A RETROFIT GROUND WIRE......................................................................... 1 INSTALLATION OF A GFCI RECEPTACLE OR SWITCH .............................................................. 3 EQUIPMENT GROUNDING AS A WORK PRACTICE TO AVOID STATIC SHOCK ...................... 4
CSD Weatherization Installation Standards 4/1/15
APPENDIX -DGROUNDING GUIDELINES FOR ELECTRIC MEASURES INTRODUCTION Purpose: This appendix provides guidelines for electrically protecting a receptacle or switch in a home with an ungrounded 2-wire system. Options addressed are installation of a: 1. Retrofit ground wire, or 2. GFCI receptacle or switch. Caveat: 1. These are basic guidelines. Detailed criteria may be found in the California Electrical Code (CEC). 2. Each installer is responsible for adhering to program policies and all requirements of the local jurisdiction, including acquisition of a permit when required. Definitions: 1. Ground Wire (also called the Equipment Ground Wire): The wire (typically 12 AWG) that provides grounding to a receptacle, switch, or metal box. 2. Grounding Electrode Conductor (GEC): A wire (typically 6 AWG) that extends from the service entrance ground rod to: a. the main service panel grounding terminal bar, or b. another location where grounding is needed. DWELLING ELECTRICAL HAZARDS Identification: Homes will have a four-wire service entrance to the panel box to ensure a wiring system that is nominally rated at 120/240 volts and allows for proper grounding. Safety Check: Evaluation of an electrical system is required of all field personnel before tools and equipment are used, electrical measures are installed, or the dwelling’s electrical system will be affected by weatherization activities. The electrical safety check shall conform to CSD WIS Section 1, Item 4.1.13.4 and CSD Field Guide Section 3 Assessor’s Guide, Items 3.10.1 and 3.10.2. Grounding at the service entrance will be checked to determine proper grounding of the home. INSTALLATION OF A RETROFIT GROUND WIRE Purpose: To install a retrofit ground wire that provides electrical protection for an ungrounded receptacle or switch, in a home with a 2-wire ungrounded system. Grounding Sources: Grounding can be provided to an ungrounded receptacle or switch by connecting a ground wire from it to either of the following: 1. Existing Ground: An existing 3-wire grounded receptacle elsewhere in the structure, or the main service grounding system. 2. Retrofit Electrode Conductor: A retrofit grounding electrode conductor (GEC) connected to the main service grounding system (e.g., the ground rod).
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Appendix D: Grounding Guidelines for Electric Measures
Ground Wire Requirements 1. Wire: Must be a copper conductor meeting the following requirements. a. Minimum 12 AWG for 20 amp circuits. b. When insulated, colored green or green with one or more yellow stripes. 2. Protection: Where exposed, the ground wire must be secured and protected as needed to avoid damage, and to safeguard the occupants. a. Indoors: Wires must be enclosed in a raceway. b. Outdoors: Wires must be enclosed in a conduit or cable armor. c. Attic or Crawlspace: Wires that run across the joists must be run either through bored holes in the joists or on running boards. GROUND WIRE PROTECTED BY A RACEWAY Grounding Electrode Conductor (GEC): When a GEC is installed, it must meet the following requirements: 1. Size: Minimum 6 AWG, or as required by local code, properly clamped/bonded to ground at the main service (e.g., clamped to the ground rod). 2. Splices: Any splices in the GEC must be secured with an irreversible compression-type connector or exothermic weld. 3. Protection: The GEC must be protected. a. Where physical damage is not likely, the GEC may be securely fastened to the building. b. Where physical damage is likely, the GEC must be enclosed in a rigid metal or nonmetallic conduit, or encased in cable armor.
Grounding Options: An ungrounded receptacle or switch may be grounded by connecting a ground wire (typically AWG 12) from it to a grounding source.1 Options include the following: 1. Option A: Connect to an existing grounded receptacle in another part of the building: a. Applies when a 3-wire grounded receptacle is available elsewhere in the home. b. Run a ground wire from the ungrounded receptacle/switch to the existing 3-wire grounded receptacle. 2. Option B: Connect to the grounding system at the main service panel: a. Applies when a ground wire can be routed without direct exposure to occupants or outdoors (e.g., in the crawlspace, wall, or attic). b. Run a ground wire (conduit not required) from the ungrounded receptacle/switch to the main panel grounding system. 3. Option C: Connect to an existing ground rod in the home’s grounding system: a. From the main service ground rod, run a retrofit GEC to a junction box near the ungrounded receptacle/switch. b. Run a ground wire from the ungrounded receptacle/switch to the GEC junction box, and connect it to the GEC inside.
1
Ground wire exposed in the living space must be in a raceway. Ground wire in the crawlspace or attic does not need to be in a conduit, unless required by local code.
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Appendix D: Grounding Guidelines for Electric Measures
EXISTING 3-WIRE GROUNDED
OPTION (A): RETROFIT GROUND
RECEPTACLE
2-WIRE RECEPTACLE (UNGROUNDED) OPTION (C): RETROFIT GROUND
OPTION (B):
EXISTING
RETROFIT GROUND
GROUND
AND GEC
INSTALLATION OF A GFCI RECEPTACLE OR SWITCH Purpose: To install a GFCI unit, rather than a ground wire, to provide electrical protection for an ungrounded receptacle or switch, in a home with a 2-wire ungrounded system. The GFCI Alternative 1. Installation of a GFCI unit is an acceptable alternative for protecting an ungrounded receptacle or switch. 2. This method may be used when installation of a retrofit ground wire is not a good option. GFCI Installation 1. Receptacle—for a plug-in appliance (except refrigerator): a. A GFCI receptacle may be connected to an ungrounded 2-wire circuit. b. Wires bringing power to the receptacle must be connected to the “line” terminals. c. When present, wires leaving the GFCI receptacle to provide power down-line must be connected to the “load” terminals. d. No wire is connected to the ground lug on the GFCI receptacle. 2. Switch—for a switched fixture: a. A GFCI-protected switch may be connected to an ungrounded 2-wire circuit. b. Wires bringing power to the unit must be connected to the “line” terminals. c. When present, wires leaving the unit to provide power down-line must be connected to the “load” terminals. d. No wire is connected to the ground lug on the GFCI-protected switch. 3. All Units a. Installation shall be in conformance with manufacturer’s instructions and local code. b. When a GFCI receptacle or GFCI-protected switch is installed where a ground wire is not present, the cover plate shall be labeled “GFCI Protected” and “No Equipment Ground”.
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Appendix D: Grounding Guidelines for Electric Measures
GFCI Limitation: GFCI protection may not be used for a circuit powering a refrigerator.
GFCI Protected
GFCI Protected
No Equipment Ground
No Equipment Ground
GFCI-PROTECTED LIGHT SWITCH
GFCI RECEPTACLE
EQUIPMENT GROUNDING AS A WORK PRACTICE TO AVOID STATIC SHOCK Purpose: To minimize static shock that occurs from an insulation fill tube moving over the ground, follow instructions in CSD WIS Section 1, Item 4.1.13.5.
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Appendix D: Grounding Guidelines for Electric Measures
