Grounding and Bonding Flashcards

Per NEC 250.30, what grounding requirements apply to a separately derived system such as a transformer?

Answer: A system bonding jumper and grounding electrode conductor must be installed at the source

NEC 250.30(A) requires separately derived systems to have a system bonding jumper and a grounding electrode conductor connected to a grounding electrode at or near the source.

What is the difference between 'grounding' and 'bonding' as defined by the NEC?

Answer: Grounding connects to the earth; bonding connects conductive parts together to ensure electrical continuity

The NEC defines grounding as connecting to the earth, while bonding is connecting conductive parts together to establish electrical continuity and conductivity.

Per NEC 250.118, which of the following is recognized as an equipment grounding conductor?

Answer: A copper conductor, EMT, IMC, RMC, or listed flexible metal conduit under specific conditions

NEC 250.118 lists approved equipment grounding conductors including copper/aluminum wire, EMT, IMC, RMC, and certain listed flexible conduits and cable assemblies.

Per NEC 250.68(A), what is required for grounding electrode conductor connections?

Answer: They must be accessible, except for connections made by listed irreversible compression-type connectors, exothermic welding, or buried connections

NEC 250.68(A) requires GEC connections to be accessible except when made with irreversible compression connectors, exothermic welds, or connections to buried electrodes.

What is the minimum size copper bonding jumper required for a 200A service per NEC Table 250.66?

Answer: 4 AWG

Per NEC Table 250.66, a 200A service with 2/0 AWG copper or 4/0 AWG aluminum service conductors requires a minimum 4 AWG copper grounding electrode conductor, which is also the basis for the bonding jumper.

Per NEC 250.24(A)(5), what is the rule regarding neutral-to-ground connections in subpanels?

Answer: The grounded conductor (neutral) must not be connected to the equipment grounding conductor or enclosure at subpanels

NEC 250.24(A)(5) prohibits reconnecting the neutral to ground at any point on the load side of the service disconnecting means, including subpanels.

Per NEC 250.122, what is the minimum size equipment grounding conductor for a circuit protected by a 60-ampere overcurrent device?

Answer: 10 AWG

NEC Table 250.122 requires a minimum 10 AWG copper equipment grounding conductor for a 60-ampere rated overcurrent device.

What is the purpose of the main bonding jumper in a service panel?

Answer: To bond the grounded conductor (neutral) to the equipment grounding conductor and enclosure at the service

The main bonding jumper connects the grounded conductor (neutral), equipment grounding conductors, and the service enclosure together, creating the effective ground-fault current path.

Per NEC 250.64(A), what protection is required for aluminum or copper-clad aluminum grounding electrode conductors?

Answer: They must not be installed where subject to physical damage or corrosive conditions, and must not be in contact with masonry or earth

NEC 250.64(A) prohibits aluminum or copper-clad aluminum GECs from being used where in direct contact with masonry, earth, or where subject to corrosive conditions.

What is an intersystem bonding termination per NEC 250.94?

Answer: An accessible device for bonding communications systems (cable, telephone, satellite) to the building grounding electrode system

NEC 250.94 requires an intersystem bonding termination at the service or disconnect that provides accessible terminals for bonding communications systems to the grounding electrode system.

Per NEC 250.104(A), what building systems must be bonded to the electrical grounding system?

Answer: Metal water piping, metal gas piping, and other metal piping systems that may become energized

NEC 250.104(A) requires bonding of interior metal water piping, and 250.104(B) requires bonding of other metal piping systems including gas piping that may become energized.

When are supplemental ground rods required in addition to a single ground rod per NEC 250.53(A)(2)?

Answer: When the single rod does not achieve 25 ohms or less to ground

NEC 250.53(A)(2) requires a supplemental electrode when a single ground rod cannot be shown to have a resistance of 25 ohms or less to ground.