Licensed Electrical Contractor Grounding and Bonding Questions and Answers Flashcards
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Read the first 6 Licensed Electrical Contractor Grounding and Bonding Questions and Answers flashcards as text
What is the minimum size copper grounding electrode conductor required for a 400-amp service per NEC Article 250?
Answer: 1/0 AWG
NEC Table 250.66 requires a minimum 1/0 AWG copper grounding electrode conductor for services up to 500 kcmil.
When using a concrete-encased electrode (Ufer ground), what is the minimum length of bare copper conductor that must be encased in the concrete?
Answer: 20 feet
NEC 250.52(A)(3) requires at least 20 feet of bare copper conductor encased in concrete for a Ufer ground.
What is the primary purpose of equipment bonding jumpers in an electrical system?
Answer: To ensure electrical continuity and conductivity between metal parts
Equipment bonding jumpers ensure electrical continuity between metal parts so fault current can flow and protective devices can operate.
Per NEC 250.104, what metal piping system within a building must be bonded to the electrical service grounding system?
Answer: Interior metal water piping
NEC 250.104(A) requires interior metal water piping to be bonded to the service equipment enclosure or grounding electrode conductor.
What is the maximum resistance to ground allowed for a single rod, pipe, or plate grounding electrode before a supplemental electrode is required?
Answer: 25 ohms
NEC 250.53(A)(2) requires a supplemental electrode if a single rod, pipe, or plate electrode exceeds 25 ohms resistance to ground.
In a separately derived system such as a transformer, where must the bonding jumper be installed?
Answer: At the source of the separately derived system
NEC 250.30(A)(1) requires the system bonding jumper to be installed at the source of the separately derived system.