Electrical Codes & Standards Flashcards

Under NEC Article 230, what is the maximum number of service disconnects permitted for a single-occupancy building?

Answer: Six

NEC 230.71 allows a maximum of six disconnecting means for a single set of service-entrance conductors.

Which NEC article governs the installation of transformers with a primary voltage over 600V?

Answer: Article 450

NEC Article 450 covers transformers and transformer vaults, including those rated over 600V.

What does the NEC require for overcurrent protection of a 480V, 3-phase, 100 kVA transformer with a secondary of 208Y/120V?

Answer: Primary protection set at 125% of rated current satisfies the NEC for most cases

Per NEC 450.3, primary overcurrent protection set no more than 125% of rated primary current is the standard requirement for most transformers.

NEC 310.15 ampacity tables are based on an ambient temperature of how many degrees Celsius?

Answer: 30°C

NEC ampacity tables in 310.15 are based on a 30°C (86°F) ambient temperature unless otherwise noted.

According to NEC 250.122, if a feeder circuit's overcurrent device is increased in size to handle a larger load, what must also be increased?

Answer: The equipment grounding conductor

NEC 250.122(B) requires the equipment grounding conductor to be proportionally increased when the OCPD is upsized.

Under NFPA 70E, what arc flash PPE category requires a minimum arc rating of 40 cal/cm²?

Answer: Category 4

NFPA 70E Table 130.5(G) assigns PPE Category 4 a minimum arc rating of 40 cal/cm².

Which NEC section defines the requirements for working clearances in front of electrical equipment operating at 600V or less?

Answer: NEC 110.26

NEC 110.26 specifies minimum working clearances, dedicated space, and headroom requirements for equipment up to 1000V.