NEC Code and Calculations Flashcards

According to the NEC, what is the maximum voltage drop allowed for a branch circuit serving lighting loads?

Answer: 3%

The NEC recommends a maximum voltage drop of 3% for branch circuits and 5% total for feeders and branch circuits combined.

A 20-ampere, 120-volt branch circuit is limited to what maximum continuous load?

Answer: 16 amperes

NEC 210.20 requires that continuous loads not exceed 80% of the branch circuit rating, so 20A × 80% = 16A maximum continuous load.

What NEC article covers wiring methods and materials for general installations?

Answer: Article 300

NEC Article 300 covers general requirements for wiring methods and materials used in electrical installations.

When calculating the load for a household electric dryer, the NEC requires a minimum demand of how many volt-amperes?

Answer: 5,000 VA

NEC 220.54 requires a minimum load of 5,000 VA for each electric dryer when calculating feeder and service loads.

Under NEC Article 210, a 15-ampere branch circuit is permitted to serve a maximum of how many general lighting receptacle outlets in a dwelling?

Answer: No specific limit by count

The NEC does not limit receptacle outlets by count on a branch circuit; load limits and circuit ampacity govern the design instead.

What is the NEC standard for the maximum length of a flexible cord used as a wiring method?

Answer: Flexible cords are not a permitted wiring method for permanent installations

NEC 400.12 prohibits flexible cords from being used as a substitute for fixed wiring; they are not a permitted permanent wiring method.

According to the NEC, what ampacity correction factor applies when four current-carrying conductors are bundled together?

Answer: 80%

NEC Table 310.15(C)(1) requires an 80% ampacity correction factor when 4–6 current-carrying conductors are bundled together.