Licensed Electrical Contractor Licensed Electrical Contractor Branch Circuit Calculations Questions and Answers 2

Question 1

A 120V branch circuit supplies a 1,500W electric water heater. What is the minimum circuit ampere rating required per NEC Article 422?

Accepted Answer

20 amperes

Answer

A 1,500W load at 120V draws 12.5A, and since a fixed appliance requires 125% sizing, the minimum is 15.625A, requiring a 20A circuit.

Question 2

What is the maximum number of 180VA receptacle outlets permitted on a 20-ampere, 120-volt general-purpose branch circuit?

Accepted Answer

13

Answer

A 20A circuit at 120V provides 2,400VA, and dividing by 180VA per outlet yields a maximum of 13 receptacle outlets.

Question 3

When calculating branch circuit loads for a commercial kitchen, a 5,000W electric oven connected to a 240V single-phase circuit draws how many amperes?

Accepted Answer

20.83 amperes

Answer

Dividing 5,000W by 240V yields approximately 20.83 amperes of current draw.

Question 4

Per NEC 210.11(C)(3), a dwelling unit requires at least how many 20-ampere small-appliance branch circuits for the kitchen and dining areas?

Accepted Answer

2

Answer

The NEC requires a minimum of two 20-ampere small-appliance branch circuits serving kitchen countertop and dining area receptacles.

Question 5

A 14 AWG copper conductor on a 15-ampere branch circuit can safely supply a maximum continuous load of how many amperes?

Accepted Answer

12 amperes

Answer

A continuous load on a 15A branch circuit is limited to 80% of the rating, which equals 12 amperes.

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Licensed Electrical Contractor Licensed Electrical Contractor Branch Circuit Calculations Questions and Answers 2