Licensed Electrical Contractor Branch Circuit Calculations 3

Question 1

A 240V, single-phase branch circuit has a 30-ampere breaker. What is the maximum continuous load permitted on this circuit?

Accepted Answer

24 amperes

Answer

For a continuous load, the maximum permitted is 80% of the breaker rating: 30A × 0.80 = 24 amperes.

Question 2

Which NEC article specifically covers branch circuit requirements including ratings, outlet requirements, and conductor sizing?

Accepted Answer

Article 210

Answer

NEC Article 210 covers branch circuits, including their ratings, conductor requirements, and outlet placement.

Question 3

A bathroom branch circuit in a dwelling supplies two GFCI receptacles. Per NEC 210.11(C)(3), what is the minimum circuit rating required?

Accepted Answer

20 amperes

Answer

NEC 210.11(C)(3) requires at least one 20-ampere branch circuit for bathroom receptacle outlets.

Question 4

When calculating branch circuit loads for general lighting in a store, what unit load in VA per square foot does the NEC Table 220.12 specify?

Accepted Answer

3.3 VA/sq ft

Answer

NEC Table 220.12 assigns a unit load of 3.3 VA per square foot for store (retail) occupancies.

Question 5

A branch circuit conductor has a calculated voltage drop of 4.8V on a 120V circuit. What is the percentage voltage drop?

Accepted Answer

4%

Answer

Voltage drop % = (4.8V / 120V) × 100 = 4%, which exceeds the recommended 3% for branch circuits.

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