NEC Load Calculations & Branch Circuits 2 — Questions and Answers
Question 1: What is the minimum general lighting load per square foot for a dwelling unit per NEC Table 220.12?
- 1 VA
- 2 VA
- 3 VA (Correct answer)
- 5 VA
Correct answer: 3 VA
Dwelling units use a general lighting load of 3 VA per square foot under the standard calculation method.
Question 2: How many small-appliance branch circuits are required as a minimum in a dwelling kitchen?
- 1
- 2 (Correct answer)
- 3
- 4
Correct answer: 2
NEC 210.11(C)(1) requires at least two 20-ampere small-appliance branch circuits for the kitchen, pantry, and dining areas.
Question 3: A 20-ampere branch circuit at 120 volts has a maximum continuous load rating of how many amperes?
- 16 A (Correct answer)
- 18 A
- 20 A
- 25 A
Correct answer: 16 A
Continuous loads are limited to 80% of the circuit rating, so 20 A x 0.80 = 16 A.
Question 4: What VA value is used for each small-appliance and laundry branch circuit in the standard dwelling calculation?
- 1000 VA
- 1500 VA (Correct answer)
- 2000 VA
- 3000 VA
Correct answer: 1500 VA
NEC 220.52 requires a minimum of 1500 VA for each small-appliance and laundry branch circuit.
Question 5: Under the standard method, what demand factor applies to the dwelling general lighting load above the first 3000 VA up to 120,000 VA?
- 100%
- 70%
- 35% (Correct answer)
- 25%
Correct answer: 35%
Per NEC Table 220.42, the portion from 3001 to 120,000 VA is taken at 35%.
Question 6: What is the minimum size THHN copper conductor permitted for a 20-ampere branch circuit?
- 14 AWG
- 12 AWG (Correct answer)
- 10 AWG
- 8 AWG
Correct answer: 12 AWG
A 20-ampere branch circuit requires a minimum 12 AWG copper conductor.
Question 7: Receptacles in a dwelling are generally NOT counted as load in the standard calc because they are covered by which allowance?
- Laundry circuit
- General lighting load (Correct answer)
- Heating load
- Motor load
Correct answer: General lighting load
In dwellings the general lighting load (3 VA/sq ft) covers general-use receptacle outlets, so they aren't added separately.
NEC Load Calculations & Branch Circuits 2
What is the minimum general lighting load per square foot for a dwelling unit per NEC Table 220.12?