Journeyman Electrician’s Exam Journeyman Electrician's Service and Feeder Calculations 5 — Questions and Answers
Question 1: For a 3,600 sq ft single-family dwelling using the standard method, how many 20A small appliance branch circuits are required, and what is their total VA load in the service calculation?
- 1 circuit, 1,500 VA
- 2 circuits, 3,000 VA (Correct answer)
- 2 circuits, 1,500 VA
- 3 circuits, 4,500 VA
Correct answer: 2 circuits, 3,000 VA
NEC 210.11(C)(1) requires at least two 20A small appliance circuits, each at 1,500 VA = 3,000 VA total per NEC 220.52.
Question 2: A service panel is supplied by a 500 kcmil aluminum feeder. What is the ampacity of this conductor using the 75°C column of NEC Table 310.15(B)(16)?
- 260 A
- 310 A (Correct answer)
- 330 A
- 380 A
Correct answer: 310 A
Per NEC Table 310.15(B)(16), 500 kcmil aluminum at 75°C has an ampacity of 310A.
Question 3: What additional load must be included in a service calculation for a dwelling that has a dedicated 20A laundry circuit per NEC 220.52(B)?
- 750 VA
- 1,000 VA
- 1,500 VA (Correct answer)
- 2,000 VA
Correct answer: 1,500 VA
NEC 220.52(B) requires 1,500 VA for each required laundry circuit in the service load calculation.
Question 4: When four current-carrying conductors are in a conduit, the ampacity adjustment factor per NEC 310.15(C)(1) is:
- 100%
- 80% (Correct answer)
- 70%
- 60%
Correct answer: 80%
NEC Table 310.15(C)(1) requires an 80% adjustment factor when 4–6 current-carrying conductors share a raceway.
Question 5: A service calculation for a 3,000 sq ft home includes general lighting, two small appliance circuits, one laundry circuit, a 12 kW range, and a 5 kW dryer. Using standard demand factors, what is the demand on the first 3,000W of the general lighting load?
- 50%
- 75%
- 100% (Correct answer)
- 125%
Correct answer: 100%
Per NEC Table 220.42, the first 3,000 VA of residential lighting load is taken at 100% demand.
Question 6: A 200A service is fed through 100 feet of 2/0 AWG copper conductors. If the calculated load is 175A, does this installation meet NEC requirements?
- Yes, because 2/0 AWG copper is rated 175A at 75°C (Correct answer)
- No, because voltage drop exceeds 3%
- Yes, because the load is less than the conductor ampacity
- No, because 200A service requires 3/0 AWG minimum
Correct answer: Yes, because 2/0 AWG copper is rated 175A at 75°C
NEC Table 310.15(B)(16) rates 2/0 AWG copper at 175A (75°C), which matches the 175A calculated load, satisfying NEC requirements.
Question 7: Per NEC 220.14(J), what load in VA must be included for each receptacle outlet in a commercial or industrial occupancy (other than a dwelling) when calculating branch circuit or feeder loads?
- 90 VA per outlet
- 125 VA per outlet
- 180 VA per outlet (Correct answer)
- 250 VA per outlet
Correct answer: 180 VA per outlet
NEC 220.14(J) assigns 180 VA per single or duplex receptacle outlet in non-dwelling occupancies.
