Journeyman Electrician’s Exam Journeyman Electrician's Service and Feeder Calculations 2

Question 1

A single-family dwelling has a 200-amp, 240V service. What is the minimum service entrance conductor size required using 75°C copper conductors per NEC Table 310.12?

Accepted Answer

2/0 AWG copper

Answer

NEC Table 310.12 allows 2/0 AWG copper at 75°C for a 200-amp service entrance.

Question 2

When calculating the demand load for electric ranges rated over 12 kW but not exceeding 27 kW in a dwelling, the NEC allows a maximum demand of 8 kW for one range, plus what percentage per additional kW over 12 kW?

Accepted Answer

5%

Answer

Per NEC Table 220.55, for ranges over 12 kW, add 5% for each additional kW above 12 kW.

Question 3

A commercial building has 50 kVA of fluorescent lighting. Using standard demand factors, what minimum amperage feeder is required on a 208Y/120V, 3-phase system?

Accepted Answer

139 A

Answer

50,000 VA ÷ (208V × 1.732) = 138.8 A, so a 139 A minimum feeder is required.

Question 4

Per NEC 220.82, the optional calculation for a single-family dwelling applies the first load increment of 10 kVA at 100%, then applies what demand factor to the remainder?

Accepted Answer

70%

Answer

NEC 220.82(B) applies 100% to the first 10 kVA and 40% to the remainder of the total connected load.

Question 5

What is the minimum feeder size for a 60A, 240V single-phase load that operates continuously for more than 3 hours?

Accepted Answer

75 A

Answer

Continuous loads must be sized at 125%, so 60A × 1.25 = 75A minimum feeder rating.

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Journeyman Electrician's Service and Feeder Calculations 2