Next Master Electrician Practice Test - Code Application & Coordination

MASTER NEC 2023

Master Electrician Practice Test - Calculations & Service Design

Master Electrician practice test focused on commercial and multifamily load calculations, service and feeder sizing, transformer protection, and motor feeder design. NEC 2023 with 2026-stable items tagged accordingly.

TOPICS COVERED

Load Calculations Motor Circuits Transformers Conductor Sizing Voltage Drop Ampacity

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Frequently Asked Questions

Yes — completely free with no signup required. All answers include detailed explanations.

Requirements vary by state but typically include 4–8 years of documented electrical work experience plus a valid Journeyman license.

Advanced NEC code interpretation, load calculations, service entrance design, motor controls, generator systems, and electrical system design.

The Master exam focuses more on design, calculations, and planning rather than installation details. Load calculation and service sizing questions are weighted heavily.

How to Use This Practice Test

This Master Electrician Practice Test - Calculations & Service Design has 25 questions with detailed answers and NEC references. Take the full test, review every wrong answer, and look up the NEC article it references before moving on.

Tip: Focus on multi-step calculations. Write each step on scratch paper — one math error means a wrong answer.

Topics covered: Load calculations, transformer sizing, three-phase circuits, service entrance, and special occupancies.
Passing score: 70–75% (most states). Master exams are calculation-heavy — practice the math, not just the lookup.
Questions: 25 multiple-choice, one correct answer each

Questions

45 min

Time

70%

Pass

Timer starts immediately. Progress is auto-saved.

Student Reviews 5.0 / 5 · 2 reviews

Frank Denton

I've been a journeyman for 8 years and finally sat for my master. These practice tests are genuinely hard which is what you want. The service design and calculation questions are on another level compared to journeyman prep. Passed by a comfortable margin.

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Mar 2, 2026

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Mar 2, 2026

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Master Electrician Practice Test - Calculations & Service Design — Question List

Question 1: A multifamily dwelling has 12 units. Using the optional method in 220.84, what demand factor is applied to the total connected load?

NEC Reference: NEC Table 220.84

Question 2: A retail store has 5,000 sq ft of floor area. What is the minimum general lighting load using the unit load from Table 220.42(A)?

5,000 VA
10,000 VA
15,000 VA
17,500 VA

NEC Reference: NEC Table 220.42(A)

Question 3: Full-load current of a 25 HP, 3-phase, 460V squirrel-cage motor from Table 430.250 is:

NEC Reference: NEC Table 430.250

Question 4: A 75 kVA, 480V–208Y/120V transformer is protected on the primary only. Primary FLC is approximately 90A. Maximum primary OCPD is:

100A
110A
125A
150A

NEC Reference: NEC 450.3(B) / 240.6

Question 5: A 400A 277/480V 3-phase 4-wire feeder uses copper conductors at 75°C. From Table 310.16, the smallest size that meets 400A is:

400 kcmil
500 kcmil
600 kcmil
700 kcmil

NEC Reference: NEC Table 310.16

Question 6: A feeder serves a heating load of 30 kW and a cooling load of 22 kW, both not in use at the same time. For service-load calculations, the value used is:

Sum of both = 52 kW
Average = 26 kW
Larger only = 30 kW
125% of larger = 37.5 kW

NEC Reference: NEC 220.60

Question 7: Five 12 kW electric ranges in a multifamily dwelling. Using Table 220.55 Column C, the demand load is:

15 kW
20 kW
25 kW
60 kW

NEC Reference: NEC Table 220.55

Question 8: Per 220.61(C)(2), the feeder neutral load for non-linear (electric-discharge or harmonic-producing) loads is calculated at:

70% of the load above 200A
100% — no reduction permitted
50% of the total
125% of the load

NEC Reference: NEC 220.61(C)(2)

Question 9: A 2,400 sq ft single-family dwelling has the following: range 12 kW, dryer 5 kW, water heater 4.5 kW, dishwasher 1.2 kW, disposal 0.8 kW, A/C 6 kW (240V), heat 7 kW. Using the optional method (220.82), the first 10 kVA at:

50%
75%
100%
125%

NEC Reference: NEC 220.82(B)(1)

Question 10: A 3-phase 480V feeder carries 100A over 250 ft using 1/0 AWG copper (resistance 0.122 Ω/1000 ft). Approximate voltage drop?

About 3V
About 5V
About 8V
About 12V

NEC Reference: NEC Chapter 9 Table 8 / 215.2 IN

Question 11: A raceway carries 6 current-carrying THWN conductors in a 40°C ambient. The 75°C ampacity from Table 310.16 must be multiplied by what combined factor?

0.80
0.88
0.70 (about)
0.65

NEC Reference: NEC 310.15(B)(1) / Table 310.15(C)(1)

Question 12: Conductors run in parallel per 310.10(G) must be:

Same length, material, size, insulation, and termination method
Different sizes mixed for ampacity flexibility
Different lengths but same insulation
6 AWG minimum

NEC Reference: NEC 310.10(G)

Question 13: Two motors share a feeder: 25 HP 3φ 460V (FLC 34A) and 10 HP 3φ 460V (FLC 14A). Per 430.24, minimum feeder conductor ampacity is:

48A
56.5A
60A
70A

NEC Reference: NEC 430.24

Question 14: For the same two-motor feeder (25 HP and 10 HP, 460V), the maximum inverse-time CB feeder OCPD is calculated by adding:

70A
90A
100A
125A

NEC Reference: NEC 430.62

Question 15: A K-rated transformer is selected when the served load is:

A heavy non-linear (harmonic) load
Single-phase resistance heating only
A motor load of constant FLC
A power-factor-corrected load below 0.7 PF

NEC Reference: IEEE / NEC 450 / harmonics

Question 16: A 200A panel has a PV interconnection at the load side per 705.12(B). The sum of the OCPDs feeding the busbar (utility + PV) is limited to:

100% of the bus rating = 200A
120% of the bus rating = 240A
200% of the bus rating = 400A
No limit applies

NEC Reference: NEC 705.12(B)(3)(2)

Question 17: A K-12 school is using the optional method in 220.86. The first 3 VA per sq ft is taken at 100%; the remainder is taken at:

50% then 25%
75% then 25%
100% then 50%
40% then 30%

NEC Reference: NEC Table 220.86

Question 18: 220.87 permits the existing-installation calculation method when:

Maximum demand data for at least one year is available (or 30-day × 1.25)
The building has been unoccupied for one year
New service is being installed for a new building
Load is unknown and must be estimated

NEC Reference: NEC 220.87

Question 19: 210.20(A) requires branch-circuit OCPD at not less than 125% of continuous load + 100% of non-continuous, except where:

The breaker and enclosure are listed for 100% continuous operation
The load is below 16A
The branch circuit is GFCI protected
No exception applies

NEC Reference: NEC 210.20(A) Exception

Question 20: Show window load per 220.43(A) is calculated at not less than:

50 VA per linear foot
100 VA per linear foot
180 VA per linear foot
200 VA per linear foot

NEC Reference: NEC 220.43(A)

Question 21: In the 200A residential panel shown, the 50A two-pole EV charger is a continuous load. Conductor and OCPD must be sized at:

200A residential panel with 50A two-pole EV charger branch circuit

100% of EVSE rating
125% of EVSE rating
150% of EVSE rating
80% of breaker rating

NEC Reference: NEC 625.41

Question 22: A 4 11/16 × 1 1/2 square box has a volume of 29.5 cu in. Maximum number of 12 AWG conductors permitted per Table 314.16(A) (no devices, clamps, or fittings counted)?

NEC Reference: NEC Table 314.16(A)

Question 23: Maximum number of 4/0 AWG THWN conductors permitted in 2-inch trade size EMT (internal area 3.356 sq in)?

NEC Reference: NEC Chapter 9 Tables 1, 4, 5

Question 24: A 2-inch raceway enters a junction box and the conductors make a U-pull (enter and exit on the same wall). Per 314.28(A)(2), minimum distance between raceway entry and the opposite wall is:

6 inches
8 inches
12 inches
24 inches

NEC Reference: NEC 314.28(A)(2)

Question 25: The motor branch-circuit one-line shows the motor at 28A FLC. If a second motor of 14A FLC is added on the same feeder, minimum feeder conductor ampacity per 430.24 is:

Motor branch-circuit one-line used for sizing a feeder serving two motors

NEC Reference: NEC 430.24

Key NEC References for This Test

Article	What It Covers
Art. 220	Load Calculations — optional and standard methods for multifamily
Art. 230	Services — service design, sizing, multiple disconnects
Art. 430	Motors — complete branch circuit design (conductor + OCPD + overload + disconnect)
Art. 445	Generators — standby systems, transfer switches
Art. 450	Transformers — sizing, primary/secondary OCPD, installation
Art. 706	Energy Storage Systems — battery/solar storage (major NEC 2026 expansion)

Study Tip: Practice transformer kVA calculations daily. Know the formula: I = kVA × 1000 ÷ (V × 1.732) for three-phase. This comes up on almost every master exam.

Master Electrician Practice Test - Calculations & Service Design

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How to Use This Practice Test

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Master Electrician Practice Test - Calculations & Service Design — Question List

Question 1: A multifamily dwelling has 12 units. Using the optional method in 220.84, what demand factor is applied to the total connected load?

Question 2: A retail store has 5,000 sq ft of floor area. What is the minimum general lighting load using the unit load from Table 220.42(A)?

Question 3: Full-load current of a 25 HP, 3-phase, 460V squirrel-cage motor from Table 430.250 is:

Question 4: A 75 kVA, 480V–208Y/120V transformer is protected on the primary only. Primary FLC is approximately 90A. Maximum primary OCPD is:

Question 5: A 400A 277/480V 3-phase 4-wire feeder uses copper conductors at 75°C. From Table 310.16, the smallest size that meets 400A is:

Question 6: A feeder serves a heating load of 30 kW and a cooling load of 22 kW, both not in use at the same time. For service-load calculations, the value used is:

Question 7: Five 12 kW electric ranges in a multifamily dwelling. Using Table 220.55 Column C, the demand load is:

Question 8: Per 220.61(C)(2), the feeder neutral load for non-linear (electric-discharge or harmonic-producing) loads is calculated at:

Question 9: A 2,400 sq ft single-family dwelling has the following: range 12 kW, dryer 5 kW, water heater 4.5 kW, dishwasher 1.2 kW, disposal 0.8 kW, A/C 6 kW (240V), heat 7 kW. Using the optional method (220.82), the first 10 kVA at:

Question 10: A 3-phase 480V feeder carries 100A over 250 ft using 1/0 AWG copper (resistance 0.122 Ω/1000 ft). Approximate voltage drop?

Question 11: A raceway carries 6 current-carrying THWN conductors in a 40°C ambient. The 75°C ampacity from Table 310.16 must be multiplied by what combined factor?

Question 12: Conductors run in parallel per 310.10(G) must be:

Question 13: Two motors share a feeder: 25 HP 3φ 460V (FLC 34A) and 10 HP 3φ 460V (FLC 14A). Per 430.24, minimum feeder conductor ampacity is:

Question 14: For the same two-motor feeder (25 HP and 10 HP, 460V), the maximum inverse-time CB feeder OCPD is calculated by adding:

Question 15: A K-rated transformer is selected when the served load is:

Question 16: A 200A panel has a PV interconnection at the load side per 705.12(B). The sum of the OCPDs feeding the busbar (utility + PV) is limited to:

Question 17: A K-12 school is using the optional method in 220.86. The first 3 VA per sq ft is taken at 100%; the remainder is taken at:

Question 18: 220.87 permits the existing-installation calculation method when:

Question 19: 210.20(A) requires branch-circuit OCPD at not less than 125% of continuous load + 100% of non-continuous, except where:

Question 20: Show window load per 220.43(A) is calculated at not less than:

Question 21: In the 200A residential panel shown, the 50A two-pole EV charger is a continuous load. Conductor and OCPD must be sized at:

Question 22: A 4 11/16 × 1 1/2 square box has a volume of 29.5 cu in. Maximum number of 12 AWG conductors permitted per Table 314.16(A) (no devices, clamps, or fittings counted)?

Question 23: Maximum number of 4/0 AWG THWN conductors permitted in 2-inch trade size EMT (internal area 3.356 sq in)?

Question 24: A 2-inch raceway enters a junction box and the conductors make a U-pull (enter and exit on the same wall). Per 314.28(A)(2), minimum distance between raceway entry and the opposite wall is:

Question 25: The motor branch-circuit one-line shows the motor at 28A FLC. If a second motor of 14A FLC is added on the same feeder, minimum feeder conductor ampacity per 430.24 is:

Key NEC References for This Test

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