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Texas Master Electrician Licensing Exam — Calculations Portion: Practice Exam Guide

What This Practice Exam Covers

The Texas Master Electrician calculations exam consists of 33 questions answered in 170 minutes, with a passing score of 70% (roughly 24 correct answers). The exam spans 10 topic areas weighted from 1 to 8 items each, covering everything from motor feeder sizing to PV system voltage calculations.

This practice site offers two options:

• Free practice exam: 10 questions per attempt drawn from a limited pool. You can retake it as many times as you like to get comfortable with the format, question style, and calculation demands before committing to deeper prep.
• Full practice exam (paid): Mirrors the real exam exactly — 33 questions, 170-minute time limit, drawn from a pool of 328+ questions so every attempt produces a unique set. No two sittings are identical, which means repeated attempts give you genuine diagnostic data rather than score inflation from memorized questions.

Start with the free exam to calibrate where you stand, then use the full exam for serious timed practice.

What You'll Be Tested On

Electrical Services, Service Equipment, and Separately Derived Systems — 8 items

This is the heaviest-weighted topic and deserves the most study time. Questions require you to size service conductors using NEC Table 310.16 and NEC 230.42(A), determine disconnecting means ratings, and build out a complete grounding electrode system. You must know Table 250.66 cold — it governs grounding electrode conductor sizing for services and separately derived systems. Main bonding jumper and system bonding jumper sizing calculations appear here, as do separately derived system grounding requirements under NEC Article 250.30. Ground-fault protection thresholds for solidly grounded wye services are also fair game.

Motors and Generators — 6 items

Six items means roughly 18% of your exam score lives here. You must be able to pull full-load current values from NEC Table 430.250 (three-phase AC motors) and Table 430.248 (single-phase), then apply the 125% multiplier per NEC Section 430.22 for branch-circuit conductor sizing. Motor feeder conductor ampacity follows NEC Table 430.250 and Section 430.24 — largest motor FLA × 125% plus the sum of remaining motors. Overload protection sizing percentages (115%, 125%, 140% depending on service factor and temperature rise) appear here, as does the 115% disconnecting means rating requirement.

Branch Circuit Calculations and Conductors — 4 items

Expect calculations involving the 125% rule for continuous loads per NEC 210.19(A)(1), standard ampere ratings under NEC 240.6(A), and dwelling unit load calculations covering general lighting, small-appliance circuits, laundry, and cooking appliances. Demand factors for household ranges (Table 220.55, Note 1) and dryers (Table 220.54) require careful step-by-step arithmetic. GFCI and AFCI protection requirements by location type round out this topic.

Electrical Feeders — 3 items

Feeder questions center on the 125% rule for continuous loads per NEC 215.2(A)(1), demand-factor load calculations from Parts III and IV, and feeder overcurrent protection sizing. Neutral load calculations — including permitted reductions — show up here. You must also know when ground-fault protection of equipment is required for feeders rated 1,000 amperes or more.

Calculations and Theory — 2 items

These questions test fundamental load calculation methods for both dwelling and non-dwelling occupancies, including optional calculation methods for dwelling units and multifamily buildings. Cooking appliance and clothes dryer demand factors (NEC Table 220.55, NEC Table 220.54) appear directly in this topic as well as in branch circuits.

Electrical Wiring Methods and Electrical Materials — 2 items

Conduit fill calculations using Chapter 9, Table 1, Table 4, and Table 5 are the core skill. You need to know the internal areas for EMT, RMC, IMC, PVC, and FMC from Chapter 9, Table 4, and match them against conductor dimensions from Chapter 9, Table 5. Ambient temperature correction factors and adjustment factors for more than three current-carrying conductors in a raceway (applied in sequence against Table 310.16) are tested here. Minimum cover requirements for underground wiring methods appear as well.

Electrical Equipment and Devices — 2 items

Motor branch-circuit protective device sizing (using NEC Table 430.250 and Table 430.52), transformer overcurrent protection under NEC Article 450, and overload protection thresholds under NEC Section 430.32 are the key calculation types. Know the difference between short-circuit/ground-fault protection and overload protection — the exam exploits that confusion.

Electrical Control Devices and Disconnecting Means — 1 item

One exam item covers disconnecting means type and rating requirements, including the 115% calculation for motor disconnecting means from NEC Table 430.250 and Section 430.110(A). Motor controller horsepower ratings and overload protection percentages from NEC Section 430.32(A)(1) also fall here.

Special Occupancies, Equipment, and Conditions — 1 item

This single item may cover electric welder ampacity (duty cycle calculations for arc and resistance welders), EVSE branch-circuit sizing at 125% of continuous load, or hazardous location classification and protection techniques.

Renewable Energy Technologies — 1 item

PV system maximum DC voltage using temperature correction factors, PV circuit current sizing, and overcurrent protection device ratings for renewable energy circuits are the likely targets. Busbar and feeder sizing for load-side interconnections may appear.

Worked Sample Questions

Question 1 — Laundry Room Dryer Demand Factor

A laundry room contains 10 dryers rated at 5 kW each, operating on 208V three-phase. Applying the NEC demand factor, what is the total calculated load?

• A. 25 kW
• B. 35 kW
• C. 40 kW
• D. 50 kW

Correct Answer: A — 25 kW

NEC Table 220.54 sets the demand factor for commercial dryer installations. For 10 dryers, the applicable demand factor is 50%. The connected load is 10 × 5 kW = 50 kW. Apply the factor: 50 kW × 0.50 = 25 kW. Many candidates choose D (50 kW) by skipping the demand factor step entirely, or choose C by misreading the table row. Always confirm the number of dryers against the correct table row before calculating.

Question 2 — Motor Feeder Conductor Ampacity

A feeder supplies three motors: 20 HP (FLA = 27A), 15 HP (FLA = 22A), and 10 HP (FLA = 17A). What is the minimum feeder conductor ampacity?

• A. 70A
• B. 75A
• C. 80A
• D. 85A

Correct Answer: B — 75A

Per NEC Table 430.250 and Section 430.24, feeder ampacity = (largest motor FLA × 125%) + sum of all other motors' FLA. Largest motor: 27A × 1.25 = 33.75A. Remaining motors: 22A + 17A = 39A. Total = 33.75 + 39 = 72.75A. The minimum conductor must be rated for at least 72.75A; the next standard ampacity that satisfies this is 75A (using NEC Table 310.16 at 75°C). Answer A (70A) is inadequate; answers C and D are oversized and not the minimum.

Question 3 — Feeder Neutral Conductor Size

A 208Y/120V feeder carries 225A on phase conductors and 150A on the neutral. What is the minimum neutral conductor size in THHN copper at 75°C?

• A. 2/0 AWG
• B. 3/0 AWG
• C. 250 kcmil
• D. 300 kcmil

Correct Answer: A — 2/0 AWG

The neutral conductor must carry the actual neutral current, which is 150A. Per NEC Table 310.16, 2/0 AWG THHN copper is rated 175A at 75°C — the smallest listed size that exceeds 150A. 3/0 AWG (200A) and larger sizes are adequate but not the minimum. Note that the 225A phase load drives the phase conductor sizing but does not control the neutral.

How to Read Your Score

The passing threshold is 70%, which means 24 correct out of 33. Treat your first practice attempt as a diagnostic, not a verdict. A score of 55–65% on the first full attempt is common for working electricians who know the trade but haven't yet reviewed the specific code sections and calculation sequences the exam tests.

After each attempt, review your results by topic. The platform's breakdown will show you which of the 10 areas cost you the most points. If Motors and Generators (6 items) and Electrical Services (8 items) are dragging your score, fixing those two areas alone can move you several percentage points.

A practice score in the 68–72% range deserves honest attention — that margin disappears under real exam pressure. Aim to hit 78–80% consistently on the full 33-question practice exam before scheduling your licensing attempt. Scoring well above the minimum gives you a buffer for the few questions every exam will include that are genuinely ambiguous or unfamiliar.

Where Candidates Lose Points

Wrong table, right calculation. Motor questions are lost most often by pulling FLA from the wrong table — Table 430.248 (single-phase) instead of Table 430.250 (three-phase) or vice versa. Confirm voltage and phase before grabbing a number.

Skipping the demand factor. Branch circuit and feeder load calculation questions routinely include a demand factor step that candidates skip in favor of adding raw wattages. Table 220.54 (dryers) and Table 220.55 (ranges) are easy to overlook under time pressure.

Correction and adjustment factors applied in isolation. Wiring methods questions often require both a temperature correction factor and a bundling adjustment factor (for more than three current-carrying conductors), applied sequentially to the Table 310.16 ampacity. Applying only one factor is one of the most common calculation errors on this exam.

Confusing overload and short-circuit protection percentages. NEC Section 430.32(A)(1) governs overload protection; Table 430.52 governs short-circuit and ground-fault protection. These use different multipliers, and mixing them up produces wrong answers that look plausible.

Time management on the heavy topics. With 170 minutes for 33 questions, you have roughly 5 minutes per question. Multi-step feeder and service calculations in the Electrical Services topic (8 items) can consume 8–10 minutes each if you're not practiced. Use the free exam to build calculation speed before attempting the full timed version.

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