Exam Cheat Sheet · Quick Reference

Maryland Master Electrician

Maryland · PSI Services Contractor

Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.

Total questions

Passing score

70%

Exam time

240 min

Administered by

PSI Services Contractor

Format

Reference materials allowed

Maryland State Portion 90 questions

Electrical Theory 10 Q · 11%

DefinitionsTheory Including Ohm's LawTechniquesTroubleshootingEquipment/DevicesInstrumentsMaterialsMathConversionsDiagramsSymbols

Wiring and Protection 14 Q · 16%

NEC Article 100NEC Article 110NEC Article 200-210NEC Article 215-225NEC Article 230NEC Article 240NEC Article 250-285

Wiring Methods and Materials 13 Q · 14%

NEC Article 300NEC Article 310-314NEC Article 320-330NEC Article 332-356NEC Article 358-374NEC Article 376-398

Equipment for General Use 9 Q · 10%

NEC Article 400-411NEC Article 422-427NEC Article 430-450NEC Article 455-490

Special Occupancies 8 Q · 9%

NEC Article 500-525NEC Article 530-547NEC Article 550-590

Special Equipment 4 Q · 4%

NEC Article 600-675NEC Article 680-695

Special Communications 2 Q · 2%

NEC Article 700-708NEC Article 720-830

Calculations 30 Q · 33%

Branch-circuit and feeder load calculations for dwelling units (standard and optional methods)Service load calculations including demand factors for multifamily and commercial occupanciesMotor circuit conductor sizing (single motor, multiple motors, and combination loads)Motor branch-circuit short-circuit and ground-fault protective device ratings (Table 430.52)Motor overload protection sizing and trip current percentagesConductor ampacity correction and adjustment factors (ambient temperature, number of conductors)Conduit and raceway fill calculations for conductorsTransformer overcurrent protection sizing (primary and secondary, Tables 450.3(A) and 450.3(B))

Key Distinctions

OverloadvsShort Circuit / Ground Fault

An overload is excess current beyond normal full-load rating that causes damage only when persistent; a short circuit or ground fault is NOT classified as an overload per NEC Article 100.

NEC, Article 100 — Definition of Overload

NEC Full-Load Current Table (430.250)vsMotor Nameplate Current

Table values from NEC 430.250 are used to size branch-circuit conductors; the nameplate current is used only for sizing separate motor overload protection per 430.6(A)(2).

NEC, Section 430.6(A)(1)

EMT Securing Distance from TerminationvsFMC Securing Distance from Termination

EMT must be secured within 900 mm (3 ft) of each termination, while FMC must be secured within 300 mm (12 in.) of each termination.

NEC, Section 358.30(A)

Transformer Primary-Only Protection (≤1000V, <9A)vsTransformer Primary-and-Secondary Protection (≤1000V, <9A)

Primary-only protection allows a maximum of 167% for primary currents less than 9 amperes, while the primary-and-secondary method allows up to 250% for the same current range.

NEC, Table 450.3(B)

Annex C Standard Fill Tables (e.g., C.1)vsAnnex C Compact Stranded Tables (e.g., C.1(A))

Standard Annex C tables apply only to concentric stranded conductors; the (A)-suffix tables must be used for compact stranded conductors.

NEC, Informative Annex C, Table C.1 Note 1

Article 706 (Energy Storage Systems)vsArticle 480 (Storage Batteries)

Article 706 governs energy storage systems with a capacity greater than 3.6 MJ (1 kWh); systems at or below that threshold fall under Article 480.

NEC Handbook, Section 706.1

Straight Pull Box Minimum LengthvsAngle Pull Box Minimum Length

For a straight pull, the box length must be at least 8 times the trade size of the largest raceway; angle pulls use a different multiplier (6×) plus the sum of other raceways per NEC 314.28(A).

NEC 314.28(A)(1)

Grounded Conductor Identification ≤6 AWGvsGrounded Conductor Identification >6 AWG

Conductors 6 AWG or smaller must have a continuous white or gray outer finish; larger conductors may use white or gray markings at terminations rather than a continuous finish.

NEC, Section 200.6(A)

One-Family Dwelling Service Disconnect MinimumvsTwo 2-Wire Branch Circuit Installation Service Disconnect Minimum

A one-family dwelling requires a minimum 100-ampere, 3-wire service disconnect, while an installation with no more than two 2-wire branch circuits requires only a 30-ampere disconnect.

NEC, Section 230.79(C)

Continuous LoadvsNoncontinuous Load

A continuous load is one where maximum current is expected to persist for 3 hours or more, requiring conductors/devices sized at 125% of that load; noncontinuous loads do not carry this 125% requirement.

NEC Handbook, Article 100 — Definitions

Rod/Pipe/Plate Grounding Electrode Conductor Max SizevsConcrete-Encased Electrode Minimum Length

The grounding electrode conductor to a rod, pipe, or plate need not exceed 6 AWG copper, while a concrete-encased electrode requires at least 20 ft of reinforcing bar to qualify.

NEC, Section 250.66(A)

Class A GFCI Trip ThresholdvsEquipment Ground-Fault Protection (230.95)

A Class A GFCI trips at 6 mA or higher to protect persons from electrocution, while equipment ground-fault protection per 230.95 is required on service disconnects rated 1000 A or more on 480Y/277V solidly grounded wye systems to protect equipment.

NEC Handbook, Article 100 — Definitions, Ground-Fault Circuit Interrupter (GFCI)

Key Terms

Ampacity NEC Handbook, Article 100 — Definitions

The maximum current, in amperes, that a conductor can carry continuously under conditions of use without exceeding its temperature rating.

Continuous Load NEC Handbook, Article 100 — Definitions

A load where the maximum current is expected to continue for 3 hours or more, per NEC Article 100.

Overload NEC, Article 100 — Definition of Overload

Operation of equipment beyond its normal full-load rating or a conductor beyond its ampacity that, when persistent, causes damage or dangerous overheating—explicitly not the same as a short circuit or ground fault.

Class A GFCI NEC Handbook, Article 100 — Definitions, Ground-Fault Circuit Interrupter (GFCI)

A ground-fault circuit interrupter that trips when ground-fault current reaches 6 mA or higher, designed to prevent ventricular fibrillation.

Effective Ground-Fault Current Path NEC, Section 250.4(A)(5)

Per NEC 250.4(A)(5), a low-impedance circuit that facilitates overcurrent device operation; the earth alone does NOT qualify as an effective ground-fault current path.

Concrete-Encased Grounding Electrode NEC, Section 250.52(A)(3)

Per NEC 250.52(A)(3), at least 20 ft of ½-in. steel reinforcing bar encased by at least 2 in. of concrete in direct contact with the earth.

Single Rod/Pipe/Plate Supplemental Electrode Exception NEC, Section 250.53(A)(2), Exception

Per NEC 250.53(A)(2) Exception, a supplemental grounding electrode is not required if the single rod, pipe, or plate electrode measures 25 ohms or less resistance to earth.

Feeder Conductor Sizing for Continuous Loads NEC, Section 215.2(A)(1)(a)

Per NEC 215.2(A)(1)(a), feeder conductor ampacity must equal at least the noncontinuous load plus 125% of the continuous load.

Ground-Fault Protection of Equipment — Feeder Threshold NEC, Section 215.10

Per NEC 215.10, each feeder disconnect rated 1000 amperes or more on solidly grounded wye systems over 150 V to ground (≤600 V phase-to-phase) shall have ground-fault protection of equipment.

Dwelling Unit Service Disconnect — One-Family NEC, Section 230.79(C)

Per NEC 230.79(C), the service disconnecting means for a one-family dwelling shall be rated not less than 100 amperes, 3-wire.

Optional Dwelling Load Calculation General Load NEC, Section 220.82(B)

Per NEC 220.82(B), the general calculated load is 100% of the first 10 kVA plus 40% of the remainder.

Fastened-In-Place Appliance Demand Factor NEC 220.53

Per NEC 220.53, a 75% demand factor may be applied to four or more fastened-in-place appliances (≥½ hp or ≥500W) served by the same feeder or service in a dwelling.

Small-Appliance Branch Circuit Load NEC 220.52(A)

Per NEC 220.52(A), each 2-wire small-appliance branch circuit in a dwelling unit is calculated at a minimum of 1500 volt-amperes.

Grounding Electrode Conductor — Rod/Pipe/Plate Maximum Size NEC, Section 250.66(A)

Per NEC 250.66(A), the grounding electrode conductor to a rod, pipe, or plate electrode need not be larger than 6 AWG copper or 4 AWG aluminum.

Box Drain Openings (Wet/Damp Locations) NEC 314.15

Per NEC 314.15, field-installed drainage openings in boxes listed for damp or wet locations shall be not smaller than ⅛ in. and not larger than ¼ in. in diameter.

Neon Sign Secondary Circuit — Transformer Current Limit NEC 600.23(D)

Per NEC 600.23(D), transformers and electronic power supplies for electric signs shall have a secondary-circuit current rating of not more than 300 mA.

Formulas to Know

Feeder/Service Conductor Ampacity (Continuous + Noncontinuous Loads)Required Ampacity ≥ Noncontinuous Load (A) + 1.25 × Continuous Load (A)

Dwelling Optional Method — General Calculated LoadGeneral Load = 100% × first 10,000 VA + 40% × (Total Listed Load VA − 10,000 VA)

Motor Branch-Circuit Conductor Ampacity (Single Motor)Conductor Ampacity ≥ 1.25 × FLC (from NEC Table 430.250 for 3-phase, or 430.248 for single-phase)

Motor Branch-Circuit Short-Circuit/Ground-Fault Protective Device Rating

Max Device Rating = FLC (table value) × Multiplier from NEC Table 430.52 (e.g., 250% for inverse-time CB, 300% for dual-element fuse)

Motor Overload Protection Trip Current (standard motors)

Max Overload Setting = Nameplate FLA × 1.25 (motors with SF ≥ 1.15 or temp rise ≤ 40°C) or × 1.15 (all other motors)

Conductor Ampacity Correction (Ambient Temperature)Corrected Ampacity = Table Ampacity × Temperature Correction Factor (NEC Table 310.15(B)(1) or 310.15(B)(2))

Conductor Ampacity Adjustment (More Than 3 Current-Carrying Conductors)

Adjusted Ampacity = Table Ampacity × Bundling Adjustment Factor (NEC Table 310.15(C)(1), e.g., 0.80 for 4–6 conductors)

Conduit Fill — Maximum Cross-Sectional Area

Sum of cable/conductor areas ≤ Fill % × Conduit Internal Area (40% for 3+ conductors, 53% for 2 conductors, 31% for 1 conductor; NEC Chapter 9, Table 1)

Transformer Primary Overcurrent Protection (≤1000V, Primary-and-Secondary Method, Primary Current <9A)Max Primary OCPD = 250% × Primary FLA (NEC Table 450.3(B))

Straight Pull Box Minimum LengthBox Length ≥ 8 × Trade Size of Largest Raceway (NEC 314.28(A)(1))

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