Master Electrician Practice study guide with diagrams.
Electrical Devices — Master Exam Study Chapter
Learning Objectives
By the end of this chapter, you will be able to:
4.Identify the code requirements for receptacles, switches, and lighting outlets in dwelling and non-dwelling occupancies.
5.Apply the correct wiring methods and termination rules for devices in commercial and industrial settings.
6.Calculate and verify the minimum number of receptacle outlets required by the code for various room types.
7.Recognize the special requirements for devices in wet, damp, and hazardous locations.
8.Supervise installations involving GFCI, AFCI, and tamper-resistant devices with full code compliance.
9.Navigate the NEC efficiently to locate device-related requirements during the open-book exam.
1.1 General Device Requirements — Article 404 and 406
The two primary articles governing electrical devices are Article 404 (Switches) and Article 406 (Receptacles, Cord Connectors, and Receptacle Mounting) . A master electrician must understand that these articles are not merely about "where to put a plug" — they contain critical engineering and safety thresholds that affect design, load calculations, and inspection.
Switches (Article 404):
404.2(C) — Switches must not disconnect the grounded conductor unless the switch simultaneously opens all ungrounded conductors. This is a common inspection point: a single-pole switch must not be installed in the grounded (neutral) conductor path.
404.4 — All switches must be rated for the voltage and current of the circuit. For inductive loads (motors, ballasts), the switch must be rated for the load or marked "HP" (horsepower) rated.
404.9 — Snap switches must be enclosed in a listed box or enclosure. The box must be sized per 314.16(B) for the number of conductors and devices.
404.11 — Switches in wet or damp locations must be weatherproof, and if installed outdoors, they must be in a weatherproof enclosure with a cover that prevents moisture entry.
Receptacles (Article 406):
406.4(D) — Replacement receptacles must comply with current GFCI, AFCI, and tamper-resistant requirements. This is a critical "existing work" rule — a master cannot simply replace a receptacle in a kitchen without upgrading to GFCI if the location requires it.
406.5 — Receptacle mounting heights and orientations. The code does not mandate a specific height for standard receptacles (that is often an accessibility or local code issue), but 406.5(E) requires that receptacles in floors not be subject to damage and be enclosed in a box flush with the floor.
406.6 — Receptacles must be listed and marked with the manufacturer's name and rating. The ampere rating must not be less than the branch circuit rating.
406.7 — A receptacle must not be connected to a circuit that exceeds its rating. For example, a 15 A receptacle cannot be on a 20 A circuit unless it is a duplex receptacle where one receptacle is rated 20 A (the "20 A feed-through" rule).
Tamper-Resistant Receptacles (406.12):
All 125 V, 15 A and 20 A receptacles in dwelling units, guest rooms, and child care facilities must be tamper-resistant. This applies to all locations, including behind appliances, unless the receptacle is not readily accessible (e.g., above a ceiling, behind a permanently installed appliance).
1.2 Receptacle Placement — Dwelling Units (Article 210.52)
The receptacle spacing rules in 210.52(A) are a classic exam trap. The "6-foot/12-foot rule" is often misremembered. The actual rule:
A receptacle must be installed so that no point along the wall space (measured horizontally) is more than 6 feet from a receptacle. This means the maximum spacing between two receptacles is 12 feet.
Wall space is defined as any wall segment 2 feet or more in width. Walls less than 2 feet wide do not require a receptacle, but if one is installed, it counts toward the spacing.
Doorways, fireplaces, and fixed panels do not count as wall space.
Specific room requirements (210.52):
Kitchen counters (210.52(C)): Receptacles must be installed above countertops so that no point along the wall countertop is more than 2 feet from a receptacle. Receptacles must be on the wall above the countertop, not more than 20 inches above the counter surface. Islands and peninsulas have their own rules — a receptacle is required for each 2 feet of island counter length (measured along the long dimension).
Bathrooms (210.52(D)): At least one receptacle must be installed within 3 feet of the outside edge of each basin. It must be on a dedicated 20 A branch circuit (per 210.11(C)(3) ).
Laundry (210.52(F)): At least one receptacle for the laundry must be installed within 6 feet of the intended washer location.
Garages and basements (210.52(G)): At least one receptacle is required in each garage and unfinished basement. In basements, the receptacle must be on a dedicated 20 A circuit if there are no other receptacles in the basement (per 210.11(C)(4) ).
1.3 GFCI and AFCI Requirements — Articles 210.8 and 210.12
Ground-Fault Circuit-Interrupters (210.8):
The 2026 NEC has expanded GFCI requirements significantly. A master must know the full list of locations requiring GFCI protection for 125 V, 15 A and 20 A receptacles:
Bathrooms (all receptacles)
Garages and accessory buildings (including grade-level, not just below-grade)
Outdoors (including at dwelling unit entrances)
Crawl spaces (at or below grade)
Unfinished basements
Kitchens (all countertop and within 6 feet of sinks)
Sinks — within 6 feet of the outside edge of any sink (this includes non-kitchen sinks like wet bars)
Boathouses
Bathtubs and shower stalls — within 6 feet
Laundry areas
Indoor damp and wet locations
Commercial and industrial (210.8(B)):
GFCI protection is now required for all 125 V, 15 A and 20 A receptacles in:
Commercial and industrial kitchens (for countertop and sink-adjacent receptacles)
Rooftops (all receptacles on rooftops, not just those servicing HVAC equipment)
Indoors in commercial/industrial — any receptacle within 6 feet of a sink
Locker rooms with associated showering facilities
Garages, service bays, and similar areas where electrical diagnostic equipment or electric vehicles may be used
AFCI Requirements (210.12):
Arc-fault circuit interrupters are required for all 120 V, single-phase, 15 A and 20 A branch circuits supplying outlets in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, and similar areas. The 2026 code has expanded this to include dormitory units and guest rooms in hotels/motels.
The AFCI must be listed as a "combination type" (series and parallel arc protection). A master must verify that the AFCI is installed at the origin of the branch circuit (the panelboard) unless a listed outlet branch circuit type AFCI is used with specific conditions.
1.4 Receptacle Ratings and Configurations — Article 406.3
Receptacle configurations are standardized to prevent mismatched voltage and current connections. The NEMA configuration chart is not in the NEC, but the code requires that receptacles be of the proper configuration for the circuit voltage and current.
Key rules:
406.3(B) — Receptacles connected to circuits of different voltages, frequencies, or types (AC vs. DC) must not be interchangeable. This is why 120 V and 240 V receptacles have different blade configurations.
406.3(E) — A receptacle installed on a 30 A or larger circuit must be rated for that circuit. For example, a 50 A range receptacle must be rated 50 A.
406.3(F) — Receptacles must not be connected to a circuit that has a higher rating than the receptacle. The exception is the 15 A duplex on a 20 A circuit, which is permitted only if the receptacle is a duplex (two receptacles) and the circuit is 20 A.
Isolated Ground Receptacles (406.3(D)):
For sensitive electronic equipment, an isolated ground receptacle has an insulated grounding terminal that is connected to a separate grounding conductor run back to the panelboard. The receptacle must be marked with an orange triangle or the word "ISOLATED GROUND." The grounding conductor must terminate at the equipment grounding terminal of the panelboard or to a separately derived system's grounding terminal.
1.5 Wiring Methods for Devices — Article 300 and 314
Box Fill Calculations (314.16):
A master must be able to verify box fill. The calculation counts:
Each conductor that terminates in the box (count as 1 each)
Each device (switch or receptacle) counts as 2 conductors for the largest conductor in the box
Each cable clamp counts as 1 conductor (based on the largest conductor entering the box)
Each equipment grounding conductor counts as 1 conductor (all grounding conductors together count as one, based on the largest)
For example, a box containing a duplex receptacle, two 14/2 cables with ground, and one cable clamp:
110.14(A) — Terminals must be torqued to the manufacturer's specification. A master must use a torque wrench or screwdriver on all device terminations.
110.14(D) — Conductors must be sized for the termination temperature rating. For devices rated 100 A or less, the conductor must be sized based on the 60 °C column (or the 75 °C column if the device is marked for 75 °C). Most modern receptacles and switches are marked "75 °C" — but the termination must be rated for the conductor's ampacity.
Wrapping the screw terminal:
The conductor must be wrapped clockwise around the screw terminal so that tightening the screw pulls the conductor tighter. The insulation must be stripped so that no bare conductor is exposed outside the terminal.
1.6 Devices in Wet and Damp Locations — Article 406.9
Wet locations (outdoors, washdown areas):
Receptacles must be weatherproof with a cover that is weatherproof whether or not a plug is inserted (an "in-use" or "bubble" cover).
The receptacle must be listed for wet locations.
406.9(B)(1) — For 15 A and 20 A receptacles in wet locations, the cover must be weatherproof with the plug inserted.
Damp locations (protected from direct water but subject to moisture):
A weatherproof cover is required, but it does not need to be the "in-use" type unless a plug will be inserted while in use.
Exception for snow and ice:
In areas where snow or ice accumulation is expected, the receptacle must be mounted at a height that prevents snow from blocking the cover. The code does not specify a height — this is a design decision based on local climate.
1.7 Devices in Hazardous (Classified) Locations — Articles 500–517
A master supervising work in hazardous locations must understand that ordinary devices are not permitted. The requirements are in Article 500 (Class I, II, III) and Article 517 (Health Care Facilities) .
Class I, Division 1:
Switches and receptacles must be in explosion-proof enclosures.
Receptacles must be listed for the class, division, and group.
406.10 — Receptacles in Class I, Division 1 locations must be rated for the specific gas or vapor group (A, B, C, or D).
Class I, Division 2:
General-purpose devices are permitted if the circuit is not normally arcing (e.g., a standard switch is permitted if it does not make or break a circuit under normal conditions). However, receptacles must be listed for the location or be provided with a listed interlock that disconnects power before the plug is removed.
Health Care Facilities (Article 517):
517.18 — Patient care areas require receptacles that are "hospital grade" (listed as such). These have a green dot marking.
517.21 — Receptacles in patient care areas must be on a ground-fault protected circuit or an isolated power system if they are within 6 feet of the patient bed location.
517.30 — The grounding system in patient care areas must be tested and verified before initial energization.
1.8 Devices for Motors and Generators — Articles 430 and 445
Motor Disconnecting Means (430.109):
A motor must have a disconnecting means that is a listed motor-circuit switch, a molded-case circuit breaker, or a listed horsepower-rated switch. The disconnect must be rated for the motor's horsepower and full-load current.
Motor Controllers (430.83):
A controller (starter, contactor) must have a horsepower rating not less than the motor's horsepower. For a motor with a full-load current of 100 A or less, the controller must be rated for the motor's horsepower. For motors over 100 A, the controller must be rated for the motor's full-load current.
Generator Receptacles (445.18):
Generators that are not permanently installed (portable) must have a transfer switch or interlock to prevent backfeeding. The receptacle on a portable generator must be a listed locking-type or pin-and-sleeve configuration to prevent accidental disconnection.
1.9 Code Navigation — Where to Find Device Requirements
Topic
NEC Location
Switch general requirements
Article 404
Switch enclosures
404.9
Receptacle general requirements
Article 406
Receptacle replacement rules
406.4(D)
Tamper-resistant receptacles
406.12
GFCI locations — dwelling
210.8(A)
GFCI locations — commercial
210.8(B)
AFCI requirements
210.12
Dwelling receptacle spacing
210.52(A)
Kitchen counter receptacles
210.52(C)
Bathroom receptacles
210.52(D)
Box fill calculations
314.16
Termination temperature ratings
110.14
Wet/damp location devices
406.9
Hazardous location devices
500–506, 406.10
Hospital-grade receptacles
517.18
Motor disconnects
430.109
Generator disconnects
445.18
1.10 Inspection and Supervision Points
As a master electrician, you are responsible for code compliance on every job. Key inspection points for devices:
129.Verify box fill before device installation — a common violation is overfilled boxes.
130.Check torque on all device terminations — use a torque screwdriver and verify against the device's marked torque value.
131.Confirm GFCI/AFCI protection is present at the required locations — test with a listed tester.
132.Verify tamper-resistant receptacles in dwelling units and child care facilities.
133.Check the neutral conductor — switches must not open the grounded conductor.
134.Inspect weatherproof covers in wet locations — ensure the "in-use" cover is installed.
135.Confirm hospital-grade receptacles in patient care areas (green dot).
136.Verify the correct NEMA configuration for the circuit voltage and current.
137.Check that all devices are listed and have the appropriate markings (UL, CSA, etc.).
138.Ensure the equipment grounding conductor is connected to the device's grounding terminal.
1.11 Common Exam Traps
The 6-foot rule is measured from the receptacle, not between receptacles. The maximum distance between two receptacles is 12 feet, but the code phrase is "no point more than 6 feet from a receptacle."
GFCI requirements are not limited to bathrooms and kitchens. The 2026 code includes laundry areas, garages, crawl spaces, and any receptacle within 6 feet of a sink.
AFCI is for "similar rooms" — this includes hallways, closets, and laundry areas in dwelling units, not just bedrooms.
A 15 A duplex receptacle on a 20 A circuit is permitted — but only if it is a duplex (two receptacles). A single 15 A receptacle on a 20 A circuit is a violation.
Replacement receptacles must be upgraded to current GFCI/AFCI/tamper-resistant requirements — there is no "grandfathering" for a simple replacement.
Box fill counts devices as two conductors — many electricians forget to add the device count.
The 60 °C termination rule applies unless the device is marked for 75 °C. Most residential devices are not marked, so use the 60 °C column for sizing.
Wet location covers must be weatherproof with the plug inserted — a standard "flip" cover is not sufficient for outdoor receptacles.
Summary
The installation of electrical devices is governed by a complex web of articles that interconnect with branch circuit design, box sizing, grounding, and location-specific requirements. A master electrician must not only know where to place a receptacle but also understand the engineering rationale, the termination requirements, and the inspection criteria that ensure safe, code-compliant installations. Mastery of Article 404, 406, and their related sections in Articles 210, 314, and 500 is essential for passing the Colorado Master exam and for supervising work in the field.
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