NEC code lookup practice
The NEC knowledge part is open book, but there is no time to read: about 2 minutes a question. The people who pass know which article to open. Practice with your 2026 NEC beside you and find each answer.
How to get fast in the book
- Use the index at the back first. Look up the key word of the question, not the whole phrase.
- Learn the chapters: 1 and 2 general, 3 wiring methods, 4 equipment for general use, 5 to 7 special occupancies and conditions, 9 tables.
- Put in the publisher's permanent tabs before the exam. PSI does not allow homemade tabs.
- Highlight while you study: you cannot mark the book during the exam.
More in the guide to open-book rules and tabs.
Definitions, theory and plans 12
You need the NEC meaning of the terms "branch circuit" and "feeder". Where are the definitions used across the Code found?
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Article 100. Article 100 holds the definitions used in two or more articles, listed in alphabetical order. Look up the term there before you apply a rule that uses it. NEC Article 100
Which article gives the general requirements for all electrical installations, such as equipment approval, terminations and working space?
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Article 110. Article 110 covers general requirements that apply to every installation: approval and use of equipment, connections, markings and the spaces about equipment. NEC Article 110
Which article explains the purpose and scope of the NEC, how it is enforced and how its rules are worded?
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Article 90. Article 90 is the introduction to the Code. It covers purpose, scope, enforcement by the authority having jurisdiction and the difference between mandatory and explanatory text. NEC Article 90
For a voltage drop problem you need the DC resistance of a 10 AWG copper conductor. Which table gives conductor resistance, area and stranding?
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Chapter 9, Table 8. Chapter 9, Table 8 lists conductor properties: size, area in circular mils, stranding and DC resistance per 1000 ft. It is the usual table for voltage drop work. NEC Chapter 9, Table 8
Which table gives the AC resistance and reactance of 600-volt cables in conduit, used for more exact AC voltage drop work?
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Chapter 9, Table 9. Chapter 9, Table 9 lists AC resistance and reactance per 1000 ft for conductors in PVC, aluminum and steel conduit. Table 8 gives only DC resistance. NEC Chapter 9, Table 9
Where in the NEC book are the worked examples of dwelling and commercial load calculations?
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Informative Annex D. Informative Annex D contains worked calculation examples. They are not enforceable, but they show how the Article 120 methods are applied step by step. NEC Informative Annex D
In the 2026 NEC, where do you find the definition of "explosionproof equipment" used in the hazardous location articles?
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Article 100. Since the 2023 edition, definitions that used to sit in the first sections of individual articles were moved into Article 100. Look there first, even for hazardous location terms. NEC Article 100
By NEC definition, a continuous load is one where the maximum current is expected to last for how long?
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3 hours or more. Article 100 defines a continuous load as one whose maximum current is expected to continue for 3 hours or more. Many sizing rules then apply 125% to that load. NEC Article 100
What does the NEC call the circuit conductors between the final overcurrent device protecting the circuit and the outlets?
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Branch circuit. Article 100 defines a branch circuit as the conductors from the last overcurrent device to the outlets. Conductors ahead of that last device are feeders or service conductors. NEC Article 100
Equipment that can be reached quickly for operation or inspection, without tools, climbing over obstacles or using a portable ladder, is described as:
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Readily accessible. Article 100 defines "accessible, readily" as reachable quickly without tools, removing obstacles, climbing or a portable ladder. Disconnects and many OCPDs must meet this standard. NEC Article 100
The maximum current a conductor can carry continuously under the conditions of use without going over its temperature rating is its:
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Ampacity. Article 100 defines ampacity as the current a conductor can carry continuously under its conditions of use without exceeding its temperature rating. Tables in Article 310 give ampacity values. NEC Article 100
Who is responsible for interpreting the NEC rules and approving equipment and materials on a job?
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The authority having jurisdiction. Section 90.4 gives the authority having jurisdiction (AHJ) the job of interpreting the rules and approving equipment, materials and installations. NEC 90.4
Services and separately derived systems 22
Which article covers service conductors and service equipment, including the service disconnecting means?
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Article 230. Article 230 covers services: service drops and laterals, service-entrance conductors, service equipment and the service disconnecting means. Article 225 is for outside branch circuits and feeders. NEC Article 230
Which article contains the rules for system grounding, grounding electrodes and equipment bonding?
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Article 250. Article 250 covers grounding and bonding: system grounding, the grounding electrode system, grounding electrode conductors, bonding and equipment grounding conductors. NEC Article 250
Where do you find the required clearances for overhead service-drop conductors passing over a roof?
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230.24. Section 230.24 gives the clearances for overhead service conductors over roofs, above grade and from building openings. 230.26 is the point of attachment and 230.28 covers service masts. NEC 230.24
Which table do you use to size the grounding electrode conductor for an AC service?
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Table 250.66. Table 250.66 sizes the grounding electrode conductor from the size of the largest ungrounded service-entrance conductor or equivalent area of parallel sets. NEC Table 250.66
Which table is used to size the main bonding jumper at a service supplied by 3/0 AWG copper service-entrance conductors?
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Table 250.102(C)(1). Section 250.28 sends you to Table 250.102(C)(1) to size main and system bonding jumpers, based on the largest ungrounded conductor supplying the equipment. NEC Table 250.102(C)(1)
Which section lists the electrode types permitted for grounding, such as metal water pipe, concrete-encased electrodes, ground rings and rods?
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250.52. Section 250.52 lists the electrode types and their basic requirements. 250.50 requires bonding together the electrodes present, and 250.53 covers how rod, pipe and plate electrodes are installed. NEC 250.52
Which section covers the installation of rod, pipe and plate electrodes, including when a supplemental electrode is needed?
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250.53. Section 250.53 covers how grounding electrodes are installed, including burial of rods and the supplemental electrode for a single rod, pipe or plate. NEC 250.53
A 480 V to 208Y/120 V transformer supplies a panelboard. Which section covers grounding this separately derived system?
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250.30. Section 250.30 covers grounding of separately derived AC systems, such as the secondary of a transformer: system bonding jumper, grounding electrode conductor and electrode. NEC 250.30
Which section covers bonding of the metal water piping system inside a building?
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250.104. Section 250.104 covers bonding of metal piping systems and exposed structural metal, including interior metal water piping. NEC 250.104
Which section covers grounding of an AC system supplied by a service, including where the grounding electrode conductor connects?
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250.24. Section 250.24 covers grounding of service-supplied AC systems: the grounding electrode conductor connection, the main bonding jumper and bringing the grounded conductor to the service. NEC 250.24
A detached garage is supplied by a feeder from the house. Which section covers the grounding electrode at the garage?
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250.32. Section 250.32 covers buildings or structures supplied by a feeder or branch circuit, including the grounding electrode at the second building and keeping the neutral separate from the equipment grounding conductor. NEC 250.32
Which section requires ground-fault protection of equipment on certain large solidly grounded wye services?
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230.95. Section 230.95 covers ground-fault protection of equipment (GFPE) for service disconnects. 230.71 limits the number of disconnects and 230.79 sets minimum disconnect ratings. NEC 230.95
A service mast will support the service drop. Which section covers service masts used as supports?
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230.28. Section 230.28 covers service masts used to support service drops: strength, guying and what may be attached to them. 230.54 covers weatherheads and drip loops. NEC 230.28
For a one-family dwelling, the service disconnecting means must have a rating of at least:
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100 A. Section 230.79 sets minimum ratings for the service disconnect. For a one-family dwelling it must be at least 100 A, 3-wire. NEC 230.79(C)
Under the 2026 NEC, where must the service disconnect for a one-family dwelling be located?
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Outdoors, on or within sight of the house. The 2026 edition of 230.70(A) requires one- and two-family dwelling service disconnects to be outdoors, on the dwelling or within sight of it and not more than 50 ft away. Older editions allowed a disconnect inside nearest the point of entrance. NEC 230.70(A)
As a general rule, a single service may have no more than how many service disconnects?
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Six. Section 230.71 permits up to six service disconnects for each service, each in its own enclosure or section, grouped as 230.72 requires. NEC 230.71
Under the general rule of 230.7, branch-circuit or feeder conductors in the same raceway or cable as service conductors are:
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Not permitted. Section 230.7 keeps service conductors separate: other conductors are not allowed in the same service raceway or service cable, apart from the few items the section lists. NEC 230.7
GFPE is required on a solidly grounded wye service of more than 150 V to ground when each service disconnect is rated:
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1000 A or more. Section 230.95 requires ground-fault protection of equipment for each service disconnect rated 1000 A or more on these solidly grounded wye systems. NEC 230.95
A ground rod electrode must have at least how much of its length in contact with the soil?
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8 ft. Section 250.53 requires rod and pipe electrodes to be installed so that at least 8 ft of length is in contact with the soil. NEC 250.53
When two ground rods are installed to form the electrode, they must be at least how far apart?
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6 ft. Section 250.53 requires a supplemental rod to be at least 6 ft from the first one, so that each rod adds to the overall electrode. NEC 250.53
In a service-supplied system, where is the grounded (neutral) conductor connected to the equipment grounding conductors?
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At the service equipment. Section 250.24 makes the neutral-to-ground connection at the service through the main bonding jumper. Downstream of the service the grounded conductor and equipment grounding conductors stay separate. NEC 250.24
On a 4-wire delta service, the service conductor with the higher voltage to ground (high leg) must be identified with which color?
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Orange. Section 230.56 requires the high-leg service conductor to be marked orange, or identified by another effective means, at each termination or junction point. NEC 230.56
Feeders 10
Which article covers the minimum rating, sizing and overcurrent protection of feeder conductors?
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Article 215. Article 215 covers feeders: minimum ampacity and size, overcurrent protection and identification. Article 210 is for branch circuits and Article 225 for outside feeders. NEC Article 215
In the 2026 NEC, which article contains the branch-circuit, feeder and service load calculation methods?
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Article 120. For 2026, load calculations moved from Article 220 to Article 120 in Chapter 1. Most section endings stayed the same, so 220.41 is now 120.41, for example. NEC Article 120
A feeder runs overhead from a house to a detached workshop on the same property. Which article covers this outside feeder?
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Article 225. Article 225 covers outside branch circuits and feeders run on or between buildings, structures or poles on the premises, including clearances and the disconnect at each building. NEC Article 225
Which section requires a disconnecting means for a building supplied by a feeder from another building?
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225.31. Section 225.31 requires a disconnecting means for all ungrounded conductors that supply or pass through a building or structure fed by an outside feeder or branch circuit. NEC 225.31
Which table gives the demand factors applied to the general lighting load in a dwelling feeder or service calculation?
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Table 120.45. Table 120.45 holds the lighting load demand factors (for dwellings, the first 3000 VA at 100% and the next block at 35%). Tables 120.54 and 120.55 are for dryers and ranges. NEC Table 120.45
Which table gives the demand loads for household electric ranges, wall-mounted ovens and counter-mounted cooking units?
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Table 120.55. Table 120.55 (formerly Table 220.55) gives demand loads for household cooking appliances, with notes for ranges over 12 kW and for separate ovens and cooktops. NEC Table 120.55
A feeder supplies 80 A of continuous load and no other load. Before any ampacity adjustment, the feeder conductors must have an ampacity of at least:
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100 A. Section 215.2(A) requires feeder conductors to carry 125% of the continuous load plus 100% of the noncontinuous load: 80 A x 1.25 = 100 A. NEC 215.2(A)
All circuit conductors between the service equipment, or the source of a separately derived system, and the final branch-circuit overcurrent device are called:
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Feeders. Article 100 defines feeders as the conductors between the service equipment (or a separately derived system or other supply source) and the last branch-circuit OCPD. NEC Article 100
Under the 2026 NEC standard method, the general lighting and general-use receptacle load for a dwelling feeder or service calculation is figured at:
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2 VA per sq ft. The 2026 edition of 120.41 uses 2 VA per square foot for dwelling feeder and service calculations (it was 3 VA under 220.41). The branch-circuit count in 120.13 still uses 3 VA. NEC 120.41
In a dwelling feeder calculation, each 2-wire small-appliance branch circuit is included at:
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1500 VA. Section 120.52(A) counts each small-appliance branch circuit at 1500 VA. Section 120.52(B) does the same for the laundry circuit. NEC 120.52(A)
Branch circuits and conductors 26
Which section lists the dwelling unit locations where 125-volt through 250-volt receptacles need GFCI protection?
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210.8(A). Section 210.8(A) lists the dwelling locations that need ground-fault circuit-interrupter (GFCI) protection, such as bathrooms, kitchens, garages and outdoors. 210.8(B) covers other than dwelling units. NEC 210.8(A)
A restaurant kitchen and a commercial rooftop both have receptacles. Which section sets GFCI requirements for these locations other than dwelling units?
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210.8(B). Section 210.8(B) lists the GFCI locations for other than dwelling units, such as commercial kitchens, rooftops and outdoor areas. 210.8(A) is only for dwellings. NEC 210.8(B)
Which section covers arc-fault circuit-interrupter (AFCI) protection for branch circuits in dwelling bedrooms and living areas?
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210.12. Section 210.12 covers AFCI protection: where it is required in dwellings and dormitories and the permitted ways to provide it. GFCI rules are in 210.8. NEC 210.12
Which section requires the dwelling small-appliance, laundry and bathroom branch circuits?
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210.11(C). Section 210.11(C) requires the dwelling branch circuits for small appliances, laundry and bathrooms (and garages). 210.52(B) tells where the small-appliance receptacles go. NEC 210.11(C)
Which section requires receptacle outlets along the walls of dwelling living rooms and bedrooms, spaced by distance along the floor line?
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210.52(A). Section 210.52(A) covers general receptacle spacing in dwelling rooms such as living rooms, bedrooms and dining rooms, including what counts as wall space. NEC 210.52(A)
Which section covers receptacle outlets that serve dwelling kitchen countertops and work surfaces?
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210.52(C). Section 210.52(C) covers countertop and work surface receptacles in dwelling kitchens and similar areas. 210.52(D) is bathrooms. NEC 210.52(C)
Which table shows the receptacle ratings permitted on a branch circuit of a given rating, such as 15 A or 20 A receptacles on a 20 A circuit?
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Table 210.21(B)(3). Table 210.21(B)(3) matches receptacle ratings to circuit ratings. Table 210.21(B)(2) is the maximum cord-and-plug load on a receptacle, and Table 210.24 is the branch-circuit summary. NEC Table 210.21(B)(3)
Which table summarizes branch-circuit requirements (minimum conductor size, OCPD rating, outlet devices and maximum load) for 15 A through 50 A circuits?
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Table 210.24. Table 210.24 is a one-page summary of the requirements for 15, 20, 30, 40 and 50 A branch circuits that serve two or more outlets. NEC Table 210.24
Which table gives allowable ampacities of insulated conductors rated up to 2000 V, with not more than three current-carrying conductors in raceway, cable or earth, based on 30 °C ambient?
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Table 310.16. Table 310.16 is the main ampacity table for conductors in raceway, cable or directly buried, based on a 30 °C ambient and no more than three current-carrying conductors. Table 310.17 is for free air. NEC Table 310.16
Conductors will run through a space where the ambient temperature is 45 °C. Which table gives the correction factor for the Table 310.16 ampacity?
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Table 310.15(B)(1)(1). Table 310.15(B)(1)(1) gives ambient temperature correction factors for ampacity tables based on 30 °C. Table 310.15(C)(1) is for the number of current-carrying conductors. NEC Table 310.15(B)(1)(1)
Six current-carrying conductors share one raceway. Which table gives the adjustment factor for their ampacity?
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Table 310.15(C)(1). Table 310.15(C)(1) gives adjustment factors for more than three current-carrying conductors in a raceway or cable. Chapter 9, Table 1 is about conduit fill, not ampacity. NEC Table 310.15(C)(1)
Which table gives the allowable ampacities of single insulated conductors in free air, based on 30 °C ambient?
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Table 310.17. Table 310.17 covers single insulated conductors in free air. Its values are higher than Table 310.16 because heat leaves a conductor in free air more easily. NEC Table 310.17
Which section limits the overcurrent protection of 14, 12 and 10 AWG copper conductors to 15, 20 and 30 A?
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240.4(D). Section 240.4(D) sets the small-conductor limits, so the OCPD for 12 AWG copper, for example, may not exceed 20 A even though the table ampacity is higher. 240.4(B) is the next-size-up rule. NEC 240.4(D)
Which article covers the use and identification of grounded conductors?
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Article 200. Article 200 covers grounded conductors: how they are identified, how their terminals are marked and when white or gray insulation may be used for other purposes. NEC Article 200
Which section covers multiwire branch circuits, including the rule for disconnecting all ungrounded conductors at the same time?
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210.4. Section 210.4 covers multiwire branch circuits: simultaneous disconnecting of the ungrounded conductors, line-to-neutral loads and grouping of the conductors in the panel. NEC 210.4
In a dwelling bedroom, receptacles must be placed so that no point along the floor line of any wall space is more than how far from a receptacle outlet?
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6 ft. Section 210.52(A)(1) requires that no point along the floor line be more than 6 ft from a receptacle, which in practice means receptacles no more than 12 ft apart. NEC 210.52(A)(1)
In a dwelling bathroom, at least one receptacle outlet must be installed within how far of the outside edge of each basin?
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3 ft. Section 210.52(D) requires at least one receptacle within 3 ft of the outside edge of each bathroom basin, on a wall or partition next to it or in another permitted spot. NEC 210.52(D)
A one-family dwelling needs an outdoor receptacle at the front and at the back. Each must be accessible from grade and no more than how high above grade?
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6½ ft. Section 210.52(E)(1) requires the front and back outdoor receptacles to be readily accessible while standing at grade and not more than 6½ ft above grade. NEC 210.52(E)(1)
A dwelling hallway needs at least one receptacle outlet when the hallway is at least how long?
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10 ft. Section 210.52(H) requires at least one receptacle in each dwelling hallway 10 ft or more in length, measured along the centerline without passing through a doorway. NEC 210.52(H)
A branch circuit supplies a 16 A continuous load and nothing else. The branch-circuit overcurrent device must be rated at least:
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20 A. Section 210.20(A) requires the OCPD to be at least 125% of the continuous load plus the noncontinuous load: 16 A x 1.25 = 20 A. NEC 210.20(A)
A dwelling must have at least one branch circuit to supply the laundry receptacle outlets, rated at:
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20 A. Section 210.11(C)(2) requires at least one 20 A branch circuit for the laundry receptacle outlets. That circuit may not serve other outlets. NEC 210.11(C)(2)
What is the minimum number of 20 A small-appliance branch circuits required for the receptacles in a dwelling kitchen, pantry and dining room?
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Two. Section 210.11(C)(1) requires two or more 20 A small-appliance branch circuits for the receptacle outlets covered by 210.52(B). NEC 210.11(C)(1)
An insulated grounded conductor of 6 AWG or smaller must be identified by a continuous outer finish that is:
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White or gray. Section 200.6(A) requires grounded conductors 6 AWG and smaller to be white or gray, or to have three continuous white or gray stripes on other than green insulation. NEC 200.6(A)
An insulated equipment grounding conductor must have a continuous outer finish that is:
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Green, or green with yellow stripes. Section 250.119 requires an equipment grounding conductor to be bare, or insulated with a green finish or green with one or more yellow stripes. NEC 250.119
Unless the equipment is marked otherwise, terminations for circuits rated 100 A or less (or marked for 14 AWG through 1 AWG) are based on which conductor temperature rating?
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60 °C. Section 110.14(C) limits conductors on equipment for circuits of 100 A or less, or 14 through 1 AWG, to the 60 °C ampacity unless the equipment is listed and marked for higher. Over 100 A the limit is 75 °C. NEC 110.14(C)
Under the 2026 NEC, outdoor outlets at dwellings supplied by single-phase branch circuits of 150 V or less to ground need GFCI protection when the branch circuit is rated:
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60 A or less. The 2026 edition of 210.8(F) raised the limit for outdoor dwelling outlets, such as those for air-conditioning equipment, from 50 A to 60 A or less. NEC 210.8(F)
Wiring methods and materials 24
Which article covers nonmetallic-sheathed cable (Type NM), the usual cable in house wiring?
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Article 334. Article 334 covers Type NM cable: uses permitted and not permitted, support, bending and ampacity. Article 330 is MC cable and Article 340 is UF cable. NEC Article 334
Which article covers electrical metallic tubing (EMT)?
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Article 358. Article 358 covers EMT. Article 342 is IMC, Article 344 is rigid metal conduit and Article 362 is electrical nonmetallic tubing. NEC Article 358
Which article covers metal-clad cable (Type MC)?
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Article 330. Article 330 covers Type MC cable. Article 320 is armored cable (Type AC), which has a different construction and its own article. NEC Article 330
Which article covers rigid polyvinyl chloride conduit (PVC)?
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Article 352. Article 352 covers rigid PVC conduit, including expansion fittings and support spacing. Article 356 is liquidtight flexible nonmetallic conduit. NEC Article 352
A motor connection uses liquidtight flexible metal conduit. Which article covers this raceway?
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Article 350. Article 350 covers liquidtight flexible metal conduit (LFMC). Article 348 is plain flexible metal conduit and Article 356 is the nonmetallic liquidtight type. NEC Article 350
Which article covers underground feeder and branch-circuit cable (Type UF)?
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Article 340. Article 340 covers Type UF cable, which may be directly buried. Article 338 covers service-entrance cable (SE and USE). NEC Article 340
Which article covers service-entrance cable, Types SE and USE?
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Article 338. Article 338 covers SE and USE cable, used for services and in some cases for feeders and branch circuits. Article 336 is power and control tray cable (Type TC). NEC Article 338
For a conduit fill problem, which table gives the internal area and the 40% fill area of each trade size of EMT?
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Chapter 9, Table 4. Chapter 9, Table 4 gives dimensions and percent areas for each conduit and tubing type and trade size. Table 5 gives conductor areas and Table 1 gives the fill percentages. NEC Chapter 9, Table 4
Which table sets the maximum percent of a conduit cross section that conductors may fill, based on the number of conductors?
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Chapter 9, Table 1. Chapter 9, Table 1 gives the fill limits by number of conductors. Its notes also cover nipples, equipment grounding conductors and when to use Informative Annex C. NEC Chapter 9, Table 1
Where do you find ready-made tables of the maximum number of same-size conductors permitted in each trade size of conduit or tubing?
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Informative Annex C. Informative Annex C has conduit and tubing fill tables for conductors of the same size, organized by raceway type. Annex D has load calculation examples. NEC Informative Annex C
Which article covers outlet boxes, device boxes, pull boxes, conduit bodies and handhole enclosures?
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Article 314. Article 314 covers boxes, conduit bodies and handhole enclosures, including box fill, pull box sizing and support. Article 312 covers cabinets and meter socket enclosures. NEC Article 314
Which article covers cable tray systems used to support cables and raceways?
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Article 392. Article 392 covers cable trays: the wiring methods allowed in them, installation, fill and grounding. Article 376 is metal wireways and Article 386 is surface metal raceways. NEC Article 392
Which article gives the general requirements that apply to all wiring methods, such as protection from physical damage and underground installations?
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Article 300. Article 300 covers general requirements for wiring methods and materials, including burial depth, protection against damage, and securing and support. NEC Article 300
Which article covers conductors for general wiring, including insulation types, markings and ampacity tables?
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Article 310. Article 310 covers conductors for general wiring: insulation types and uses, markings, minimum sizes, parallel conductors and the ampacity tables. Flexible cords are in Article 400. NEC Article 310
EMT must be securely fastened within how far of each outlet box, junction box, cabinet or other tubing termination?
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3 ft. Section 358.30 requires EMT to be fastened within 3 ft of each box, cabinet, conduit body or other termination, and supported at intervals of no more than 10 ft. NEC 358.30
As a general rule, rigid metal conduit must be supported at intervals not exceeding:
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10 ft. Section 344.30 generally requires RMC to be supported at least every 10 ft and fastened within 3 ft of each box or termination. Longer spacing is allowed only in the specific cases the section lists. NEC 344.30
A conduit will hold five conductors (not a nipple). The conductors may fill no more than what percent of the conduit cross section?
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40%. Chapter 9, Table 1 allows 53% fill for one conductor, 31% for two and 40% for more than two conductors. NEC Chapter 9, Table 1
Between pull points, such as boxes or conduit bodies, a run of EMT may have no more than how many degrees of bends in total?
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360°. Article 358 allows no more than the equal of four quarter bends, 360° total, between pull points. The same rule appears in the other conduit and tubing articles. NEC Article 358
A conduit nipple no longer than 24 in. connects two enclosures. Its conductors may fill up to what percent of the nipple total area?
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60%. Note 4 to the Chapter 9 tables lets a nipple of 24 in. or less between boxes or enclosures be filled to 60% of its total area, and adjustment factors do not apply to it. NEC Chapter 9, Table 1, Note 4
Under the general cover table in Article 300, rigid PVC conduit with no concrete encasement, not under a building, driveway or road, needs a minimum cover of:
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18 in.. The minimum cover table in Article 300 requires 18 in. for nonmetallic raceways listed for direct burial in general locations. Direct-buried cable needs 24 in. and rigid metal conduit 6 in. NEC Article 300
At each outlet, junction or switch box, at least how much free conductor must be left for splices or connecting devices?
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6 in.. Article 300 requires at least 6 in. of free conductor at each box, measured from where the conductor leaves the raceway or cable. If the box opening is less than 8 in., at least 3 in. must extend outside it. NEC Article 300
NM cable passes through a bored hole in a wood stud. The edge of the hole must be at least how far from the nearest edge of the stud, or a steel plate is needed?
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1¼ in.. Article 300 requires bored holes to be at least 1¼ in. from the nearest edge of the framing member. Closer than that, a steel plate at least 1/16 in. thick must protect the cable. NEC Article 300
As a general rule, conductors connected in parallel (electrically joined at both ends) must be at least what size?
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1/0 AWG. Article 310 generally permits parallel conductors only in sizes 1/0 AWG and larger. Each parallel set must also match in length, material, size, insulation and termination. NEC Article 310
Under 310.5(A) of the 2026 NEC, the smallest copper conductor size generally permitted for general wiring is:
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16 AWG. The 2026 edition of 310.5(A) lowered the general minimum to 16 AWG copper (14 AWG copper-clad aluminum, 12 AWG aluminum). Older editions started at 14 AWG copper. Small conductors still have OCPD limits in 240.4(D). NEC 310.5(A)
Equipment and devices 22
Which article covers switches and circuit breakers used as switches, including switch enclosures in wet locations and the maximum height of the operating handle?
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Article 404. Article 404 covers switches: enclosures, accessibility and grouping, maximum handle height and bonding. In 2026, general-use snap switches and dimmers moved to Part III of Article 406. NEC Article 404
Which article covers receptacles, cord connectors and attachment plugs, including tamper-resistant and weather-resistant receptacles?
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Article 406. Article 406 (titled "Wiring Devices" in 2026) covers receptacles, cord connectors and attachment plugs, including tamper-resistant, weather-resistant and replacement rules. NEC Article 406
Which article covers switchboards and panelboards, including the circuit directory and panelboard overcurrent protection?
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Article 408. Article 408 covers switchboards and panelboards: circuit identification, phase arrangement, overcurrent protection of panelboards and clearances. NEC Article 408
Which article covers luminaires, lampholders and lamps, including luminaires in closets and near bathtubs?
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Article 410. Article 410 covers luminaires, lampholders and lamps: locations, supports, wiring and special rules such as clothes closets and bathtub zones. Article 411 is low-voltage lighting systems. NEC Article 410
A dishwasher, a water heater and a trash compactor are being installed. Which article covers these appliances?
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Article 422. Article 422 covers appliances in any occupancy: branch-circuit sizing, disconnecting means and cord connections for items such as water heaters, dishwashers and disposers. NEC Article 422
Which article covers fixed electric space-heating equipment, such as electric baseboard heaters?
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Article 424. Article 424 covers fixed electric space-heating equipment, including baseboard heaters, duct heaters and radiant heating cables. NEC Article 424
Which article covers the installation of transformers, including their overcurrent protection and ventilation?
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Article 450. Article 450 covers transformers and transformer vaults: overcurrent protection, location, ventilation and grounding. Article 445 is generators. NEC Article 450
Which table gives the maximum overcurrent protection for transformers rated 1000 volts and less, as a percent of rated current?
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Table 450.5(B). In the 2026 NEC, transformer overcurrent protection moved from 450.3 to 450.5. Table 450.5(B) (Table 450.3(B) in 2023) gives the maximum primary and secondary OCPD ratings, as a percent of rated current, for transformers of 1000 V and less. NEC Table 450.5(B)
A bank of stationary batteries is being installed for a UPS. Which article covers stationary batteries?
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Article 480. Article 480 (Stationary Batteries) covers battery installations, terminations and ventilation. Article 706 covers energy storage systems as complete systems. NEC Article 480
Which article covers listed low-voltage lighting systems operating at 30 volts or less, such as landscape lighting?
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Article 411. Article 411 covers low-voltage lighting systems and their power supplies, such as listed landscape and track systems. Article 410 is general luminaire rules. NEC Article 411
Which article covers flexible cords and flexible cables, including where they may and may not be used?
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Article 400. Article 400 covers flexible cords and cables: types, ampacity, uses permitted and uses not permitted. Conductors for general wiring are in Article 310. NEC Article 400
Which section covers the working space and access required around electrical equipment rated 1000 V or less?
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110.26. Section 110.26 covers spaces about electrical equipment: depth, width and height of working space, entrance, illumination and dedicated equipment space. NEC 110.26
Which section requires arc-flash hazard marking on service and feeder equipment in other than dwelling units?
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110.16. Section 110.16 covers arc-flash hazard marking. In 2026 the label must show items such as nominal voltage, arc-flash boundary and the date of the assessment. 110.22 is identification of disconnects. NEC 110.16
For a 120/240-volt panelboard, the minimum depth of working space in front of it is:
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3 ft. Table 110.26(A)(1) requires 3 ft of depth for 0 to 150 V to ground in all three conditions. A 120/240 V system is 120 V to ground. NEC Table 110.26(A)(1)
A 480Y/277-volt switchboard has exposed live parts on one side of the working space and grounded parts (a concrete wall) on the other. The minimum working space depth is:
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3½ ft. This is Condition 2 in Table 110.26(A)(1). For 151 to 600 V to ground, Condition 2 requires 3½ ft. Condition 1 is 3 ft and Condition 3 is 4 ft. NEC Table 110.26(A)(1)
The width of the working space in front of electrical equipment must be at least:
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30 in. or the equipment width, whichever is greater. Section 110.26(A)(2) requires a working space width of 30 in. or the width of the equipment, whichever is greater, and room for doors to open at least 90°. NEC 110.26(A)(2)
Working space in front of a panelboard must be clear from the floor to a height of at least (or the height of the equipment, if greater):
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6½ ft. Section 110.26(A)(3) requires the working space to extend from the floor to 6½ ft or to the height of the equipment, whichever is greater. NEC 110.26(A)(3)
Switches and circuit breakers used as switches must be installed so the center of the operating handle, in its highest position, is no more than how high above the floor?
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6 ft 7 in.. Section 404.10 (404.8 in 2023) limits the center of the grip of the operating handle, at its highest position, to 6 ft 7 in. above the floor or working platform. NEC 404.10
Pendant luminaires and ceiling-suspended (paddle) fans may not be located in a zone 3 ft horizontally from a bathtub rim and up to how high above the top of the rim?
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8 ft. Section 410.10(D) keeps cord-connected and hanging luminaires and ceiling-suspended fans out of the zone 3 ft horizontally and 8 ft vertically from the top of the bathtub rim or shower threshold. NEC 410.10(D)
Unless specifically permitted, flexible cord may NOT be used as:
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A substitute for the fixed wiring of a building. Section 400.12 lists uses not permitted for flexible cords, starting with use as a substitute for the fixed wiring of a structure. Portable lamps, pendants and portable appliances are permitted uses in 400.10. NEC 400.12
Each circuit and circuit modification in a panelboard must be legibly identified by:
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Its clear, evident and specific purpose. Section 408.4(A) requires a circuit directory that identifies each circuit by its specific purpose or use, detailed enough to tell it apart from all others. NEC 408.4(A)
Under 110.3(B) of the 2026 NEC, manufacturer installation instructions included with listed equipment:
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Must be followed but cannot lower NEC requirements. Section 110.3(B) requires listed equipment to be installed according to its listing and labeling instructions. The 2026 edition adds that those instructions may go beyond the NEC but may not reduce its requirements. NEC 110.3(B)
Motors and generators 16
Which article covers motors, motor branch circuits, motor overload protection and motor controllers?
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Article 430. Article 430 covers motor circuits, controllers and adjustable-speed drives: conductor sizing, overloads, short-circuit protection, controllers and disconnects. NEC Article 430
A rooftop unit has a hermetic refrigerant motor-compressor. Which article has the special rules for this equipment?
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Article 440. Article 440 covers air-conditioning and refrigeration equipment with hermetic refrigerant motor-compressors. It adds to or changes the Article 430 rules for that equipment. NEC Article 440
Which article covers the installation of generators, including conductor sizing and disconnecting means?
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Article 445. Article 445 covers generators: overcurrent protection, conductor ampacity from the terminals and the disconnecting means. Article 702 covers optional standby systems as a whole. NEC Article 445
You need the full-load current of a 10 hp, 460-volt, three-phase induction motor. Which table do you use?
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Table 430.250. Table 430.250 gives full-load currents for three-phase AC motors. Table 430.248 is single-phase and Table 430.247 is DC motors. NEC Table 430.250
Which table gives the full-load current of single-phase AC motors, such as a 2 hp, 230-volt motor?
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Table 430.248. Table 430.248 lists full-load currents of single-phase AC motors by horsepower and voltage. Use these values, not the nameplate, to size conductors and short-circuit protection. NEC Table 430.248
Which section sets the maximum rating of the motor branch-circuit short-circuit and ground-fault protective device?
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430.52. Section 430.52 and its table set the maximum fuse or breaker rating, as a percent of motor full-load current, for motor branch-circuit short-circuit and ground-fault protection. 430.32 is overloads. NEC 430.52
Which section covers overload protection for continuous-duty motors?
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430.32. Section 430.32 covers overload protection of continuous-duty motors, sized from the nameplate current. Short-circuit and ground-fault protection is a separate item in 430.52. NEC 430.32
Which section covers sizing the branch-circuit conductors that supply a single motor?
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430.22. Section 430.22 covers conductors for a single motor. 430.24 covers conductors that supply several motors, and 430.52 covers the short-circuit protective device. NEC 430.22
A feeder supplies three motors and no other load. Which section covers the minimum ampacity of the feeder conductors?
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430.24. Section 430.24 covers conductors supplying several motors, or motors and other loads. The feeder overcurrent device for motors is in 430.62. NEC 430.24
A 5 hp, 240-volt DC motor drives a hoist. Which table gives its full-load current?
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Table 430.247. Table 430.247 gives full-load currents for direct-current motors. Tables 430.248 and 430.250 are for single-phase and three-phase AC motors. NEC Table 430.247
When sizing the branch-circuit conductors for a general-purpose AC motor, which current do you start from?
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The full-load current from the Article 430 tables. Section 430.6(A)(1) requires the table full-load currents (Tables 430.248 and 430.250) for sizing conductors and short-circuit protection, not the nameplate value. NEC 430.6(A)(1)
Separate overload protection for a general-purpose motor is sized from which value?
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The nameplate full-load current. Section 430.6(A)(2) bases separate motor overload protection on the motor nameplate current rating, while conductors and short-circuit protection use the table values. NEC 430.6(A)(2)
Conductors supplying a single continuous-duty motor must have an ampacity of at least what percent of the motor full-load current?
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125%. Section 430.22 requires branch-circuit conductors for a single continuous-duty motor to be at least 125% of the table full-load current. NEC 430.22
A motor disconnecting means for a motor circuit of 1000 V or less must have an ampere rating of at least what percent of the motor full-load current?
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115%. Section 430.110(A) requires the disconnecting means to have an ampere rating of at least 115% of the motor full-load current. NEC 430.110(A)
Conductors from the output terminals of a generator to the first overcurrent device must have an ampacity of at least what percent of the generator nameplate current?
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115%. Article 445 requires these conductors to have an ampacity of at least 115% of the generator nameplate current rating. NEC Article 445
Branch-circuit conductors for a single hermetic refrigerant motor-compressor must have an ampacity of at least:
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125% of the rated-load current. Article 440 requires branch-circuit conductors for a single motor-compressor to have at least 125% of the motor-compressor rated-load current or the branch-circuit selection current, whichever is greater. NEC Article 440
Controls and disconnecting means 6
Which section explains what the NEC means by "in sight from" or "within sight" when locating a disconnect?
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110.29. Section 110.29 defines in sight from (within sight) as visible and not more than 50 ft away. Disconnect rules in Articles 430 and 440 rely on it. NEC 110.29
Which section requires a disconnecting means in sight from a motor controller and from the motor location?
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430.102. Section 430.102 covers the location of motor disconnects: in sight from the controller, and in sight from the motor unless a permitted alternative applies. 430.109 covers the type of disconnect. NEC 430.102
In the 2026 NEC, which new article covers non-power-limited remote-control and signaling circuits?
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Article 206. Article 206 is new in 2026 and covers non-power-limited remote-control and signaling circuits in Chapter 2. Article 724 covers Class 1 power-limited circuits and Article 725 covers Class 2. NEC Article 206
A thermostat circuit is supplied by a listed Class 2 transformer. Which article covers Class 2 power-limited circuits?
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Article 725. Article 725 covers Class 2 power-limited circuits. Article 726 covers Class 4 fault-managed power systems and Article 206 covers non-power-limited control circuits. NEC Article 725
Under the NEC, a disconnect that must be "within sight" of equipment must be visible from it and no more than how far away?
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50 ft. Section 110.29 treats equipment as in sight from other equipment when it is visible and not more than 50 ft away. NEC 110.29
The disconnecting means for an outdoor air-conditioning condensing unit must be located:
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Within sight of and readily accessible from the unit. Article 440 requires the AC disconnect to be within sight from and readily accessible from the equipment. It may be on or inside the unit, but not on access panels of the unit or where it hides the nameplate. NEC Article 440
Special occupancies and equipment 22
Which article covers the wiring and bonding of swimming pools, spas, hot tubs and fountains?
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Article 680. Article 680 covers pools, spas, hot tubs, fountains and hydromassage bathtubs. Article 682 is natural and artificially made bodies of water, and Article 555 is marinas and docks. NEC Article 680
A customer is adding an outdoor hot tub. Which part of Article 680 covers permanently installed and self-contained spas and hot tubs?
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Article 680, Part IV. Article 680, Part IV covers spas and hot tubs, including outdoor and indoor installations and GFCI protection. Part II is permanently installed pools, Part III storable pools and Part V fountains. NEC Article 680, Part IV
Which article covers electrical installations at marinas, boatyards and docking facilities?
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Article 555. Article 555 covers marinas, boatyards and commercial and noncommercial docking facilities, including shore power receptacles and ground-fault protection on docks. NEC Article 555
Which article covers the wiring of hospitals, nursing homes and other health care facilities?
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Article 517. Article 517 covers health care facilities: wiring and protection in patient care spaces, the essential electrical system and related rules. NEC Article 517
A church fellowship hall is designed to hold 200 people. Which article covers this type of assembly occupancy?
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Article 518. Article 518 covers assembly occupancies for gatherings of 100 or more persons, such as halls, auditoriums and places of worship, including the wiring methods permitted. NEC Article 518
Which article covers temporary power and lighting for construction, remodeling and holiday lighting?
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Article 590. Article 590 covers temporary installations: time limits, wiring methods and GFCI protection for personnel on construction sites. Article 525 is carnivals and fairs. NEC Article 590
A dairy barn and a poultry house are being wired. Which article covers agricultural buildings?
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Article 547. Article 547 covers agricultural buildings with dust, moisture or corrosive conditions, such as livestock barns, including wiring methods and equipotential planes. NEC Article 547
Which article covers the electrical requirements for mobile homes, manufactured homes and mobile home parks?
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Article 550. Article 550 covers mobile homes, manufactured homes and mobile home parks, including the service equipment and feeder to the home. Article 551 is recreational vehicles. NEC Article 550
An RV park is adding new site supply equipment with 50 A receptacles. Which article covers recreational vehicles and RV parks?
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Article 551. Article 551 covers recreational vehicles and recreational vehicle parks, including site supply equipment and its receptacles. NEC Article 551
Which article covers gasoline stations and other motor fuel dispensing facilities, including the classified areas around dispensers?
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Article 514. Article 514 covers motor fuel dispensing facilities, with a table that sets the classified areas around dispensers and tanks. Article 511 is commercial garages. NEC Article 514
Which article gives the general rules for hazardous (classified) locations, including how Class I, II and III locations are defined?
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Article 500. Article 500 is the general article for hazardous (classified) locations under the class and division system. Articles 501 and 502 give the wiring rules for Class I and Class II. NEC Article 500
Exit lighting in a building must stay on when utility power fails, as required by the building code. Which article covers these emergency systems?
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Article 700. Article 700 covers emergency systems required by law for life safety, such as egress and exit lighting. Article 701 is legally required standby and Article 702 is optional standby. NEC Article 700
Which article covers electric signs, including the required sign outlet at commercial occupancies?
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Article 600. Article 600 covers electric signs: the sign branch circuit, disconnecting means, grounding and bonding. Article 410 covers general luminaires. NEC Article 600
A server room has a raised floor and a disconnect for the computer equipment at the exit door. Which article covers information technology equipment rooms?
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Article 645. Article 645 covers information technology equipment (ITE) rooms, including wiring under raised floors and the remote disconnecting means. NEC Article 645
A wall-mounted underwater pool luminaire must be installed so the top of its lens is at least how far below the normal water level, unless it is listed for a lesser depth?
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18 in.. Section 680.23 requires wall-mounted underwater luminaires to have the top of the lens at least 18 in. below normal water level, unless listed and identified for a lesser depth. NEC 680.23
Temporary electric power and lighting for holiday decorative lighting is permitted for a period of not more than:
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90 days. Article 590 permits temporary wiring for Christmas and similar holiday decorative lighting for no more than 90 days. NEC Article 590
On a construction site, 125-volt, single-phase, 15-, 20- and 30-ampere receptacle outlets that are not part of the permanent wiring and are used by personnel must have:
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GFCI protection for personnel. Section 590.6 requires ground-fault circuit-interrupter protection for personnel on these temporary receptacle outlets. NEC 590.6
In a Class I, Division 1 location, a conduit seal required at an enclosure containing arcing devices must be placed no more than how far from the enclosure?
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18 in.. Section 501.15 requires that seal to be as close as practical to the enclosure and not more than 18 in. from it. NEC 501.15
Service equipment for a mobile home must be located outside the home, in sight from it, and no more than how far from its exterior wall?
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30 ft. Article 550 requires mobile home service equipment to be next to the home, not mounted in or on it, in sight from it and within 30 ft of its exterior wall. NEC Article 550
As a general rule, wiring from an emergency source to emergency loads must be:
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Kept independent of all other wiring. Section 700.10 requires emergency wiring to be kept entirely independent of all other wiring and equipment, except in the specific places the section allows, such as transfer equipment enclosures. NEC 700.10
A location is classified as Class II because of the presence of:
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Combustible dust. Section 500.5 classifies locations by the hazard: Class I for flammable gases or vapors, Class II for combustible dust and Class III for ignitible fibers or flyings. NEC 500.5
The required sign outlet at the entrance of a commercial tenant space must be supplied by a branch circuit rated at least how many amperes, supplying no other load?
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20 A. Section 600.5 requires at least one sign outlet at each entrance of each commercial tenant space accessible to pedestrians, on a branch circuit of at least 20 A that supplies no other load. NEC 600.5
Renewable energy and EV charging 10
Which article covers rooftop solar photovoltaic (PV) systems on homes and businesses?
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Article 690. Article 690 covers solar PV systems: circuit sizing, disconnects, rapid shutdown, wiring methods and grounding. Article 691 is for large-scale PV electric supply stations. NEC Article 690
A home battery system stores energy from solar panels. Which article covers energy storage systems?
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Article 706. Article 706 covers energy storage systems (ESS), including disconnects, circuit sizing and commissioning. Article 480 covers stationary batteries as equipment. NEC Article 706
A PV inverter will connect to a panelboard that is also supplied by the utility. Which article covers interconnecting power sources with the utility?
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Article 705. Article 705 covers interconnected electric power production sources that operate in parallel with another source, including supply-side and load-side connections. NEC Article 705
A homeowner wants a 48 A Level 2 charger for an electric car in the garage. Which article covers this electric vehicle equipment?
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Article 625. Article 625 covers electric vehicle power transfer systems, including EVSE branch circuits, disconnects and GFCI protection. Article 624 is for self-propelled vehicles such as forklifts and golf carts. NEC Article 625
A warehouse is installing charging stations for electric forklifts. In the 2026 NEC, which new article covers power transfer to this type of self-propelled vehicle?
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Article 624. Article 624 is new in 2026 and covers electric self-propelled vehicle power transfer systems for equipment such as forklifts, golf carts and similar vehicles. Road EVs stay in Article 625. NEC Article 624
Which section requires PV systems on buildings to have a rapid shutdown function to reduce shock hazard for firefighters?
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690.12. Section 690.12 covers PV rapid shutdown on buildings. 690.7 is maximum voltage, 690.8 is circuit sizing and current, and 690.13 is the PV system disconnecting means. NEC 690.12
For sizing the overcurrent device and conductors, the load of electric vehicle supply equipment is treated as:
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A continuous load. Section 625.41 treats EV charging equipment as a continuous load, so the OCPD and conductors are sized at no less than 125% of the maximum load. NEC 625.41
The maximum current of a PV source circuit is the sum of the parallel module short-circuit current ratings multiplied by:
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125%. Section 690.8 sets the maximum PV source circuit current at 125% of the module short-circuit current. Conductor and OCPD sizing then apply a further factor to that value. NEC 690.8
An inverter breaker sits at the opposite end of a panelboard busbar from the main breaker. The main OCPD rating plus 125% of the inverter output current may not exceed what percent of the busbar rating?
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120%. For a load-side connection with the sources at opposite ends of the busbar, 705.12 limits the sum of the busbar OCPD rating and 125% of the power source output current to 120% of the busbar rating. NEC 705.12
The PV system disconnecting means must be installed at:
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A readily accessible location. Section 690.13 requires the PV system disconnecting means to be in a readily accessible location and to be marked to identify it. NEC 690.13