Chapter 34: NEC Quick-Reference Card

This is the chapter you photocopy and tape to the inside of your toolbox. It's the most-asked, most-cited NEC requirements in residential work, organized by topic, in plain English. The actual NEC has more nuance than this, treat this as the starting point, not the final word. When in doubt, look up the specific code section, or call us.

All references are to NEC 2023, which is what Oklahoma adopted statewide. Specific cities may have local amendments, so check with your local building department before you start.

Outlet Spacing in Living Areas

NEC 210.52(A) is the famous "6 and 12 rule" for receptacle spacing in habitable rooms.

The rule: in any living space (bedroom, living room, family room, dining room, hallway), no point along a wall should be more than 6 feet from an outlet.

Translated to "where do I put outlets": place an outlet within 6 feet of any door opening, and then no more than 12 feet between outlets after that.

• Walls 2 feet wide or wider need an outlet. Short walls (less than 2 feet) don't.
• Hallways 10 feet or longer need at least one outlet.
• Floor outlets count if they're within 18 inches of the wall.

This rule doesn't apply to kitchens, bathrooms, garages, basements, or laundry rooms. Those have their own (mostly tighter) spacing rules.

Kitchen Outlets

NEC 210.52(C):

• Counter outlets: at least one outlet within 24 inches of any point along the counter (so 4-foot maximum spacing). Every counter section 12 inches wide or wider needs at least one outlet.
• Islands and peninsulas: NEC 2023 changed this. Islands and peninsulas are no longer required to have outlets, but if they do have outlets, those outlets must be GFCI-protected. (The old rule required at least one outlet on islands; this was relaxed because of the safety concerns with cords trailing off counters near small kids.)
• Counter outlets must be 20A circuits, two minimum. This means you need at least two 20A countertop circuits in any kitchen, both serving the counter outlets, both GFCI-protected.
• Refrigerator can share a 20A counter circuit, or be on its own dedicated circuit. Either is allowed in NEC, though dedicated is much better practice.
• Dishwasher: dedicated 20A circuit recommended. Can sometimes share with garbage disposal, but check the appliance specs.
• Microwave (over-the-range or built-in): dedicated 20A circuit, GFCI-protected per NEC 2023.

Bathroom Outlets

NEC 210.52(D), 210.11(C)(3), 210.8(A):

• At least one outlet, within 36 inches of the outside edge of every basin. GFCI-protected.
• Bathroom outlets are on a dedicated 20A circuit that serves only bathrooms. (You can have one circuit serving multiple bathroom outlets, or each bathroom can have its own 20A circuit.)
• Lights and fans on the bathroom circuit are not allowed unless the circuit serves only one bathroom. If your bathroom 20A circuit serves outlets in multiple bathrooms, then the lights have to be on a separate circuit. If the 20A circuit only serves a single bathroom, then the lights and fan can be on it too.
• Outlets within 6 feet of a bathtub or shower: GFCI-protected. (This includes outlets in bedrooms or hallways within 6 feet of a tub or shower in an adjacent room.)

GFCI Required Locations (NEC 210.8)

Where Ground-Fault Circuit Interrupter protection is required:

• All bathroom outlets
• All kitchen outlets serving the counter
• All laundry outlets
• All garage outlets
• All outdoor outlets (including under porch eaves, even if covered)
• Outlets within 6 feet of any sink (including basement sinks, wet bars, utility tubs)
• Outlets within 6 feet of a bathtub or shower (regardless of room)
• Crawl space outlets
• Unfinished basement outlets
• Boathouse outlets
• Outlets serving dishwashers
• Outlets serving electric drinking fountains
• Outlets within 6 feet of a swimming pool
• Outlets in indoor damp/wet locations

The list grew significantly in NEC 2020 and 2023. If you're working in any of those areas, GFCI is required, no exceptions.

AFCI Required Locations (NEC 210.12)

Arc-Fault Circuit Interrupter protection is required for branch circuits supplying:

• Outlets and devices in dwelling unit kitchens.
• Outlets in family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, and similar rooms.

In other words: pretty much all habitable spaces. The only places AFCI is not required are bathrooms, garages, unfinished basements, crawl spaces, and outdoor.

For circuits where both AFCI and GFCI are required (kitchens and laundry), use dual-function (combination GFCI/AFCI) breakers.

Tamper-Resistant Outlets (NEC 406.12)

Required in all 15A and 20A, 125V receptacle outlets in dwelling units. Means the receptacle has internal shutters that prevent objects from being inserted into a single slot (basically, a plug has to go in both slots simultaneously).

Exceptions: receptacles more than 5.5 feet above the floor, receptacles that are part of a hardwired appliance, receptacles in dedicated locations not normally accessible (behind built-in appliances).

If you're replacing an outlet in your house and you buy any standard 15A or 20A residential receptacle made in the last decade, it's probably tamper-resistant. They cost the same now.

Working Space Around Panels (NEC 110.26)

We covered this in Chapter 33 but it bears repeating, because it's one of the most-failed inspection items:

• 30 inches wide (centered on the panel)
• 36 inches deep
• 6.5 feet of headroom
• The space must be clear of stored items, water heaters, ductwork, etc.
• Panels in clothes closets are not allowed (NEC 240.24(D))
• Panels in bathrooms are not allowed (NEC 240.24(E))

If your panel is in a finished basement and you're planning to wall it in, leave the working clearance and put a door for access. Don't bury it.

Box Fill Quick Rules

Already covered in Chapter 33, but the cliff notes:

• Each conductor: 2.0 cu in (14 AWG), 2.25 cu in (12 AWG), 2.5 cu in (10 AWG).
• Each device: 2 × the largest conductor allowance.
• Cable clamps inside the box: 1 conductor of the largest size in the box (count once, regardless of how many clamps).
• All grounds: count as 1 conductor of the largest size.

The math gets fiddly when you have multiple cables and multiple devices. For typical residential work, here's a useful shortcut: a single-gang 18 cu in plastic box can usually accommodate one device with two NM cables. A 22 cu in box can handle one device with three cables, or two devices with two cables. Anything more, go to a 4-square box (21 or 30 cu in) with a mud ring.

Cable Support and Securing (NEC 334.30)

NM cable (Romex) requirements:

• Within 12 inches of every box. A staple or cable clamp must support the cable within 12 inches of every box where the cable enters.
• Every 4.5 feet along the run. Staples, straps, or other supports.
• Through framing: drilled holes in studs/joists count as support, but they must be at least 1.25 inches from the edge of the framing (or protected with a steel nail plate).
• No support needed for cable running through bored holes in studs/joists (the framing supports it).
• Cable in attics or crawl spaces: see 334.23 and 334.10. Special rules apply for unfinished spaces, especially attics with limited access.

Cable Protection at Holes (NEC 300.4)

When cable passes through framing within 1.25 inches of the edge (or in any drilled hole that nails could reach), you must protect the cable with a steel nail plate. The plates are sold in 16-gauge steel, sized for studs and joists. Use them. They prevent the most common cable damage in residential construction.

Service Entrance Conductors and Sizing (NEC Article 230)

For most residential services:

These are for typical residential installations using standard conductor types. Specific applications and conditions may require different sizes.

Service drop or service lateral height clearances:

• Over driveways: 18 feet.
• Over sidewalks accessible to pedestrians: 12 feet (but commonly 15 feet for safety margin).
• Over a residential property line, not over driveways: 10 feet.
• Above a roof (not a flat roof): 8 feet from highest roof point if conductors pass over.

Grounding Electrode System (NEC 250.50)

What needs to be grounded together:

• Metal water pipe (within 5 feet of entrance to building)
• Metal frame of building (if effectively grounded)
• Concrete-encased electrode (Ufer ground, in a footing or slab)
• Ground ring (rare in residential)
• Ground rods (driven, two required if the rod is the only electrode, or one if combined with another type)

For a typical OKC house: usually a Ufer (concrete-encased) electrode in the foundation, plus two driven ground rods near the meter. Sometimes a metal water pipe is also bonded.

Ground wire size (NEC Table 250.66):

Bonding Hot and Cold Water Pipes (NEC 250.104)

The metal water piping in your house must be bonded to the grounding system, even if it's not used as a grounding electrode. Bond to the cold water pipe near the entry point. Connect to the panel ground bar with appropriate-size copper wire.

For residential, this is usually 6 AWG copper for typical 200A services.

Smoke and CO Detector Requirements

NEC doesn't actually specify smoke detector requirements (those are in your local building code or fire code), but here are the typical residential rules in Oklahoma:

Smoke detectors required:

• One in every bedroom.
• One outside each sleeping area (in the hallway, typically).
• One on every level of the house, including basements.
• Hardwired with battery backup.
• Interconnected (when one alarms, all alarm).

CO detectors required:

• One outside each sleeping area (typically the same hallway as the smoke detector).
• Required in homes with fuel-burning appliances or attached garages.
• Hardwired with battery backup, or 10-year battery only.

Combination smoke/CO detectors are common and meet both requirements at one location.

Common Code Violations on Inspection

Most-failed inspection items in OKC residential work, in rough order:

1. Cable not protected through framing (no nail plates).
2. Box fill exceeded.
3. AFCI breakers missing where required.
4. Working clearance around panel obstructed.
5. Wire connections under wire nut not properly twisted.
6. Insufficient cable support (staples spaced too far apart, or missing within 12" of boxes).
7. Backstabbed connections in 20A circuits.
8. Bathroom or kitchen outlets not GFCI-protected.
9. Service entrance grounding electrode missing or improperly sized.
10. Tamper-resistant outlets missing in habitable spaces.