Chapter 1: General Requirements

Learning Objectives

Upon completing this chapter, you will be able to:

4.Identify the scope and purpose of the National Electrical Code (NEC) as it applies to residential inspections.

5.Apply the fundamental rules for voltage drop, conductor ampacity, and overcurrent protection.

6.Distinguish between the various types of grounding and bonding systems required for a dwelling unit.

7.Locate and interpret key tables (e.g., Table 310.12, Table 250.66) during an open-book exam.

8.Recognize common residential installation violations related to general requirements.

1.1 Scope and Authority of the NEC

The NEC (NFPA 70) is not a design manual; it is a minimum safety standard. For the Residential Electrical Inspector (E1), your authority comes from the adoption of the NEC by local or state jurisdiction. You inspect to the adopted edition — always verify which edition (e.g., 2023, 2020) is in force in your area.

Key definitions you must know:

Dwelling unit: A single unit providing complete and independent living facilities, including permanent provisions for living, sleeping, cooking, and sanitation.

Accessible (as applied to equipment): Admitting close approach; not guarded by locked doors, elevation, or other effective means.

Readily accessible: Capable of being reached quickly for operation, renewal, or inspections, without climbing over or removing obstacles.

Inspection point: Verify that the service disconnecting means is readily accessible — not behind a locked door requiring a key, not in a closet with stored items, and not more than 6 feet 7 inches above the floor (per 230.70).

1.2 Voltage Drop (NEC 210.19, 215.2, 310.15)

The NEC does not mandate a specific voltage drop percentage for branch circuits, but Informational Note No. 2 to 210.19 recommends a maximum of 3% for branch circuits and 5% total (branch + feeder). While not a code requirement, many local jurisdictions adopt these values as enforceable.

Formula (for single-phase, copper):

Voltage drop (Vd) = (2 × K × I × L) / Cmils

K = 12.9 (copper) or 21.2 (aluminum)

I = current in amperes

L = one-way length in feet

Cmils = circular mils of conductor (from NEC Chapter 9, Table 8)

Practical rule of thumb for 120V circuits: For a 15A circuit, keep the one-way run under 100 feet with 14 AWG copper to stay near 3%.

Inspection point: When a homeowner complains of dim lights or slow motors, check the actual conductor length, not just the blueprint distance. Also verify that the neutral is counted in the voltage drop calculation for multiwire branch circuits.

1.3 Conductor Ampacity and Temperature Ratings (NEC 310.12, 310.15)

For residential services and feeders, Table 310.12 (formerly 310.15(B)(7)) provides reduced ampacities for dwelling units. This table applies only to 3-wire, single-phase, 120/240V systems serving the entire dwelling load.

Critical values from Table 310.12 (copper, 75°C column):

100A service: #4 AWG copper (or #2 AWG aluminum)

125A service: #2 AWG copper (or #1/0 AWG aluminum)

150A service: #1 AWG copper (or #2/0 AWG aluminum)

200A service: #2/0 AWG copper (or #4/0 AWG aluminum)

Important: These ampacities are not permitted for branch circuits. For branch circuits, use Table 310.16 (or 310.17 for free air). Also note the temperature limitation rule: if the termination is rated 60°C (common for residential breakers), you must use the 60°C column, even if the wire is rated 90°C.

Inspection point: Check the breaker terminal temperature rating. Most residential breakers are 60/75°C. If the label says "60°C," you cannot use the 75°C ampacity column for that circuit.

1.4 Overcurrent Protection (NEC 240.4, 240.6)

Standard overcurrent device ratings (240.6(A)): 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000.

The "next size up" rule (240.4(B)): If the conductor ampacity does not correspond to a standard rating, you may use the next higher standard rating, but only if:

The conductor is not part of a multioutlet branch circuit supplying receptacles for cord-and-plug-connected loads.

The ampacity is not less than the load.

The overcurrent device rating does not exceed 800A.

Inspection point: For a 14 AWG copper conductor (15A ampacity at 60°C), you cannot use a 20A breaker — even if the load is only 10A. The rule is absolute for branch circuits.

1.5 Grounding and Bonding (Article 250)

This is the most heavily tested area for the E1 exam. You must separate grounding (connection to earth) from bonding (connection to establish electrical continuity).

1.5.1 System Grounding (250.24)

The service neutral must be grounded at the service disconnecting means.

The grounding electrode conductor (GEC) must connect the neutral to the grounding electrode system.

Table 250.66 gives GEC sizes based on the largest ungrounded service conductor.

Example (Table 250.66): For a 200A service with #2/0 AWG copper ungrounded conductors, the GEC must be #4 AWG copper (or #2 AWG aluminum).

1.5.2 Grounding Electrode System (250.50, 250.52)

All electrodes present at the dwelling must be bonded together:

Metal underground water pipe (at least 10 feet in contact with earth)

Concrete-encased electrode (Ufer ground) — 20 feet of #4 AWG bare copper in the footing

Ground rod (at least 8 feet long, 5/8 inch diameter)

Other approved electrodes

Inspection point: If a concrete-encased electrode exists, you must use it. You cannot skip it and just drive a ground rod. Also, the connection to the water pipe must be within 5 feet of where the pipe enters the building (250.52(A)(1)).

1.5.3 Bonding (250.102, 250.104)

Service equipment: Bond the neutral to the equipment grounding bus (the main bonding jumper).

Subpanels: The neutral must be isolated from the grounding bus (no bonding screw or jumper).

Bonding of metal piping: Bond all metal water pipes, gas pipes, and structural steel within 5 feet of the service.

Common violation: A subpanel with the neutral bonded to the enclosure. This creates parallel paths for neutral current and is a shock hazard.

1.6 Services (Article 230)

Service disconnecting means (230.70, 230.71):

Must be at a readily accessible location.

For a dwelling, a maximum of six disconnects is permitted (230.71), but modern practice is a single main breaker.

The disconnect must be rated for the load and have a marked "Suitable for Use as Service Equipment" label if it is the service disconnect.

Service entrance conductors (230.42):

Must have an ampacity of at least the calculated load (per Article 220).

Must be protected against physical damage (230.50).

Inspection point: Check that the service mast is properly guyed or supported, and that the weatherhead is at least 18 inches above the roof (for a 2-foot rise) per 230.54.

1.7 Branch Circuits (Article 210)

General requirements for dwelling units (210.11, 210.12, 210.52):

Small-appliance branch circuits (210.52(B)): At least two 20A circuits for kitchen, pantry, and dining areas. These circuits must not supply lighting (except in the kitchen).

Laundry circuit (210.52(F)): At least one 20A circuit for the laundry outlet.

Bathroom circuits (210.11(C)(3)): At least one 20A circuit for bathroom receptacles (can also supply a bathroom light fan, but not other rooms).

Arc-fault circuit interrupters (AFCI) (210.12):

Required for all 120V, single-phase, 15A and 20A branch circuits supplying outlets in dwelling unit bedrooms, living rooms, family rooms, dining rooms, kitchens, hallways, and similar areas.

Exception: AFCI protection is not required for a branch circuit supplying only a fire alarm system or a fixed electric space heater.

Inspection point: Verify that the AFCI breaker is installed at the panel, not just a receptacle-type AFCI at the first outlet (unless the manufacturer's instructions and the code permit it — which is rare for new work).

1.8 Receptacles and Outlets (Article 406, 210.52)

Spacing rule (210.52(A)(1)): In every habitable room, receptacles must be installed so that no point along the wall is more than 6 feet from a receptacle. This means a maximum spacing of 12 feet between receptacles.

Wall space definition: Any wall space 2 feet or more in width is considered wall space. Doorways, fireplaces, and fixed cabinets do not count.

Kitchen countertops (210.52(C)): Receptacles must be installed above countertops so that no point is more than 2 feet from a receptacle. All countertop outlets must be GFCI-protected (210.8(A)(6)).

Bathrooms (210.52(D)): At least one receptacle within 3 feet of the sink edge. It must be GFCI-protected.

Inspection point: Measure the distance along the wall, not in a straight line. A receptacle behind a door that is open 90° does not count for the spacing rule if the door blocks access.

1.9 GFCI Protection (210.8)

Dwelling unit locations requiring GFCI (210.8(A)):

Bathrooms

Garages (including unfinished basements)

Outdoors

Crawl spaces

Kitchens (all countertop and within 6 feet of sink)

Laundry areas (within 6 feet of sink)

Wet bars

GFCI types: Receptacle-type, breaker-type, and portable. For inspection, the receptacle must be labeled "No Equipment Ground" if installed on a 2-wire circuit without a ground (406.4(D)(2)).

Inspection point: Test GFCI devices with the built-in test button. Also verify that the GFCI is accessible — you cannot bury a GFCI behind a refrigerator or a built-in microwave.

1.10 Code Navigation — Where to Find It

Use this quick-reference for the open-book exam:

Concept	NEC Location
Definitions (dwelling unit, accessible)	Article 100
Voltage drop (informational)	210.19, 215.2, 310.15
Conductor ampacity (dwelling)	Table 310.12
Conductor ampacity (general)	Table 310.16
Overcurrent protection	240.4, 240.6
Grounding electrode system	250.50, 250.52
GEC sizing	Table 250.66
Bonding	250.102, 250.104
Service disconnects	230.70–230.71
Branch circuit requirements	210.11, 210.12
AFCI requirements	210.12
GFCI requirements	210.8
Receptacle spacing	210.52(A)
Kitchen countertop receptacles	210.52(C)
Receptacle ratings	406.3, 406.4
Service entrance conductors	230.42
Weatherhead and mast	230.54

1.11 Practical Inspection Checklist

When you arrive on site, use this mental checklist for general requirements:

112.Service panel: Is the main breaker rated correctly? Is the neutral bonded to the enclosure? Is the GEC properly sized and connected to the electrode?

113.Subpanel: Is the neutral isolated from the ground bus? Are the grounds and neutrals on separate bars?

114.Branch circuits: Are all 120V circuits in living areas AFCI-protected? Are all kitchen, bath, and outdoor receptacles GFCI-protected?

115.Conductor sizes: Does the 200A service use at least #2/0 copper or #4/0 aluminum? Are branch circuits 14 AWG on 15A breakers and 12 AWG on 20A breakers?

116.Receptacle spacing: Measure the wall distances in every room. Check for the 6-foot rule and the 2-foot rule for countertops.

117.Accessibility: Can you reach the service disconnect without moving furniture? Are all junction boxes accessible (not drywalled over)?

118.Bonding: Are the water pipe, gas pipe, and any metal siding bonded within 5 feet of the service?

1.12 Common Exam Traps

Table 310.12 vs. 310.16: Do not use Table 310.12 for a subpanel feeder — it only applies to the entire dwelling service.

The 60°C rule: When in doubt, use the 60°C column for residential terminations.

AFCI vs. GFCI: AFCI protects against arcing; GFCI protects against ground faults. They are not interchangeable, though combination devices exist.

Six-disconnect rule: The six disconnects must be grouped, and each must be rated for the load. A single main breaker is always simpler and safer.

Ground rod spacing: If you use two ground rods, they must be at least 6 feet apart (250.53(A)(2)) — otherwise, they are treated as a single electrode.

Summary

The General Requirements chapter of the NEC sets the foundation for every residential inspection. Master the definitions, the ampacity tables, and the grounding/bonding rules first — these appear in nearly every exam question and every real-world inspection. Always verify the adopted edition, and use the Code Navigation table above to find answers quickly during the open-book exam. Remember: you are enforcing the minimum safety standard, not the ideal design. Your job is to protect life and property, not to redesign the electrical system.

General Requirements