Residential Electrical

Wire Gauge & Amperage

Wire gauge determines the maximum current a wire can safely carry. Lower gauge number = thicker wire = higher amperage capacity.

Understanding Wire Labels

Romex (NM-B) cable is the standard for residential wiring. The label tells you everything:

What the Numbers Mean

• 14/2: 14-gauge wire, 2 insulated conductors (black hot + white neutral) + bare copper ground. Use for lighting circuits on 15-amp breakers.
• 12/2: 12-gauge wire, 2 conductors + ground. Required for all outlet circuits (20-amp). This is what you run to receptacles.
• 14/3: 14-gauge wire, 3 insulated conductors (black + white + red) + bare ground. The red wire is the "traveler" used for 3-way switch circuits.
• 12/3: 12-gauge wire, 3 conductors + ground. For 3-way switches on 20-amp circuits.
• 10/3: 10-gauge wire, 3 conductors + ground. Used for 240V dryer circuits (30-amp).
• 6/3: 6-gauge wire, 3 conductors + ground. Used for 240V range/stove circuits (50-amp).

14/2 vs 14/3: The Traveler Wire

The difference between /2 and /3 wire is the extra conductor:

• 14/2 (or 12/2): Contains hot (black), neutral (white), and ground (bare). This is your standard wire for single switches, lights, and outlets.
• 14/3 (or 12/3): Contains hot (black), neutral (white), traveler (red), and ground (bare). The red "traveler" wire is needed when two switches control the same light (3-way switches). It carries the switching signal between the two switch locations.

You only need /3 wire between the two switches in a 3-way setup. The rest of the circuit (from panel to first switch, from second switch to light) uses standard /2 wire.

Wire Color Coding

• Black: Hot (carries current to device).
• White: Neutral (return path to panel).
• Red: Second hot (for 240V or 3-way switches).
• Bare Copper: Ground (safety path to earth).
• Green: Ground (in conduit or appliance cords).

Circuit Requirements by Location

General Lighting

• Wire: 14/2 NM-B on 15-amp breaker.
• Load Limit: Max 1,440 watts (80% of 15A at 120V).
• LED Lights: At 10-15 watts each, a 15-amp circuit can handle 10-15 LED fixtures easily.

General Outlets (Bedrooms, Living Room)

• Wire: 12/2 NM-B on 20-amp breaker. While code technically allows 14/2 on 15-amp for general outlets, running 12 gauge to all outlets is best practice and increasingly required.
• Spacing: Outlets required every 12 feet along walls, within 6 feet of any doorway.
• AFCI Required: Bedrooms and living areas require AFCI protection (at the breaker or first outlet).

Kitchen (Code Strict)

• Countertop Outlets: Two separate 20-amp circuits required (12/2 wire). GFCI protected.
• Refrigerator: Dedicated 20-amp circuit recommended.
• Dishwasher: Dedicated 20-amp circuit, GFCI protected (2023 code).
• Garbage Disposal: Can share circuit with dishwasher or be dedicated 15-amp.
• Microwave: Dedicated 20-amp circuit if built-in.

Bathroom

• Wire: 12/2 NM-B on 20-amp breaker.
• GFCI: Required for all bathroom outlets.
• Circuits: Each bathroom needs at least one 20-amp circuit. Can serve multiple bathrooms but nothing else.

Garage & Outdoor

• Wire: 12/2 NM-B on 20-amp breaker minimum.
• GFCI: Required for all garage and outdoor outlets.
• Outdoor: Must be weather-resistant (WR) and in-use covers required.

Laundry

• Washer: Dedicated 20-amp circuit (12/2 wire). GFCI protected (2023 code).
• Electric Dryer: 30-amp 240V circuit using 10/3 wire with 4-prong outlet (NEMA 14-30).
• Gas Dryer: Just needs 120V 15 or 20-amp outlet for controls.

Large Appliance Circuits

Breaker Types Explained

• Single-Pole Breaker: Takes one slot in the panel. Provides 120V. Used for lights, outlets, washer.
• Double-Pole Breaker: Takes two slots (or one double-width slot). Provides 240V by connecting both hot bus bars. Used for stove, dryer, water heater, A/C.
• Stove: 50-amp double-pole breaker. The breaker handle is linked so both poles trip together.
• Dryer: 30-amp double-pole breaker. Same concept as stove but lower amperage.
• Washer: 20-amp single-pole GFCI breaker (or standard breaker with GFCI outlet). Washers run on 120V, not 240V.

For 240V circuits, both hot wires carry 120V each (180 degrees out of phase, giving 240V potential between them). The neutral is only needed if the appliance has 120V components (like oven lights or dryer controls). Pure 240V loads like water heaters use only 2 conductors + ground.

Daisy Chaining Explained

Daisy chaining connects multiple outlets or lights in series along a single circuit. Power comes from the panel, goes to the first device, then jumps to the next, and so on.

How It Works

• Feed Wire: Hot and neutral from the panel enter the first junction box.
• Pigtails: At each outlet, connect the incoming hot, outgoing hot, and a short pigtail to the outlet's brass screw using a wire nut. Same for neutral on silver screws.
• Last Device: Only has incoming wires, no outgoing.
• Ground: All grounds tie together with a pigtail to the green screw.

Daisy Chain Best Practices

• Use Pigtails: Never rely on outlet terminals to pass power through. If the outlet fails, everything downstream dies.
• Box Fill: Count wires carefully. Each 12-gauge wire = 2.25 cubic inches, each 14-gauge = 2 cubic inches. Standard single-gang boxes are 18-22 cubic inches.
• Max Devices: General rule of 8-10 outlets per 20-amp circuit, though code doesn't specify a hard number for residential.

Load Calculations

15-Amp vs 20-Amp Circuits

How Many Lights Per Circuit?

• 15-Amp Circuit (14/2 wire): Max 1,440 watts at 80% rule.
• LED Recessed (10-15W each): Easily 12-15 LED fixtures on a 15-amp circuit.
• Practical Limit: Keep lighting circuits to 8-12 fixtures to leave headroom and allow for future changes.
• 20-Amp Circuit (12/2 wire): Max 1,920 watts. Could handle 15-20 LED fixtures, but lighting circuits typically stay on 15-amp.

How Many Outlets Per Circuit?

• Code: NEC doesn't specify a hard limit on outlets per circuit for residential. The 80% rule governs actual load.
• 15-Amp Circuit: 8-10 outlets max (though you should run 12 gauge to outlets anyway).
• 20-Amp Circuit: 10-13 outlets is the practical rule of thumb.
• Reality: A bedroom circuit with 6-8 outlets rarely pulls more than 3-5 amps unless someone plugs in a space heater (1,500W = 12.5 amps).
• Best Practice: Limit to 8-10 outlets per 20-amp circuit and don't mix rooms if possible.

Electrical Panel Basics

Panel Sizing

• 100-Amp: Minimum for older homes without heavy electric loads. May limit future expansion.
• 200-Amp: Standard for modern homes. Required if adding EV charger, electric range, or heavy AC.
• 400-Amp: Large homes or all-electric with multiple high-draw appliances.

Breaker Spaces

• Typical Panel: 20-42 spaces. Each space holds one single-pole (15/20A) or half a double-pole (240V) breaker.
• Tandem Breakers: Two 15/20A breakers in one space. Only allowed in designated slots.
• Planning: For a remodel, list all circuits needed and add 20% for future expansion.

AFCI vs GFCI Breakers

• GFCI: Protects against ground faults (shock hazard). Required in wet locations: kitchen, bathroom, garage, outdoor, laundry.
• AFCI: Protects against arc faults (fire hazard). Required in bedrooms, living areas, and most habitable rooms (2023 code).
• Dual-Function: AFCI/GFCI combo breakers exist for areas needing both.

3-Way Switches

3-way switches control a light from two locations (like top and bottom of stairs). This is where 14/3 wire is actually needed.

Wiring

• Power to First Switch: 14/2 from panel to first switch box.
• Between Switches: 14/3 connects the two switches. Black and red are travelers, white is neutral (or marked as hot if switch loop).
• To Light: 14/2 from second switch to light fixture.
• Travelers: Connect to brass screws on 3-way switches. Common terminal (black or copper screw) gets either the hot feed or the load to the light.

Basic Installation Steps

Running New Wire

• 1. Plan Route: Map the path from panel to each device. Shortest path through studs and joists.
• 2. Drill Holes: Center holes in studs (min 1.25" from edge). Use nail plates if closer.
• 3. Pull Cable: Leave 12-18" of wire at each box. Don't kink or damage sheathing.
• 4. Secure: Staple within 12" of each box and every 4.5 feet along the run.
• 5. Strip & Connect: Remove 6-8" of outer sheathing at boxes. Strip 3/4" of insulation from conductors.

Outlet Installation

• Hot (black): Brass screw (right side).
• Neutral (white): Silver screw (left side).
• Ground (bare): Green screw (bottom).
• Orientation: Ground down is traditional. Ground up arguably safer (falling metal hits ground first).

Code Requirements Summary (NEC 2023)

• Tamper-Resistant: All 15 and 20-amp outlets in dwelling units must be TR rated.
• GFCI: Kitchen, bathroom, garage, outdoor, laundry, basement, pool areas.
• AFCI: Bedrooms, living rooms, dining rooms, hallways, closets, and most habitable spaces.
• Smoke/CO Detectors: Hardwired with battery backup in each bedroom, outside sleeping areas, and every level.
• Box Fill: Calculate cubic inches required based on wire count and gauge.

Tools Needed

• Voltage Tester: Non-contact and plug-in tester. Always verify power is off.
• Wire Strippers: Sized for 14, 12, and 10 gauge.
• Lineman's Pliers: For twisting wires and cutting.
• Fish Tape: For pulling wire through finished walls.
• Stud Finder: Avoid drilling into wires or pipes.
• Right-Angle Drill: For drilling through studs in tight spaces.
• Wire Nuts: Tan (22-16 AWG), red (18-10 AWG), yellow (18-12 AWG), or lever-style Wago connectors.