A standard simple electrical wiring diagram for a 120V switched light routes the ungrounded (hot) conductor through a single-pole switch while passing the grounded (neutral) conductor directly to the load. This configuration ensures the light socket shell remains at 0V potential relative to ground when the switch is off, satisfying NEC Article 404.2(A) requirements for switching the ungrounded conductor. Below is a complete, node-by-node walkthrough for wiring a hardwired LED shop light using 14/2 NM-B cable and a standard 15A single-pole switch.

Decoding the Simple Electrical Wiring Diagram Symbols

Before pulling wire, you must translate the schematic symbols into physical actions. A basic lighting diagram relies on four core ANSI/IEEE standard symbols:

  • Circle with an 'X' inside: Represents the lighting load (the shop light fixture). The 'X' historically denoted the filament in incandescent bulbs but applies to LED drivers today.
  • SPST Switch Symbol: A line broken by a hinged lever. Single-Pole, Single-Throw. It has two current-carrying terminals (Line and Load) and one grounding terminal.
  • Parallel Lines: Represents a multi-conductor cable (like 14/2 NM-B). The number of wires inside the cable is usually noted adjacent to the line.
  • Three Decreasing Horizontal Lines: The universal earth ground symbol, indicating the equipment grounding conductor (EGC) bonded to the metal chassis or green screw.
Bench Tip: Never confuse the schematic ground symbol with the neutral bar. In your physical panel, neutral and ground are bonded only at the main service disconnect. Downstream at your switch box, they must remain strictly isolated.

Node-by-Node Trace: Source to Load

This trace assumes a 'Power-at-Switch' topology, which is the most straightforward method for new construction or running a new branch circuit from a subpanel. We are using 14 AWG copper wire protected by a 15A breaker.

Node 1: The Breaker Panel

The 14/2 NM-B cable originates at a 15A single-pole breaker. The black (hot) wire terminates on the breaker's load lug. The white (neutral) wire terminates on the neutral bus bar. The bare copper (ground) terminates on the equipment grounding bus bar. Polarity check: The breaker only interrupts the black wire.

Node 2: The Switch Junction Box

The 14/2 cable enters the single-gang switch box. 1. The bare ground wire is pigtailed: one end connects to the metal box (if metal) or ground clip, and the other connects to the green grounding screw on the switch. 2. The white neutral wire does not land on the switch. It passes straight through the box, spliced with a wire nut to the white neutral wire of the 14/2 cable heading up to the light. 3. The black hot wire from the panel connects to the bottom brass terminal (Line) on the switch. 4. A second black wire (the 'switched hot' or 'load' wire) from the cable heading to the light connects to the top brass terminal (Load) on the switch.

Node 3: The Light Fixture

The cable arrives at the ceiling junction box or the fixture's integrated whip. 1. The bare ground bonds to the fixture's green ground screw or metal chassis. 2. The white neutral connects to the fixture's silver terminal or white lead wire. 3. The black switched hot connects to the fixture's brass terminal or black lead wire. When the switch closes, 120V potential is applied across the LED driver.

Terminal and Pin Mapping Table

Physical devices vary slightly by manufacturer. This table maps the physical terminals for the industry-standard Leviton R62-05601 15A Decora Switch and a standard hardwired LED shop light.

Device Terminal Name / Color Wire Color Connection Method
Leviton Switch Line (Bottom Brass Screw) Black (Panel Hot) Side-wire screw (12-14 in-lbs)
Leviton Switch Load (Top Brass Screw) Black (Fixture Hot) Side-wire screw (12-14 in-lbs)
Leviton Switch Ground (Green Screw) Bare Copper Side-wire screw
LED Shop Light Hot Lead / Brass Black (Switched Hot) Wire nut or push-in connector
LED Shop Light Neutral Lead / Silver White (Neutral) Wire nut or push-in connector
Safety Warning: Avoid using the 'backstab' (push-in) terminals on the back of the switch. While UL-listed for 14 AWG solid wire, they rely on a small spring-metal bite that can loosen under thermal cycling. Always use the side-wire brass screws and torque them until the wire is firmly seated and the loop cannot be pulled out.

Verification: Testing with a Multimeter

Do not rely on visual inspection alone. Use a CAT III rated multimeter (like a Fluke 117) to verify your simple electrical wiring diagram was executed correctly. Follow this exact sequence:

Step 1: De-Energized Continuity Test (Breaker OFF)

Set your meter to Continuity (the diode/beep symbol). 1. Place one probe on the switch's Line brass screw and the other on the black wire at the ceiling fixture. With the switch OFF, the meter should read 'OL' (Open Loop). 2. Toggle the switch ON. The meter should beep and read less than 1.0 ohm, confirming a solid copper path. 3. Place one probe on the white neutral wire at the switch box and the other on the white wire at the fixture. It should read < 1.0 ohm continuously, regardless of switch position.

Step 2: Energized Voltage Test (Breaker ON)

Set your meter to AC Voltage (V~). Ensure you are wearing safety glasses and standing on a dry surface. 1. Measure between the black Line wire and the bare ground wire at the switch box. You should read between 114V and 126V (nominal 120V). 2. Measure between the white neutral and bare ground at the switch box. You should read < 2V. If you read 120V here, you have an open neutral or a crossed wire—shut the breaker off immediately. 3. At the ceiling fixture, measure between the black switched hot and the white neutral. With the switch ON, read 120V. With the switch OFF, read 0V.

Decision Tree: Power Routing and Cable Selection

Not every installation allows for power to enter the switch box first. Use this decision matrix to select the correct topology and cable type for your specific physical constraints. For reference on safe meter usage during these tests, consult Fluke's guide on measurement categories.

Installation Condition Topology Required Cable to Switch Concrete Pick / Action
Running a brand new circuit from the panel to a new switch location. Power-at-Switch 14/2 NM-B Default Pick: Use standard 14/2. White is neutral, Black is hot.
Adding a wall switch to an existing pull-chain light where power already feeds the ceiling box. Power-at-Light (Switch Loop) 14/2 NM-B Action: Use 14/2, but wrap the white wire in black electrical tape at both ends to re-identify it as a hot conductor feeding the switch.
Installing a smart switch (e.g., Lutron Caseta) that requires a neutral wire to power its internal radio. Power-at-Switch with Neutral 14/3 NM-B Action: Run 14/3. Use Black for Line, Red for Load, White for Neutral, Bare for Ground.

The Final Verdict: If you are framing a new garage, shed, or workshop and have open walls, always choose the Power-at-Switch topology with 14/2 NM-B. It is the most intuitive to troubleshoot, leaves a neutral in the switch box for future smart-home upgrades (if you upgrade to 14/3 later), and perfectly matches the standard simple electrical wiring diagram found in every trade textbook. Buy a 250-foot spool of Southwire 14/2 NM-B and a 10-pack of Leviton R62-05601 switches to standardize your build.