The Direct Answer: Wire Diagram for GFCI and Downstream Outlet

To wire a standard duplex outlet so it is protected by an upstream GFCI, the incoming power (hot and neutral) must connect to the LINE terminals on the GFCI, while the outgoing cables feeding the downstream outlet must connect to the LOAD terminals. The equipment grounding conductor (bare or green) bypasses the GFCI's internal sensing circuitry and bonds directly to the grounding terminals of both devices and the metal boxes.

Decision Path: Which Setup Do You Need?

Use this table to determine your exact configuration. Do not mix 15A and 20A components on a 20A circuit.

Breaker Size Wire Gauge (Copper) GFCI Amperage Downstream Amperage Concrete Pick (GFCI)
15 Amp 14 AWG 15A 15A (or 20A feed-through) Eaton GFTR15-W
20 Amp 12 AWG 20A 15A or 20A Leviton 8280-W

Default Recommendation: If you are wiring a modern kitchen or bathroom circuit (which requires 20A per NEC 210.11 and 210.23), buy the Leviton 8280-W (20A GFCI) and use 12 AWG NM-B cable. If you are replacing an existing 15A receptacle in a living area, use the Eaton GFTR15-W with 14 AWG wire.

Decoding the Diagram Symbols and Device Terminals

When looking at a manufacturer's wire diagram for a GFCI, the schematic uses standardized NEMA/IEEE symbols. A circle with a 'G' or a rectangle with 'TEST/RESET' represents the GFCI. Two parallel lines with a 'T' shape represent the standard downstream duplex receptacle. A circle with a cross inside indicates a wire nut (splices), and a solid dot at an intersection indicates a bonded connection.

Here is the exact terminal mapping for the physical device you will be holding in your hand:

Terminal Label Screw Color Function Wire Color to Connect
LINE Hot Brass (Black tape on back) Receives incoming power from the breaker panel Black (Hot)
LINE Neutral Silver (White tape on back) Receives incoming return path from the panel White (Neutral)
LOAD Hot Brass (Yellow/Red tape on back) Sends protected power to the downstream outlet Black (with red electrical tape)
LOAD Neutral Silver (Yellow/Red tape on back) Sends protected return path to downstream outlet White (with red electrical tape)
Ground Green Equipment bonding path (fault current return) Bare copper or Green
Critical Polarity Note: The GFCI internal sensor compares current on the hot and neutral. If you reverse LINE and LOAD, the outlet will still power on, but the downstream protection will fail, and the GFCI will not trip during a ground fault. Always verify LINE vs LOAD with a meter before terminating.

Node-by-Node Trace: Source to Load

To understand the wire diagram for this setup, trace the current path node-by-node from the breaker panel to the final downstream device.

  1. Node 1 (Panel to GFCI Box): The 2-wire cable (12/2 or 14/2 NM-B) leaves the breaker. The black (hot) and white (neutral) conductors enter the GFCI junction box. The bare ground bonds to the metal box (if applicable) via a grounding screw and pigtail.
  2. Node 2 (GFCI LINE Termination): The incoming black wire terminates on the LINE brass screw. The incoming white wire terminates on the LINE silver screw. The ground pigtail terminates on the GFCI's green ground screw.
  3. Node 3 (GFCI to Downstream Box): A second 2-wire cable enters the GFCI box. Its black wire terminates on the LOAD brass screw, and its white wire terminates on the LOAD silver screw. The bare ground of this second cable is spliced (wire-nutted) to the incoming ground and the GFCI ground pigtail.
  4. Node 4 (Downstream Box Grounding): The second cable enters the downstream box. The bare ground bonds to the box and runs a pigtail to the downstream receptacle's green ground screw.
  5. Node 5 (Downstream Termination): The black wire from the second cable connects to the brass screw on the standard duplex outlet. The white wire connects to the silver screw.

Ground Path Explicit Callout: Notice that the equipment grounding conductor (bare/green) never passes through the LOAD terminals. The GFCI does not monitor the ground wire; it only monitors the imbalance between the LINE hot and LINE neutral. The ground path must remain continuous and unbroken from the panel to both receptacles to ensure fault currents can trip the breaker if the GFCI fails.

Step-by-Step Wiring Procedure

Follow these exact bench-tested steps to ensure a secure, code-compliant installation.

  1. De-energize and Verify: Turn off the breaker. Use a non-contact voltage tester (NCVT) on the outlet, then verify dead with a multimeter set to VAC (Line-to-Neutral and Line-to-Ground must read 0V).
  2. Strip and Prep: Strip exactly 3/4-inch of insulation from the solid copper conductors. Do not nick the copper. If using stranded THHN in conduit, twist the strands tightly and tin them with solder or use ferrules.
  3. Identify LINE vs LOAD: If you are replacing an existing outlet and don't know which cable is the source, cap all wires, turn the breaker on briefly, and use your multimeter to find the cable reading 120V. Tag that cable's wires with black electrical tape to mark them as LINE. Turn the breaker back off.
  4. Ground Splice: Connect all bare/green wires in the GFCI box using a copper crimp sleeve or a green wire nut. Add a 6-inch bare copper pigtail to the GFCI's green screw.
  5. Terminate LINE: Hook the incoming black wire clockwise around the LINE brass screw. Hook the incoming white wire clockwise around the LINE silver screw.
  6. Terminate LOAD: Wrap a small flag of red electrical tape around the outgoing black and white wires to visually distinguish them as LOAD wires. Terminate them on the LOAD brass and silver screws, respectively.
  7. Torque to Spec: Use an inch-pound torque screwdriver. UL 498 and NEC 110.14(D) require terminations to be torqued to the manufacturer's spec. For standard 15A/20A Leviton and Eaton receptacles, this is typically 14 in-lbs. Hand-tightening leads to loose connections that arc and melt the terminal block over time.
  8. Downstream Wiring: At the second box, terminate the black wire to the brass screw, white to the silver screw, and ground to the green screw on the standard duplex receptacle. Torque to 14 in-lbs.

Verification: Testing with a Multimeter

Do not just plug in a lamp and assume the wire diagram was executed correctly. Perform this meter-based verification sequence.

  • Step 1 (Pre-Power Ground Check): Before turning the breaker on, set your multimeter to Ohms (Ω). Measure between the downstream outlet's ground slot and the GFCI's ground slot. You should read < 1.0 Ω, confirming a continuous equipment bonding path.
  • Step 2 (Voltage Check): Turn on the breaker. Set the meter to VAC. Measure Hot-to-Neutral at the GFCI. You should read 118V to 122V (nominal 120V). Measure Hot-to-Ground; it should read the same.
  • Step 3 (Downstream Voltage): Measure Hot-to-Neutral at the downstream outlet. It must also read 118V to 122V. If it reads 0V, your LOAD wires are either not terminated, or you accidentally wired the downstream cable to the LINE terminals (leaving the LOAD terminals empty).
  • Step 4 (Trip Test): Press the 'TEST' button on the GFCI. The 'RESET' button should pop out. Measure voltage at both the GFCI and the downstream outlet. Both must read 0V. If the downstream outlet still has 120V, it is wired to the LINE side and is entirely unprotected.

Sizing and Component Selection Guide

When sourcing materials for this wire diagram, match your components to the circuit ampacity. According to the National Electrical Code (NEC), specifically Article 210.8, GFCI protection is mandatory in kitchens, bathrooms, garages, and outdoor locations.

For a 20A kitchen small-appliance branch circuit, you must use 12 AWG copper wire. While a 15A GFCI receptacle is legally permitted on a 20A circuit (NEC 406.4), the internal pass-through contacts of a 15A device are only rated for 15A. If you plug a 15A appliance into the GFCI and a 10A appliance into the downstream outlet, you will pull 25A through the GFCI's internal busbars, risking thermal failure before the 20A breaker trips.

Final Component Pick: For any 20A circuit, purchase a 20A GFCI (like the Leviton 8280-W). It features 20A pass-through contacts, ensuring the downstream outlet can safely handle the full circuit load without bottlenecking at the GFCI device. Use 12 AWG NM-B (Romex) for the run, and ensure your junction boxes have a minimum volume of 22.5 cubic inches to accommodate the bulky GFCI body and the extra wire nuts required for the downstream splice.