How to Wire a GFCI Outlet? – GFCI Receptacle Installation
How to Install a 15A – 120V and 20A – 120V GFCI Receptacle Outlet
What is a GFCI?
GFCI (Ground Fault Circuit Interrupter) is a protective device that automatically detects ground faults and leakage currents, providing personal protection against electrocution. As an outlet/receptacle, combo unit, or circuit breaker, a GFCI disconnects the power supply within milliseconds when an electric shock hazard is detected.
According to the NEC (National Electrical Code), GFCIs must be installed in locations where water and electricity are likely to come into contact. These include bathrooms, kitchens, laundry areas, workshops, swimming pools, hot tubs, and other damp or wet environments (e.g., near water pipes). See NEC Code Requirements for GFCI.
GFCI devices are especially important for cord-connected appliances and equipment used outdoors or near water. There are several types of GFCIs, including:
- GFCI Outlet (Receptacle)
- GFCI Combo (Switch and Outlet)
- GFCI Circuit Breaker
- Portable GFCI
Related Post: GFCI: Ground Fault Circuit Interrupter. Types, Working & Applications
In today’s wiring tutorial, we will demonstrate how to wire and install a GFCI outlet in residential settings to protect ordinary receptacles, light switches, and other connected devices.
The figure below illustrates what a GFCI is and how to wire it.
Before installation, it is important to understand the difference between a GFCI outlet and a standard (ordinary) receptacle. As shown in the figure above, the Line (Hot/Live/Phase) terminals are connected to the narrow blade, while the Neutral terminals are connected to the wide blade.
In a standard receptacle, there is a breakaway fin between the upper and lower terminals, which allows both outlets to share the same supply connection. This means that connecting the incoming phase and neutral wires to one side will power both outlets.
In contrast, a GFCI outlet has no such breakaway fin. Instead, it is equipped with clearly marked LINE and LOAD terminals. The correct identification of these terminals must be verified by the nameplate data rating printed on the device or in the manufacturer’s user manual.
In the example diagram above, the LOAD terminals are not connected, meaning any downstream outlets, switches, or additional loads are not protected by the GFCI. In this case, only the two outlets built into the GFCI device itself are protected.
Next, let’s see how to wire a GFCI receptacle so that it also provides protection to additional downstream loads.
Wiring 15A – 120V GFCI Receptacle Outlet
As shown in the wiring diagram, the line terminals of a 15-amp GFCI receptacle are connected to the 120V supply using #14 AWG wire. The hot wire (black) and the neutral wire (white) from the 15-amp breaker in the 120V/240V main panel are connected to the narrow blade (hot terminal) and the wide blade (neutral terminal) of the GFCI receptacle, respectively.
The ground wire (green or bare copper) is connected to the ground terminal of the outlet. The 15-amp GFCI receptacle typically comes in the NEMA 5-15R configuration.
Click image or open in a new tab to enlarge
This wiring method ensures that the receptacle is GFCI protected. According to the NEC 80% rule, a 15-amp GFCI receptacle can safely supply up to 12 amps for continuous loads and 15 amps for non-continuous loads.
Wiring 20A 120V GFCI Outlet
The wiring method for a 20-amp, 120V GFCI receptacle is the same as for the 15-amp version. The main difference is that the neutral slot is T-shaped on a 20-amp receptacle, whereas it is a straight wide slot on a 15-amp receptacle. This receptacle type is classified as NEMA 5-20R.
Click image or open in a new tab to enlarge
For this circuit, use #12 AWG wire and a 20-amp breaker. As per the NEC continuous load rule, a 20-amp GFCI receptacle can safely supply up to 16 amps for continuous loads and 20 amps for non-continuous loads.
Wiring a GFCI Outlet with a Light Switch
In the first diagram, the single way switch and light bulb is connected to the load terminal of GFCI. This way, the switch and light bulb is GFCI protected.
In the second diagram, the light switch is connected to the line terminals of GFCI. It means, the light switch is not GFCI protected and will operate as a normal circuit.
Wiring a GFCI Outlet with a Ordinary Outlet / Receptacle
Same like above GFCI wiring diagrams, the ordinary outlet is connected to the load terminals of GFCI. So the GFCI outlet and ordinary outlet connected to the load terminals of GFCI is protected from the ground and earth leakage current.
In the following diagram, the normal outlet is connected to the direct line supply i.e. line terminals of GFCI. This way, the ordinary outlet is not GFCI protected.
- Related Post: How to Wire Combo Switch and Outlet?
Wiring a GFCI Outlet with Combo Switch – Outlet, Receptacle & Light Switch
In this GFCI outlet wiring and installation diagram, the combo (switch + outlet), SPST (single way) switch and ordinary outlet is connected to the load side of GFCI. It means, all the connected loads to the load terminals of GFCI are protected. The toggle switch in the combo switch outlet controls the first light bulb while the single way switch controls the second bulb. In short, all the loads is GFCI protected.
In the following diagram, the above load mentioned before i.e. components and devices are connected to the line terminals of GFCI i.e. they are connected to the direct main supply. This way, the combo switch – outlet, light switch and ordinary outlet are not GFCI protected.
You can add more loads according to your needs but keep in mind that the maximum allowable number of boxed per circuit breaker is 12 where one circuit consists of all boxes on one circuit breaker. In addition, see the following general rules of thumbs and safety precautions for GFCI installation as well.
Rule of Thumbs for GFCI
- Only one GFCI/AFCI per circuit. If you increase the limit, it may leads to trip the circuit.
- GFCI circuit breaker protects the whole circuit while a GFCI outlet can be installed to protect additional outlets and switches etc.
- No need to install an additional GFCI if the circuit is already protected by the GFCI circuit breaker.
- For perfect operation of a GFCI, it is must to properly ground the GFCI or it will not trip instantly but will trip before the serious damage and electric shock.
- No GFCI should be used with some devices like power vented water heater or it will interrupt the proper operation of the circuit.
- Both Test and Reset button on a GFCI is for testing purpose only i.e. GFCI must be tested before final operation to make sure it is working properly.
- Use 14 and 12 gauge wires for 15A and 20A circuit breakers.
- 15A and 20A GFCI can be installed on 15-20A and 20A only (not 15 and 30A) circuit breaker respectively.
Precautions:
- Switch off the main circuit breaker to make sure the power supply is OFF before wiring a GFCI outlet.
- Use the suitable voltage and ampere rating of switch with appropriate wire size and proper size MCB according to the load rating.
- Use the correct polarity i.e. verify the Load and Line terminals while installing a GFCI for protection. In other words, connect the wires to the correct side of outlet for proper operation.
- Regular maintenance, check and test is recommended while test the portable GFCI before each operation.
- Contact the authorized and licensed electrician for GFCI installation if you are not sure about the wiring diagrams.
- The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.
Resources:
Related Wiring Tutorials
- How to Wire a 30A, NEMA 14-30 Industrial Grade EV Outlet?
- How to Wire a 50A, NEMA 14-50 Industrial Grade EV Outlet?
- How to Wire a 60A, NEMA 14-60 Industrial Grade EV Outlet?
- How to Wire a 30A, NEMA 6-30R Receptacle Outlet for EV?
- How to Wire a 50A, NEMA 6-50 Outlet for EVs and RVs?
- How to Wire a 30A, NEMA TT-30 for RVs and Travel Trailers?
- How to Replace an Outdated 20A, NEMA 10-20 Outlet?
- How to Replace a 30A, NEMA 10-30 Outlet Using 2P Breaker?
- How to Replace a 50A, NEMA 10-50 Outlet Using 2-P Breaker?
- How to Wire an Outlet Receptacle? Socket Outlet Wiring Diagrams
- How to Wire 120V & 240V Main Panel? Breaker Box Installation
- How to Wire a Subpanel? Main Lug Installation for 120V/240V
- How to Wire 277V & 480V, 1-Phase & 3-Phase, Commercial Main Service Panel?
- How to Wire 240V Water Heater Thermostat – Non-Continuous?
- How to Wire 3-Phase Simultaneous Water Heater Thermostat?
- How to Wire Twin Timer for 120V/240V Circuits – ON/OFF Delay
- How to Wire ST01 Timer with Relay & Contactor for 120V/240V Motors?
- How to Wire Multifunction ON/OFF Delay Timer for 120V/240V Motors?
- How to Wire 4-Way Switch (NEC) or Intermediate Switch as 3-Way (IEC)?
- How to Wire Double Switch? 2-Gang, 1-Way Switch – IEC & NEC
- How to Wire Double Pole, Double Throw Switch? Wiring DPDT
- How to Wire Double Pole, Single Throw Switch? Wiring DPST
- How to Wire Single Pole, Double Throw (SPDT) as 3-Way Switch?
- How to Wire Single Pole, Single Throw (SPST) as 2-Way Switch?
- How to Wire an AFCI Breaker?
- How to Wire an AFCI Outlet?
- How to a Wire 3-Way Combination Switch and Grounded Outlet?
Related Posts:
- Should GFCI Protection Be in the Main Panel or Receptacle?
- Difference Between NEMA 14-50 Standard Vs EV Receptacle
- Difference Between Socket, Outlet and Receptacle
- What is the Right Wire Size for a 30A Breaker and Outlet?
- How to Find the Number of Outlets on a Single Circuit Breaker?
- What is the Difference Between 15-Amp and 20-Amp Outlet?
- How to Find Voltage & Ampere Rating of Switch, Plug, Outlet & Receptacle
- Can You use a 15A Outlet on a 20A Circuit and Vice Versa?
- Ground Terminal Up or Down: Which Way Should Outlets Face?
- What Do the Green Dot or Orange Triangle Outlets Mean?
- What Do the Different Colors of Electrical Outlets Indicate?
- Why are Outlets and Receptacles in Hospitals Upside Down?
- How to Size a Load Center, Panelboards and Distribution Board?
- How to Determine the Number of Circuit Breakers in a Panelboard?
- How to Find the Proper Size of Circuit Breaker? Breaker Size Calculator & Examples
- How to Find The Suitable Size of Cable & Wire for Electrical Wiring Installation?
- Why is the Neutral Prong or Slot Wider on a Plug or Outlet?
- What Will Happen If You Connect a Male-to-Male Plug Between Outlets
Circuit to control three tunnel doors with robots connected with proximity switches located at each door.
Now I know the difference between Normal and GFCI outlet and their wiring methods. Thanks for the good work.
The caption “Test Button” points to the red button which says “RESET” on it, and the caption “Reset” points to the dark blue button which says “TEST” on it. I am confused.
Thank you for pointing it out. We have corrected the labels.