How a GFCI Works – Your Guide to GFCI’s

What Does a GFCI do?

GFCI’s Prevent Electrical Shocks

The primary role of GFCI outlets is to prevent injury due to electrical shocks. When a person comes into contact with an electrical current, it can cause muscle contractions, burns, and even cardiac arrest. GFCIs reduce this risk by quickly cutting off the power at the first sign of a fault, thus preventing potentially lethal shocks. 

Statistics on Electrical Safety

According to reports by the Electrical Safety Foundation International (ESFI), nearly 200 people die from electrocution in the United States every year, and many more are injured by electrical hazards in the home. The installation of GFCI outlets in high-risk areas can significantly reduce these incidents, as they are designed to protect not just against shocks but also against burns and other injuries. 

How does a GFCI work?

To understand how GFCIs work, it’s helpful to know a bit about the flow of electrical current. In a properly functioning circuit, the current flowing into a circuit should equal the current flowing out. The GFCI monitors this flow, and if it detects any discrepancy (as small as a few milliamperes) between the incoming and outgoing current, it assumes a fault in the circuit. Within as little as 1/40th of a second, the GFCI shuts off the electrical power to that outlet and any others downstream. This rapid response helps to prevent the harmful effects of electrical shock. 

Imagine using a hair dryer in the bathroom; if it slips from your hands into a sink full of water, a GFCI outlet would cut off the power immediately upon detecting any electrical current leakage into the water, potentially saving you from a dangerous shock. 

Understanding the functionality of GFCIs highlights their importance in household safety, protecting against the hidden dangers of electrical faults that might not be evident until it is too late. 

Can GFCI Outlets go bad?

GFCI (Ground Fault Circuit Interrupter) outlets are designed to provide protection against electrical shocks by monitoring the flow of electrical current and quickly interrupting the circuit when a fault is detected. However, like any electrical device, GFCI outlets can degrade or fail over time. Understanding the common reasons for GFCI failure and how to address them is essential for maintaining the safety and integrity of your home’s electrical system. 

Reasons for GFCI Outlet Failure

• Wear and Tear: Regular use can naturally degrade a GFCI outlet’s internal components over time. Each time a GFCI trips, it experiences a small amount of wear, which can accumulate and eventually affect its performance and reliability.

• Power Surges: Sudden surges of electrical power, often caused by external events like lightning strikes or fluctuations in grid power, can damage the sensitive circuitry inside GFCI outlets.

• Moisture and Corrosion: GFCI outlets in areas with high humidity or direct exposure to water, such as bathrooms or outdoors, are susceptible to moisture intrusion. This can lead to corrosion of internal components, interfering with the mechanism’s ability to function properly.

• Improper Installation: If a GFCI outlet is not installed correctly, it might fail prematurely. Incorrect wiring can lead to frequent tripping and eventual failure as the outlet cannot handle the electrical load appropriately.

• Age: The lifespan of a GFCI outlet can vary, but they generally need to be replaced every 10 to 15 years, depending on usage and environmental conditions. Over time, internal components can degrade and lose their effectiveness.

• Manufacturer Defects: It is not uncommon for a new GFCI from your supplier to fail out of the box or to stop working a short time after installation. By design however, a failed GFCI will not provide electrical current to an item which is plugged in, and will remain safe.

Signs of a Failing GFCI Outlet

• Frequent Tripping: If your GFCI outlet trips frequently without a clear reason, it could be a sign of internal failure.

• Failure to Reset: A GFCI outlet that won’t reset when the “Reset” button is pressed is likely malfunctioning and no longer providing protection.

• No Power to Outlet: If appliances or devices plugged into a GFCI outlet do not receive power and the outlet has not tripped, it might indicate a failure within the outlet.

• Physical Damage: Visible signs of wear, such as cracks, burns, or discoloration on the outlet, suggest it may be compromised and in need of replacement.

How to Wire a GFCI

Wiring a GFCI outlet is a simple process that anyone can complete with the right tools. The following is a guide to best practices in wiring GFCI’s in a safe manner:

Step 1: Turn Off the Power 

Before beginning any electrical work, ensure that the power is turned off at the circuit breaker panel. Verify that the power is off using a voltage tester at the outlet by inserting each lead of the multimeter into the two slots on top of the outlet.  

Your meter should read a number close to zero.  If you read a number over 100 volts, the circuit may still be live and you should confirm that the correct breaker has been turned off at your electrical panel.  

Step 2: Prepare the Outlet Box 

Remove the existing outlet cover and outlet from the outlet box. Carefully disconnect the wires from the old outlet. Inspect the wires for any signs of wear or damage and trim or restrip the wires if necessary to expose fresh wire for better connections. 

If you are removing an existing GFCI, note which wires come from where on the outlet. There may be two pairs of black and white wires, switching their locations on the new outlet will cause it to trip. 

Step 3: Identify the Wires 

Typically, you will find three wires: a black (hot) wire, a white (neutral) wire, and a green or bare (ground) wire. In some cases, if the outlet is in the middle of a circuit run, there will be two sets of these wires. 

If it is unclear which wires belong to the line side, separate all of the wires and ensure none of them are touching one another, or any other object. Return to the panel and switch your breaker back on. You may now touch one lead of your multimeter to each of the black wires, and the other lead to a white wire or ground wire. If your meter shows a number close to 120 volts, you have identified which black wire belongs on the “Line” terminals of your GFCI. 

Remember to turn your breaker back off before continuing! 

Step 4: Connect the Ground Wire 

Connect the ground wire (or wires if there are two) to the green grounding screw on the GFCI outlet. If there are two ground wires, they can be twisted together and connected under the same screw, or you can use a pigtail connection. 

Step 5: Connect the White Wires 

Identify the set of screw terminals on the GFCI outlet marked as “LINE” and “LOAD”. The “LINE” side is for incoming power, while the “LOAD” side is used if the GFCI protection is to extend to other outlets downstream. Connect the white (neutral) wire that comes from the service panel to the silver screw on the “LINE” side. Ensure that the “LOAD” side is used only if necessary, following the same color coordination. 

Step 6: Connect the Black Wires 

Connect the black (hot) wire that comes from the service panel to the brass colored screw on the “LINE” side of the GFCI outlet. Similar to the neutral wires, ensure that any wires connected to the “LOAD” side match the correct terminals. 

Ensure you have tightened the wire screws down enough by wiggling the wires back and forth, then tightening the screws down a second time. You do not need to use full force, but a firm pressure is sufficient. The portion of the wire which is underneath the screw should not be able to move. 

This is how a single GFCI outlet should be wired. Other outlets are fed from the “Load” terminals.

Step 7: Mount the GFCI Outlet 

Carefully push the wires back into the outlet box and align the GFCI outlet into the box. Screw the outlet into the box securely and attach the faceplate.  

If your electrical box is narrow, you may wrap the outside of the GFCI (overtop of the wire screws) with several wraps of black electrical tape to ensure the screws cannot make contact with the side of the box. 

Step 8: Test the Installation 

Turn the power back on at the circuit breaker. Press the “RESET” button on the GFCI outlet; the outlet should now be operational. Test the GFCI by pressing the “TEST” button; the power should immediately cut off. Press “RESET” again to restore power. Use a voltage tester or a small appliance to ensure the outlet is working correctly. 

How to Test a GFCI

Ensuring that your GFCI outlets are functioning correctly is important for maintaining the safety they are designed to provide. Here’s how you can identify these outlets and test them to ensure they are working properly: 

Identifying GFCI Outlets

GFCI outlets are easy to recognize. They are different from standard outlets in that they have two buttons in the middle: one labeled “Test” and the other “Reset.” These outlets are usually found in areas of your home where there is a higher risk of electrical shock, such as bathrooms, kitchens, garages, basements, and outdoor spaces. 

Testing GFCI Outlets

It’s important to test GFCI outlets regularly to ensure they are providing the protection they’re designed for. Here’s a simple step-by-step process to test a GFCI outlet: 

1. Plug in a Device: Insert a small lamp or other device into the GFCI outlet and turn it on. The device should be working normally if the outlet is active.

2. Press the Test Button: With the device still plugged in and turned on, press the “Test” button on the GFCI outlet. This should cause the built-in switch to trip and automatically cut off the power to the outlet. The device should turn off.

3. Check the Reset Function: Press the “Reset” button to restore power to the outlet. The device should turn back on.

4. Frequency of Testing: It’s recommended to test GFCI outlets once a month to ensure they are functioning properly. This is particularly important in high-use areas and in places where outlets may be exposed to moisture.

What to Do If a GFCI Fails to Test Properly

If the GFCI outlet does not cut power when you press the “Test” button, or if it does not restore power when you press “Reset,” it may be malfunctioning. In this case, it is crucial to contact a licensed electrician to check the outlet and replace it if necessary. A non-functioning GFCI outlet cannot protect you from electrical shock and items which are wired downstream of it are unlikely to function should this occur. 

Will a GFCI work without a ground?

A common question about GFCI (Ground Fault Circuit Interrupter) outlets is whether they require a ground wire to function properly.  In short, the answer is yes. A GFCI will work without a ground wire attached. GFCI’s do not monitor electrical current flowing to ground, but operate by monitoring the balance of current along the hot and neutral wires in a circuit. 

Functionality Without Ground 

• Basic Operation: GFCIs are designed to monitor the balance of electrical current moving through a circuit and to cut off the power when a fault is detected. This safety mechanism is independent of a ground wire and focuses on the incoming and outgoing current.

• Ground Wire Role: While the ground wire in a typical electrical outlet is a safety feature that provides a path for stray electrical current, helping to prevent the risk of shock or fire, a GFCI does not rely on this path to detect ground faults. Instead, it directly measures the current imbalance within the hot and neutral wires.

• Installation: GFCI outlets can be installed without a ground wire and will still provide protection from electrical shocks. This is particularly useful in older homes where wiring systems may not include a ground wire.

Limitations and Recommendations 

• Surge Protection: It’s important to understand that while a GFCI outlet can function without a ground wire, it does not provide protection against surges or overloads like a grounded system would. Devices plugged into an ungrounded GFCI are still vulnerable to damage from power surges.

• Best Practices: In situations where no ground wire is present, using a GFCI outlet adds a significant layer of safety by protecting against electrical shocks. It is recommended to test these outlets more frequently to ensure they are functioning correctly, as they are a critical safety feature in the absence of grounding.

In summary, a GFCI outlet will indeed operate without a ground wire and provide protection against electrical shocks by detecting imbalances in electrical current. However, for complete protection of your electrical system, including from surges, a properly grounded system is preferable. If upgrading your wiring to include a ground wire is not feasible, installing GFCI outlets is an effective method of improving electrical safety. 

GFCI to GFCI Wiring

Generally speaking, it is not necessary to wire GFCI’s to one another. Anything which is connected downstream of a GFCI on the same circuit will be protected by one GFCI, a second is not typically necessary for Canadian Electrical Code or electrical safety purposes. Consult a professional electrician if you are unsure of safety or electrical code requirements.

Considerations for GFCI to GFCI Wiring 

• Redundancy: Wiring GFCI to GFCI can provide redundant protection, which might be unnecessary and can lead to nuisance tripping. It is important to assess whether such redundancy is required or if a single GFCI followed by regular outlets would be sufficient. In most cases 2 or more GFCI’s on the same circuit are not necessary.

• Cost and Complexity: Additional GFCIs add cost and complexity to the electrical installation. A GFCI outlet at your local supplier will be $30-40 each whereas a standard outlet is $2-3. Each GFCI will also need to be tested regularly to ensure it is functioning properly.

• Troubleshooting: Having multiple GFCIs on a single circuit can complicate troubleshooting efforts when issues arise, as it may not be immediately clear which GFCI has tripped or why. This means doubling the time required to identify issues in an electrical circuit.

However, if you wish to wire GFCI’s in series, the following is a guide to best practices in doing so safely: 

Step 1: Turn Off the Power

Ensure that the power supply to the circuit where you plan to work is turned off at the breaker panel. Verify that the power is completely off using a multimeter or voltage tester. Your multimeter should read a number close to zero. If you read a number of 100 volts or higher it is likely that you have turned off the wrong breaker. 

Step 2: Prepare the Wiring

If you are installing new wiring, run an appropriate gauge cable (#14 for 15amp, #12 for 20amp) from the first GFCI outlet box to the second. The cable you use should include a ground wire (bare copper), a neutral wire (white), and a hot wire (black). 

Perform a pigtail connection inside the box by cutting a length of black and white wire, stripping it and twisting it together, capping with a wire nut. The wiring should be arranged as shown below.

 

Step 3: Connect the First GFCI Outlet

• Ground Connection: Attach the ground wire from the incoming power source and the ground wire going to the second GFCI outlet first to the electrical box, and second to the green grounding screw on the first GFCI.

• Line Connections: Attach the incoming hot (black) wire to the brass screw marked “Line” on the first GFCI and the incoming neutral (white) wire to the silver screw marked “Line”.

• Load Connections: Normally, the “Load” terminals would be used to protect downstream outlets. However, in this setup, you will not use the “Load” terminals on the first GFCI if the second outlet is also a GFCI. Tighten down the “Load screws and leave them empty. If your electrical box is narrow, put several wraps of black electrical tape around the outlet (over the wire screws) before putting it back into the box.

Step 4: Connect the Second GFCI Outlet

• Ground Connection: Connect the ground wire coming from the first GFCI to the green grounding screw.

• Line Connections: Since the second GFCI acts independently, connect the hot and neutral wires coming from the first GFCI to the “Line” terminals on the second GFCI. Ensure that these connections are secure and that the wires are not connected to the “Load” terminals. Tighten down the “Load” screws as before and leave them empty, unless you have other non-gfci outlets which will be fed from this box.

Step 5: Mount and Test the Outlets

Mount both GFCI outlets in their respective boxes and secure them with screws. Attach the faceplates once the outlets are in place. Turn on the power at the breaker panel and test each GFCI individually using the built-in test buttons. Each outlet should trip and reset independently. Should one or both of the GFCI’s fail to reset or operate normally, it is likely that you have wired something incorrectly. If so turn the power off, remove the outlets and review your wiring. 

Still having issues with your GFCI’s? Call the team of specialists at Celtex Electric & Automation for a zero-cost consultation and let us set it right.