What is Reverse Polarity? Keeping those Outlets in Working Order

Have you ever been zapped when touching a lamp? How about plugging in a perfectly good blender, only to have it crackle and smoke… even when SWITCHED OFF! If you’re experiencing these or any other similar occurrences, then you could have a dangerous, yet very fixable situation on your hands. 

Reverse polarity is a rare electrical problem for most home and business owners, but when it is suspected to be the culprit when troubleshooting a faulty outlet, action should be taken in order to prevent further damage to appliances and keep you, your family, and(or) your business out of harm’s way.

Reverse Polarity Definition

This can cause devices both simple and complex to become energized even when the power switch is in the off position. Devices plugged into a reverse outlet can become shorted and damaged, and can also become a potential shock hazard. 

What Does “Hot,” “Neutral,” and “Ground” mean?

Hot

When wiring an electrical outlet in a modern home, you have at minimum, three wires that need to be connected. One wire is responsible for the incoming electrical power. This is referred to as the “hot” wire, which is always black. 

Neutral

The outgoing current returns to the neutral ground tie block behind the main panel. The wire that carries this current away from the outlet is the neutral wire, which will usually be white, but can sometimes be gray. 

Ground

The grounding wire serves as a bit of extra safety, by protecting you from getting shocked by charged objects such as plumbing or metal-cased appliances by sending any excess current into the ground. This is usually the green-coated, or naked wire. 

All these wires work together by providing a path from the main breaker to your outlet, through your device and back to the panel, while dissipating any excess charge by sending it to the ground.

How an Electrical Outlet is Wired

Most outlets you see on your wall(usually 120v) have three slots on the receptacles for hot(small slot), neutral(larger slot), and ground(sideways “D”-shaped slot at bottom). When you remove the outlet from the wall and turn it around, you will usually see five screws. 

You’ll notice a set of two screws on each side. On one side, the screws are brass-colored. The screws on the other side are plain metallic or silver-colored.

The black or “hot” wire connects to one of the screws on the brass side, and the white or “neutral” wire connects to a screw on the silver side. On the bottom right, you’ll see a single screw that is typically green. This will be where the ground wire connects.

Reverse Polarity in an Outlet

With reverse polarity as you may have already assumed, the black wire has been connected to the silver side and the white wire to the brass side, therefore reversing the poles. 

This is not a common mishap, and has been largely eradicated due to the advent of color-coding the wires, but it can occur when home builders, electricians, or DIY-ers rush their work or don’t pay attention to what they are wiring.

Always take your time when installing any electrical outlet and take precautionary measures like disconnecting the main breaker and, assuming all the wires are equally dangerous and require equal attention.

What Is a GFCI Electrical Outlet For?

GFCIs are becoming more and more ubiquitous in modern homes. Dangerous ground faults are slowly becoming a thing of the past, thanks to the advent of these special outlets.

What Does GFCI Stand For?

GFCI stands for ground fault circuit interrupter. A specially designed outlet for protecting against the effects of sudden surges and shocks through contact to ground.

What is a Ground Fault?

When these outlets sense an electrical imbalance of five milliamps or more, or a surge of excess current, they will shut off power within milliseconds in order to prevent electrocution.

GFCI outlets are designed to protect you from dangerous ground faults and prevent you from unintentionally becoming part of a completed circuit. Any area in a building with internal metal structures, or areas with water and plumbing should have these safety devices in place.

How to Wire a GFCI Outlet

Paying attention to the labeling on the back of these outlets is crucial in keeping these outlets and your overall home safe. Any mistakes can negatively affect any outlets and devices downstream along the circuit.

What Does “Line” and “Load” Mean?

The term “line” and “Load” are used with respect to the device/component receiving or delivering power. For example the cable that feeds power to the main breaker is referred to as “line.” The wire that sends power on down to the electrical outlet is the “load.” 

From the outlet’s frame of reference, the wires coming from the breaker are “line” wires and any leaving the outlet, perhaps to another outlet along the same circuit, are considered “load” wires. Those same outgoing load wires, now incoming wires with respect to the next outlet are considered “line” wires, and so on.

The wiring of a GFCI outlet is similar to that of a normal 120v outlet, except that on the back of a GFCI, you’ll notice that the brass set of screws are moved further apart on the sides towards the top and bottom of the outlet, as are the silver set. 

Also, the screws at the top, depending on the particular outlet, are labeled, “line” and the screws at the bottom are labeled, “load.” Although, some GFCIs have these labels in reverse(load on top, line on bottom).

When wiring the outlet, it is important to pay attention to these labels as the screws labeled “line” are incoming from a power source. The “load” wires are meant to pass power onto the next outlet on the same circuit. 

With the first outlet in a circuit being the GFCI, any and all other subsequent outlets on the circuit will also have GFCI protection.

Is Reversing “Line” and “Load” on a GFCI the Same as Reversing Polarity?

GFCI outlets have specific designations for line and load that should be strictly followed. They can only provide protection downstream when wired correctly. Only the reversing of the hot and neutral wires reverse electrical polarity. 

Reversing the line and load wiring however, is not ideal. Although the outlet will continue to deliver power as normal and a surge will still cause the outlet to trip and shut off the circuit downstream, any attempt to reset the outlet afterward will not work. 

The outlet, along with any others downstream from it, will remain off and will be rendered unusable. Always take the “line/load” wiring on a GFCI as seriously as you would the polarity.

How Reverse Polarity Affects Devices and Why it’s Dangerous

If you plug in an appliance, it may appear to work correctly, even when you switch it off. But even though the device is switched off, parts of it, whether it be a button, or metal casings or connectors, may still be energized. 

Although nothing may happen and no current may be flowing, once you touch the device in one of those energized areas, current could indeed flow and a shock may occur.

Reversing polarity could not only endanger you, but it could also have an adverse effect on the internal electrical hardware in your devices. Sending current to the wrong areas could cause a short, causing components within the device to overheat, melt, and become damaged.

This could also cause an electrical fire hazard that may not be apparent, and may materialize when no one is at home or after your business is closed for the day. It would be quite unfortunate to have to receive a phone call from your local fire department informing you of the damages.

If you suspect that reverse polarity is an issue, disconnect any device(s) from the affected outlet, cover up the receptacles with plastic outlet covers, and invest in an outlet tester that specifically checks for polarity. The small investment could end up saving you much more down the road.

Reverse Polarity at the Breaker Panel

You can be experiencing issues with plugged-in appliances, and you seem to suspect that reverse polarity is to blame. However, you shut off the main breaker and remove the outlet to inspect it and much to your surprise, all the wiring seems to be correct! 

So what’s the problem? Well, your issue may still be reverse polarity, but the reversal may be situated upstream from the outlet. Possibly at the breaker that feeds the outlet.

If this is the case, then you’ve just encountered a serious wiring error. The neutral wire has been fed into the individual circuit at the breaker panel, and the hot has been fed into the neutral tie block. 

Fixing Reverse Polarity at the Panel

To remedy this, grab a flashlight first, then shut off the subpanel(if any) that directly feeds the circuit that the outlet is on. Then, shut off the main breaker to the building. 

If there is a subpanel feeding the outlet, your mixup could be there. If there is no subpanel feeding the outlet, then it’s the main breaker.

At the main/subpanel, remove the switch board cover, then remove the individual circuit. Unscrew the neutral wire from the individual circuit. Now unscrew the hot wire from the neutral tie block. 

Screw the hot and neutral wires into their correct positions. Hot wire into the individual circuit, and the neutral wire into the neutral tie block. Replace the switch board cover. Switch the main/subpanel back on. 

How to Detect Reverse Polarity in your Receptacle

There are two very simple ways to detect reverse polarity, without opening the outlet:

Using Voltage Tester

Voltage testers are pretty simple devices. When buying a good voltage tester, the price will depend on any extra features added. Prices range from $40 to as much as $300. Using a voltage tester is pretty straight forward.

Normally, you would stick the probe into the “hot” slot and the voltage tester would indicate voltage via a “beep” and/or light. However, in a reverse polarity outlet, plugging a voltage tester into a hot slot would give no signal. Instead, it’s the neutral slot that would give the voltage signal.

Using an Outlet Tester(For Polarity)

Using an outlet tester is pretty simple and straight forward. You can purchase a great tester at your local hardware store for as little as $5 and up to $40. These testers have three prongs that fit your typical outlet receptacle.

You simply plug it into the outlet, and the device will give you a reading using different combinations of three(typically) LEDs located at the end of the tester. Different makers and brands will have different configurations as far as readings and signals go, so make sure you refer to your outlet tester’s included manual.

Things to Remember…

Home outlet wiring is pretty simple, but any little mistake can be unforgiving. Breakers, their circuits, and the sections of the house that they power should be properly labeled. Before troubleshooting, always shut off power to the main breaker panel and use insulated tools when working on outlets. 

Be on the lookout for the effects of reverse polarity in your outlets by paying attention to your devices and how they behave when on and especially when off. 

Reverse polarity is a simple issue that can cause complicated problems down the road. If the situation is beyond your ability to handle, hire a licensed and experienced electrician.