Reversed polarity electrical receptacles:

Definition of reversed polarity at an electrical receptacle, its causes, cures, and dangers. What happens if you reverse the hot and neutral wires at an electrical receptacle? We also explain the difference between reversed polarity and reversed LINE - LOAD connections in a building electrical circuit.

This article series describes how to choose, locate, and wire an electrical receptacle in a home. Electrical receptacles (also called electrical outlets or "plugs" or "sockets") are simple devices that are easy to install, but there are details to get right if you want to be safe.

FAQs on Reversed Polarity at Electrical Receptacles

These questions & answers about reversed-polarity or mis-wired electrical receptacles ("outlets") were posted originally

at REVERSED POLARITY ELECTRICAL DEVICES / CIRCUITS - please also read the advice given there.

On 2021-01-31 by (mod) - trace source of reverse-polarity at electrical receptacle starting at the electric panel

Thank you for the photo [above], and for your reversed polarity circuit troubleshooting, and follow-up, Pol; that will assist other readers.

It's a reminder that when we find reversed polarity wires at a switch or receptacle we may want to start tracing the circuit right at the electrical panel.

We'll keep this example with the article series as your reminder to check for mis-wiring in the panel will assist other readers.

On 2021-01-31 by Polarity 2

I figured out why the new outlet was showing reverse polarity. The circuit was also reversed, causing a continuation downstream.

[Photo above] [Click to enlarge any image]

I swapped out a single pole switch with a switch/plug combo on the left.

The two hot feeds are pigtailed fo the hot line and run to the common/black screws and the load is secured to the bronze screw.

The neutral is attached to the white screw and the rest of the whites in the box. Ground is green.

I’ve followed the wiring diagram.

My outlet tester says reverse polarity. Can’t figure out why. Any help would be appreciated.

Thanks

Scott

On 2020-12-20 - by (mod) -

Sounds like a damaged switch or shorted wiring. I'm a little concerned that there could be a shock hazard. It would be better to turn off power to that light uununtuntil it can be repaired.

On 2020-12-19 by Sue

I have a push in switch on pantry door - all of a sudden the light inside is off when the door is open ( button out) and light is on when I close the door (push button goes in) it is weird something caused this switch why would this happen

On 2020-09-23 - by (mod) -

Eric

Yes InspectApedia.com is still active.

Since inception in the 1980s our readership has grown; we have thousands of readers a day, so sometimes the question volume is more than we can handle promptly but we try to reply to everyone ASAP.

On 2020-09-23 by Eric

Have an electrical question, not sure if this forum is still active?

On 2020-07-20 - by (mod) -

Tracey

I don't think that reversed polarity on electrical receptacles in a building could possibly cause an electric meter to display numbers backwards. It's worth noting that the digital display on some smart meters can be tricky to read and sometimes the numbers and letters are a bit hard to decipher.

You might want an electrician to work at your paddle to identify the high current using circuits in your home. The electrician can also make sure that you don't have any improper wiring.

On 2020-07-16 by Tracey

My meter box in my power pole reads backword numbers, my neighbors do not. Is this normal? My power bill is outrageous.

On 2020-01-08 - by (mod) -

That's confusing, Marlon, I agree; I'm not sure what signs you've seen, nor how they're generated.

But an "upstream" reversed-polarity problem would mean to me that ahead of the point where you're making measurement the hot and neutral are reversed.

I've seen that, for example, at an improperly-fed sub-panel.

On 2020-01-08 by Marlon Conway

I’ve checked my outlets for polarity and everyone was fine. But, signs outside the house involving my cable tv wire indicates there’s a reverse polarity issue somewhere. What’s meant by an “upstream” RP problem?

On 2019-11-01 - by (mod) -

Yes - I would be careful about a device that's mis-wired right from the factory. If you can post a photo and give me the brand and model information I'll do some research.

On 2019-11-01 by Paul

I installed a hanging led shop light in my garage. It plugs into a standard 110 outlet with correct polarity. The light has a female receptacle on it, I supposed for daisy chaining to another similar light. The odd thing is that the polarity of this receptacle is reversed. Is there a reason the manufacturer would do this? I was planning to plug in a small trickle battery charger (2A) but now I'm afraid that would be a bad idea. Do you agree?

On 2018-01-17 by Odelia Murch

Thanks for the information.

On 2018-08-23 by (mod) - Whites wire on silver terminals and still have reverse polarity.

I've done that, using black tape to mark the hot wire, white tape to mark the neutral wire. But it's a bit unsafe as we don't know where the problem originates nor what else is mis-wired. THe best solution is to follow the circuit backwards from the first point where you see reversed polarity and find the mis-wire. Or start at the electrical panel and follow the circuit forward.

Watch out: if you're not familiar with electrical wiring safety and procedures - a mistake can start a fire or shock or kill someone

On 2018-08-22 by Brian

Whites wire on silver terminals and still have reverse polarity.

If I switch the whites to the gold terminals and place a piece of electrical tape on white wire indicating hot wire the tester shows open ground now. Stumped. Guesing switched somewhere in junction box. New home owner

On 2018-07-25 by (mod) -

A licensed electrician, sure. But I'm confused: you posted this on an article about reversed-polarity electrical outlets: simply reversed polarity wouldn't explain what you describe.

And a lightning strike won't reverse polarity - those are wire hard-wired connections.

Your friend may be thinking of the problem that a power surge or lightning strike can indeed damage a motor or capacitor causing the motor to run backwards.

On 2018-07-25 by Anonymous

Two weeks ago we had bad thunderstorms in my area. The next morning my desktop computer failed to turn on. I took it to the computer repair shop and it works fine there.

They and a friend suggested that the polarity of my outlets in my home might now be reversed. Should I get the power company to come out and see or get a licensed technician? I've tried many of the plugs in my home and they all seem now to have the same problem. I've lived in this home now for 5 years and its the first time this issue has come up. Signed: Stumped In Florida.

On 2018-07-02 by (mod) -

Reversing polarity itself does not cause an electrical fire it simply swaps the role of the individual wires from carrying current to carrying the neutral return load.

However indirectly reversed polarity could damage an appliance or (less likely) cause even a fire in an appliance if the appliance design expects the electrical power Live Wire to arrive at the appliance at a particular point on a control board or circuit.

On 2018-07-02 by Anonymous

I noticed an electrical outlet have the hot wire connected to the brass screw and neutral to the silver one side of the outlet.

Then the wires were reversed on the opposite side of the outlet. How could this work and not cause an electrical fire?

On 2018-06-11 by Anonymous

It might cause a motor to run backwards but it's not going to reverse the polarity of the electrical wiring in your building

On 2018-06-10 by Anonymous

can lightning cause reverse polarity

On 2018-05-24 by (mod) -

Steve

Well you "could" physically rig up a wire swap. The danger is that you and I don't know who'll come along another time and plug something in that causes a fire or shock.

If you can find the wires "upstream" from the outlet at a junction box, reverse them there and label them in the box accordingly. Or if you're not an electrician, have her do it. Fooling with wires can kill you.

On 2018-05-23 by Steve

I have an outlet that was wired in reverse polarity. It's under a cabinet and is used only for the cooktop, which won't work under the reverse polarity. Unfortunately, the outlet is half covered by the cabinetry and is difficult to fix without damaging the cabinetry. Can I correct the situation by simply reverse wiring male and female connectors and plugging the cooktop into that? Sort of like a cross-over computer network cable.

On 2018-05-10 by (mod) -

Sorry I can't make sense out of the situation that you described

On 2018-05-10 by J King

PLEASE HELP. Any valid info regarding this issue would be greatly appreciated. If an owner of a large older un-inspected building was attempting to create a fire or hurt someone or both. Would a reverse of the polarity by inserting a gold plated prong into the surrounding outlets on a regular basis potentially cause a fire or other mass problem?

On 2017-03-16 by (mod) -

Correcting reversed polarity outlets means correcting an UNSAFE condition as described in the article above, Philip, but it won't change the level of usage of electrical energy.

And "grandma" laws or what some refer to as "grandfathering" meaning no legal requirement to bring a property up to current electrical codes, by no means includes improper electrical wiring.

I would fix the reversed polarity mis-wiring. It's trivial to do.

On 2017-03-16 by Philip

I live in a very old colonial home. Approximately 100 years old. The inspector says everything electrical checks out okay. However the grandma law says that the home can function safely. Some of the receptacles are reverse polarity. Which are currently working fine. There are only 5 of them reversed in a three story home. Question! Will I save on energy if I correct these outlets?

On 2017-03-16 by (mod) - do I need to correct reversed-polarity outlets in an older "grandma" or "grandfathered" home

Correcting reversed polarity outlets means correcting an UNSAFE condition as described in the article above, Philip, but it won't change the level of usage of electrical energy.

And "grandma" laws or what some refer to as "grandfathering" meaning no legal requirement to bring a property up to current electrical codes, by no means includes improper electrical wiring.

I would fix the reversed polarity mis-wiring. It's trivial to do.

On 2017-03-16 by Philip

I live in a very old colonial home. Approximately 100 years old. The inspector says everything electrical checks out okay. However the grandma law says that the home can function safely.

Some of the receptacles are reverse polarity. Which are currently working fine. There are only 5 of them reversed in a three story home. Question! Will I save on energy if I correct these outlets?

On 2016-05-29 by (mod) - live wire stops working if I connect two neutral wires

BL

WATCH OUT: mis-wiring or electrical wiring damage or hookup mistakes can cause fire, shock, or death. That warning made, you may be joining two neutrals one or both of which is carrying current - something that should occur ONLY if an appliance or device on the circuit (lighting, an appliance, etc) is operating;

I suspect that the two neturals may be carrying current from two different buses in your electrical panel, and /or that there is a wiring error somewhere connecting neutral to "hot" in the system.

I would turn off all of your circuits, then turn on and test them individually.

On 2016-05-29 by Mr B Lockwood

My live wire stops working when I join the neutral wires together. What's wrong please.

On 2016-04-12 by (mod) - should you reverse-wire a GFCI outlet if home was built before 2003? NO!

NO Sam. That is not correct.

On 2016-04-10 by Sam

Are you supposed to wire a gfi outlet reverse if the construction was done before 2003?

On 2016-03-27 by (mod) - why would someone deliberately reverse wires

Sounds like wiring errors to me. I've seen deliberate cross-wiring of receptacles in a desperate situation where someone could not find where, upstream from the receptacle, somebody has made a wiring error - say at another device (receptacle perhaps or a splice in a junction box).

Watch out: wiring a receptacle backwards - hot wired to neutral and neutral wire to hot side of the receptacle - won't be obvious to users. Stuff plugged in will still "work" - it's alternating current after all. We explain in the article above that such mis-wiring is unsafe and that some things plugged into such a receptacle can be damaged or destroyed.

On 2016-03-27 by Anonymous

Why would someone wire an end run outlet and reverse wiring as white to brass and hot wire to silver? Upon replacing outlet and wiring it correctly; it does not work but the rest of the circuit works

On 2015-11-21 by (mod) - why would a receptacle "push the plug back out"

Thanks CB. do keep us posted: what you learn will help other readers.

Perhaps she means that receptacles in the home are worn and loose - which would be unsafe, or perhaps that the receptacles are installed improperly - back-to-back through a wall.

On 2015-11-20 by Cowboy

That is the first thing I thought of but took her to the company bathroom and showed her the GFC. She said that is not what she has, she has just the two slots, no ground. I asked her for a video showing what she is telling me. I will let you know.

On 2015-11-19 by (mod)

Cow

Perhaps part of the confusion is that normal people don't necessarily call building or mechanical parts by their official names.

I suspect and am guessing that she means that there is a GFCI-protected receptacle or circuit that is tripping. In that case a problem with the vacuum or the circuit would shut it off by popping the "reset" button on the GFCI receptacle or breaker powering the circuit.

On 2015-11-18 by Cowboy

One of my office girls says she has several outlets in her 1970's house that, when one appliance is already plugged into a duplex and she tries to plug in another (phone charger, vacuum, etc.) it "pushes" that plug out. I have never heard of this. Any ideas?

On 2015-01-08 by (mod) - reverse polarity is a red flag to look for other electrical wiring mistakes

Met

When we find all or even a few mis-wired receptacles - with reverse polarity or "RP" as you put it, I have to guess that an untrained person did the wiring in the building. That means it's likely that there are other mistakes, possibly dangerous ones.

FIRST: turn off any odd-acting circuits as you're risking shorts, shocks, fire.

NEXT: ask for help from an experienced electrician who's going to start right at the panel inspecting for proper wiring of all connections.

NEXT: I'd take one of the bad circuits, possibly lighting, and trace, inspect and correct EVERY connection from the panel onwards. I suspect that when you trie to "swap back" polarity by swapping hot and neutral wires you missed a connection or junction box or several of them. That's going to result in shorts, odd circuit behavior, and unsafe conditions.

On 2015-01-07 by metcalft93@gmail.com

After testing all the outlets in a new shop building on the property we just bought, all outlets were RP and I turned all power and corrected the problem. Now I have lights dimming and appliances that are hard wired not working properly; can you assist?

On 2014-12-02 by (mod)

Jones

If you are talking about a simple neon tester and AC current it should make no difference which side has the resistor. If you have concerns about validity of this answer please consider this is a general reply to a vague question and that, with respect, your question is unclear with regard to what you are testing, current type, voltage, circuit, and many other details.

On 2014-12-02 by JONES

We are using a simple line tester in normal case the construction will be like that( Live contact rod+resistor+ neon lamp+ spring+metal cap)
If we use the same tester in Reverse what will happen (i.e) Live contact rod+ noen lamp+resistor+spring+metal cap

please give a valid reply

On 2014-09-05 by (mod) - where to check for mis-wired electrical circuit errors

Brian

You want to start at the beginning of each circuit and check for not just reversed polarity but shorted wires including both short to neutral and short to ground, and also neutral shorted to ground.

I've found, especially in older apartments such as in NYC, that someone who over-tightens the connectors on armored cable wiring (BX wire) can cause the metal wire jacket to cut into the hot or neutral wire.

In general I'm never comfortable correcting the wire at just a single outlet in a mis-wired outlet chain. Given that incompetent wiring was performed, you don't know where down the line someone "fixed" an operating problem by connecting a white to a black wire in a junction box.

So what makes sense is to start at the first receptacle in the electrical panel and follow all of the connections and splices throughout the circuit.

Where a receptacle is not working you want to open the electrical box and check each of the incoming and outgoing wires for power and check that it's the black wire that's the "hot" wire not the white one (due to a reversed connection in the circuit)

Carson Dunlop Associates' sketch shown above points out that the white wire, i.e. the neutral wire, will be connected through the receptacle's internal parts to the wide slot on the receptacle face in order to assure that the neutral wire side of an appliance being plugged-in there is properly connected.

On 2014-09-05 by Brian C.

Apartment in a 90 year-old New York city building. Upgraded mid-century to BMX conduits. 20 years ago replaced fuses with breaker boxes in each apartment (2 or 3 breakers per 750 saq. ft. apartment.) Next to electrical meters in the basement there's a breaker for each apartment.

In my apartment, the BMX doesn't have a ground wire. I replaced some recepticals with GFCIs. Living room has four recepticals. The last receptical in daisy chain doesn't work (since my experience began last year.) First I replaced old single receptacle in middle of daisy chain. This receptical had white and black wires. My bad was to assume it was wired correctly. Installed a new single receptical, black to bronze. Flipped on breaker, heard pop and smelled something acrid. Breaker off.

Checked other room (living room) recepticals. The one I think is first in chain smelled acrid. Inside: reversed polarity. Besides two wires attached incorrectly, it had one black and one white wire bundled separately, not connected to receptical. Perhaps they were prior to short - wire is brittle. I corrected polarity and attached all wires to bronze and silver screws. The receptical worked again.

Other three recepticals in living room still dead. Light switch works, so do other recepticals in other rooms on the same breaker switch.

Found that all recepticals in the living room had reversed polarity. First question: If the living room daisy chained recepticals were all reverse polarized, and I replaced one correctly polarized, can that cause a short upstream or downstream?

I corrected receptical polarity on all living room recepticals. The three recepticals still don't work. I tried reconfiguring connections. I reversed polarity on all again, to diagnose.

First receptical works, others don't. Corrected polarity, then starting at end of chain reversed polarity on each receptical, one at a time.

Nothing. Replaced the three recepticals with new ones. Nothing.

Configuration: first receptical (that was shorted) has two black and two white wires. I replaced, wired correctly, and now works. Next is the single receptical, with one white and black wire in box. I replaced this receptical and caused the short. Third receptical has two black and two white wires, originally reversed, and working before the short.

I replaced receptical, wired correctly, doesn't work. Last receptical never worked, had reversed polarity. I replaced, wired correctly, doesn't work.

Second question: how to diagnose?

Thank you.

Question: When wiring an electrical receptacle, what do I do with the red wire? Can I ground it?

I have a 3 wire (Black, White, Red and ground) feeding a outlet and I want to add another receptacle to run further down the line. The line out is 14/2. What do I do with the Hot Red wire? Can i attach it to the ground. - Rick

Reply: NO!!

Rick:

NEVER connect a hot (red or black) wire to ground (nor to the white neutral wire) - doing so would form a dead short, should trip a breaker, or if not, could cause a fire or could cause a dangerous shock.

If there is a hot wire that is not used in a junction box, SOP would be to cap it off with a twist-on connector.

It sounds as if you'd be best served by hiring a licensed electrician.

Reader follow-up:

After capping off the red wire, can I extend the line to the next plug by following the diagram above and adding the black and white wires to the respective second screw connections?

You see, the wiring has already been installed by the builders and they left the boxes without receptacles so all I have to do is connect them to the. I don't know why the extra red wire is there. It was done over a year ago. I want to finish the connections. It runs 14/3 and then 14/2. That's why I have the extra red.

Question: what do I do with a third white wire attached to the side of the old receptacle when I'm moving them

I have changed several receptacles in my 1994 home, but this time when removing the receptacle from the wall I see a third white wire attached to the side of the old receptacle. Can you explain to me what this third neutral wire is? - DW 6/12/12

 

Reply:

Dave, your wiring or perhaps the switch itself is unsafe; sounds as if it's shorted. Leave the circuit off until the wiring has been traced, lest you start a fire or zap someone.

Question: are receptacles wired after a GFI receptacle OK?

Are receptacles wired after GFI receptacles OK? - Denny 11/25/12

Reply:

Denney,

Yes, and if wired correctly the downstream receptacles will also be GFCI protected.

Watch out: When wiring a GFCI the incoming leads are connected to the LINE terminals and the downstream receptacles are connected to the LOAD terminals marked on the back of the receptacle. If the devices is not wired correctly it is unsafe and does not provide the intended safety protection from ground faults.

Question: 3 plugs on one of my walls went out

Ok from everything I can tell I'm having trouble with trouble with 3 plugs on my outer wall has went out. I've did the common thing checked my breakers they are fine. Must not I have 2 switches in this room one on each wall but they do nothing I feel somehow those switches are connected to those 3 plug

s. I've pulled the covers off each plug and noticed the wires are secured. I've flipped the switches in many combos with something plugged in and they still don't work at all. What can I do to fix it. I wanna avoid calling a electrician if possible. - Josh DeBerry 12/11/12

Reply:

Josh:

Start by checking fuses or circuit breakers. If there is no tripped breaker or blown fuse, I suspect a damaged receptacle, wire, or wire connector. Your electrician will track down the location of the fault. But if you know which receptacles were all wired on a given circuit, and with power on at the electrical panel, using a receptacle tester you can check to see if any of the devices on the circuit have power.

Since receptacles are most often wired in a daisy-chain or series circuit, the last one that has power tells you that the problem is between that receptacle and the next one in the chain.

Watch out: Electrical components in a building can easily cause an electrical shock, burn, or even death. 

Even when a hot line switch is off, one terminal on the switch is still connected to the power source.

Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse.

See SAFETY for ELECTRICAL INSPECTORS

...

Continue reading  at REVERSED POLARITY ELECTRICAL DEVICES / CIRCUITS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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