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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.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
FAQs on Reversed Polarity at Electrical Receptacles
Recently-posted questions & answers about reversed-polarity or mis-wired electrical receptacles ("outlets")
On 2017-03-16 17:24:37.178601 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 01:56:59.156654 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 20:37:57.222628 by (mod) - live wire stops working if I connect two neutral wires
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 14:37:38.356600 by Mr B Lockwood
My live wire stops working when I join the neutral wires together. What's wrong please.
On 2016-04-12 13:37:57.997574 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 00:34:05.596893 by Sam
Are you supposed to wire a gfi outlet reverse if the construction was done before 2003?
On 2016-03-27 15:40:00.505072 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 09:10:50.555825 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 16:51:17.517903 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 20:19:15.141350 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 18:22:38.117915 by (mod)
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 15:58:13.216351 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 02:42:54.755620 by (mod) - reverse polarity is a red flag to look for other electrical wiring mistakes
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 22:17:45.706740 by firstname.lastname@example.org
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 22:29:03.065320 by (mod)
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 04:58:34.216400 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 21:20:08.686450 by (mod) - where to check for mis-wired electrical circuit errors
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 20:17:26.149160 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?
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
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.
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
DW, it is just too dangerous to claim to know what wiring connections someone has made in a building that is unseen and untested.
It would be common for an additional white wire connected to an electrical receptacle to be carrying the neutral line to another receptacle downstream. In other words the incoming neutral is connected to one terminal and the outgoing neutral is connected to a second screw that is electrically common with the first.
Check for a second hot wire also present in the same box.
Question: I've lost electrical power to the whole room after testing power at the light switch
I've lost elec to the whole room.
I tested the wiring at the light switch.
If I turn the switch off I get elec to the switch,If I turn it on I get no elec.to the switch. I've lost electricity to the whole room - Dave
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
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 plugs. 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
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
Timothy Hemm has provided photographs of various electrical defects used at the InspectAPedia TM Website. Mr. Hemm is a professional electrical inspector in Yucala, CA.
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: email@example.com
 The 2008 NEC National Electrical Code (ISBN 978-0877657903) Online Access LINK (you'll need to sign in as a professional or as a visitor)
 Special thanks to our reader Steve who pointed out prior errors in our illustrations.
 Simpson Strong-Tie, "Code Compliant Repair and Protection Guide for the Installation of Utilities in Wood Frame Construction", web search 5/21/12, original source strongtie.com/ftp/fliers/F-REPRPROTECT09.pdf, [copy on file as /Structures/Framing/Simpson_Framing_Protectors.pdf ]. "The information in this guide is a summary of requirements
from the 2003, 2006 and 2009 International Residential Code
(IRC), International Building Code (IBC), International Plumbing
Code (IPC), International Mechanical Code (IMC), 2006 Uniform
Plumbing Code (UPC) and the 2005 National Electrical Code."
"Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
"Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
"Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
"Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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