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I moved into a new home and several receptacles have the hot and neutral reversed. I confirmed this with a basic receptacle tester. I opened one up and found the white wire on the brass terminal, and the black wire on the silver terminal.

Is there any scenario where this would have been done on purpose? Perhaps as a workaround for some other issue? If not, then I would assume I could safely correct it myself.

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Have you traced the circuits back to the service panel? Are the wires reversed there too? –  Niall C. Aug 1 at 15:49
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If the panel wires were also reversed then the plug-in receptacle tester would not have indicated a problem. –  Jimmy Fix-it Aug 1 at 16:06
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While you're at it, you might check to see if the light switches in that room interrupt the neutral rather than the hot. Someone who is careless enough to swap neutral and hot in a plug might well do the same in a light switch. And remember the fundamental rule of rewiring old houses: everyone who lived there before you was an idiot. I just hope to not be the next owner's idiot. –  Eric Lippert Aug 1 at 18:34
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I suppose I should say how to do that. With the switch off, see if there is a voltage between any terminal of the light fixture and a known ground. If there is voltage in the fixture even with the switch off then the neutral, not the hot, is being interrupted. –  Eric Lippert Aug 1 at 18:37
    
If you want to blow up old equipment connected to A/V house/building cabling, then this is the easiest method. But it's also a fire and shock hazard, so it's strongly discouraged. –  Adam Davis Aug 1 at 20:34

3 Answers 3

up vote 21 down vote accepted

There is no reason why they should be reversed. Fix the receptacles and double check all the electrical in your house. It looks like you had someone living there that was comfortable making electrical changes that didn't know anything about electrical.

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You could tell there were two different people wiring our house when it was built, the experienced guy and the flunky. Half the house was wired backwards and obviously, the experienced guy didn't bother to check the flunky's work. –  Fiasco Labs Aug 2 at 1:56
    
@FiascoLabs: That or someone came along and did work after the fact. In our house, there's a very clear line between the quality of the work in the main house (probably a modern replacement circa 1980 of 1960s or 1950s work in a ~1900 house), which is very good, and the quality of the work in an extension (~1995), which is abysmal. –  T.J. Crowder Aug 2 at 14:46
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I must emphasize that you check all the receptacles in the house. I had an expensive way of finding out that they were 50/50 in a house by connecting an audio cable between two devices where one had this mix-up and thus they had a 220V difference between their 'ground'. Having some receptacles reversed is more dangerous than if all of them are. –  Peteris Aug 2 at 17:28
    
@FiascoLabs: Wouldn't that be 100% flunky if he simply wired each outlet at random? –  wallyk Aug 2 at 17:39
    
@wallyk - No, there was a distinct demarcation as to where the outlets were wired wrong. The flunky did the bedrooms and a bathroom and the other guy did all the more technical areas which were correct. The bathroom used a ground crimp ring to connect all hots together to enable power to two switches and a socket. I wondered why the lights were kind of dim when a hair dryer was plugged in and ended up rewiring the box. Which led to checking polarity and reversing all the other miswired connections. –  Fiasco Labs Aug 2 at 21:16

Make sure that your ground is not hot. I found so receptacles in my house that were apparently wired in reverse (according to a receptacle tester). In reality, some had connected the ground for that are to the live wire with no connected to actual ground. As a result, the ground and live are at the same voltage and there's a 120V difference between ground and neutral. This shows up on a tester as reversed. I struggled to believe that someone would do that, but there it was before my eyes.

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Oh, I've seen an electrician do that. It was in the living room with home theater devices on different outlets connected by s-video cables which have a ground wire. Having 120V going through all the devices made for a lot of repairs. –  Alan Shutko Aug 1 at 20:20
    
I've seen it where a non-grounded outlet was replaced with a grounded one. The biggest problem was the hot wire was shorting to the box. –  Brad Gilbert Aug 3 at 14:17

This is never necessary and is potentially lethal.
Correct it or have it corrected as soon as you can.

It is worth noting that you can get
wiring reversals in sockets that allow properly wired appliances to work
AND reversals in appliances that allow them to work with properly wired sockets
but the two faults together may be non functional.

I saw this happen where a "sleepout" was wrongly wired and a tape player was wrongly wired. The player would work everywhere except when plugged into power in the sleepout. I was asked to find out what was wrong and to fix it. In the process I discovered that when the player was plugged into the sleepout power outlet , phase (live) appeared on its "grounded" body. Had earthed metal been present nearby a fatality could have occurred.

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