Electricians ?: reverse polarity

mrjohneel said:

used a circuit tester (2 yellow lights, one red) to test an outlet. It showed reverse polarity. The white neutral wire was attached to the silver screw and the black to the gold. The outlet worked. So I switched white to gold screw and black to silver and the oulet works, and the circuit breaker shows ok. Two other outlets on the circuit are wired correctly and are ok. What?s going on? Am I at risk with that one flip-flopped outlet? Thanks in advance.

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Your home inspector should have caught that when you bought the house but its no biggie, nothing to worry about we get that all the time and just switch the wires over

If other outlets on the same circuit test fine, and their wiring color is correct, then it wouldn’t appear to be an issue of wires swapped at the breaker panel. A few questions:

1. Got a volt meter?
2. Is this receptacle controlled by a wall switch?
3. Have you verified no wire colors are swapped at all receptacles on this circuit? This would mean removing receptacle wall plates, and checking wiring colors.

agree with above somewhere up the line something is wired backwards.. Personally i would find it and fix it so next time you have a problem or someone else comes and works on things its proper. Only 3 outlets on this circuit? Usually their is more unless its a kitchen or bathroom plugs. Any GFI plugs in the system?

mrjohneel said:

I don't have a volt meter.
The receptacle is not controlled by a wall switch.
The two other outlets in the room are correctly wired (black wire to gold; white/silver). This outlet was the only one wired incorrectly.

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Good catch on the “in the room” comment. Also, I want to be sure we are saying the same thing, as you said this one was wired incorrectly. I thought your OP said the colors on this one were correct, but it was testing as reverse polarity, which implies a crossed wire somewhere upstream of this receptacle. Now you are saying this one was wired incorrectly, which is a different situation.

A voltmeter would enable you to test from ground to each receptacle blade, which could be useful in tracing this problem, but is not necessary. Pull the covers off all receptacles on this circuit and just verify all black wires are on side with small blade, and all white wires are on side with large blade. This would be black on right and white on left, if mounted in the traditional “ground down” orientation, or reverse if mounted in the silly new “ground up” orientation.

mrjohneel said:

But my main question is: When I switched the wires on that third outlet, did I do more harm than good? The polarity is now correct, but the hot and neutral wires are switched. Thanks.

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Only if what you're seeing on the circuit tester is indicative of another problem.

Are you sure the brass and white screws aren't just switched on this outlet? Seems unlikely, but so is every other cause we've postulated. Black screw goes on side with small blade hole, nickel screw on side with large blade hole.

Your only issue would be if an appliance is on the same ckt and is rev'd going to it.

Ashful said:

Only if what you're seeing on the circuit tester is indicative of another problem.

Are you sure the brass and white screws aren't just switched on this outlet? Seems unlikely, but so is every other cause we've postulated. Black screw goes on side with small blade hole, nickel screw on side with large blade hole.

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i was just going to say this! I have seen quite a few times when the outlet screws have been switched. Also check to make sure that the wire nuts are connected to the correct wire.

You can disconnect the previous outlet in the stream and make sure that your polarity is still good. if you reconnect and you still have an issue, then there is probably a junction box or other symptom going on.

paulnlee said:

Your only issue would be if an antique, not double-insulated appliance is on the same ckt and is rev'd going to it.

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There, I fixed it.

Ashful said:

There, I fixed it.

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No you didn't. You obviously don't repair appliances

paulnlee said:

No you didn't. You obviously don't repair appliances

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No, but I design components for them, for commercial applications. Maybe I’m making assumptions of how our commercial requirements carry down to consumer grade. We are governed mostly by CE compliance, but I don’t see many consumer grade items not also carrying a CE badge.

So - if the reversed polarity thing wasn't found, what bad stuff could happen exactly? Sounds like this situation was like this for a while before it was found?

(Electrical dummy here....)

Most if not all of appliances today have circuit boards. 120V in along with a neutral. When they're reversed strange things happen along with a possibility of the frame being HOT. I've seen some strange troubles because of a reversal

paulnlee said:

Most if not all of appliances today have circuit boards. 120V in along with a neutral. When they're reversed strange things happen along with a possibility of the frame being HOT. I've seen some strange troubles because of a reversal

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Can you provide a schematic of a modern appliance with a connected chassis? I have a hard time believe this is still done on any major appliance. This is astoundingly bad design, and bad practice.

As for circuit boards, very few electronics operate at line voltage. The first stop is usually a switching power supply, and conversion to low voltage DC for the electronics, the only usual exception being motor controllers.

I ask because I have been told at a motor repair shop that it doesn't matter which wire goes to which side. Also think I have found the odd thing here where one was wired one way & another was wired the opposite. But I've never done any testing with a tester - have also not experienced any problems, that I know of.

Ashful said:

Can you provide a schematic of a modern appliance with a connected chassis? I have a hard time believe this is still done on any major appliance. This is astoundingly bad design, and bad practice.

As for circuit boards, very few electronics operate at line voltage. The first stop is usually a switching power supply, and conversion to low voltage DC for the electronics, the only usual exception being motor controllers.

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I've yet to see a Wolf oven or any other for that matter where the bake&broil elements operate on DC. Usually the DC voltage is for lighting and on some appliances the fans.

paulnlee said:

I've yet to see a Wolf oven or any other for that matter where the bake&broil elements operate on DC. Usually the DC voltage is for lighting and on some of the gook appliances the fans.

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Oven elements aren’t on circuit boards, and certainly don’t care about polarity. I’m going off your earlier post about reversed wires on an ac circuit causing trouble with electronics on circuit boards.

maple1 said:

I ask because I have been told at a motor repair shop that it doesn't matter which wire goes to which side. Also think I have found the odd thing here where one was wired one way & another was wired the opposite. But I've never done any testing with a tester - have also not experienced any problems, that I know of.

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Correct, standard induction motors don’t care. If marked with wire colors (wh/Bk or brown/blue), then adhere to them, but most old single phase induction motors aren’t even marked for hot vs neutral, all winding leads are the same color. On three phase motors, legs are labeled or color coded, and we swap two legs to reverse. Same can be done between start and run windings on some capacitor start single-phase induction motors, although most tie one end of start winding to a run winding to prevent this.

Ashful said:

Oven elements aren’t on circuit boards, and certainly don’t care about polarity. I’m going off your earlier post about reversed wires on an ac circuit causing trouble with electronics on circuit boards.

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Every newer Thermador, Dacor or Wolf oven has at least one leg of 220V switched thru a relay board sometimes both.

paulnlee said:

Every newer Thermador, Dacor or Wolf oven has at least one leg of 220V switched thru a relay board sometimes both.

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I understand that, and totally follow what you’re saying, but we’re getting hung up on the original point. Relays are electromechanical devices, not “electronics”. Modern electronics, with very few exceptions, run on low voltage DC. Most frequently 3.3VDC. The OPs reversed outlet will have no bearing on them.

Most modern appliances are double-insulated, they likewise will not care about the reversed wiring. Some old appliances bonded the chassis to neutral, but folks figured out that was a problem 50 years ago, when mom got shocked by touching the electric range and refrigerator at the same time. Today, all major appliances have a separate (un-bonded) earth ground connection to the chassis (3 prong outlet), and it is illegal for manufacturers to bond neutral to the chassis.

I’m not sure this argument is still in the best interest of answering the OP’s question, nor am I saying you don’t know your appliances, I think we’re just getting hung up on semantics.