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Can a light switch or fixture cause hot neutral reverse readings at receptacles?

Can a light switch or fixture cause hot neutral reverse readings at receptacles?

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  #1  
Old 03-22-19, 04:26 PM
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Can a light switch or fixture cause hot neutral reverse readings at receptacles?

I've got hot neutral reverse readings on all receptacles on a circuit in my home. I've verified correct wire color orientation (black to narrow, white to wide terminal) on all outlets. Only thing I haven't checked are light switches and fixtures, which I didn't think mattered but now I'm not sure.

I'm in a 60s NYC apartment that we own fwiw and some of these receptacles are probably original. The circuit breaker box is a federal pacific and we are budgeting to replace as soon as we have the funds, since they are fire hazards. I'm just trying to narrow down this hot neutral reverse problem so we have a better idea on the scope of work we need done and perhaps save a little money by correcting it myself.

Also, is there a way to check light fixture polarity without pulling them down?
 
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Old 03-22-19, 05:17 PM
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Switches themselves cannot cause hot and neutral to reverse, but it is possible something is wired wrong inside the junction box for the switch or light fixture.
 
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Old 03-22-19, 05:32 PM
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Do you have a meter ?

Everything is tested to ground.......
From the large slot of the receptacle to ground - 0v.
From the small slot to ground - 120v
With a switch turned on - 120v from either screw to ground.
At the fixture - 120v from center pin to ground.
 
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Old 03-22-19, 06:37 PM
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Somewhere before the power gets to the receptacles the black and white have been swapped. That will make everything downstream test reversed.
 
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Old 03-23-19, 05:16 AM
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PJMax: I took meter to a light fixture and initially saw 20V with light switch off then after checking other light fixtures, and returned to it, it had returned to 0volts and 120v with switch on.

I should also mention we have slight arc/popping on cord prongs when plugging into outlets, intermittently, not everytime.

These two issues related and where do I start troubleshooting?
 
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Old 03-23-19, 06:16 AM
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I should also mention we have slight arc/popping on cord prongs when plugging into outlets, intermittently, not everytime.
Completely normal. Not part of your problem.
 
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Old 03-23-19, 06:18 AM
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I think what JOED said is where your problem is. You need to check every junction box.
 
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Old 03-23-19, 06:38 AM
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Is the arcing normal if it's enough to leave small black scorch marks?
 
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Old 03-23-19, 06:44 AM
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No it's not. If you're getting scorch marks that leads me to believe that the connections to the outlet are not secure. Are you using the screws or the stab connections? Use the screws.
 
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Old 03-23-19, 07:47 AM
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To leave scorch marks where..... on the plugs..... the wall ?
If a plug causes a small spark when it's plugged in..... then yes.... you may see a little black on the plug.
 
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Old 03-23-19, 11:00 AM
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Is the arcing normal if it's enough to leave small black scorch marks?

If the item you are plugging in is in the "On" position then yes, you will get light arcing. In the "Off" position there would be no load so then there would be no arcing.
 
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Old 03-23-19, 11:04 AM
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Is the arcing normal if it's enough to leave small black scorch marks?
Arcing is normal anytime you plug in something that is turned on. The larger the load the larger the arc.

The arcing has nothing to do with your problem of hot neutral reversed. You have a swapped connection somewhere else on the circuit. Depending on how your cabling is run it could be in a switch box, fixture box, receptacle box or any other junction box on the circuit.
 
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Old 03-23-19, 11:47 AM
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The scorch marks were on the plug and yes it was happening when the item (treadmill) was in on position when plugging in. I've just replaced that receptacle and it has not arced yet. It was intermittent before. Arcing is non issue for now....

I just measured my bathroom receptacle. It is a newer gfci that was installed before we moved in. It does not have a ground. I'm measuring 120v between hot and neutral and 46v from wide terminal to ground terminal and 31v from narrow terminal to ground terminal. Is this normal for ungrounded gfci? I think this may be the culprit. I actually have not pulled this one yet to check wiring. Will report back.

Edit: pulled bathroom receptacle and didn't find any miswires.
 

Last edited by axxel; 03-23-19 at 12:08 PM.
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Old 03-23-19, 11:54 AM
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OK, I'm not an electrician, so I'm only going on my own experience. Any time I'v plugged in an appliance (never thought about the appliance being on or off) and saw a spark, it never caused a problem. But I've had an arc take place a few times and that was a problem. Burned plug and/or outlet, sometimes smoke. I differentiate between a small spark and an arc.
 
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Old 03-23-19, 02:39 PM
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Is this normal for ungrounded gfci?
If ground is not connected, then it will be just floating and you will get an arbitrary reading.

To find if ungrounded receptacle or cable has correct polarity, you will have to test it against a known good grounded conductor (neutral or ground). You can archive this by using extension cord from a known good receptacle.
Non-contact tester may be able to determine hot wire as well, (will beep on hot wire and not on neutral) but it is not fool proof method and may get a wrong reading.
 
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Old 03-23-19, 04:38 PM
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Check your bathroom receptacle to the faucet (ground) since there is no ground in the box.
 
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Old 03-23-19, 07:26 PM
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I think I've isolated it down a bit further. I want to reverse hot neutral in a receptacle upstream to see if it corrects everything downstream. I just don't know which direction is upstream. Anyway to find out? There are several walls with outlets in the vicinity of this circuit.
 
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Old 03-23-19, 07:48 PM
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Disconnecting one wire at a location will render everything downstream.... out.
I won't say dead since the hot and neutrals are reversed,
 
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Old 03-24-19, 09:21 AM
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Sorry dumb question but when you have multiple rooms on same circuit, are they still up and down stream of each other? Having trouble deciding whether to inspect forgetf in bathroom or bedroom. Both are on same circuit and not sure which one comes first.

Fwiw, my bathroom originally only had a light switch and fixture. At some point someone added the non grounded receptacle which i assume is spliced into the fixture which is closest to it.

What would your guess be which room would come first in line and is it possible that another room can be separate stream while being on same circuit? Like the bathroom outlet polarity could have no affect on the bedroom receptacles irregardless of up or down stream?

Appreciate the help. You guys are great.

 
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Old 03-24-19, 09:45 AM
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Upstream is when you open a wire and it's not affected.
Downstream is after the connection and is affected.

A circuit normally follows a logical pattern. It starts at the panel and usually follows an inline path. So breaking a connection closer to the panel usually kills more of the circuit. However.... the power can go to a box and then be tee tapped and go off in two different directions.

Typically you determine everything on the affected circuit. Then you see what is working correctly and what is not. That usually gives you an indication of where to start.
 
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Old 03-24-19, 09:45 AM
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My GUESS would be the rooms closest to the panel are first on the circuit. You would normally start at the panel and work you way out on the circuit.
 
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Old 03-24-19, 06:21 PM
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On back to back outlets, will one still be first in line, upstream from the other?
 
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Old 03-24-19, 08:00 PM
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It could come into one and then loop to the second one and then on..... OR..... it could come in to the first one, loop out to somewhere else and have a tee tap feeding the back to back outlet.

Usually if there are two cables it goes in and then passes on to the next location.
 
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Old 03-25-19, 01:06 PM
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Found the flow of stream on the receptacles and made some adjustments and seem to be all good now.

As for light fixtures, still a bit stumped. I know my bathroom has a miswire but I'm not sure where and not sure what's normal. I'm measuring 120v on both the shell and center pin with the standard switch in off position. With it on, only the shell has 120v.

What are normal readings when a standard switch is off?
 
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Old 03-25-19, 01:27 PM
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When the switch is on.... just the center pin should be hot.
 
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Old 03-25-19, 02:11 PM
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Gotcha. If the switch was miswired, would the light turn on when switch was in off position?

The white wire feeding the light fixture is the hot one. I've tried connecting it to both the black light wire and the white one, and either way I did it, the light still had some voltage when the switch is off. Not sure where to be looking now.
 
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Old 03-25-19, 02:44 PM
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If the switch was miswired, would the light turn on when switch was in off position?
No. Unless you have a 3 way (or 4 way switch), the switch will either, not work, work (hot and load on the terminals) or short (hot and neutral on the terminals).

The white wire feeding the light fixture is the hot one.
Is that white wire on the switch or is it just 2 wires wirenutted together?
If it is later, you have hot and neutral reversed before the switch.
If white wire is on the switch, then it is a switched loop. Should been marked with a tape or a marker, but rarely done in practice.

I've tried connecting it to both the black light wire and the white one, and either way I did it, the light still had some voltage when the switch is off.
How are you testing and with what?
You will get a induced voltage (aka phantom voltage) if one of the wire is floating (light bulb of fixture removed and switch off) at the time of testing and will show up in non-contact tester and digital multi-meter.
 
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Old 03-25-19, 03:31 PM
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Is that white wire on the switch or is it just 2 wires wirenutted together?
If it is later, you have hot and neutral reversed before the switch.
If white wire is on the switch, then it is a switched loop. Should been marked with a tape or a marker, but rarely done in practice.
It's the ceiling box wiring. The white one was the hot one. I did not pull the switch yet.

I'm using a digital meter. I'll pick up analog when I get a chance. When i get a weird reading on the digital though, restarting the meter usually corrects it.
 
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Old 03-25-19, 04:27 PM
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No. Unless you have a 3 way (or 4 way switch), the switch will either, not work, work (hot and load on the terminals) or short (hot and neutral on the terminals).
Bit confused. Do you mean on a single pole switch, it matters which screw the hot wire is on? I've thought it doesn't matter if it's top or bottom screw.

Also, does it matter whether there are any bulbs in the fixture still when I'm measuring socket voltage on an empty socket?
 

Last edited by axxel; 03-25-19 at 05:06 PM.
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Old 03-25-19, 07:12 PM
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Do you mean on a single pole switch, it matters which screw the hot wire is on?
No. That does not matter on regular switch.
However, with 3 way or 4 way switch it will reverse which side is on position.

Also, does it matter whether there are any bulbs in the fixture still when I'm measuring socket voltage on an empty socket?
It keeps hot side wire from just floating with switch off. The light bulb will keep hot wire connected to neutral through a load (light bulb).
This way, you don't get a induced voltage on hot wire with switch off.
 
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Old 03-25-19, 09:49 PM
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If you found the hot/neutral reverse problem at the receptacles..... the lights should be fine.
Now it sounds like you are working with switch loops where white and black can be hot.
 
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Old 03-26-19, 07:42 AM
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Just removed the switch. I have the following in switch box:

3 cable (Black, red white)
2 cable (Black, white)

The blacks from both cables are wirenutted together, then going to bottom terminal of switch.

The red is going to top terminal of switch.

Both whites are wirenutted together and tucked in box.

So with both light fixture and switch removed, my readings are:

Light box: 120v at white wire whether switch is on/off or removed
18v on black wire (phantom volt?-using digital) when switch is off or removed and 0v when switch is on.


Switch box readings with switch and light fixture removed: Red wire 18v red wire 0v black wire.

Is it normal to have a constant 120v at the light box and not have a constant at the switch box?

See linked images of light box, and light fixture.

I'm attempting to remove voltage at socket with switch off. Appreciate anymore suggestions.

https://imgur.com/a/pr4645S

https://imgur.com/NABfSmp
 
  #33  
Old 03-26-19, 09:13 AM
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What are the voltage reading in reference to. You should be measuring voltage black to white and red to white. The red should go on and off with the switch.
The light fixture should be connected black to red and white to white.
 
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Old 03-26-19, 10:30 AM
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Your test result tells me that you have hot and neutral reversed before the switch. You will have to find switch or outlet upstream of the switch and check again.

You have to have a constant 120V at the switch on that can be switched. However you are switching neutral on black wire instead because your polarity is reversed. This can create dangerous situation.

You probably have 3 wire (red, black, white) between the switch and light, and black wire is feeding another downstream circuit from lighting junction box.
Black stranded wire you see at the light is probably connected to red wire inside junction box.
 
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Old 03-26-19, 11:50 AM
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Thanks everyone for the help. Decided to call in an electrician to be safe.

​​​ Had one last question. Is genmax a good brand gfci? That's what is installed in bathroom outlet. Can't find much online. Local hardware store carries them and they are UL listed UL 943. Also says UL E491779.
 
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Old 03-27-19, 06:40 AM
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I have never heard of Genmax. I prefer Leviton, but there are several other good brands such as Eaton, P&S, Legrand........ I do not like the Hubbel GFCI devices.
 
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Old 03-27-19, 09:49 AM
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I've never heard of them either. The UL license is granted to SHANGHAI LINSKY ELECTRICAL CO.
If It carries a UL listing it should be safe. It's the quality that is questionable.
 
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