Can a light switch or fixture cause hot neutral reverse readings at receptacles?
#1
03-22-19, 04:26 PM
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?
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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#3
03-22-19, 05:32 PM
Group Moderator
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.
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.
#5
03-23-19, 05:16 AM
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?
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?
#9
03-23-19, 06:44 AM
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.
#10
03-23-19, 07:47 AM
Group Moderator
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.
If a plug causes a small spark when it's plugged in..... then yes.... you may see a little black on the plug.
#11
03-23-19, 11:00 AM
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.
#12
03-23-19, 11:04 AM
Is the arcing normal if it's enough to leave small black scorch marks?
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.
#13
03-23-19, 11:47 AM
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.
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.
#14
03-23-19, 11:54 AM
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.
#15
03-23-19, 02:39 PM
Is this normal for ungrounded gfci?
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.
#16
03-23-19, 04:38 PM
Group Moderator
Check your bathroom receptacle to the faucet (ground) since there is no ground in the box.
#17
03-23-19, 07:26 PM
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.
#18
03-23-19, 07:48 PM
Group Moderator
Disconnecting one wire at a location will render everything downstream.... out.
I won't say dead since the hot and neutrals are reversed,
I won't say dead since the hot and neutrals are reversed,
#19
03-24-19, 09:21 AM
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.
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.
#20
03-24-19, 09:45 AM
Group Moderator
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.
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.
#23
03-24-19, 08:00 PM
Group Moderator
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.
Usually if there are two cables it goes in and then passes on to the next location.
#24
03-25-19, 01:06 PM
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?
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?
#26
03-25-19, 02:11 PM
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.
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.
#27
03-25-19, 02:44 PM
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.
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.
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.
#28
03-25-19, 03:31 PM
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.
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'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.
#29
03-25-19, 04:27 PM
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).
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.
#30
03-25-19, 07:12 PM
Do you mean on a single pole switch, it matters which screw the hot wire is on?
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?
This way, you don't get a induced voltage on hot wire with switch off.
#31
03-25-19, 09:49 PM
Group Moderator
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.
Now it sounds like you are working with switch loops where white and black can be hot.
#32
03-26-19, 07:42 AM
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
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
03-26-19, 09:13 AM
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.
The light fixture should be connected black to red and white to white.
#34
03-26-19, 10:30 AM
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.
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.
#35
03-26-19, 11:50 AM
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.
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.
#37
03-27-19, 09:49 AM
Group Moderator
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.
If It carries a UL listing it should be safe. It's the quality that is questionable.
