Author Topic: Electrical Question - Open circuit  (Read 5127 times)

GuitarStv

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Electrical Question - Open circuit
« on: May 31, 2016, 08:58:04 AM »
Last weekend I was doing some vacuuming and the machine stopped working.  I figured that maybe I'd tripped a breaker.  Went down, checked the breakers . . . no problem.  Went back upstairs and plugged the vacuum into another outlet.  No problems.

So, I started checking everything electrical that was nearby.  There are two plugs and a light switch (for the overhead lamp) in our dining room that aren't getting any power.  Circuit tester says there's nothing coming through the black hot wire.  My multimeter says that power is passing through the switch correctly between the two white terminals/ground, and between the two black terminals.  No signs of damage or burning.

The breaker that they're on is fine, because it controls three plugs and two light switches on the second floor which all work OK.

I figured that maybe a wire had come loose inside one of the electrical outlets that weren't working, so pulled them out of the wall.  The connections were all tight, but I removed and reconnected the black wires again just to be sure.  Still no power coming thorough.

I pulled the working boxes that were on the same circuit out of the wall upstairs and checked the connections in them . . . which all looked fine.  I didn't disconnect/reconnect the black wires.  Multimeter says that the two black terminals are connected, and the two white terminals/ground are connected as they should be.  The wires on the switches are connected by pushing in to the back rather than by the screw terminals, and seem firmly connected so I didn't do anything with them.


So far, all that I can think of for debugging this thing is:
- pull the black wires out of the working outlets on the circuit and connect them via screws to be sure they've got a good connection.
- pull all the switch boxes that are working on the circuit open and see if anything is disconnected in there.

Is there something else I should do?  I've never had an electrical problem this obstinate before.  I'm hoping that this isn't indicative of a break in the wire behind the drywall somewhere.

Syonyk

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Re: Electrical Question - Open circuit
« Reply #1 on: May 31, 2016, 10:09:39 AM »
Do you have a wiring diagram for the house? :)  You could see what the last outlet on the circuit with power is...

GuitarStv

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Re: Electrical Question - Open circuit
« Reply #2 on: May 31, 2016, 10:13:19 AM »
Do you have a wiring diagram for the house? :)  You could see what the last outlet on the circuit with power is...

Sadly the builders were not kind enough to provide one.  Hell, I'd have been happy to get markings on the breakers to tell me what's on each circuit.

Midwest

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Re: Electrical Question - Open circuit
« Reply #3 on: May 31, 2016, 10:20:52 AM »
http://www.amazon.com/Extech-TG20-Wire-Tracer-Generator/dp/B00APD16D2?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_search_detailpage

You could use a tone tester to see where the problem outlet wire leads to.  I would turn the power off before using, but this might allow you to find a loose connection.


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Re: Electrical Question - Open circuit
« Reply #4 on: May 31, 2016, 10:33:54 AM »
Dumb question, but is there a GFCI anywhere in this picture?  And I do mean anywhere.  I had a house where all the GFI circuits were run through one spot in the house.  There were 4 or 5 GFCI receptacles all side by side... each protecting a different circuit downstream.

GuitarStv

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Re: Electrical Question - Open circuit
« Reply #5 on: May 31, 2016, 11:26:58 AM »
There are three GFCIs in the house (one in each bathroom), but they're all on a different breaker and working fine.

I may have to buy a tone tester to do the trace, that would be very handy to see where stuff is going wrong.

Midwest

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Re: Electrical Question - Open circuit
« Reply #6 on: May 31, 2016, 11:40:34 AM »
Tone tester works well.  Amazon was cheaper than local.

You don't have a GFCI near the panel do you?  Mine controls bathrooms and the garage.  The suggestion above on the GFCI's was good.  Wondering if you could have another one somewhere.
« Last Edit: May 31, 2016, 11:44:01 AM by Midwest »

forummm

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Re: Electrical Question - Open circuit
« Reply #7 on: May 31, 2016, 12:05:33 PM »
Tone tester works well.  Amazon was cheaper than local.

You don't have a GFCI near the panel do you?  Mine controls bathrooms and the garage.  The suggestion above on the GFCI's was good.  Wondering if you could have another one somewhere.

I had some outlets stop working inside because they were on the GFCI that tripped outside. Took me forever to figure that out.

ncornilsen

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Re: Electrical Question - Open circuit
« Reply #8 on: May 31, 2016, 12:59:31 PM »
Are there any accessible junction boxes on this circuit? Perhaps a wire nut came loose.

Another thing to check is the white/neutral wires, to make sure they aren't loose somewhere.

And finally, do you have any mystery light switches in a closet or something?  I was chasing a similar gremlin at one point in my house, when I found that one of the far bedrooms had it's outlets run through a switch in the master room. My guess is someone put that in to shut off a teenagers TV or something after curfew.


GuitarStv

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Re: Electrical Question - Open circuit
« Reply #9 on: May 31, 2016, 01:03:25 PM »
No mystery light switches for sure.  There may be hidden junction boxes somewhere, but they're under drywall.  I checked the white/neutral wires with my multimeter, and they seem to be working properly.  It's definitely the black wire that has the break somewhere.

lthenderson

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Re: Electrical Question - Open circuit
« Reply #10 on: May 31, 2016, 03:50:51 PM »
You won't believe this but I just had the exact same thing happen to me using a vacuum a few days ago and today I just figured out what caused it. If you have a multimeter, you can test continuity between wires without buying a tone tester. With the power off, touch the hot and neutral wire together on one end and go to the other end and test resistance. That should tell you if the wire is continuous and verify that it is going where you think it should. I did this method and worked my way back towards the breaker panel until I found the culprit. In my case, someone had used 14 gauge wire between two outlets on a 20 amp circuit and the insulation on the nearest outlet to the breaker panel in the circuit had melted and shorted out against the side of the box. This outlet happened to be 20 feet away and in a different room of where I had my vacuum cleaner plugged in. I restrung new 12 gauge wire and put in a new outlet and just got everything back up and running before checking the new posts on here.

In my experience, the problem will be at an outlet or junction box and is rarely caused by a break in the middle of the wall provided you haven't recently been adding screws, nails or other things into  it.

BudgetSlasher

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Re: Electrical Question - Open circuit
« Reply #11 on: May 31, 2016, 07:04:35 PM »
Last weekend I was doing some vacuuming and the machine stopped working.  I figured that maybe I'd tripped a breaker.  Went down, checked the breakers . . . no problem.  Went back upstairs and plugged the vacuum into another outlet.  No problems.

So, I started checking everything electrical that was nearby.  There are two plugs and a light switch (for the overhead lamp) in our dining room that aren't getting any power.  Circuit tester says there's nothing coming through the black hot wire.  My multimeter says that power is passing through the switch correctly between the two white terminals/ground, and between the two black terminals.  No signs of damage or burning.

I do not know what you consider "nearby", but I would not limit myself to one room or maybe even nearby. The reason being most houses are built with multiple circuits serving one room (so that a bad circuit will not leave the room without power); as a result circuits wind up serving multiple rooms and all of the outlets might not be "nearby"

The breaker that they're on is fine, because it controls three plugs and two light switches on the second floor which all work OK.

I figured that maybe a wire had come loose inside one of the electrical outlets that weren't working, so pulled them out of the wall.  The connections were all tight, but I removed and reconnected the black wires again just to be sure.  Still no power coming thorough.

I pulled the working boxes that were on the same circuit out of the wall upstairs and checked the connections in them . . . which all looked fine.  I didn't disconnect/reconnect the black wires.  Multimeter says that the two black terminals are connected, and the two white terminals/ground are connected as they should be.  The wires on the switches are connected by pushing in to the back rather than by the screw terminals, and seem firmly connected so I didn't do anything with them.

As an aside, I despite the push in the back style of wiring at least the older version that is not secured by a screw.

It sounds like you have checked every box on the circuit for an obvious flaw and have found none, if you haven't I suggest you do. I would look to see if maybe there is another outlet on the circuit in an odd place; as houses get older and wiring changes you can get some odd combinations (I have a circuit that is half-bath, kitchen fan, 2 outlets in the basement, and the stair lights). I had a similar problem that turned out to be a loose neutral box upstream of the first outlet showing the problem



So far, all that I can think of for debugging this thing is:
- pull the black wires out of the working outlets on the circuit and connect them via screws to be sure they've got a good connection.

I what you are called a "screw" is what I refer to as a "wire nut" and not the screws on the side of the outlet.

If you go this route also consider the switches (see below), but this shouldn't be necessary . . . except in the situation where you do not want to acquire "new-to-you" electrical tools.


- pull all the switch boxes that are working on the circuit open and see if anything is disconnected in there.

This is worth doing; a hot wire could enter the box and via wire nut be connected to the switch and a hot leaving the box.

Is there something else I should do?  I've never had an electrical problem this obstinate before.  I'm hoping that this isn't indicative of a break in the wire behind the drywall somewhere.

Unless you have done work that penetrated the walls and severed a wire or the circuit was wired with way to small of a gauge of wire, I believe that it is unlikely that there is a break in the wire. Of course, it is always possible that there is a concealed junction box buried under the drywall (in most circumstances against code) that you are missing . . . in which case a tone tester/wire tracer will be your best friend

One thought that occurs to me, is to bypass or replace the outlet the vacuum was plugged into. . . if that outlet was somehow damaged (say my a good yank on the cord) if might not be obvious. That is just a guess but if you are looking for a place to start, I would start with what was in use/different about the time of the failure.


See the read above.

zolotiyeruki

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Re: Electrical Question - Open circuit
« Reply #12 on: May 31, 2016, 07:14:50 PM »
where's paddedhat when you need him? :D

I'd second the suggestion of figuring out if there's anything else on that circuit.  Also, try flipping the breaker off then on again--I seem to remember having a breaker once that would trip, but the switch wouldn't move.

paddedhat

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Re: Electrical Question - Open circuit
« Reply #13 on: May 31, 2016, 08:18:06 PM »
where's paddedhat when you need him? :D

I'd second the suggestion of figuring out if there's anything else on that circuit.  Also, try flipping the breaker off then on again--I seem to remember having a breaker once that would trip, but the switch wouldn't move.

Sorry to be late to the party. I'm reading my way through this cluster-f and thinking at the moment.  First, view the whole circuit as being roughed in as logically as possible. Most competent residential electricians get paid to do things quickly, and with as little material as possible.  This means that the circuit typically loops logically from one outlet to another, and doesn't jump all over hell and creation, since it wastes material.  This doesn't mean that the same circuit doesn't loop from one room to another, since the closest outlet to the point of failure may be on the other side of a wall, and serving another bedroom. In bedrooms and halls, these are called "convenience outlets" and the code allows you to cover a shockingly large amount of square footage on one 15 amp circuit. Loosing continuity in a circuit because a push wired connection failed is common, and can be difficult to troubleshoot. When you insert a stripped wire into the back of a receptacle (push wire) instead of wrapping it around a screw, you are jamming the conductor into a spring steel contact. As a high amperage load cycles,( like an iron, or space heater), the wire expands and contracts at the point where the spring clip is biting into the wire. The spring contact can, and will, eventually cut through the conductor and burn off. The best way to trouble shoot this is to first pull the outlet out of the box, and physically try to yank the conductors out of the push in holes. If you need to remove the conductors you can take a small pin and push the release near the hole to release the wire. There is a tool for this, but a four penny finish nail, held with a pliers works well. To follow the current path I use a "tick tracer" this is also called a non-contact voltage tester. They are a pen like device that costs about $15 at the big box store. It can be held against the side of a conductor and it will beep if there is voltage in the wire. You can quickly find an open circuit if the device (switch or outlet) is at fault by reading the side of the hot line wire ( typically the black wire that is feeding this device from the previous hot one) If the wire is hot and the screw terminal on the side of the device is not, the wire is broken off inside the device. Using a tick tracer, you can quickly determine exactly where the break is. Remember that all this testing takes place with the breaker on, the circuit hot, and the devices hanging out of the boxes. This is dangerous, and you need to be on your game, and have no bystanders around that could get hurt.

This process of troubleshooting I described so far does not address neutrals (white wires) and they are just as important. The neutral completes the circuit, and even though it is far less like to suffer from being burned off in a push connection, it also needs to be thoroughly inspected. Yanking on the conductors that are push wired, checking lose screws, and checking connections with a volt meter, are all important. You can take a volt meter and find a broken neutral by comparing reading from hot to neutral and hot to ground. If you have a good set of connections, you should be able to read line voltage ( 120 volts, more or less) from the hot to neutral, and get the same reading from the hot to ground. if you have 120V from hot to ground at an outlet, and a zero reading from hot to neutral, you lost your neutral at that point.

Never discount a hidden junction. Hidden in the sense that they could be either up or down, as in hidden in the attic or basement floor joists. There can also be splices behind switches and receptacles, and my favorite, behind ceiling fixtures like lights or fans. I have seen rooms wired like a damn octopus, with a hot feed going to a ceiling box and wire heading across the ceiling and dropping to individual boxes like tentacles.  As at least one other poster mentioned, never eliminate a hidden GFCI receptacle as part of the problem. I have been on service calls that were exactly as the OP describes, and found that the original "electrician" decided to feed an outside outlet, or one in a nearby half bath, installed a GFCI outlet in that location, then continued the circuit. This can be a real PITA to find, and I have found them behind a bush, and hidden under a workbench in a garage. In cases like this the homeowner is typically shocked to learn that the outlet even existed at all. Finally, don't assume that an white wire involved in switch wiring is a neutral. There are plenty of reasons that a white wire in this application could be a hot wire. They are supposed to be remarked as a black wire, with tape or a marker, but seldom are. Good luck, I find that problems like this are often pretty basic to correct, but can be a bitch to find.

paddedhat

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Re: Electrical Question - Open circuit
« Reply #14 on: May 31, 2016, 08:37:11 PM »
You won't believe this but I just had the exact same thing happen to me using a vacuum a few days ago and today I just figured out what caused it. If you have a multimeter, you can test continuity between wires without buying a tone tester. With the power off, touch the hot and neutral wire together on one end and go to the other end and test resistance. That should tell you if the wire is continuous and verify that it is going where you think it should. I did this method and worked my way back towards the breaker panel until I found the culprit. In my case, someone had used 14 gauge wire between two outlets on a 20 amp circuit and the insulation on the nearest outlet to the breaker panel in the circuit had melted and shorted out against the side of the box.

This is a frequently misunderstood concept. The Code in the US limits #14 to 15 amps as a safety measure, this does not mean that catastrophic failure is inevitable if a #14 is being protected by a 20 amp breaker. When doing load calculations for things like voltage drop, the same code requirements provide amperage values of 20 or 25 amps on a #14 circuit. Oddly, this is the second time recently where somebody here on MMM commented about a fire, or failure, as a result of a #14 on a 20 amp circuit. The likely cause is a loose connection or poor workmanship, and not because the #14 was overloaded. Limiting #14 to a total of 15 amps,  or #12 to 20 amps, is extremely conservative, and even more so when you concider that most branch circuits are limited to 80% of the breaker rating, or 12 amps for a #14 and 16 amps for a #12, as design values for these circuits. Bottom line?  Most melting, shorting or other failures are not caused by wire that is one gauge smaller that normal.



This outlet happened to be 20 feet away and in a different room of where I had my vacuum cleaner plugged in. I restrung new 12 gauge wire and put in a new outlet and just got everything back up and running before checking the new posts on here.

In my experience, the problem will be at an outlet or junction box and is rarely caused by a break in the middle of the wall provided you haven't recently been adding screws, nails or other things into  it.

Excellent point on failure of existing cable in the wall. It happens, but it's really uncommon. Hack DIYers who install wall finishes like paneling or similar, with fasteners that are way too long,  are typically the culprits.
« Last Edit: May 31, 2016, 08:40:55 PM by paddedhat »

GuitarStv

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Re: Electrical Question - Open circuit
« Reply #15 on: June 01, 2016, 07:10:33 AM »
Last weekend I was doing some vacuuming and the machine stopped working.  I figured that maybe I'd tripped a breaker.  Went down, checked the breakers . . . no problem.  Went back upstairs and plugged the vacuum into another outlet.  No problems.

So, I started checking everything electrical that was nearby.  There are two plugs and a light switch (for the overhead lamp) in our dining room that aren't getting any power.  Circuit tester says there's nothing coming through the black hot wire.  My multimeter says that power is passing through the switch correctly between the two white terminals/ground, and between the two black terminals.  No signs of damage or burning.

I do not know what you consider "nearby", but I would not limit myself to one room or maybe even nearby. The reason being most houses are built with multiple circuits serving one room (so that a bad circuit will not leave the room without power); as a result circuits wind up serving multiple rooms and all of the outlets might not be "nearby"

The breaker that they're on is fine, because it controls three plugs and two light switches on the second floor which all work OK.

I figured that maybe a wire had come loose inside one of the electrical outlets that weren't working, so pulled them out of the wall.  The connections were all tight, but I removed and reconnected the black wires again just to be sure.  Still no power coming thorough.

I pulled the working boxes that were on the same circuit out of the wall upstairs and checked the connections in them . . . which all looked fine.  I didn't disconnect/reconnect the black wires.  Multimeter says that the two black terminals are connected, and the two white terminals/ground are connected as they should be.  The wires on the switches are connected by pushing in to the back rather than by the screw terminals, and seem firmly connected so I didn't do anything with them.

As an aside, I despite the push in the back style of wiring at least the older version that is not secured by a screw.

It sounds like you have checked every box on the circuit for an obvious flaw and have found none, if you haven't I suggest you do. I would look to see if maybe there is another outlet on the circuit in an odd place; as houses get older and wiring changes you can get some odd combinations (I have a circuit that is half-bath, kitchen fan, 2 outlets in the basement, and the stair lights). I had a similar problem that turned out to be a loose neutral box upstream of the first outlet showing the problem



So far, all that I can think of for debugging this thing is:
- pull the black wires out of the working outlets on the circuit and connect them via screws to be sure they've got a good connection.

I what you are called a "screw" is what I refer to as a "wire nut" and not the screws on the side of the outlet.

If you go this route also consider the switches (see below), but this shouldn't be necessary . . . except in the situation where you do not want to acquire "new-to-you" electrical tools.


- pull all the switch boxes that are working on the circuit open and see if anything is disconnected in there.

This is worth doing; a hot wire could enter the box and via wire nut be connected to the switch and a hot leaving the box.

Is there something else I should do?  I've never had an electrical problem this obstinate before.  I'm hoping that this isn't indicative of a break in the wire behind the drywall somewhere.

Unless you have done work that penetrated the walls and severed a wire or the circuit was wired with way to small of a gauge of wire, I believe that it is unlikely that there is a break in the wire. Of course, it is always possible that there is a concealed junction box buried under the drywall (in most circumstances against code) that you are missing . . . in which case a tone tester/wire tracer will be your best friend

One thought that occurs to me, is to bypass or replace the outlet the vacuum was plugged into. . . if that outlet was somehow damaged (say my a good yank on the cord) if might not be obvious. That is just a guess but if you are looking for a place to start, I would start with what was in use/different about the time of the failure.


See the read above.

My initial investigation was to check the switches and outlets in the room.  Then I widened my search to the whole house, and I'm pretty sure that we've mapped out everything attached to the circuit with the problem.

I've checked all the outlets on the circuit for an obvious flaw, but haven't checked all the light boxes in the ceiling or all the switch boxes.  I figured that if the light is controlled by a switch, they wouldn't run the hot wire through it . . . because then the switch would control everything else further down the line.  I hadn't really considered that there might be splicing back there.

We had some mice in the house over the winter, which is where my concern about an in-wall break comes from.

GuitarStv

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Re: Electrical Question - Open circuit
« Reply #16 on: June 01, 2016, 07:17:14 AM »
where's paddedhat when you need him? :D

I'd second the suggestion of figuring out if there's anything else on that circuit.  Also, try flipping the breaker off then on again--I seem to remember having a breaker once that would trip, but the switch wouldn't move.

Sorry to be late to the party. I'm reading my way through this cluster-f and thinking at the moment.  First, view the whole circuit as being roughed in as logically as possible. Most competent residential electricians get paid to do things quickly, and with as little material as possible.  This means that the circuit typically loops logically from one outlet to another, and doesn't jump all over hell and creation, since it wastes material.  This doesn't mean that the same circuit doesn't loop from one room to another, since the closest outlet to the point of failure may be on the other side of a wall, and serving another bedroom. In bedrooms and halls, these are called "convenience outlets" and the code allows you to cover a shockingly large amount of square footage on one 15 amp circuit.

Yeah, sadly all the plugs and lights that are working are on the 2nd floor and all the plugs and lights not working are on the first floor.  If there were a couple working and a couple not working on the same floor I think it would be easier to guesstimate where the problem is happening.

Loosing continuity in a circuit because a push wired connection failed is common, and can be difficult to troubleshoot. When you insert a stripped wire into the back of a receptacle (push wire) instead of wrapping it around a screw, you are jamming the conductor into a spring steel contact. As a high amperage load cycles,( like an iron, or space heater), the wire expands and contracts at the point where the spring clip is biting into the wire. The spring contact can, and will, eventually cut through the conductor and burn off. The best way to trouble shoot this is to first pull the outlet out of the box, and physically try to yank the conductors out of the push in holes. If you need to remove the conductors you can take a small pin and push the release near the hole to release the wire. There is a tool for this, but a four penny finish nail, held with a pliers works well

If the wires seem to be held firmly in the push connector, does that mean that they're connected properly?  Or should I pull them all out and use the screws on the boxes just to be sure?

This process of troubleshooting I described so far does not address neutrals (white wires) and they are just as important. The neutral completes the circuit, and even though it is far less like to suffer from being burned off in a push connection, it also needs to be thoroughly inspected. Yanking on the conductors that are push wired, checking lose screws, and checking connections with a volt meter, are all important. You can take a volt meter and find a broken neutral by comparing reading from hot to neutral and hot to ground. If you have a good set of connections, you should be able to read line voltage ( 120 volts, more or less) from the hot to neutral, and get the same reading from the hot to ground. if you have 120V from hot to ground at an outlet, and a zero reading from hot to neutral, you lost your neutral at that point.
Quote

If it's the neutral that's broken this would show up on my plug in tester I think.  I'm certain that it's the black wire where the break is.

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Re: Electrical Question - Open circuit
« Reply #17 on: June 01, 2016, 08:14:00 AM »
I had the exact same thing happen at my in laws house a couple of months ago right down to the vacuum. It ended up being a failed outlet. Pull all the outlets on the circuit out of the wall and check the connections. Vacuums, specifically old vacuums, pull a lot of amperage and can burn up old devices on a circuit.   

lthenderson

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Re: Electrical Question - Open circuit
« Reply #18 on: June 02, 2016, 07:05:48 AM »

This is a frequently misunderstood concept. The Code in the US limits #14 to 15 amps as a safety measure, this does not mean that catastrophic failure is inevitable if a #14 is being protected by a 20 amp breaker. When doing load calculations for things like voltage drop, the same code requirements provide amperage values of 20 or 25 amps on a #14 circuit. Oddly, this is the second time recently where somebody here on MMM commented about a fire, or failure, as a result of a #14 on a 20 amp circuit. The likely cause is a loose connection or poor workmanship, and not because the #14 was overloaded. Limiting #14 to a total of 15 amps,  or #12 to 20 amps, is extremely conservative, and even more so when you concider that most branch circuits are limited to 80% of the breaker rating, or 12 amps for a #14 and 16 amps for a #12, as design values for these circuits. Bottom line?  Most melting, shorting or other failures are not caused by wire that is one gauge smaller that normal.

I agree with you that in theory, #14 gauge should handle 20 amps but I disagree "poor" workmanship is the cause in this case. The outlet where it happened used screw terminals and they were very tight. The melted insulation on the wire was in the back of the box at a kink in the wire (about 2 inches from where the wire insulation had been stripped off) caused from pushing the electrical outlet and wires back into the box, something that can't be seen by who ever installed it. This is why I say it isn't poor workmanship since it could have happened to anyone. After the insulation melted it arced to the back of the box that the wire was pushed against. In this case, the kink created a stress point in the wire and the vacuum cleaner probably drew more amps on that circuit than had been previously used by the occupants over the last 40 years since the house had been built. I have never had this happen on a 15 amp circuit but I've run into this a handful of times on 20 amp circuits which is why I always follow the National Electrical Code which states for others reference:

NEC 240.4(D)(3) states that 14 AWG must be protected at 15A. You can not use 14 AWG anywhere on a circuit that has a 20A breaker. If you are putting 15 amp receptacles on a 20 amp circuit with 12 gauge wire, then you MUST use the screw terminals, not the back stab terminals.

zolotiyeruki

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Re: Electrical Question - Open circuit
« Reply #19 on: June 02, 2016, 07:27:56 AM »
This is just my opinion, but feeding power into an outlet through the screw connection and out through the stab connection (or vice versa) to the rest of the circuit is just bad practice.  It introduces an additional point of failure, and makes it that much harder if/when you have to replace the outlet.

Syonyk

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Re: Electrical Question - Open circuit
« Reply #20 on: June 02, 2016, 11:42:35 AM »
^^ Yeah, but it's quicker and easier to install!  And that's how contractors get paid! :D

**sigh**

zolotiyeruki

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Re: Electrical Question - Open circuit
« Reply #21 on: June 02, 2016, 04:06:07 PM »
This is just my opinion, but feeding power into an outlet through the screw connection and out through the stab connection (or vice versa) to the rest of the circuit is just bad practice.  It introduces an additional point of failure, and makes it that much harder if/when you have to replace the outlet.
Ooh, I should stick this one in my back pocket as well when arguing against the requirement for EMT.  Since EMT *is* the ground in our village, that means that between the last outlet on a circuit and the breaker panel, there are at least, 20-30 different contact points where ground could be broken.  Just think--every time it goes through a box, that's four contact points (conduit->connector->box->connector->conduit), plus any couplings along the way.

paddedhat

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Re: Electrical Question - Open circuit
« Reply #22 on: June 02, 2016, 06:11:14 PM »

This is a frequently misunderstood concept. The Code in the US limits #14 to 15 amps as a safety measure, this does not mean that catastrophic failure is inevitable if a #14 is being protected by a 20 amp breaker. When doing load calculations for things like voltage drop, the same code requirements provide amperage values of 20 or 25 amps on a #14 circuit. Oddly, this is the second time recently where somebody here on MMM commented about a fire, or failure, as a result of a #14 on a 20 amp circuit. The likely cause is a loose connection or poor workmanship, and not because the #14 was overloaded. Limiting #14 to a total of 15 amps,  or #12 to 20 amps, is extremely conservative, and even more so when you concider that most branch circuits are limited to 80% of the breaker rating, or 12 amps for a #14 and 16 amps for a #12, as design values for these circuits. Bottom line?  Most melting, shorting or other failures are not caused by wire that is one gauge smaller that normal.

I agree with you that in theory, #14 gauge should handle 20 amps but I disagree "poor" workmanship is the cause in this case. The outlet where it happened used screw terminals and they were very tight. The melted insulation on the wire was in the back of the box at a kink in the wire (about 2 inches from where the wire insulation had been stripped off) caused from pushing the electrical outlet and wires back into the box, something that can't be seen by who ever installed it. This is why I say it isn't poor workmanship since it could have happened to anyone. After the insulation melted it arced to the back of the box that the wire was pushed against. In this case, the kink created a stress point in the wire and the vacuum cleaner probably drew more amps on that circuit than had been previously used by the occupants over the last 40 years since the house had been built. I have never had this happen on a 15 amp circuit but I've run into this a handful of times on 20 amp circuits which is why I always follow the National Electrical Code which states for others reference:

NEC 240.4(D)(3) states that 14 AWG must be protected at 15A. You can not use 14 AWG anywhere on a circuit that has a 20A breaker. If you are putting 15 amp receptacles on a 20 amp circuit with 12 gauge wire, then you MUST use the screw terminals, not the back stab terminals.

First, just to be clear, I am not, not have I ever advocated for anything that is not code approved, best practice, or simply doing the right thing. That said, you just described, in detail, the fact that this has nothing to do with an undersized conductor, and everything to do with piss poor workmanship. I have quite literally installed tens of thousands of receptacles and switches. The art of dressing everything in a box, neatly, and with no stress on any wires, connections, or devices is a learned skill. By the time you are at maximum fill of conductors and devices, per the NEC, you have got one of two possible outcomes. Either the conductors are properly spliced, and neatly folded and shaped in the box, with the devices in their proper positions, and ready to be screwed tight, without twisting, racking or straining, or................... you have a rat's nest of shit, and the clown installing it needs to smash it all into the box and try to get everything contained by quickly screwing the receptacle in. In your case it was done by a clown, and you incorrectly gave him slack by thinking that his folding, kinking and eventually shorting the conductor against the box was just unavoidable. Your claim that a kink in the wire may be the fault doesn't ad up. Individual copper conductors are amazingly resistant to bending stress failure. They are specified as "soft drawn" and it can take hundreds of cycles of kinking and straightening before they physically fail. As for an electrical failure due to a kink, they happen, but on much larger wires, at voltages in the thousands of volts, not what you find in residential wiring.  When it comes to any connection in residential wiring getting so hot that it melts the insulation, there are bigger issues here than whether it was wired with a #14 instead of a #12.  The overcurrent protection on the circuit would limit the draw to a maximum of 20 amps +/- a small percentage. There is simply no way in hell that a sub-20amp load,  on a perfectly functional and properly installed outlet, would generate enough heat to melt insulation. You claim you have seen it more than once. Absent loose connections, Aluminum Romex, or other obvious issues, I have never seen a situation exactly as you describe in thirty years in the industry. Bottom line, there is more to it that you may have noticed. Possibly an internally defective receptacle, a failing breaker, or some other issue.

paddedhat

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Re: Electrical Question - Open circuit
« Reply #23 on: June 02, 2016, 06:20:45 PM »
This is just my opinion, but feeding power into an outlet through the screw connection and out through the stab connection (or vice versa) to the rest of the circuit is just bad practice.  It introduces an additional point of failure, and makes it that much harder if/when you have to replace the outlet.
Ooh, I should stick this one in my back pocket as well when arguing against the requirement for EMT.  Since EMT *is* the ground in our village, that means that between the last outlet on a circuit and the breaker panel, there are at least, 20-30 different contact points where ground could be broken.  Just think--every time it goes through a box, that's four contact points (conduit->connector->box->connector->conduit), plus any couplings along the way.

It's funny, but one of the things that I was taught in my apprenticeship, way back, was that relying on EMT as a ground may be in the code book, but it's a half-assed way to do things. Your right about all the failure points in a system. It's nothing to pull a drop ceiling in a fifty year old school, or hospital, and see conduit that has separated and held together by the wires running through it, or open a box and find a lock-nut or two that is not even finger tight. Given the wasted money, and total lack of an real justification for it, I can't believe that there are places that still manage to hold on to the EMT rules. I guess the same can be said of copper plumbing also.

Cyaphas

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Re: Electrical Question - Open circuit
« Reply #24 on: June 02, 2016, 06:44:46 PM »
This is pretty difficult without being there... Heres a few suggestions.


Reset all of your GFCI's.

Check to see if your attic light is on the same circuit and see if it's in parrallel with it. Check to see if you have power in and power out at the outlet. Similiar issues might be a nearby electrical circuit on the out side of the house if it's an outer facing wall. Maybe a motion detection flood light or automatic attic fan.

Essentially you're trying to find either a junction box (they're not supposed to exist where you can't get to them IE behind drywall, that's against code) with loose wire nuts OR most likely you're trying to find a loose plug-in wire in an outlet, it may be one of the working plugs but the 'out' side is the loose or blown contact . It's tedious, my condolences. It goes a lot quicker if you have a decent wireless drill.

My apologies if I didn't add anything new.

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Re: Electrical Question - Open circuit
« Reply #25 on: June 03, 2016, 07:50:02 AM »
First, just to be clear, I am not, not have I ever advocated for anything that is not code approved, best practice, or simply doing the right thing. That said, you just described, in detail, the fact that this has nothing to do with an undersized conductor, and everything to do with piss poor workmanship. I have quite literally installed tens of thousands of receptacles and switches. The art of dressing everything in a box, neatly, and with no stress on any wires, connections, or devices is a learned skill. By the time you are at maximum fill of conductors and devices, per the NEC, you have got one of two possible outcomes. Either the conductors are properly spliced, and neatly folded and shaped in the box, with the devices in their proper positions, and ready to be screwed tight, without twisting, racking or straining, or................... you have a rat's nest of shit, and the clown installing it needs to smash it all into the box and try to get everything contained by quickly screwing the receptacle in. In your case it was done by a clown, and you incorrectly gave him slack by thinking that his folding, kinking and eventually shorting the conductor against the box was just unavoidable. Your claim that a kink in the wire may be the fault doesn't ad up. Individual copper conductors are amazingly resistant to bending stress failure. They are specified as "soft drawn" and it can take hundreds of cycles of kinking and straightening before they physically fail. As for an electrical failure due to a kink, they happen, but on much larger wires, at voltages in the thousands of volts, not what you find in residential wiring.  When it comes to any connection in residential wiring getting so hot that it melts the insulation, there are bigger issues here than whether it was wired with a #14 instead of a #12.  The overcurrent protection on the circuit would limit the draw to a maximum of 20 amps +/- a small percentage. There is simply no way in hell that a sub-20amp load,  on a perfectly functional and properly installed outlet, would generate enough heat to melt insulation. You claim you have seen it more than once. Absent loose connections, Aluminum Romex, or other obvious issues, I have never seen a situation exactly as you describe in thirty years in the industry. Bottom line, there is more to it that you may have noticed. Possibly an internally defective receptacle, a failing breaker, or some other issue.

Again, I am not in disagreement with you. However, the reality is that in my experience 90% of professional electricians don't neaten up wiring in boxes as you describe. Whether it is poor workmanship or just the standard in the majority of the industry is up for debate.

paddedhat

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Re: Electrical Question - Open circuit
« Reply #26 on: June 03, 2016, 04:50:34 PM »

Again, I am not in disagreement with you. However, the reality is that in my experience 90% of professional electricians don't neaten up wiring in boxes as you describe. Whether it is poor workmanship or just the standard in the majority of the industry is up for debate.

Nope, I wouldn't spend a moment defending, or debating the qualifications of most residential grade electricians. In my area, most either picked up the trade from what they learned from dear old dad, or uncle, and the balance were hired as helpers, and one day magically elected themselves to the position of "electrician". I just had a PM conversation with a member here, regarding stab wiring of devices. For many decades the code said that you could not rely upon a device to maintain the continuity of a circuit. So each conductor in a circuit would have to be spliced to a tail that fed an outlet. This was, and is, widely ignored, since far too many electricians lack the skills to successfully do a few hundred wire nutted splices in a single family home, and not create an unreliable mess. So the trade has devolved into a bunch of Romex monkeys, who avoid doing anything that requires any real skill, and need to be able to use push wired devices to get the job done. Hell, my local supply house now carries huge canisters of the push wire connectors that allow a monkey to "splice" four or five conductors by just stripping them, and pushing them into the holes of the little plastic cube. No skill, or wire nuts required, LOL.

 Not that any of that is a surprise, our society places little value on skill sets, or craftsmanship. A couple of times, while running large electrical projects, I had "carpenters" sneak into my job trailer to ask me to lay out stairs for them.  Four years of apprenticeship school and they didn't have a clue where to start. I have an older friend in the trucking industry who is astounded by the number of big hauling companies that are now ordering fleets of over the road tractors with automatic transmissions, because they can not find qualified drivers who know how to shift a manual.

 My son is an engineer in the oil fields. He makes a good living designing and manufacturing equipment that is nearly "idiot proof", since a big issue in the industry is having rig hands that could break an anvil with a rubber mallet, and can turn a new, rented,  $50K vacuum pump into a useless pile of metal in more ways that you can dream of.  He builds stuff as simple and rugged as possible, installs sensors and kills switches to shut it down before the help can successfully blow it up, and covers it with warning stickers that cover the most common ways that the machine has been destroyed by previous monkeys.

I know by this point I'm ranting, and sound like the crotchety old neighbor screaming, " get off my lawn", but  the decline is the skilled tradesman in this country is a serious issue.  As we do everything from letting millions of underpaid illegals become a dominate force in our trades, to trying hard to make sure that every kid ends up with a four year degree, regardless of their suitability for one, we are creating a crisis, and there will be a heavy price to pay down the road.

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Re: Electrical Question - Open circuit
« Reply #27 on: June 03, 2016, 07:10:47 PM »

Again, I am not in disagreement with you. However, the reality is that in my experience 90% of professional electricians don't neaten up wiring in boxes as you describe. Whether it is poor workmanship or just the standard in the majority of the industry is up for debate.

Nope, I wouldn't spend a moment defending, or debating the qualifications of most residential grade electricians. In my area, most either picked up the trade from what they learned from dear old dad, or uncle, and the balance were hired as helpers, and one day magically elected themselves to the position of "electrician". I just had a PM conversation with a member here, regarding stab wiring of devices. For many decades the code said that you could not rely upon a device to maintain the continuity of a circuit. So each conductor in a circuit would have to be spliced to a tail that fed an outlet. This was, and is, widely ignored, since far too many electricians lack the skills to successfully do a few hundred wire nutted splices in a single family home, and not create an unreliable mess. So the trade has devolved into a bunch of Romex monkeys, who avoid doing anything that requires any real skill, and need to be able to use push wired devices to get the job done. Hell, my local supply house now carries huge canisters of the push wire connectors that allow a monkey to "splice" four or five conductors by just stripping them, and pushing them into the holes of the little plastic cube. No skill, or wire nuts required, LOL.

 Not that any of that is a surprise, our society places little value on skill sets, or craftsmanship. A couple of times, while running large electrical projects, I had "carpenters" sneak into my job trailer to ask me to lay out stairs for them.  Four years of apprenticeship school and they didn't have a clue where to start. I have an older friend in the trucking industry who is astounded by the number of big hauling companies that are now ordering fleets of over the road tractors with automatic transmissions, because they can not find qualified drivers who know how to shift a manual.

 My son is an engineer in the oil fields. He makes a good living designing and manufacturing equipment that is nearly "idiot proof", since a big issue in the industry is having rig hands that could break an anvil with a rubber mallet, and can turn a new, rented,  $50K vacuum pump into a useless pile of metal in more ways that you can dream of.  He builds stuff as simple and rugged as possible, installs sensors and kills switches to shut it down before the help can successfully blow it up, and covers it with warning stickers that cover the most common ways that the machine has been destroyed by previous monkeys.

I know by this point I'm ranting, and sound like the crotchety old neighbor screaming, " get off my lawn", but  the decline is the skilled tradesman in this country is a serious issue.  As we do everything from letting millions of underpaid illegals become a dominate force in our trades, to trying hard to make sure that every kid ends up with a four year degree, regardless of their suitability for one, we are creating a crisis, and there will be a heavy price to pay down the road.
Mike Rowe, is that you? :P

Syonyk

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Re: Electrical Question - Open circuit
« Reply #28 on: June 03, 2016, 07:29:25 PM »
^^ Mike Rowe raises very valid points.

I hadn't seen the "push joiner" things until I dug into some switchboxes in my new house.  They're certainly common.

On the plus side, I've got 20A and 12 gauge everywhere. :)  Cheap upgrades from the factory!

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Re: Electrical Question - Open circuit
« Reply #29 on: June 06, 2016, 06:22:14 AM »
FYI, I did some more testing and found the problem yesterday.

The light switch/fan box in the upstairs bathroom contained five different hot wires all screwed together and one of them had fallen out of the wire nut that was used to fasten them.  This probably happened because there were so many wires in the box that you couldn't easily put the switches back without pushing really hard and putting pressure on everything.  I shortened the wires, used a larger wire nut (the one in the box was too small and didn't cover all the wires), and everything is working now.

Thanks for the advice!

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Re: Electrical Question - Open circuit
« Reply #30 on: June 06, 2016, 12:11:50 PM »
Awesome!

And sort of proves the point of the "comedy bill" you see from professionals every now and then:

Wire nut: $0.25
Time to install wire nut: $5
Knowledge needed to find where to install the wire nut: $294.25.

Cyaphas

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Re: Electrical Question - Open circuit
« Reply #31 on: June 06, 2016, 04:11:50 PM »
Awesome!

And sort of proves the point of the "comedy bill" you see from professionals every now and then:

Wire nut: $0.25
Time to install wire nut: $5
Knowledge needed to find where to install the wire nut: $294.25.

I've been on the otherside of this. Insurance, truck insurance, bonding, fuel, vehicle, vehicle maintenace, tools, tool upkeep and maintenance, schooling/certifications/dues, drive time too/from location, drive time to/from parts locations, GOOD HELP, LIABILITY, advertising, call center fees.... $300 for 1/2 of a professional's day is pretty reasonable.