The Dangers of Shared Neutrals: How To Avoid Being Shocked

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In today’s age of electrical work, shared neutrals are relatively rare. Most of us run an independent neutral with our phase conductors. But can you receive an electrical shock from a shared neutral even if the breaker is in the off position? In the latest episode of Electrician U, Dustin explores this topic to bring some light to the subject.

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As discussed in previous videos, electricity travels in loops to function. On a single pole circuit (120v for example) the flow typically leaves out on the hot wire, goes thru the load, and returns to source (usually a breaker) on the neutral conductor. In addition, in most current residential work, a single dedicated cable, comprised of one hot, one neutral, and one grounding conductor, is run for each separate circuit. So, when you shut the breaker off, there isn’t a chance to receive a shock on that circuit (on the load side of the breaker anyhow) since the loop is broken.
However, in past years, shared neutrals were fairly common. A shared neutral is where you have multiple hot conductors sharing the same neutral. This was done to save wires and therefore save money. However, there are dangers present when using shared neutrals. That being, even if you turn off the breaker for the circuit you are physically going to perform work on, that neutral conductor can still have current flowing on it from the other circuit. To combat this issue the NEC now requires us to install a multipole breaker (or place handle ties on the single pole breakers of a multipole shared neutral circuit) so you are made to shut off ALL the breakers involved with a shared neutral circuit. But this provision is a fairly recent change (within the past 15 years or so) and you can still find single pole breakers for a shared neutral circuit all throughout the country.
There are a few scenarios where you could receive a shock on the neutral conductor of a shared neutral circuit. If you left the breaker on but took apart the joint on the neutral drop in the box and touched the white wire headed to the panel and either of the other 2 white wires headed to the actual device, you will just be completing the loop itself! Another way to get an even worse shock would be to leave the breaker on, take apart the neutral joint, and then touch the 2 white wires headed to the devices themselves. By doing this, you are basically completing a 240v loop and will get a wicked shock!
The easiest way to avoid all of this would be to simply turn the circuit off that you are working on. And if you are working on an older shared neutral circuit with single pole breakers, then shut them both off! This eliminates the chance of having any voltage on the neutral. Another prudent thing to do is to test if with your meter. Test your meter on a known live circuit first, then test the circuit you are attempting to work on, then retest again on the live circuit to prove that your meter is operating properly. Another thing to consider regarding receptacles. The loop is NOT complete, so current CANNOT flow, until something is plugged in somewhere in that circuit. The loop is open at the device itself. Lighting on the other hand, is connected via the lightbulb itself (or the filament within the light bulb) so current will flow as soon as you turn the breaker and the switch on! Another thing to consider, is that current does NOT care about the color of the wire! So just because you are touching a white wire, doesn’t mean you won’t get shocked if you are doing something you shouldn’t be doing with it!! Always get your journeyman’s tips or advice before attempting to work on a circuit until you fully understand the exact scenario you are up against.
We hope this has been helpful in understanding a bit how one could get shocked by touching the shared neutral conductor even if the breaker is off. Is there a topic you would like to see discussed on Electrician U? Leave a comment in the comments section and let us know. Please continue to follow Dustin and Electrician U as we are constantly updating our content to assist our followers in becoming the best electricians that they can be

#electrician #electrical #electricity #dangers #shared #neutral #shocked

[davidwoodard]

Great video! Your statement that will stick with me from this day forward is "Electricity doesn't care about the color of wires".

[binkleyt]

Love that whiteboard addition to the videos -- super helpful to see things visualized like that with the fast changes (less clunky than a real whiteboard..writing, erasing, etc...)

[johnsaake]

one thing I was taught when taking apart joints is to break the hots, neutrals, then the grounds; and the opposite order when putting joints together. That and keep your boots on the ground and your idle hands off of metal boxes cans or cabinets. Both are good habits to form alongside not working energized whenever possible

[jasonirion]

You can melt that neutral wire like a candle if both positive wires are landed on the same phase. If they are loaded up double the amount of current is returning back on that neutral. The breakers won’t trip but that neutral will fail spectacularly. Maybe a video should be done on this because it is easy to make this mistake. Keep up the great work !!

[danhardhat]

Single pole breakers are allowed on exterior lighting circuits with a shared neutral [NEC 225.7(B)]. NEC recognizes the voltage drop benefits of sharing the neutral because typically long distances are involved with exterior lighting and they recognize the liability of loosing multiple exterior lighting circuits from a single short if multipole breakers were required. So, extra heads up when working on parking lots and street lighting.

[drband]

Great explanation. I came searching for why I got a shock from a neutral when the breaker for the circuit was off while installing a LED power supply in place of a light fixture. It was a shared neutral situation I found out here! Something new to watch for. Thanks for the info!

[HaffDeadFred]

Great thing for me to learn about, we just did a panel upgrade for a customer and the inspector wanted me to “handle tie” all ckt breakers that share a neutral and zip tie the neutral wires together to ID them

[perryallan]

Great explanation... I'm a homeowner who was taught by an electrician in my youth on how to wire houses and all kinds of electrical safety items - and went on to become an Engineer; but still do most of my own wiring.

Unfortunately I live in a 70 year old house (just a few years older than I am). While I have rewired the basement the plaster walls in the living areas are too nice to open up the walls and redo it.

In my past I have dealt with 2 houses with nob and tube wiring among family members.... Assume everything is live unless a test to ground confirms otherwise (and you might have to run a cable to a bathroom or the basement to have a good ground).

I rewired both of those houses starting with having an electrician install a new breaker panels and me doing all the work past that (and yes there were building permits and I was inspected multiple times).

Interesting story is that in one city the electrical inspector came in to inspect my brothers new large 2 car garage wiring which I had done for my brother. The inspector recognized me and said he was glad to see me as my work was always 1st class. In this case my brothers old original very solidly built 1 car garage had been moved a 100 ft or so down the alley to ladies lot who did not have a garage and there was only room on her property for a 1 car garage (reused the old garage). So this lady was really happy to get a garage for just he cost of a cement slab and anchoring my brothers old garage to the slab.

During the wiring inspection of my brothers new garage this lady came over and talked to the inspector about her desire to get her garage wired but could not afford the prices the electricians quoted; and did the inspector have any advice or options. The inspector asked her if she knew me to which she replied "of course - he's been helping his brother on his house with a lot of things." The inspector then told her that if she could convince me to do the work that he would approve it. Technically, he should not have done that. In my State a person can do their own wiring as long as proper permits and inspection is done. A person can assist an immediate family member as well. But my understanding in my State is that's where it legally ends. I thought it was a nice complement. She was happy even though she had to dig and fill in the trench for the underground service to her new garage.

[kkalafus]

The most basic question that I wish the video spoke to is, how do you know if there's a shared neutral? Inside my panel I saw red wires used for 120 v circuits. That caused me to trace where the wire was going, which was Romex that also had a black conductor from another circuit. I hadn't seen this before and ended up learning more about it on your channel. IMO it's crazy that shared neutral circuits are allowed in residential construction because over the life of a home, someone can easily rearrange things in the panel in a way that's unsafe. In one of my circuits, someone had put the red and black wires on the same phase and ended up with double current on the neutral, which was a fire hazard and had to be fixed. Our home inspection missed this issue.

[raymondsciara]

Awesome video. I want to take this opportunitty to say thank you Dustin for this great content in your channel. I passed my Journeyman test in August 2023. I would not have done it without your videos and all the help I got along the way from knowledgeable electricians that went out of their way to make sure I understood theory and field practices. I want to learn more stuff. I am currently working at an industrial work area. I am still a bit intimidated by the environment, but the experience I am gaining keeps me motivated. I have learned that failure is apart of the learning experience. I will never let past and future failures keep me from trying my best as an electrician.

[drewwassel]

One potential way you can get shocked from a neutral is if the breaker is off but there is a device with a large capacitor connected then it could energize the circuit

[csimet]

Great explanation, as usual!

I ran a new 2-pole 20A breaker with 12/3 dedicated line for my shop table saw, splitting the duplex 5-20R receptacle into 2x 120V 20A with the shared neutral. It is so I can upgrade it down the road to a 220V 20A simplex 6-20R receptacle when I upgrade my table saw from 120V to 220V. In the mean time, it provides the saw's 120V and an extra outlet for some lights until then. The key thing is it all ties back to that 2-pole breaker so both "legs" are shut off and never just the one. Hopefully this meets code... chime in if not please!

[christobaldaetz]

Back when I first started as an electrician, we ran a 12/3 for two circuits. But in the panel, we installed a two pole breaker. So that when you had to work on that circuit, you could do it safely. Now they make 12/2/2 makes it easier to deal with.

[phildegruy]

Super good video. It is good to instruct the helpers/apprentices to be very careful in old houses and make it a requirement to turn everything off at the main before working on any circuit where the neutrals will be broken apart. One for safety and two to keep from blowing random things in the house up from open neutrals. Bought an older house and discovered that every single 120v circuit in the house were ran in a loop of conduit (from and back to panel) with a junction box every 10'. The circuits had 4 neutrals total from the panel and every neutral was half ass twisted together as no wirenut would fit with a piece of tape for cover at every junction box. Honestly don't know why the house had not burned down.

[Ephesians-tsze]

I went to work for the state (TX) recently and it’s pretty common for the electrical contractors to share neutrals on new installations. I’m a maintenance electrician and I’m getting pretty frustrated with the crap they leave behind for us to deal with. There’s shared neutrals everywhere and an “anything goes” color code. In Austin it’s red, black, blue for low voltage and brown, yellow, purple for high voltage. But within Austin’s jurisdiction State jobs are not subject to AHJ. So some contractors do it by Austin code and others do it by everywhere else color code.

[Bobcat]

Several years ago I built a post and beam garage. I intended on doing a little woodworking and other projects. I was very busy and couldn’t find the time to wire it myself. I hired a seasoned electrician with a great reputation. I had already set the sub panel and pulled the cables. I explained that I wanted 3/4” conduit with metal boxes and GFCI receptacle on each circuit. I came home and found that he used 1/2” conduit and shared the commons and grounds and had not installed the GFCIs. I called him and he said, “The GFCIs were not necessary and that he was able to pull all the wires through the 1/2” conduit. I paid him and a few weeks later installed the GFCIs which wouldn’t work. After asking an electrical engineer, I found out that a GFCI meters between the neutral and the hot wires not the hot and ground. They shouldn’t be wired using a shared neutral.

[KameraShy]

Glad to see this issue is being addressed. I am in a 30's house where wiring is all in conduit. Everywhere they could, shared neutrals were used. When I added some circuits years ago, I just assumed this was standard practice, followed it and did not fix them. But somehow it just did not feel right. This was long before the days of the internet, YouTube and all the learning resources now available. I did go back and check the circuits. I actually made and kept detailed diagrams of the wiring because of how they mushed so many wires together in a single conduit run. They all seem to be on different phases. If I ever need to do more, I will run separate neutrals.

[AaronSchmid]

We installed multi-wire branch circuits on the west coast well into the 2000's. Once arc faults started being required in more areas is when we moved away from it.

So expect to see it in houses up to 2008+.

[barryomahony]

3:26 You could still get a mild shock from the upper white conductor if you touch it while grounded; a small portion of the return current will flow through you.

[kls]

When you're dealing with wiring of questionable installation quality something I started doing was to use a clamp on current ammeter or current probe whenever I came across commoned up neutral wires (such as multiple white wires in a wire nut) to solve the mystery . Before removing the wire nut and separating these mystery neutrals check each wire with the clamp on ammeter for presence or absence of current . If there is different current reads on each neutral wire you can compare the load current going out from each breaker and when you have a match mark the neutral wire with that breaker number then turn off the load breaker and verify both line and neutral reads go to zero amps . If two circuits both read the same current value add more load to one circuit to make them easy to distinguish between the two circuits.