12

Recently one wall of outlets quit working. Testing shows the hots are all good and the grounds are all good but the neutrals are all dead. They are all connected to each other but somewhere have lost the connection to the panel.

Can I add a neutral from another nearby outlet which will make these outlets work without tearing up the walls to find where the neutral has become disconnected?

21

No, you cannot do this. Assuming the nearby outlet you want to borrow neutral from is on a different circuit, you will be overloading its neutral. Even if it is the same circuit, it's very bad practice to leave broken wiring energized without fixing it -- what if it moves a little and reconnects just enough to arc? Then your house is on fire.

However, fixing this properly probably isn't as much work as you think. You most likely will not need to tear up your walls. Unless you recently drove a nail through a wire, the wire inside the walls usually doesn't just break. Rather, things usually go wrong at the outlets themselves. The so-called "backstab" outlets are especially prone to having the wires come loose over time. So the fix for this will involve pulling out each outlet in turn, making sure all screws, wirenuts, etc are tight, and ideally replacing any backstabs in the circuit. Most likely you'll find one of the outlets had the white wire come loose, and when you tighten it, everything starts working again.

  • 8
    The failure is usually at the last working outlet or the first non working outlet. In rare cases where nothing on the circuit works it can be in the panel. – Ed Beal Apr 3 at 18:44
  • If a breaker was tripping you might think about damage to the wire between boxes more (drove a nail into a wire, etc) but it would be hard for wire damage to result in only a broken neutral. Find all the outlets that do work and start checking them starting with the closest one to the broken outlet. – JPhi1618 Apr 3 at 19:01
  • 3
    That's true; most likely OP can get away with only checking only two outlets IF they know what order the circuit is wired in. However, I still recommend opening them all up since most likely they were all wired at the same time with the same techniques, and if one failed, the others might not be far behind. And that way you don't need to know the circuit order, which most likely OP doesn't. – Nate Strickland Apr 3 at 19:55
  • 2
    "wires come lose" should be "wires come loose" (not enough characters to edit) – Kat Apr 4 at 8:00
  • @EdBeal The 'nearby' outlet seems like a likely candidate. – JimmyJames Apr 4 at 20:37
15

Absolutely not. That sort of thinking works with safety ground, which does not ever carry current, except during a fault condition (and we hope there aren't 2 independent fault conditions occurring at once).

However, current flows in loops. Neutral is the normal "return half" of the loop, and it needs to be dedicated to this circuit. In fact, neutrals don't have fuses and rely on the circuit breaker on the hot side to protect the neutral. You can't have two circuits sharing a neutral, or you get this!

enter image description here


But there's another problem. This is AC power. It reverses polarity 100/120 times a second, which throws electro-magnetic force into everything around the wires. That's why transformers work. To keep that from causing a lot of problems, we require that all the current that goes out one wire comes back on another in the same cable or conduit. Among the wires, currents are equal and opposite, so their electro-magnetic forces cancel each other out.

Now, borrowing a neutral means current is now making a big loop - "out" (really, it's AC) this circuit's "hot" wire and returning via another circuit's "neutral" wire. That will throw EMF on both circuits, causing all sorts of mischief - eddy current heating, wire vibration leading to noise and metal fatigue leading to cracking and spot heating, etc. Nope.

Because of this, all practical wiring is done on a physical "tree" topology -- a branch may "split", but it may never "loop back" onto itself or another branch (except in one particular way, and even then, only in the UK where this is officially sanctioned).


Now, it can be hard to see when you're not practiced in a field. But this is most likely an easy problem. Wire breaks inside walls are rare. Wire problems are almost always at terminations of the cable run... And by definition, this must occur at either the last working outlet or the first failed outlet in the sequence.

As Nate discusses in his answer, backstab connections are the usual culprit. You're best changing it to a screw connection, but current Code advises using an $80 torque screwdriver, because "too loose" is more of a problem than "too tight".

If it's at the service panel, the neutral may go to a neutral bar, or a GFCI or AFCI breaker. Torque matters here too.

Lastly, if this diagnosis is given you by a 3-light tester, know that some of us call it a "Magic 8-ball" tester. It is made as a pass-fail device for new wiring e.g. During new construction. When troubleshooting old existing work, the legends can be wrong to the point of whimsical. The lights are useful; they save you the trouble of making 3 measurements with a neon tester.

  • Excellent answer as always. The only small quibble is that the cost of torque screwdrivers has come down significantly recently, and decent ones can now be had for ~$45. Though for regular outlets with Cu wire, I feel like "as tight as you can get it" with a regular screwdriver is fine -- it's probably a bit more torque than spec but the screw head will usually strip out long before the wire gets damaged. – Nate Strickland Apr 3 at 23:37
  • Another point I didn't see mentioned is if you bridge your neutral to another circuit derived from another phase of the mains in a multi-phase installation, the outlets will get a lot more than 120v! – Drunken Code Monkey Apr 4 at 2:57
  • @DrunkenCodeMonkey Oh, so true. I have an old factory with two 120/240 transformers and main panels right next to each other. I noticed the two had been initially setup to grab different 480 phases, but were moved to the same phase. As I got into the 120 wiring, I discovered the neutrals were crisscrossed in several places. Some circuits even grabbed any convenient neutral, even out of the wrong panel. SMH... – Harper Apr 4 at 3:58
  • Good answer. "Neutrals don't have fuses" is however not necessarily true. This depends on your local code. In general, just wanted to point out that the person asking (or other readers) might be from different countries with different regulations. – istepaniuk Apr 4 at 10:43
  • @istepaniuk I would be keenly interested in hearing about any country that fuses neutrals as a contemporary practice. Other than the Phillippines... There are good reasons to not fuse neutral. – Harper Apr 4 at 14:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.