Open Neutral: What It Means, and When It's an Emergency

An open neutral is one of the few wiring faults whose seriousness depends entirely on where the break is.

Short answer: an open neutral means the neutral conductor, the return path for 120-volt current, is broken somewhere. On a single circuit it's usually a loose or burned neutral at a receptacle or splice: the outlet stops working, and a plug-in tester shows its "open neutral" pattern. If the service neutral or the shared neutral of a multiwire branch circuit opens, 120-volt loads end up in series across 240 volts, so some lights go bright while others dim and equipment can be damaged. That second case is an emergency.

Generator manuals use "neutral" for a different question, whether the generator's neutral is tied to its frame; that is covered in generator neutral bonding.

What does "open neutral" mean on an outlet tester?

A plug-in tester checks for voltage between the three slots. "Open neutral" means it finds voltage from hot to ground but not from hot to neutral. The hot and the ground reach the outlet; the neutral path back to the panel doesn't.

Read the lights against the tester's printed legend; patterns differ by brand. Two limits:

• A tester draws almost no current. A neutral connection that is corroded or loose but still touching can read "correct" with nothing plugged in, then fail under load.
• It can't see a lost service neutral. The outlet's neutral is still tied to ground at the panel, so the light pattern stays "correct" even when the outlet has drifted to 140 volts. Only a tester or meter that shows the actual voltage catches that.

What causes an open neutral on one circuit?

The usual culprits:

• A loosened push-in (backstab) connection on a receptacle, especially one that feeds other outlets through its terminals
• A loose screw terminal or a failed wire-nut splice in a box
• A loose neutral at the panel's neutral bar
• A damaged conductor, such as a nail or screw through a cable

Because receptacles are daisy-chained, one bad neutral connection kills everything downstream of it on that circuit, while the hot stays live.

The neutral beyond the break is not safe to touch. With a lamp or appliance switched on anywhere downstream, that load connects the neutral to the hot, and the "dead" white wire sits at roughly 120 volts to ground. No current flows, so nothing works, but the voltage is there. If a receptacle on that run also has a bootleg ground, the same voltage lands on the ground pin and on the metal case of whatever is plugged in.

What happens when the service neutral is lost?

A home service is 120/240-volt split phase: two energized legs, each 120 volts to the neutral and 240 volts to each other. The neutral is what holds each leg at 120 volts no matter how unevenly the house is loaded.

Lose it, through a corroded connection at the service drop, the meter base or the main neutral lug, or a damaged underground conductor, and the 120-volt loads on the two legs are now in series across 240 volts. The voltage divides in proportion to load resistance: the lightly loaded leg gets more than 120 volts, and the heavily loaded leg gets less.

Illustrative example

Treat each leg's running loads as a fixed resistance, R = V² ÷ P:

• Leg A, 1,200 W: 120² ÷ 1,200 = 12 Ω
• Leg B, 300 W: 120² ÷ 300 = 48 Ω
• In series: 12 + 48 = 60 Ω, so current = 240 ÷ 60 = 4 A
• Leg A: 4 × 12 = 48 V. Leg B: 4 × 48 = 192 V

Two lessons. A lost neutral can hide while the loads happen to be balanced. And the moment a big 120-volt load starts on one leg, lights on that leg dim while lights on the other leg brighten, which is the signature.

Real loads aren't fixed resistors, and some current usually returns through the grounding electrode and metal water piping, so real swings are often smaller. The direction is the same. Loads that run on 240 volts only, like a water heater or an AC compressor, keep working normally because they don't use the neutral. For the wider question of lights that vary around the house, see flickering lights causes.

Open neutral on a multiwire branch circuit

A multiwire branch circuit is the same arrangement in miniature: two 120-volt circuits on opposite legs sharing one neutral. Open that shared neutral upstream of the loads and the two circuits are in series across 240 volts, with the same bright/dim split, but limited to the outlets on those two circuits. See what is a multi-wire branch circuit.

The shared neutral has to be spliced so that removing a receptacle doesn't break it (NEC 300.13(B)), and both hots need a means of simultaneous disconnect (NEC 210.4(B)).

What should you do right now?

For whole-house symptoms:

1. Switch off or unplug electronics and large 120-volt appliances.
2. If voltages are swinging hard, anything smells hot, or something has already failed, switch off the main breaker. See how to shut off power to your house.
3. Call the utility. The service drop usually belongs to them, and they can check their side. See who owns what on your electrical service.
4. Then call a licensed electrician for anything on your side of the meter, and have equipment that saw overvoltage checked before you rely on it.

Don't wait to see whether it settles. An intermittent neutral is a connection that is arcing or corroding.

What you can check safely, and what's electrician-only

Safe for a homeowner, from the outside:

• A plug-in tester at each outlet maps which outlets show an open neutral and where the dead run starts.
• Note which rooms are affected: one circuit, two interleaved circuits, or the whole house.
• Watch the lights when a big load starts. Run a microwave or hair dryer; lights elsewhere brightening points to a shared or service neutral.
• Check whether 240-volt appliances still run normally while 120-volt loads misbehave.

A tester with a voltage readout adds what a light pattern can't: whether the outlet is sitting near 120 volts or has drifted well outside the roughly 114–126 V band utilities design to under ANSI C84.1. One unit that does both:

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Electrician-only:

• Opening receptacle or junction boxes to find the failed connection
• Anything inside the panel, including checking and torquing neutral bar terminations
• The meter base and service entrance conductors, coordinated with the utility

Why is this electrician work?

The fix is always a connection remade inside a box, the panel or the meter base. On a service neutral, the conductors involved stay live even with the main breaker off, because they come from the utility ahead of it. On a branch circuit, tracing the failed splice means handling a neutral that can be energized through connected loads.

Standards and code reference

• NEC 200.2(B): the neutral's continuity must not depend on a metal enclosure, raceway or cable armor
• NEC 250.24: the neutral is brought to the service disconnect and bonded to the grounding system there, through the main bonding jumper in 250.24(B)
• NEC 210.4: multiwire branch circuits; 210.4(B) requires a means to simultaneously disconnect all ungrounded conductors
• NEC 300.13(B): on a multiwire branch circuit, removing a device must not interrupt the shared neutral
• NEC 110.14: electrical connections and splices; 110.14(D) requires listed torque values to be applied with a calibrated tool
• ANSI C84.1: the standard voltage ranges utilities design their service to

Code editions and local amendments vary. Confirm the adopted edition with your AHJ, and treat manufacturer instructions as governing wherever they are more restrictive.

Where to go next

• Voltage between neutral and ground
• Outlet not working: troubleshooting
• Backstabbed receptacles
• Breaker torque and loose connections

More in our wiring and home electrical safety guides.