Why do my outlets show reversed ground and neutral?

Question

Suddenly my house (built in late 60s) has a circuit that all the outlets have tested (with 3 light Klien Tester) have ground neutral reverse code.

Steps Taken:

1. replaced all 6 outlets and 1 switch on the circuit.
2. Replaced 15amp breaker in the box
3. Tested voltage at the breaker in the box across hot to neutral (120V)
4. Tested Neutral to Ground at 1st outlet upstream on the circuit (120V)
5. Disconnected all outlets after first on that circuit (still Ground Neutral reverse).
6. Tested all other outlets in house with breaker with affected circuit off and no other outlet is off.
7. Tightened all neutrals on the bus bar in the box.
8. Shut breaker for circuit off had a beer.

After much research I think I understand I have a loose neutral AND a load that would give me that ground neutral reverse error on a tester. It just confuses me that the only outlet connected now is the 1st and I still have the error. Could it be a bad panel ground? A broken neutral between the box and outlet 1? (Doesn't make sense since I it would give me open neutral then.)

Answer 1

The labeling on those testers is meaningless, wrong, and wildly misleading. We see novices waste hours on indications that simply are not so.

They're so wrong because they are tuned for wiring mistakes in new construction, not wiring failures in old work.

What is more useful is the 3 lights. The center one connects hot-neutral. The red one connects neutral-ground. The yellow on the end connects hot-ground.

When a neutral wire breaks, if there are any loads on the far side of the break, that means hot and neutral will be connected to each other via the load. That will float neutral up to 120V on the far side of the break. This will extinguish the center lamp and light the outers.

Answer 2

The magic cube testers don't accurately diagnose every fault. I suppose they're somewhat reliable when they indicate "all's well" but I'm not entirely certain of that. Since you have a volt meter, rely on that.

The measurement of 120 V from neutral to ground at the 1st outlet upstream on the circuit tells most of the story: either the neutral or the ground is open, meaning not continuous to the main panel. I'll guess that it's more likely the neutral is the one with the fault.

Get a 3-wire extension cord and plug it to an outlet on some other circuit, then bring its end near the 1st outlet on the circuit under test. Confirm that the extension cord is correct: 120 from line to neutral; 120 from line to ground; just a few volts (near zero) from neutral to ground.

Next measure voltage between the extension cord and the test outlet. Line to line should be near-zero or near-240. Neutral to neutral should be near-zero. Ground to ground should be near-zero.

If the line-to-line is wrong then add "line-neutral reversed" to your list of potential problems. If neutral-to-neutral is wrong, but line-to-line was right, then you've got an open neutral. If ground-to-ground is wrong then there is more wrong than can be reasonably fixed through the internet..

Answer 3

Those testers are pretty unreliable.

Really at this point the best tool you can use is an clamp on ammeter. Put a significant load on the circuit, then at the panel clamp the black and white to check for equal numbers, and clamp the ground to confirm no (or minimal induced) current on the ground.

If numbers don't line up then I would suspect you may not have identified the actual first device, or somebody overdrove a staple and pinched the white to ground.

Answer 4

This can happen if the connections have been switched at supply. This happened a few times in my house as novice electricians would connect the hot wire from the utility provider to the neutral terminal on the meter. I remember one instance where the utility company had misconnected the wiring from their end. It can be hazardous as switching off appliances will still feed them power and any leaked earthing will complete the circuit.