By measure hot-neutral voltage, neutral-ground voltage and hot-ground voltage you room well ~ above your way to answering this questions:

Is the outlet wired incorrectly?Is the branch circuit too heavily loaded?Do sensitive digital loads have actually the voltage castle need?

These 3 measurements, every taken quickly at one outlet, administer you through a solid understanding of the building"s electrical supply.

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Testing a three-slot receptacle for grounding polarity

Incorrectly wired receptacles space not uncommon. A three-slot receptacle has actually a hot-slot (short), a neutral slot (long) and a ground connection slot (U-shaped). Room the warm (black) and neutral (white) wires reversed? are the neutral and also ground (green) wires reversed or shorted?

These problems can walk undetected for a lengthy time. Countless loads aren"t sensitive to polarity—they don"t care if hot and neutral room reversed. ~ above the other hand, sensitive digital loads such as computer equipment and instrumentation carry out care around a clean floor (a ground through no voltage and no-load currents on it). A solitary reversed neutral and also ground deserve to compromise the entire ground system.

So, what carry out you find?

Hot-neutral is the pack voltage. Voltage have to read about 120 V (typically 115 V come 125 V). You measure specifically 118.5 V.

Neutral floor is a voltage drop (also called IR drop) resulted in by load existing flowing v the impedance the the white wire. Let"s speak you measure 1.5 V.Hot ground deserve to be thought of as the source of voltage available at the receptacle. You read 120.0 V. You keep in mind that hot-ground is higher than hot-neutral. In fact, hot-ground is same to the amount of the hot-neutral and neutral-ground voltages.

Are these readings normal? Is the outlet wired correctly?

How to detect mis-wired receptacles

The most common mis-wiring wake up if hot and neutral room switched, or if neutral and ground are either switched or shorted. Exactly how do friend spot this conditions?

Measuring hot-neutral by itself does no tell friend if they"ve to be switched. You need to measure neutral-ground or hot-ground. If neutral-ground voltage is about 120 V and also hot-ground is a few volts or less, climate hot and also neutral have been reversed.Under load conditions, there should be part neutral-ground voltage - 2 V or a small bit much less is quite typical. If neutral-ground voltage is 0 V - again assuming that there is load on the circuit - then examine for a neutral-ground link in the receptacle, whether inadvertently or intentional.To examine if neutral and ground room switched, measure up hot-neutral and hot-ground under load. Hot-ground should be higher than hot-neutral. The better the load, the much more the difference. If hot-neutral voltage, measure up with pack on the circuit, is greater than hot-ground, then the neutral and ground are switched. This is a potential safety hazard and the problem should be repair immediately.

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Hot-ground reading need to be the highest of the 3 readings. The floor circuit, under normal, non-fault conditions, should have actually no current and therefore no IR drop on it. You can think that the ground link as a wire running ago to the source (the main panel or the transformer), whereby it"s linked to the neutral. On the receptacle end of the soil path, whereby the measure is gift made, the ground is not connected to any voltage resource (again, assuming there is not a fault). So the ground wire is prefer a long test lead ago to the resource voltage. Once there is a fill connected, the hot-ground receptacle resource voltage have to be the amount of the hot-neutral voltage (the voltage across the load) and the neutral-ground voltage (the voltage fall on the neutral all the means back come its connection to the soil circuit).