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AC Neutral - Maximum Voltage referenced to earth

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mrmain

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What is the maximum voltage that would normally be experienced (with reference to earth) on AC Neutral in a 120VAC system?
 

BradtheRad

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You might measure a volt or two when a heavy load is on the circuit.

This is due to there being a fraction of an ohm resistance in the neutral wire.

Say you have 40 feet of 14 gauge in the wall going to the breaker box. That makes 1/10 ohm.

Using Ohm's law this means a 15A load would cause 1.5 VAC to appear on the neutral wire (as referenced to the earth).

The volt reading will be more if your wiring uses thinner gauge wire, or has long cable runs between the breaker box and your appliance.

A bad connection anywhere in the neutral will have the effect of raising resistance, and you'll get higher voltage readings. This can be serious since a fire may result.
 

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