In home wiring, the color black is "hot," white is "neutral," and green or a bare wire is "ground." If you were to look inside a breaker panel, the neutral and ground are both tied to common tie-in strips, usually attached to the back of the panel. Because ground and neutral are electrically tied together, inexperienced laypersons mistakenly conclude they are the same circuit. In reality, they are not. Neutral normally carries current, whereas ground should never carry current. According to accepted wiring practices, neutral and ground should never be intermixed. Doing so invites a variety of dangers, up to and including electrical fires. If you suspect a neutral-ground reversal, have the electrical system checked out by a licensed or qualified electrician.
Breakers are designed to trip when a short happens between hot and neutral. The purpose of the ground wire is to divert the momentary surge to the ground rod. If the ground and neutral are reversed, the voltage spike may be "backfed" to the breaker instead. The end effect is the breaker may be damaged internally, and it may not function properly the next time it has to.
GFCI Malfunction Danger
A Ground Fault Circuit Interrupter (GFCI) is a specialized type of breaker, found installed in wet areas such as bathrooms or around pools. When the breaker senses a voltage surge in the ground wire, it trips. Electrician Tomi Engdahl points out that since the ground should carry no current, the GFCI senses a voltage, and may trip constantly. Conversely, some GFCIs may not trip at all when they should. The end effect is that a severe risk of electrocution is present if the GFCI malfunctions when the critical time comes for it to work correctly.
Appliances, such as refrigerators, are designed to sense current on the hot and the neutral. The ground is internally wired directly to the chassis of the appliance. If the neutral and ground are reversed, electricity is backfed through the appliance chassis. The end result is the outside cabinet, including the handle, has electricity flowing through it. If you are standing on a damp floor barefoot, electrocution is a very real danger if you grab the metal handle.
Another effect is electricity backfeeding through the chassis, which is very hard on internal components, such as motors or compressors. As a result, the longevity of the appliance is severely reduced.
Ground Loop Danger
All the grounds in a home or building must have zero volts. If a neutral and ground are reversed in part of the building, grounds have voltages on them. This causes a ground loop condition. A ground loop is different voltage levels at different grounding points. Since some grounds have voltages, some appliances will not work correctly, particularly audio gear such as amplifiers. You may hear a constant buzz coming from the speakers. Also, ground loops are very hard on internal electronic components, which, over time, will eventually destroy sensitive electronics.
Electrical Fire Danger
Electrical fires are a very real danger when the ground and neutral are reversed. Dr. V. Babrauskas, lecturing at the Seventh International Fire & Materials Conference in San Francisco in 2001, described conditions that lead to an electrical fire. Babrauskas, citing extensive studies, detailed how a floating neutral or a ground fault leads to fires. A floating neutral is a condition in which the house neutral is not directly tied to the main neutral on the grid transformer. Overvoltage conditions develop between the transformer hots, leading to a house fire.
A ground fault is a defect in the grounding system. Babrauskas pointed out that because voltage is flowing where it should not, it can create sparks igniting flammable materials. Many older homes had the main ground wire tied to pipes, even natural gas lines. If voltage flows through a natural gas line, the sparks caused by stray electricity can ignite the gas.
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