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Alternating current (AC)  Diagram

Ground Fault Protection

There are two major reasons for ground fault protection on electrical circuits.

  1. The equipment grounding conductor (EGC) on electrical tools, appliances, and electronics provide ground fault protection on metal parts. This should eliminate the chance of an electric shock during the event of a ground fault.
  2. An EGC will provide a good ground fault return path to the electrical panel so the circuit breaker will immediately trip in the event of a ground fault.

Electrical ground is very important for the safety of electrical systems. New residential dwellings need to be grounded because of changes to the 1962 Electrical Code.

Ground and Neutral Definitions

(* Indicates NEC (National Electrical Code) 2014 Article 100 Definitions)

Ground - An electrical reference point that connects to the earth. Ground connects to neutral at one single neutral point on an electrical system measuring zero (0)volts.

Ground fault – This happens when an ungrounded conductor (line wire) comes in contact with anything that is grounded, (i.e. motor winding touching case, or line wire of appliance touching the metal frame.)

Grounded Conductor* - A system or circuit conductor that is intentionally grounded. (i.e. neutral conductor).

Grounding Conductor - Equipment (EGC)* - The conductive path(s) installed to connect normally non-current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.

Neutral Conductor - Is a conductor that carries current in normal conditions. It is connected to ground at the neutral point in the system. The voltage on a neutral conductor is 0 volts (or very close to 0 volts under load conditions). Warning: A neutral conductor can carry voltage on a live circuit when opened and be a shock hazard.

Ground on Electrical Cords

3-prong electrical plug

Electrical Ground

Difference Between Ground and Neutral Wire

A ground wire is not intended to carry current except under ground fault conditions. A neutral wire is intended to carry current as a return from line current. A ground wire (EGC) carries ground fault current to ground at the electrical panel.

The ground pin on this plug connects to the EGC inside the cord.

The electrical cord on tools, appliances, and electronics may have a three-wire plug with the EGC built-in to the cord. When there is a two-wire plug and cord, tool, appliance, or electronic device is properly insulated and does not need an EGC.

Extension Cords and Plug Adapters

A two-wire extension cord has no EGC or ground connection on the plug and socket. Never use a 2-wire extension cord or plug adapter on equipment with a 3-wire cord and plug. This would eliminate any ground fault protection.

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Ground on a Hard-Wired Appliance

When replacing a hard-wired appliance (like a dishwasher) in a dwelling that has ground, it is very important to connect the ground wire (EGC) to the new appliance frame. This connection is usually next to the line and neutral terminals on the appliance.

If a line wire came loose and touched the frame of a dishwasher, the EGC will provide a path from line voltage to ground at the electrical panel and immediately trip the circuit breaker on that circuit. If the EGC was not connected to the dishwasher properly, and a line wire touched the frame, the metal parts of the dishwasher would become energized, causing an electric shock.

Broken Ground Pin on Electrical Cords

Never use an extension cord that has a broken ground pin or an electrical device with a broken ground pin on the electrical cord. This will eliminate ground fault protection.

Homes with no Ground

Older dwellings may have been built before ground was required by code. The electrical system in some of these dwellings have been updated to include new wiring and an electrical panel with ground.

If your home does not have ground, you may want to get a quote from a licensed electrical contractor to update the wiring. If extensive remodeling is needed, it would be cheaper and easier to have the wiring updated at this time.

Difference Between AC and DC Ground

DC and AC grounds are different types of ground. AC ground uses the earth as its ultimate ground. DC ground is not connected to earth ground. DC ground is a common term for the negative (-) side of a DC circuit.

In most automobiles, the negative terminal of the car battery is connected to the frame and is often referred to as the ground connection.