Electrical System Grounding – Explained

Electrical system grounding is a way to help prevent people from getting hurt or killed, and property from being damaged when there is an electrical problem. It entails connecting all the metal objects in an electrical system, that shouldn’t be carrying electricity, to the ground. Yes, the ground you walk on when you are outside. These objects include metal boxes behind switches and outlets, electrical panels, electric motor housings, hot tub pumps, the metal parts on switches and outlets, and the frames of appliances like clothes washers, dryers, dishwashers, furnaces, air conditioners, carpet cleaners, and refrigerators. Without proper grounding, your electrical system can be a potential hazard.

What Homes have Electrical System Grounding?

Grounding electrical systems in homes began in the 1960’s. So any homes after that time should have a grounding system. Before that, grounding wires were not installed in the electrical cables that were run through a home. Retrofit grounding is possible in some cases but is not the subject of this article.

How Are Electrical Systems Grounded?

Your property’s grounding system is installed right along with the rest your property’s electrical wiring. Inside electrical cables there is a bare wire that is usually copper (sometimes aluminum). These bare wires make up the grounding system. To make your property safer, they need to be:

  1. Connected together inside every electrical junction box in the home.
  2. Connected to every metal box in the system.
  3. Connected to the round (usually bottom) opening on a regular electrical outlet. This is how grounding is provided for the chassis of what ever gets plugged into an outlet like tools, appliances, etc. If there are appliances that are directly wired into the electrical system, like a furnace or dishwasher, the chassis of those appliances are connected to the grounding system too.

Back at the main electrical panel, the grounding wires come together and are connected to a larger bare copper wire. This larger wire is connected to the actual ground in one or more of the following ways:

  1. Via a piece of rebar that was buried in the foundation of the home when it was built.
  2. Via a clamp that connects the grounding system to the main water line if it is a metal pipe. Some main water lines are plastic and won’t provide grounding.
  3. Via a grounding rod driven into the ground near the main electrical panel.

Note that the neutral wires, the ones covered with white insulation inside a main electrical panel, are also connected to the grounding system, but ONLY inside the main panel. This causes the neutral wires in a home to always be at ‘ground potential’. If neutral wires are ever connected to the grounding system other than in the main panel, it’s a problem. This is because in these circumstances the ground wire can actually be carrying electrical current all the time instead of only during an emergency.

Why Electrical System Grounding is Often Done Incorrectly?

Most of the time electrical system grounding components sit idly by doing nothing. This is because they only “do something”, meaning carry electricity, when there’s a problem. So, if someone installs grounding components incorrectly you won’t know until there’s an actual problem or someone knowledgeable inspects their work. This is why you only want a competent electrician to do electrical work in your home.

How Does Electrical System Grounding Protect People and Things?

To understand how electrical system grounding can protect people and things, let’s first look at a situation where there is no grounding system installed, or it’s installed incorrectly.

Let’s say that you have a refrigerator that has been working fine for years. But over the years, one of the wiring connections in the back of the refrigerator begins to wiggle loose from the small movements or vibration from opening and closing the refrigerator doors and drawers over time. Eventually this wire comes loose, on Thanksgiving day, and touches the metal chassis of the refrigerator, which in turn is connected to the sides and doors of the refrigerator. Since this wire is charged with electricity, now the sides and doors are charged with electricity. Next you go to get something out of the refrigerator and touch the metal door at the same time you’re touching the metal sink. This sink is touching the metal faucet, which is touching metal water pipes, which are touching the earth as the pipes come into the home from the city water main underground. All of a sudden there’s a complete electrical circuit and your body is a part of it. You get shocked, your hair starts to sizzle, you fall to the ground. Maybe you live and maybe you die, but either way it’s not a good situation! You’re either in the hospital or being buried over Thanksgiving weekend.

Now if this refrigerator was properly grounded, when that charged wire inside broke loose and touched the grounded chassis, too much electrical current would flow through the circuit breaker in the electrical panel and it would trip, cutting off electricity to the refrigerator. Now, when you go to open the refrigerator while touching a nearby sink you would look inside and the light would not come on. You may notice that the food is not as cold as it should be. But you’d still be standing, alive, and capable of handling the problem at hand. The refrigerator is not working, we need to get it fixed or replaced ASAP so all our food does not rot. But even if the food rots, you’re still alive to tell your friends the story of your refrigerator dying during your preparations for Thanksgiving dinner, instead of them telling the story of going to your funeral during the Thanksgiving holiday.

How Grounding Protects Computers, TV’s and Other Electronics

To protect computers, TVs and other electronics from electrical power surges, from lightning for example, they need to be plugged into a surge protector. A surge protector monitors the electricity moving though the circuit and if there is too much it will send some of that energy to the ground. In order for surge protectors to work they need to be plugged into a grounded electrical outlet. So if the outlet isn’t grounded, your surge protector can’t do its job.

I hope this article has convinced you that electrical system grounding is important even though it does nothing most of the time. I hope it also convinces you to have wiring in your home done by a professional electrician.

Be well, stay safe, stay alive!

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