LETS TALK GROUNDING

By: Jonathan Z. Kremer

When someone mentions electrical grounding, what exactly are they talking about?

Grounding is defined by the NEC (National Electrical Code - US) as "a conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth."

Still confused? Don't worry. What follows briefly explains some aspects of grounding - what it is and why we have it.

WHERE IT ALL BEGINS

The earth has the ability to absorb or disperse an unlimited amount of electrical charge. This  makes it the ultimate electrical "ground". It was decided a long time ago that the actual earth we stand on will be considered 0 volts (often called "ground" or "zero" potential), thus providing a reference voltage level against which all other voltages in a system are established and measured. For this reason every structure or device using electricity is grounded by connecting it directly or indirectly to the actual earth.

HOW IS THIS GROUNDING DONE?

Grounding can be done in several ways. The more common types used in Israel are as follows:

Most new buildings employ a structural design that includes a concrete footing or foundation, which connects the building (or other structure) to the earth. Footings and foundations are typically constructed using concrete and reinforcing rods and/or bars for structural strength. These rods and bars are connected in such a way as to form a "grounding grid". If done correctly, this is one of the better forms of grounding a structure can have.

Another method of grounding consists of a set of grounding rods driven into the soil. These rods are highly conductive, and are used to ground a home or office. A whole system of these grounding rods can be used for a building or other structure, although the previous "foundation technique" is preferred. Sometimes these rods are used in conjunction with metal sheets or mesh.

In many of the older buildings the main cold water pipe (if metal) is used for grounding. Many homes have a ground wire attached straight to the main water pipe or to one of the metal pipes leading to it.

Even though the main water pipe usually makes for a good ground when done correctly, this is never-the-less one of the less desirable methods used for grounding. Due partly to the growing use of plastics in the plumbing field (pipes, fittings, etc), this method is opened to abuse and changing circumstances that can leave you in an unprotected state. It only takes one small plumbing repair using plastic material to break the continuity of the line, leaving you with no grounding and no protection. This can even happen without your knowledge. Also, using metal water pipes as grounding causes them to corrode quicker. This sort of grounding is not excepted by the Israel Electric Company anymore, and will not pass "test" except under very limited circumstances.

AND THE GROUNDING CONTINUES ON

Continuing on from anyone of the grounding methods mentioned above, the main grounding wire makes its way to your electrical panel (there may be grounding bars and other such things on the way, but these don't concern us at this moment), where it is connected to it's designated bus bar. This is now your "main grounding" bus bar.

Every electrical line running through your home includes (or should include) a ground wire. All these ground wires are connected one to another throughout your electrical system, and then work their way back to the electrical panel where they are connected to the bus bar together with the main grounding wire. These ground wires are not only connected one to another, but are brought to each outlet and light point in your home. This is how your appliances, and everything else in your home, are grounded.

OK. BUT WHY IS THIS GROUNDING SO IMPORTANT?

Scenario: You're living in an apartment that uses electric room heaters. One of your heaters has a "hot wire" which worked loose and is making contact with the metal body of the heater. Not knowing all this, you plug in the heater, fully touching the heater at the same time.

In the above scenario, if this heater was not properly grounded, its body would become electrified as soon as it was plugged into the wall socket. This could cause whoever touching it to get a severe, if not lethal, electric shock..

If the heater was properly grounded (and the grounding of the apartment was in working order), the circuit breaker would jump as soon as the heater was plugged in. The grounding system would have immediately directed the current to the earth. Not having much resistance, the amperes would soar, causing the breaker to jump quickly, preventing a dangerous situation from occurring.

Your life isn't the only thing that the grounding protects. A good ground system protects your electrical and electronic equipment. It will improve the reliability of your equipment and reduce the likelihood of damage as a result of lightning or fault currents.

Computers are very sensitive electronic devices, and commonly experience data corruption in non-grounded environments, as well as outright physical damage. This can easily happen at extremely low voltages. Even static electricity frequently damages many computer parts, which is why many computer technicians wear grounding bracelets before opening a computer.

CONCLUSION:

When working with anything electrical, safety should be your first priority. A good grounding is not only a very important and basic safety consideration, it helps protect your appliances, tools and electronic devices from damage as well.

Keep yourself and your family safe - make sure you have proper grounding in your home.