Dear Mr. Electrician: I recently hired an electrician to fix something in my very old house. He told me that the electrical service to my house did not have a good grounding electrode system and gave me a ball park price to fix it up. Why do I need this and what is involved with fixing or installing a grounding electrode system?
Answer: The primary function of the grounding electrode system is voltage stabilization and lightning protection. The power company has their power transformer grounded with a ground rod. If the neutral conductor from the transformer to your house ever got disconnected, the return current would travel through the earth to get back to the transformer. When lightning strikes on or around your house the ground rod creates a path for the high voltage electrical charge to go directly to the earth and avoid causing damage to your home. Very important to have this installed and functioning properly!
The grounding electrode system consists of a wire or two that originate on the grounding terminal in your main electrical panel or disconnect switch. From there the wire(s) will connect to the home’s water pipes and to one or more grounding electrodes. The grounding electrodes can be ground rods, concrete encased rebar, copper plates, copper wire in the footings, concrete embedded steel or other means that provide an approved electrical path to earth. NOTE: Text links below go to applicable products on Amazon.com
Components of The Grounding Electrode System
The main grounding electrode connection for many houses is at the metal water pipe at the point where it enters the home before the water meter. Look at this area and you should see a copper or aluminum wire; bare, insulated, metal armor jacketed, enclosed in conduit, or taped green. It should be connected to the water pipe using an approved ground clamp usually of bronze construction. The connection should be tight and free of corrosion. If the ground clamp and wire appear corroded or feels loose you should remedy this right away. A new ground clamp costs only a few dollars and can be purchased at any electrical supply company and at many home improvement stores. You will also need some emery cloth or sandpaper to clean the pipe. A good precaution when doing this would be to shut off the main circuit breaker or pull the main fuse in your electrical panel. It is possible that a tiny amount of current may be traveling over your grounding conductor. I also suggest wearing gloves and avoid touching the bare wire and the water pipe at the same time.
If your home gets its water supply from a private well or through a plastic pipe, your primary ground connection may be a ground rod or two. In many cases the ground rod(s) are completely buried and therefore are not easy to inspect. According to published data, a copper plated ground rod can have a life expectancy beyond 40 years. However when working on customers homes and other buildings I have discovered, loose ground rod clamps, incorrectly installed ground rod clamps, ground rods that have not been driven fully into the earth, cut grounding electrode conductors, ground rods that have been damaged from landscaping and construction excavation, and short galvanized pipes driven in the earth instead of an approved ground rod.
Something to consider at this time is upgrading your grounding electrode system to the latest “National Electrical Code” requirements. The current code requires that new installations have at least one supplementary ground rod installed and to also have all interior metal piping connected (Bonded) to the grounding electrode system.
In some jurisdictions the requirement to bond the interior gas pipes has been waived. Check with your local electrical inspector for the correct procedure regarding article 250.104 (A) and (B). A bonding jumper wire is also required from one side of the water meter to the other side to maintain ground continuity on the metal pipe if and when the water meter is replaced. Read article 250 in the latest edition of the “National Electrical Code” for all of the requirements.
Upgrading Your Grounding Electrode System
To bring your house up to today’s standards you will need the following: Five, six or maybe more ground clamps suitable in size and compatibility with your water pipes, gas pipe, heating pipes, and any other interior metal piping, two 5/8″ x 8’ copper clad ground rods, two acorn style clamps for connecting wire to the ground rod #6 or #4 copper wire bare or insulated, 3/8″ one hole straps, an approved connector for the grounding conductor, green electrical tape if using insulated wire, a ground bar for the main electrical panel if there is no available empty slot for a large wire, an “Intersystem Bonding Termination” and suitable staples for fastening the ground electrode conductor wire.
Additionally you will need the following tools to facilitate the installation of your upgraded grounding system: Claw hammer, 3-pound or heavier hammer to drive ground rods, emery cloth or sandpaper, flat head screwdrivers, and heavy duty wire cutters or lineman pliers, an adjustable wrench, and a six foot ladder. You may also need a drill and drill bits suitable for drilling through floor joists, a hammer drill and masonry drill bits to drill into masonry, and a flat metal file. A rotary hammer with a ground rod driver attachment will make the driving of the ground rods much easier and quicker. An alternative is a 35 or 40 pound jack hammer in which the ground rod can be inserted directly into the bit holder. The ease at which the ground rod goes into the ground is determined by soil conditions.
The most difficult part of this job is driving the ground rods. Although one ground rod is the minimum standard set by the “National Electrical Code”, two are often required due to soil conditions. Soil resistance varies across town, county, and state lines. Without expensive detailed testing of your soil, there is no way to determine if it has a low or high resistance to electrical current. Therefore to be on the safe side it is better to drive two ground rods. Eight foot ground rods should be installed no less than sixteen feet apart for optimum performance, and there is no maximum distance restriction. Ten foot rods should be at least twenty feet apart. Please note that the “National Electrical Code” minimum requirement for ground rod spacing is six feet.
Start by choosing an area outside near your electric meter that is free of underground electric, water, gas, telephone, oil, and any other utility lines. Call 811 to arrange a markdown of the area if you suspect underground utilities are in place. Try to stay close to the house but at least a foot away to avoid contact with the concrete footings. Keep in mind that you will need to run a wire from the ground rods to your main electrical panel. You should plan on how you intend to do that before proceeding further. Generally speaking the ground rods would be driven straight down into the earth with the top being slightly below the surface. A continuous #6 or #4 wire would be run from one ground rod to the other without cutting or splicing and then directly into the main electrical panel. If your main electrical panel is in the basement, then you will need to drill a hole slightly larger than the wire (7/16″ -5/8″) into your foundation wall or into your siding near where it meets the foundation.
Dig a hole approximately one foot deep for the insertion of each ground rod. The holes should be one to two feet away from the foundation to avoid contact with the concrete footings of your house. Then dig a connecting trench close to the foundation between the ground rod holes. The trench is to facilitate the connection of the un-spliced continuous grounding electrode conductor from ground rod to ground rod and then to the main electrical panel. Alternatively you can run a wire from each ground rod directly to your main electrical panel (As per 250.64(F)(2). You could also attach the wire to the side of the house. The copper grounding electrode wire should be no smaller than #8.
Take one of the eight foot ground rods and insert the pointy end into one of the holes that you have dug. Stand on a ladder and hammer it down into the earth using a 3 pound or heavier hammer in one hand while holding the ground rod with the other. An assistant would be good for holding the rod as it tends to move around and vibrate. It will probably go in easy at first, but after a while it only sinks in a very short distance with each hammer blow. This would be a good time to have a rotary hammer with a ground rod driver attachment or a jack hammer. After you have one ground rod driven, proceed to the next one.
Once the ground rods are slightly below the surface of the earth you can attach the copper wire to them using the acorn style clamps. Depending on the circumstances it may be easier to start from the main electrical panel’s location and run the wire to the ground rods from there. Run the wire through the trench to the ground rods and put it through the acorn clamp with the wire between the clamp and the rod. Do not put it between the clamp screw and the rod. I usually strip 4″ – 6″ of insulation off and double the wire over to make good contact with the rod. Bring the wire into the house through a small hole in the foundation or siding and continue on to the main electrical panel. If you are running this in a basement and need to cross some joists, you should drill small holes in the center of each joist and run the wire through the joists instead of under them. The wire should be secured every 3′ – 4′ using cable staples if you are running it on the side of a wood joist. If you are using insulated wire, though not required it is a good idea to wrap green electrical tape around it in a few visible areas so.
The final connection is inside the main electrical panel. Bring the grounding electrode conductor into the electrical panel through a 1/2″ trade size (7/8″ actual) hole using a connector approved for the grounding electrode conductor. Sometimes the inspector will accept clamp type metal 3/8″ squeeze connector or a plastic strain relief button. Each wire must be terminated in it’s own termination screw. If there aren’t any available screw terminals, then you will need to add a terminal bar in the main electrical panel. After marking, drilling, and tapping two holes (Usually 8/32), screw the additional ground bar directly to the metal enclosure of the main electrical panel using fine thread machine screws.
Other Utilities Grounding
An update In the 2014 “National Electrical Code” article 250.94 requires an “intersystem bonding termination”. Basically a means must be provided for other utilities such as telephone and cable TV to attach their own grounding conductor. This must be located near the electric meter. Several manufacturers have products available to easily meet this requirement by merely attaching it to your grounding electrode conductor and fastening it to an outside wall or the electric meter. When installing your grounding electrode conductor leave a 8″ – 12″ loop in the area of the electric meter for this terminal block to be installed later.
To fully protect your home against lightning it is imperative that the cable TV service and the telephone service be bonded to the grounding electrode conductor. Use a #10 copper wire to connect the cable TV at its entrance point. There is usually a screw terminal on the cable splitter or termination point for grounding purposes. The telephone demarcation point or box should also have a grounding terminal. Look for a green screw or a lug. If you have a satellite dish antenna it should also be bonded to the intersystem bonding termination as should any roof mounted TV antenna.
Lastly a bonding jumper must be installed between your hot and cold water metal pipes using water pipe ground clamps and a piece of #6 aluminum or #8 copper wire. This can be done at any point along the piping system, but is commonly connected at the water heater so that the electrical inspector can see it.
Bonding to the ground rods is necessary to prevent lightning damage to your home. Lightning wants to go to earth, but sometimes things get in the way and are sacrificed. By providing a good solid path to earth via the grounding electrode conductor and the ground rods, you are minimizing the damage that could occur. The lightning strike that does damage may not hit directly on your home. It could hit a telephone pole across the street and travel down the utility wires until it finds a path to earth.
An additional enhancement and level of protection can be made to your grounding electrode system by the installation of a whole house surge protector. This gets wired directly into your electrical panel and is connected to a dedicated two pole circuit breaker. You can read my post about surge protectors here.
Click here for my photos of grounding and bonding for TV, Telephone, and Power.