Grounding the Service

A word about grounding and bonding. At first, these two terms seem interchangeable but, although similar methods are used for both, they are technically different. To keep it simple, grounding is providing a path back to an earth ground whereas bonding is connecting two conductive items so that there can be no current or voltage flow between them. All grounds in your house eventually go back to the main service and, through the grounding electrodes, to the earth.
    In this section I will cover grounding the main service and bonding the required items to it. Grounding and bonding of other systems or parts will be covered in their respective articles.

Grounding Electrode(s)

The grounding electrode is the item that actually makes contact with the earth. There are several options for this in the NEC, but really only two main ones you will use in house wiring. In most new houses, when your foundation is framed and the re-bar installed, there will be a piece of re-bar stubbed up at or near the service location. This piece of re-bar is called a "concrete encased electrode" or informally a "ufer" (pronounced "you-fir") ground. If you do not have a ufer ground, you will need to drive ground rods. Check your local codes, but in most areas you need two 8' long ground rods driven at least 6' apart.

Grounding Electrode Conductor

The grounding electrode conductor is the conductor that connects the ground bar or lug in the service equipment to the grounding electrode. There are options here also, if you want to get technical, but for the purpose of simplicity, I'm only going to give you one. For your grounding electrode conductor, you will use #4 copper, it can be bare or insulated, stranded or solid. The reason I give only one choice is simple, it fits for any type installation I cover on this website!

Select the proper clamp

There are several clamp types that are approved for this connection. The most popular for use with a ufer ground is the two-piece clamp. The most popular used with ground rods is called an "acorn" clamp. Note: the ufer clamp can be used for ground rods also, but not all acorn clamps can be used for a ufer!

Attaching the acorn clamp

Your grounding electrode conductor must be continuous! This means you need to run the #4 copper from the service, through the first clamp, and to the second clamp without cutting it. The acorn clamp slides down over the top of the ground rod, with the wire resting in the "v" shape opposite the bolt, between the clamp and the ground rod. Then just securely tighten the bolt. Route your wires neatly and secure them out of harms way. The wire running across the ground to the first ground rod, and between the ground rods will need to be buried in a small trench or secured against the house.

Acorn clamp on ground rod

Attaching the ufer clamp

You only have one ufer, so keeping the grounding electrode conductor continuous here should not be a problem. Run the #4 copper from the service to the ufer, attach the clamp securely to the ufer and, using the set screw, secure the wire into the small hole in the clamp. Note: the connection to your ufer must be accessible, so if your connection is inside the wall, now is a good time to install an access ring so you don't forget it.

UFER clamp connection  UFER ground mud ring

Connecting to the service

If you are using a main-breaker panel type service, you will connect the #4 copper to the ground/neutral bar (in most panels, all the holes on the bar will accept up to a #4). If you are using a meter-main type service, you will connect the #4 to the ground/neutral bar in the meter-main cabinet. Both the panel and meter main cabinets usually have a small knockout in the bottom that is just the right size for the #4 copper, if you use this hole you don't need any other connector.

320A Service?

A special note for if you are using a 320A meter and two 200A main breaker panels:
In this situation, you will need to run a separate #4 copper to each panel. You can use the same ground rods or ufer for both panels, just install a separate clamp for each wire.

On to Service Bonding