Do I Need a Ground Rod For a Detached Garage?

Detached garages are a feature in many homes and they are also a popular, DIY construction project for those who want to expand their parking capabilities. However, a detached garage comes with its own culpability in terms of what it needs to meet the local building codes and NEC.

According to the NEC, if you have a detached garage, it has to have a grounding rod. In other words, if you have any power to the garage, whatsoever, it will have to have the appropriate grounding mechanism as well.

The NEC is pretty specific on it as well. According to code 250.32, “A building(s) or structure(s) supplied by a feeder(s) or branch circuit(s) shall have a grounding electrode system and grounding electrode conductor installed in accordance with Part III of Article 250.”

Running a Sub Panel to a Detached Garage

Because everything has to be termed in such a way that your passing pedestrian has no earthly clue what is being discussed, the term “sub panel” is just another, must-have, new name for a breaker box.

The kind of breaker box that you need for a detached garage is related to what you want to do in your detached garage. If you are looking at the 3-5 amps required for a garage opener, along with standard lighting, you won’t need anything super fancy and a 60A sub panel will do.

If you are planning on setting up a woodworking shop out there, a side business offering welding services, or you will just be operating a host of power-hungry equipment, you will need something a little more potent, such as a 100A sub panel.

Putting it Together

You will have to trench your way out to the sub panel from the main breaker box and use a 1 and ¼” PVC pipe to house the wire. The wire’s size is dependent on the type of sub-panel that you are using.

You want your trench to be about a foot and a half in depth. On the sub panel, you will connect your red wire to the main bus as well as the black wire, with the white wire running to the neutral bus.

Now, the green wire is going to be your grounding wire and it will go to the ground bus. Outside, you will need 2, 6’ ground bars, which should be placed as out of the way as possible while still remaining close enough to the sub panel that it doesn’t require a long stretch of wire to connect.

Simply run your ground wire from your sub panel to the ground rods outside, where you can wrap it around the ground bars and pound them into the ground. However, you should definitely check the sub panel with a voltage meter to make sure everything is on the up and up.

Placing Grounding Rods

Before you get started with grounding your sub-panel, you need to know what the grounding requirements for your sub-panel are. The size of the wires that you are running from the main breaker to the sub-panel and the types of wire.

You should have four wires to work with which are red, black, white, and green. If you happen to be looking at an existing sub-panel in a detached garage and it only has three wires, that setup is no longer valid with the NEC.

You also need to check with your local building codes because some of them may be different from what is required in the NEC. You have the grounded conductor for the equipment (the ground wire ‘green’), along with the grounded conductor, which is your neutral wire.

The two grounding wires have to be isolated and, when you have a look at your sub-panel, you will see that the terminal bar is insulated from the rest of the sub-panel. Now, the grounding wire, which should be a 6-gauge wire, has to have its own bar that is separate from the others in the panel.

The grounding wire will then run from the sub panel, through the wall, and outside. According to the NEC, the grounding wire, when connected to the two ground rods, must be installed to both of them in a continuous loop.

So, wrap your wire around your first rod, and run the remaining ground wire to your second rod (which should have a distance of 6’ between it and the first rod). The ground wire can be bare as it does not require any insulation. It simply runs from a bar inside of the sub-panel to the two grounding rods outside in a continuous loop.

Do You Have to Have a Sub Panel in the Garage?

If you want to have any kind of power in your garage, you will definitely need a sub-panel. Of course, the definition of a sub-panel is somewhat loose. Even if you would consider it to be a small breaker box, it is still, technically a sub-panel.

That doesn’t include a main breaker. If you place your sub panel in the garage, the NEC code doesn’t require you to have a main breaker built into the sub-panel. However, it is highly recommended if you appreciate the convenience.

If you want to control the power to your garage while you are in the garage, you will want the convenience of the main breaker. That way, you don’t have to go all the way over to the main panel to control the power in the garage.

It’s a bit of an extra headache but it’s far more convenient in the long run.

All Things Considered

For a detached garage that requires power, you have to have a sub-panel and it has to be properly grounded with two grounding rods. The rules on the grounding rods changed with the NEC, starting in 2008 and they’re likely to change again.

But for the present, if you are using a sub-panel to power a detached garage, it will have to be properly grounded as well.

Do I Need a Ground Rod For a Detached Garage?