If your electrical panel is full, but you need additional circuits, you can install a subpanel. A subpanel performs the same function as the main electrical panel.
Do you Have To Put A Ground Rod For A Subpanel?
A subpanel needs a ground rod because it protects your home by defending against surges that lightning strikes and short circuits cause. Lightning doesn’t have to strike your home to cause an overflow of electricity. It can hit the area near your home’s power lines. Grounding rods will also protect you and your home’s appliances from overvoltage.
A ground rod is exactly what it sounds like; a metal rod (Copper or copper-coated steel) that provides a ground connection to the main service panel.
The average ground rod is roughly eight feet long and ½ inch in diameter.
If you have a subpanel in a detached structure, you must install at least one ground rod.
It is equally important to run a ground wire between the main and detached structures. But if you have a main panel and subpanel in the same building, you can forego the rod. A ground wire is enough.
If you have experience grounding the main panel, you can apply your knowledge to the subpanel. Main panels and subpanels have several similarities.
But you have to check the rules before you proceed.
- What does your local code have to say about subpanels?
- Are the rules for grounding a subpanel similar to the regulations governing the main electrical panel?
- Does the local code have an opinion on subpanels in the detached structure compared to subpanels in the main building?
- What about the wire type and size?
As you can see, you must take several considerations into account before you proceed. You are better off leaving this work in the hands of a professional contractor. The last thing you want is to break the rules governing electrical installations in your region. Mistakes may earn you a hefty fine if you installed the subpanel and grounding rods in a commercial setting.
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How To Install Ground Rod For Subpanel?
Grounding a subpanel doesn’t differ that drastically from grounding the main panel. You can expect the following:
- Identify a suitable location for the rod. Remember that the rod must go eight feet into the ground when choosing a site. Rocky spots won’t do. You should also avoid places with pipes or wires.
- Make sure the location is convenient. You must run a grounding electrode conductor between the rod and the panel. Don’t dig any holes until you’ve planned the path the conductor will follow.
- Find a suitable grounding rod. The specifications will depend on your region. For instance, rods in the US must be at least 2.4 cm long and ½ inch wide.
- You can try hammering the rod directly into the ground. But it is much easier to dig a hole. You don’t have to dig all the way. Four feet is enough. After that, you can hammer the rod until it reaches the appropriate depth. Again, your location will determine the depth. In the US, the rod should be eight feet deep.
- Use a clamp to connect one end of the grounding conductor to the rod. Run the other end of the conductor to the ground bus.
If these instructions sound complicated, probably because you’ve never seen a grounding rod or a grounding electrode conductor, wikiHow has diagrams explaining this process. Better yet, hire a professional.
Don’t tinker with the subpanel unless you know what you’re doing. A subpanel needs a four-wire feeder with a grounding connector between the main electrical panel and subpanels. You don’t bond the neutral and ground in the subpanel.
Purpose of a Ground Rod at Subpanel
A grounding rod is part of the grounding system. The grounding system protects your home by creating a path for excess current to flow to the earth.
The rod is only relevant when a ground fault occurs. Electricity needs a path back to the source. Without a path to the source or ground, the current will pass through the equipment it is connected to, destroying sensitive electronic components.
It can also electrocute people and start fires. This is why grounding rods are so important. They add a safety feature to your electrical system. But they can only help you if you install them correctly.
You should also inspect them routinely. The rods are not immune to damage. They can freeze or corrode. Additionally, the ground wire can disconnect from the rod, compromising your home’s grounding system.
Grounding Rod – Attached VS Detached Structure
- If you have a subpanel in a detached structure, add at least one grounding rod. Some local regulations may encourage you to install two or more grounding rods depending on the conditions.
- If you added the subpanel to the main building, it doesn’t require a grounding rod. The ground wire is enough.
- You can run a ground wire between the main building and the sub-panel ground of the detached property.
Subpanel Grounding Requirements
- If you want to ground a subpanel in the main building, you have to separate the neutral and ground bars.
- Rather than grounding the subpanel’s neutral terminal, you join it to the panel’s enclosure using spacers.
- Make sure the subpanel has four wire feeders. Inspect older structures. They probably have three wire feeders. This configuration was prevalent in the past, but it is no longer acceptable.
- Connecting the ground and neutral wires in the subpanels if the facility in question has a grounding rod and you’ve gone ahead and bonded the rods to create a grounding electrode system (Detached Buildings).
- Separate the neutral and ground bars in a subpanel found in the building with the main electrical panel.
- You can use the main panel to connect the ground and neutral wires.
Don’t add a grounding rod without checking the local code. The electric code in some places wants consumers to secure a permit before they perform any significant electrical installations.
Some regulations prohibit consumers from installing electrical components unless licensed to perform such operations. In other words, they expect laypeople to hire licensed experts.
Therefore, even if you have the skill and experience, you must hire an electrician to install the grounding rod. Otherwise, you may incur hefty penalties.
You should also keep the basic requirements associated with ground rods in mind, including:
- In the US, ground rods should be eight to ten feet long.
- If the ground is too dry, you can reduce the resistance by stacking multiple ground rods.
- Your local code may ask you to install two rods for each panel. Keep these rods six feet apart.
- The ground wires should be coper (6AWG). You can use 4AWG conductors for 200 Amp services.
How Many Grounding Rods For A Subpanel?
You must install two ground rods per panel to pass inspection.
EC&M has further clarified this issue by pointing out that the NEC expects consumers to add a second ground rod if the ground resistance of the first one is 25ohms or higher.
Few electricians apply this rule. Most of them will install two grounds simply because the NEC says so. They won’t bother to measure the resistance.
Your local code’s regulations may differ from the NEC. Consult a local electrician. Local electricians understand the electric code that governs their area. They can advise you accordingly.
Most electric codes have nothing to say about the maximum number of rods allowed. In other words, you can add as many grounding rods as you want. No one will penalize you for the decision.
If you have two grounding rods, keep them six feet apart. This is the minimum distance. For the best results, you should maintain a separation of 16 to 20 feet.
If the distance between the rods is too small, they may interfere with one another because of their resistance. If their resistance overlaps, the net resistance will increase. This will make your grounding system less effective.
How Far Can A Ground Rod Be From Panel?
The NEC doesn’t say anything about the minimum distance between the grounding rod and the panel. Your decision will probably depend on the length of the grounding wire.
The NEC is just as silent about the distance between the grounding rod and the house. Your decision will depend on the obstacles in the soil surrounding your home. For instance, you don’t want to plant the rod in a location with wires and pipes.