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How To Install Subpanel In A Detached Garage: Solution In 8 Steps

It’s essential to keep sub-panels in the garage. But you’re worrying because you don’t know how to do it. Anyone can face this trouble. I understand it can be quite frustrating. 

How to install a subpanel in a detached garage?

You can install the subpanel by following 8 steps. To be safe, turn off the main power first. Then decide where you want the subpanel to go. One of the main steps is trench construction. Then you can set the subpanel box. You’ve to connect the wires in the final stage.

You’ll need precise directions to complete the entire process. And there’s this full article to walk you through the whole operation.

Curious to know? Then keep reading!

Know The Need for Subpanel 

You can use subpanels to extend the wiring for several branch circuits to a specific region of a home. Or to a building that is some distance from the main panel.

This is based on how much power you use in your garage regularly. You’ll need a 100-amp sub-panel if you’re using high-voltage equipment. Like welders and compressors. 

If you’re only completing a few little projects, a 50- to 60-amp subpanel will suffice.

But if you’re looking for some bigger projects, then you’ll need 400-amp service. This is a very rare case.

Now, Let’s see how you can install a sub-panel in your garage. 

How To Install Subpanel: Know It All

Installing a sub-panel is much easier if you follow the instructions attentively. You’ll find the entire technique here. 

You’ll need a few essential tools to set up a subpanel. You don’t need to buy anything if you already have it. Purchase a sub-panel box first if you don’t already have one. Check to see if all of the necessary tools are in the box.

Step 1: Choosing the Best Location  

Determine the placement of the subpanel before installing it on any side.

If you wish to install a subpanel in your garage, you’ll need to choose a location outside of it. Inside the garage, there is usually the main panel.

Step 2: Preparation

In your garage, you can ground the subpanel, but you must first build a 6-foot ground bar outside the garage. Then run the ground wire from the sub-panel to the ground rod.

Remember that your ground wire doesn’t need to be run through a conduit.

Follow proper safety measures when working with electricity, as you should whenever you operate with power.

Step 3: Turn Off The Main Power Panel

The next step for you is to turn off the main panel.

If you don’t close the primary panel or forget to close it in any way, you’ll be in danger. You must open the central panel before the sub-panel can be added.

You’ll get shocked if you begin working without first turning off the main panel.

The most critical step is disconnecting the main panel’s power supply.

Step 4: Trench Construction

The next step is to dig a trench for your outside electrical wire. 

You have to start by digging an 18-inch-deep trench for the wiring that will run from the main panel to your garage sub-panel. You can even dig the trench by hand without using any machine. 

If you’re running a 100-amp sub-panel, use a 1-1/4″ PVC conduit. If you’re running a 50-amp sub-panel, use 1″.

You’ll need to connect your circuit from the garage to your house’s main breaker. 

Before doing anything else, it’s a good idea to mark the breaker’s location.

Step 5:  Run The Cable

If you haven’t finished the concrete yet, you can run your cable down into the ground on the garage’s interior. 

To make it easier to tug the wiring through, utilize a 90-degree sweep connector instead of a pointy 90-degree connector.

If the concrete has been poured and allowed to harden within the garage, you’ll use a special route. 

Use a PVC LB access fitting to travel through the surface to where your sub-panel box and main panel box will eventually be installed.

While making use of this process, you’ll need good PVC fittings. Here are some affordable PVC fittings available in the market:

Product 1
Product 2

A quality fitting is actually a necessity. You can use it without any worries.

Step 6: Time For Subpanel Box 

Now that your wiring has been arranged out and connected to your home’s main breaker, it’s time to mount the subpanel box. 

Begin by fastening a 6-inch-larger-than-your-sub-panel piece of plywood to the wall where you’ll be installing the subpanel. This is your supporter, and it holds the sub-panel box in place.

Connect your circuit to your subpanel box after screwing your sub-panel box to the middle point of the backer.

Step 7: Connecting the Subpanel Box to the Wiring

When it comes to running the conduit wiring into the subpanel box, there is one item to bear in mind.

If your sub-panel box is 50 amps or less, use #8 THHN wire; if it’s 100 amps, use #2 THHN wire. You should know the right type of wire for your use.

Run the wire from your main panel into the sub-panel hold, then into your main panel box together with your red, white, black, and green wires. 

If you’re doing this while it’s cold outside, keep your wiring inside to keep it warm. There are no immediate concerns; they will become more challenging to work with.

Step 8: Connecting the Wires Together

While working within the subpanel, connect your black and red wires to the connectors. Which is on top of the panel wire’s main bus.

The neutral bus bar on the panel box, which usually is on the side of your main bus, will be connected to the white wire.

It would be best to attach the green wire to the bottom bus bar last. This is often the one that connects to the subpanel directly.

You’ll need to put the breaker on the main bus within the main panel box. Connect your black and red wires to the screws on the breaker that you can see. 

Similar to the sub-panel hold, the white wire will connect to the neutral bus bar and therefore the green cable to the bus bar on the bottom.

That’s it! You’re finished with the installation of the subpanel. If you can install an MDF subfloor, then you can install the subpanel as well.


Question: Is it necessary to have a main breaker on a sub-panel in a detached garage?

Answer: The main breaker does not need to be in an electrical panel, but one that protects the wiring going to the panel from the electrical utility’s transformer and the panel itself from overload is required.

Question: Is it possible to have a bus bar with both neutral and ground?

Answer: No, there’s no problem to mix grounds and neutrals on the identical bus bar. Suppose the main service panel is also where the grounded conductor is linked to the grounding electrode. 

Question: What is electrical double-tapping?

Answer: When an electrician connects two wires to one breaker or one terminal on a breaker, it’s referred to as a double-tap. Almost all breaker terminals are only intended to accommodate one wire.

Final Verdict

After a long discussion regarding how to install a subpanel in a detached garage, we’re finally at the end of it. By following these 8 steps you can do it very easily. 

Hopefully, I was able to assist you with installing your sub-panel. Follow it step by step until the installation is complete.

Take care until the next time!