How to Wire a 200 Amp Subpanel for Your Garage

Introduction

Adding a 200 amp subpanel to your garage can provide the extra power needed to run larger tools and appliances like welders, air compressors, heaters, etc. Wiring a subpanel is not extremely difficult, but does require following proper safety precautions and electrical codes. In this guide I will walk through the complete process of wiring a 200 amp subpanel for a garage from start to finish.

Safety Precautions

When working with electricity, safety should always be the top priority. Here are some key safety tips to follow when wiring a subpanel:

• Turn off the main breaker - This cuts power to the entire house and prevents shock or electrocution while working.

• Use personal protective equipment - Wear insulated gloves, safety goggles, sturdy shoes, and appropriate work clothes when handling wires.

• Exercise caution - Work slowly and double check connections before restoring power.

• Inspect the work area - Ensure the area is dry and clear of flammable materials.

• Follow all electrical codes - Adhere to NEC and local regulations for proper, safe installation.

Step 1: Choose a Location

When selecting where to mount the subpanel, consider the following:

• Near the main electrical service panel
• In an accessible area of the garage, like near an entry door
• At least 3 feet away from ignition sources like furnaces
• At a comfortable working height to access circuit breakers

Also check that there are no obstructions like ducts or pipes where you plan to mount the subpanel.

Step 2: Select a Subpanel

For a garage, I recommend choosing a 200 amp feed-through subpanel like those made by Square D or Eaton. Key features to look for include:

• Main breaker - This allows you to shut off the subpanel separately from the main panel.

• Ample breaker spaces - Choose a size that allows room for future expansion.

• Copper bus bars - These safely distribute power to the breakers.

• Neutral and ground bars - Provide termination points for neutral/ground wires.

• ** Sturdy enclosure** - Look for sturdy galvanized steel or aluminum construction.

Step 3: Install the Conduit

Rigid metal conduit is recommended for subpanels as it provides the most protection. Determine the route the conduit will take from the main panel to the subpanel. Then:

• Use conduit hangers to securely mount the conduit every 5-6 feet along the route.

• Use waterproof fittings and conduit seals if the conduit crosses between interior and exterior.

• Use sweeps and long radius elbows for smoother wire pulling.

• Ensure at least one pull point with access for wiring the conduit.

Size the conduit for the wire gauge that will be used (see next step).

Step 4: Pull and Connect the Wires

For a 200 amp subpanel, you will need:

• 2 hot wires - 4 AWG THHN/THWN copper wires.

• 1 neutral wire - 4 AWG THHN/THWN copper wire.

• 1 ground wire - 4 AWG THHN/THWN copper wire.

Use wire lube to pull the wires through the conduit without damaging insulation. Leave at least 8 extra inches of wire. Then connect the wires:

• Hot wires - to the main breaker lugs in the subpanel.

• Neutral wire - to the neutral bar in the subpanel.

• Ground wire - to the ground bar in the subpanel.

Ensure wires are tightly secured with no copper exposed.

Step 5: Bonding and Grounding

Proper bonding and grounding is critical for safety. This involves:

• Connecting the neutral bar to the ground bar in the subpanel using a bonding jumper wire. This bonds neutral and ground.

• Running a grounding electrode conductor from the ground bar to two ground rods 8 feet apart outside the garage. This provides an earth ground connection.

Use 6 AWG copper wire and proper ground clamps for these connections.

Step 6: Mount and Connect the Subpanel

You're now ready to permanently install the subpanel:

• Mount the subpanel securely to the wall using appropriate fasteners. Ensure it is level and plumb.

• Remove the cover and inspect all wiring connections. Double check the neutral and ground are properly bonded.

• Connect the conduit to the subpanel using fittings and bushings to protect wire insulation.

• Install a proper grounding screw or wire to bond the subpanel enclosure.

Step 7: Add Breakers and Label

The subpanel is now ready to be powered up after:

• Installing circuit breakers - Match the amperage rating for the branch circuits you plan to run.

• Providing labels - Clearly label each circuit breaker according to the final circuit. This is for safety and easy identification.

• Replacing the subpanel cover.

With the cover secured, you can switch the main breaker on to energize the subpanel.

Conclusion

Adding a new 200 amp subpanel involves careful planning, attention to safety, and adherence to electrical code requirements. Taking a methodical approach and double checking your work ensures a safe, successful installation. The subpanel provides the capacity to handle larger electrical loads, allowing you to get more use and enjoyment from your garage.