What Size Sub Panel For A Workshop

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What Size Sub Panel For A Workshop

Today we’re diving into garage panel wiring—specifically how to properly wire a sub-panel for your garage. Whether you’re building a workshop or just adding power to a detached garage, here’s a practical breakdown of what you’ll need to consider.

Step 1: Choosing the Right Sub-Panel Size

The first thing you’ll want to determine is what size sub-panel you’ll need to bring from the main house.

In this case, we installed a 60-amp sub-panel, fed from the main panel in the house. The feed was buried underground for protection and code compliance.

Step 2: Sub-Panel Setup and Disconnect

Inside the garage, the panel includes a 100-amp main breaker, which acts as a disconnecting means only. Although the panel is rated for 100 amps, it’s actually protected by a 40, 50, or 60-amp breaker at the house, depending on the homeowner’s needs.

We used tech cable (TECK90) for the run, which is designed for underground use and provides both durability and safety.

Step 3: Garage Wiring Overview

Inside the garage, we wired:

  • Standard 15-amp outlets for benches and general use
  • Garage door opener plugs
  • Three switches for exterior lights and internal control
  • Basic layup light holders fitted with modern LED tri-panel fixtures
    (We’ll link to those on Amazon in the description.)

Step 4: Important Sub-Panel Grounding Practices

In a sub-panel:

  • The bonding screw or strap must be removed (the neutral and ground must not be connected together).
  • The neutral wire from the feed lands on the neutral bus bar.
  • The ground wire lands separately on the ground bar or panel casing.

This separation is key to preventing stray current from running on the ground wires—a common code issue.

Step 5: Underground Trenching for the Feed

We trenched from the house to the garage, ensuring all code requirements were met:

  • Minimum trench depth: 450mm or 18 inches (non-vehicle areas)
  • 6 inches of sand placed at the bottom of the trench to protect the cable
  • Burial warning tape placed near the top to alert future diggers

At both ends, we used LB fittings to sleeve the tech cable and provide a clean, professional look where the cable enters and exits the ground.

Step 6: Generator Outlet Prep

We also included a dedicated generator outlet. This gives the homeowner the option to install a proper generator panel inside the garage in the future for backup power needs.

Step 7: House Panel Termination

Back at the main panel in the house:

  • The neutral wire is connected to the neutral bar.
  • The ground wire is connected to the casing or ground bar.
  • The black and red hot wires are terminated on a two-pole breaker.

We used an empty breaker space in the Square D panel to tie everything in neatly and safely.

Final Thoughts

This setup offers a safe, code-compliant way to bring power to your garage with plenty of room for outlets, lights, and future upgrades.

If you’re planning to wire your garage or workshop, always consult your local electrical code and get the right materials from a trusted electrical supply shop.

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⚡ Stay safe, and we’ll see you in the next one!

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