Okay, let's break down the situation and address your questions. You're essentially creating a second service disconnect (the 125A breaker at the meter) and running a subpanel to your workshop.

Understanding the Key Concepts Service Entrance

This is the wiring from the utility company's connection point (usually the transformer) to your main service disconnect (the 200A breaker at your meter).

Service Disconnect

This is the main breaker that disconnects all power to your property. In your case, this is the 200A breaker after the meter.

Subpanel

Any panel fed after the service disconnect is considered a subpanel. Important for understanding grounding requirements.

Separated Neutrals and Grounds

In a main service panel, the neutral (white wire) and ground (bare or green wire) are bonded together (electrically connected). In subpanels, they must be kept separate.

Your Specific Situation and Questions1. Workshop as a Subpanel

You are correct. Because you are installing a breaker at the meter and feeding the workshop from that breaker, the workshop panel is considered a subpanel.2.

Neutral/Ground Separation in Workshop



YES, you absolutely need to separate the neutral and ground in your workshop panel. This is a crucial safety requirement. Even though your main panel in the house has the neutral and ground bonded, that connection only applies to the main service panel. Why? Because if you don't separate them in the subpanel, you could create a parallel path for neutral current to flow through the grounding system. This can cause several problems: Electrocution Hazard

Grounded metal parts in your workshop could become energized.

Nuisance Tripping

GFCI breakers could trip unnecessarily.

Equipment Damage

Sensitive electronic equipment might malfunction.3.

1/0 Aluminum Conductors - 3 or 4? You need 4 conductors: Two Hot Conductors (typically black and red)

These carry the current from the meter to your workshop panel.

One Neutral Conductor (white)

This provides the return path for the current.

One Grounding Conductor (bare or green)

This provides a low-impedance path back to the service entrance in case of a fault.4.

What will Work vs. What's Safe

You're asking "what will work" vs. "what's safe." While a 3-wire setup might seem to work temporarily, it is not safe and is a violation of electrical code. It's not worth risking your safety or causing potential problems down the line.

How to Wire Your Workshop Panel Correctly1. Run 4 conductors (2 hots, 1 neutral, 1 ground) from the 125A breaker at the meter to your workshop panel. Use appropriate conduit and fittings for outdoor/underground wiring. Also, ensure the 1/0 Al is rated for the environment (direct burial if buried) and is approved for use at 125 amps.2. At the workshop panel

Connect the two hot wires to the main breaker lugs. Connect the neutral wire to the

neutral bus bar. This neutral bus bar must be isolated from the panel enclosure. It will have an insulating spacer between the bus bar and the metal panel. Connect the ground wire to the ground bus bar. This ground bus bar is bonded to the metal enclosure of the panel.3. Install a separate grounding electrode system at the workshop. This typically involves driving one or two ground rods into the earth near the workshop. Connect the ground bus bar in the workshop panel to this grounding electrode system with the appropriate size grounding electrode conductor (typically #6 AWG copper or #4 AWG aluminum).4. Ensure ALL metallic conduit and boxes are properly grounded.Important Notes and Recommendations Local Codes and Permits

Even if you're not "terribly worried about new code," I strongly advise you to check with your local building department and obtain the necessary permits. They can inspect your work and ensure it meets safety standards. This protects you, your property, and future owners.

Professional Advice

Electricity is dangerous. If you're not completely comfortable with electrical work, hire a qualified electrician. It's better to be safe than sorry.

Aluminum Wire Connections

When using aluminum wire, be sure to use connectors and lugs that are specifically rated for use with aluminum conductors. Apply an anti-oxidant paste (like Noalox) to the aluminum wire before making connections to prevent corrosion.

Torque Specifications

Always tighten all connections to the manufacturer's specified torque. Loose connections can cause overheating and fires.

In summary: Run 4 conductors (2 hots, 1 neutral, 1 ground) to your workshop, separate the neutral and ground in the workshop panel, and install a separate grounding electrode system at the workshop. This is the safe and proper way to wire your workshop subpanel. Good luck with your project! Flag for review