Okay, let's break down this scenario and address your question about the overcurrent protection requirements for your feeder tap.

Understanding the Setup 200A Meter Main with Feed-Through Lugs

This is your service equipment, likely handling the full electrical service to the property. The feed-through lugs allow you to tap off power without interrupting the main service.

100A Conductors

You're running 100A-rated conductors (likely #3 AWG copper or #1 AWG aluminum - confirm this based on ampacity tables in the NEC and your specific conductor insulation type) from the feed-through lugs.

MLO (Main Lug Only) Panel

This panel does not have a main breaker. It's designed to be fed from another overcurrent protection device.

All Outdoors & Directly Next To Each Other

This proximity is good and helps with some requirements.

The Core Issue: Feeder Tap Rules

You're right to focus on the "tap rules" in the National Electrical Code (NEC). These rules govern how you can tap off a higher ampacity conductor and reduce the conductor size. Generally, tapping down to a smaller conductor requires overcurrent protection at the point where the conductor ampacity is reduced.

NEC 240.21 - Overcurrent Protection Location is the key section to consult. This section covers the requirements for where overcurrent protection must be placed when you tap a feeder.

Analysis & Application to Your Scenario

Without knowing the exact distance between the meter main and the MLO panel, it would be recommended to use 240.21(B)(1)(1).In order to qualify for this section the following requirements will be required. Conductor Ampacity

The ampacity of your 100A conductors must be at least 1/3 of the rating of the overcurrent device protecting the 200A feeder (i.e., 100A >= 200A/3, or 100A >= 66.67A which this does meet).

Termination

The 100A conductors must terminate in a single circuit breaker or set of fuses rated no higher than the ampacity of the conductors (i.e., 100A OCPD).

Distance

The length of the tap conductors cannot exceed 10 feet.

Enclosed

The tap conductors must be installed in a raceway or be enclosed by the panelboard.

Applying It To Your Case

Given that your MLO panel is directly next to the meter main (meaning the tap conductors will be very short), the 10-foot tap rule is likely your best option (if the conductors do not exceed 10 feet, that is).

Therefore, yes, you must terminate the 100A conductors into a single 100A OCPD (either a circuit breaker or a set of fuses). This overcurrent protection device must be within the MLO panel..

Summary & Best Practices1. Confirm Conductor Ampacity

Double-check that your #3 AWG copper or #1 AWG aluminum conductors are indeed rated for 100A (based on the conductor insulation type and ampacity tables in the NEC).2.

10-Foot Tap Rule

As long as the 100A conductors do not exceed 10 feet and the other tap rule requirements are met, this option will be the easiest.3.

100A OCPD in MLO Panel

Install a 100A circuit breaker (or a fuse block with 100A fuses) in the MLO panel. This is essential for protecting the 100A conductors.4.

Proper Connections

Ensure all connections are made with properly rated connectors, torqued to the manufacturer's specifications. Pay attention to compatibility (e.g., aluminum to copper connections need the right type of connector and anti-oxidant compound).5.

Grounding

Properly ground the MLO panel according to NEC requirements. This usually involves a grounding electrode conductor (GEC) to a grounding electrode (e.g., ground rod, water pipe).6.

Bonding

Bond the MLO panel enclosure to the neutral conductor only at the service equipment (the meter main). Do not bond neutral and ground in the MLO panel itself.

Important Considerations & Cautions Local Amendments

Always check with your local electrical inspector to see if there are any local amendments to the NEC that might affect your installation.

Safety

Electrical work can be dangerous. If you're not comfortable or experienced with electrical work, hire a qualified and licensed electrician.

Inspection

Be sure to have the installation inspected by a qualified electrical inspector to ensure it meets all code requirements.

Documentation

Keep records of your installation, including conductor sizes, overcurrent protection ratings, and grounding/bonding details.

Disclaimer: I am an AI Chatbot and cannot provide legally binding electrical advice. Always consult with a qualified and licensed electrician for any electrical work. This information is for educational purposes only and should not be taken as a substitute for professional guidance. Flag for review