Okay, let's break down the difference between connecting power source output conductors at a feeder versus at a breaker within the context of Article 705 (Interconnected Electric Power Production Sources) and how this relates to SPD (Surge Protective Device) installation at the main distribution panel.

Key Concepts to Understand First



Power Source Output Conductors

These are the wires carrying power from a distributed generation source (like solar panels, wind turbines, generators) to the electrical system of a building or the utility grid.

Feeder

A feeder is a set of conductors that originate at the service equipment and supply one or more branch circuits. Think of it as a main "trunk line" within your electrical system that carries power from the service entrance (where the power comes into your building) to a subpanel or a large piece of equipment. Feeders can be protected by a breaker at the service equipment or a subpanel.

Branch Circuit

A branch circuit is the wiring between the last overcurrent protective device (breaker or fuse) and the outlets, lights, or appliances it supplies. It's the "end of the line" for power distribution.

Main Distribution Panel (MDP)

This is the primary electrical panel in a building where the service entrance conductors terminate and the main breaker is located. From the MDP, power is distributed to various feeders and branch circuits.

Overcurrent Protective Device (OCPD)

A breaker or fuse used to protect electrical circuits from overcurrents, such as short circuits or overloads.

SPD (Surge Protective Device)

A device designed to protect electrical equipment from voltage surges (transient overvoltages). SPDs divert excess energy to ground, preventing it from damaging sensitive electronics.

Scenario: Distributed Generation Source & SPD at MDP

Imagine you have a solar panel system (a distributed generation source) and want to connect it to your home's electrical system. You also want to install an SPD at your main distribution panel for surge protection.1. Connecting Power Source Output Conductors at a FEEDER



How it Works

The power source output conductors from the solar inverter are connected to a feeder coming out of the MDP. This feeder then carries the combined power (grid power + solar power) to a subpanel or specific load. This connection typically occurs using a breaker (or other disconnect means) within the subpanel supplied by the feeder.

705 Considerations

Article 705 dictates specific requirements for interconnecting these power sources, including proper breaker sizing, labeling, and protection to prevent backfeed onto the utility grid when it is de-energized (loss of utility source).

SPD Placement (In this case)

The SPD at the MDP is protecting the entire electrical system from surges coming from the utility grid. It may also offer some protection to the solar inverter, but it won't protect against surges originating within the solar system itself (e.g., lightning strike directly to the panels). Ideally, in this setup, you would also install an SPD at or near the solar inverter itself to protect it from surges from the solar array.

Why Connect to a Feeder? It's often done when there's not enough space or capacity on the main service bus to directly connect the solar breaker, or when the load being supplied is localized to a specific area served by a feeder.2. Connecting Power Source Output Conductors at a BREAKER



How it Works

The power source output conductors are connected directly to a dedicated breaker in the MDP. This breaker then feeds a dedicated circuit or load.

705 Considerations

The same Article 705 rules apply: proper breaker sizing, labeling to indicate the presence of the distributed generation source, and anti-islanding protection are critical.

SPD Placement (In this case)

Similar to the feeder scenario, the SPD at the MDP primarily protects against surges coming from the utility grid. It might offer some protection to the solar inverter, but is still not the best approach for surge protection from the solar array. You'll likely still want an additional SPD at the solar inverter.

Why Connect to a Breaker Directly? This is often the preferred method if there's available space and capacity in the MDP. It simplifies the wiring and provides a direct connection.

SPD Installation and Power Source Output Conductors

Here's the key point concerning SPDs when you have distributed generation: Main SPD Protection

The SPD installed at the MDP primarily protects the building's electrical system from surges entering from the utility grid. It also can mitigate the backflow of surge current toward the grid.

Distributed Generation Equipment Protection



The SPD at the MDP may not adequately protect the distributed generation equipment (e.g., solar inverter) from surges originating within the generation system itself. These could be caused by lightning strikes to the solar panels, switching surges within the inverter, or other internal faults. Best Practice: Multi-Layered Protection

The best practice is to use a multi-layered approach to surge protection:

SPD at the MDP

Protects the building's electrical system from grid-based surges.

SPD at or near the Distributed Generation Equipment (Inverter)

Specifically protects the inverter and other sensitive components of the generation system from surges originating within the system.

SPD Selection

Ensure that the SPDs you select are appropriately rated for the voltage and surge current levels expected in the specific application. Consult with a qualified electrician or SPD manufacturer for proper sizing.

In Summary

Connecting power source output conductors at a feeder or a breaker within the MDP involves different wiring configurations, but both are governed by Article 705. When installing an SPD at the MDP in conjunction with distributed generation, understand that the MDP SPD primarily protects against grid-based surges. For comprehensive protection, install an additional SPD at or near the distributed generation equipment itself to protect it from surges originating within the generation system. This multi-layered approach is the most effective way to safeguard your entire electrical system and sensitive equipment.

Disclaimer: I am an AI chatbot and cannot provide electrical advice. Consult with a qualified and licensed electrician for all electrical work and SPD selection and installation. They will be able to assess your specific situation and ensure that all work is done safely and in compliance with local codes and regulations. Flag for review