Solar Safety Relies on ACDC Disconnect Switches

In any residential solar photovoltaic (PV) system, alternating current (AC) and direct current (DC) circuit breakers serve as essential safety components. These devices play a vital role in emergency situations, allowing for the rapid shutdown of power flow to ensure the safety of both property and emergency responders.

The AC circuit breaker isolates the inverter from the grid and is typically mounted on a wall between the inverter and the electric meter, either as a separate switch or as part of the main electrical panel. The DC circuit breaker, capable of interrupting direct current flow, is installed between the solar panels and the inverter, often integrated directly into the inverter unit itself.

Proper installation of these solar disconnects not only ensures residential safety but also enables quick power shutdown when necessary. Most U.S. building codes mandate the installation of these solar disconnect switches, making it crucial to understand their operation.

Solar panel installations require both AC and DC circuit breakers for these five critical reasons:

• Compliance with Codes and Regulations: Local building codes universally require AC and DC disconnects. Many jurisdictions adopting the latest National Electrical Code (NEC) now mandate rapid shutdown functionality.
• Fire Safety: During residential fires, AC disconnects prevent power flow that could accelerate fire spread and create electrocution hazards for emergency personnel.
• Severe Weather Protection: DC disconnects allow homeowners to isolate their systems during tornadoes, hurricanes, or severe thunderstorms, minimizing potential damage to inverters and internal wiring.
• Flood Preparedness: Complete system shutdown using both AC and DC disconnects becomes essential during flood events.
• Utility Worker Safety: When utility crews perform line maintenance or transformer installations, the ability to disconnect solar systems from the grid provides critical protection.

Circuit breakers are available in various specifications ranging from 30 to 800 amps, requiring careful system planning to determine appropriate sizing. Proper selection involves evaluating four key system parameters:

• System voltage
• Circuit load requirements
• Amperage rating/breaker size
• Wire and cable specifications

These factors collectively determine the total load capacity and corresponding breaker size requirements. Completed system designs must be submitted for permitting approval.

Properly specified AC and DC circuit breakers serve as crucial safety features that can help solar installers build trust with homeowners. Correct breaker selection ensures optimal system pricing while meeting all safety requirements.

These disconnects represent just one component of the broader Balance of System (BOS) equipment that completes a solar installation. When properly integrated with other system components, they create a safe, efficient, and code-compliant solar energy system.

A solar AC circuit breaker isolates the solar inverter from the electrical grid, allowing for safe disconnection of alternating current power when needed. These breakers are typically mounted on exterior walls near the electric meter, either as standalone switches or as breakers within the main service panel.

A solar DC circuit breaker (or PV disconnect) interrupts the flow of direct current from solar panels to the inverter. Most modern inverters incorporate these disconnects directly into their housing.

Local building codes universally require AC and DC disconnects in all solar installations. NEC Section 690.13 mandates disconnect switches for all U.S. photovoltaic systems, with many municipalities now requiring rapid shutdown switches that function as panel-level DC disconnects.

Standard solar disconnects range from 30-800 amps. Proper sizing depends on the PV system's total load, determined by evaluating system voltage, circuit load, breaker capacity, and conductor specifications.