Quick Answer
When wiring a solar subpanel, follow best practices by using a dedicated ground rod and ensuring the subpanel is properly sized and matched to the solar array's capacity. Install breakers in the subpanel to protect the solar array and downstream loads. Use a main bonding jumper to connect the subpanel's grounding to the main electrical panel.
Subpanel Sizing and Installation
When selecting a subpanel for a solar array, consider the total power output of the array and the maximum current draw of the connected loads. A general rule of thumb is to size the subpanel to accommodate 80-100% of the solar array’s maximum power output. For example, a 5 kW solar array may require a 4 kW subpanel. Ensure the subpanel is rated for the maximum voltage and current of the solar array, and is installed in a location accessible for maintenance.
Grounding and Bonding
A dedicated ground rod is essential for a solar subpanel, as it provides a low-impedance path to ground and helps prevent shock hazards. The ground rod should be driven 8 feet deep into the earth, and connected to the subpanel’s grounding system using a #6 or #8 copper grounding conductor. The main bonding jumper should be connected between the subpanel’s grounding and the main electrical panel’s grounding to ensure a continuous path to ground.
Breaker Selection and Installation
Breakers in the subpanel should be sized to protect the solar array and downstream loads from overcurrent conditions. Use a 125% or 150% inverse time circuit breaker to protect against short circuits and ground faults. Ensure the breakers are properly installed, with the correct size and type for the connected loads. Label each breaker with its corresponding load or circuit, and verify that the subpanel’s labeling and documentation comply with NEC code requirements.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.