Mounting equipment and California's ballasted solar rule

What the code requires

Section 110.13 has two parts. Under 110.13(A), electrical equipment must be firmly secured to the surface it is mounted on. Anchoring with wooden plugs set into masonry, concrete or plaster is not allowed.

Under 110.13(B), equipment that relies on natural air movement for cooling must be installed so that its airflow is not blocked, and its ventilation openings must be kept clear.

California adds an exception to 110.13(A) for buildings under the rules of the Building Standards Commission, the State Fire Marshal, and HCD 1 and HCD 2 (housing). Roof-mounted solar arrays held in place by ballast do not have to be fastened to the roof, as long as the wiring and interconnections can accommodate the system's maximum movement.

On the job

• With a ballasted array, the wiring and interconnections must be designed to handle the array's maximum movement.
• Some building departments require electrical and structural plan review for ballasted arrays; Ventura County did under the 2022 codes.
• Panels and boxes must be anchored to their mounting surface with proper fasteners, not wooden plugs in masonry or concrete.

Exceptions that matter

• California only: ballasted rooftop solar need not be fastened to the roof if its wiring and interconnections accommodate the system's maximum movement. This applies only to occupancies under the agencies named in the amendment.

In California

This is a California-only amendment, and because it covers HCD 1 and HCD 2 occupancies, it can apply to ballasted arrays on residential buildings.

Related sections

• NEC 110.12: Professional and skillful installation work
• NEC 110.3(B): Install equipment per its listing instructions
• NEC 690.31
• NEC 690.43

Where this comes from

• California Building Standards Commission: 2025 California Electrical Code amendments (rev. 2025-11-20)
• Ventura County Building and Safety: Solar Photovoltaic Systems
• Read the official NEC free at NFPA