CSLB C-46 Solar ContractorPhotovoltaic System InstallationMedium
An installer is designing a PV system for a commercial building with a flat roof. The modules will be installed using a ballasted racking system. What is the primary reason for using ballast in this type of installation?
- ATo facilitate easier module replacement and maintenance.
- BTo provide electrical grounding for the PV modules and racking.
- CTo increase the aesthetic appeal of the array by concealing mounting hardware.
- DTo prevent wind uplift without penetrating the roof membrane.
Show answer & explanationAnswer & explanation
Correct answer: D. To prevent wind uplift without penetrating the roof membrane.
Ballasted racking systems use weight (ballast blocks) to hold the PV array in place on a flat roof. This is primarily done to resist wind uplift forces without requiring penetrations into the roof membrane, which helps prevent leaks and maintains roof warranty.
Why the other options are wrong
- A. Ballast adds weight and complexity, making module replacement potentially more difficult, not easier.
- B. Ballast does not provide electrical grounding; separate grounding conductors are required.
- C. Aesthetics are not the primary function of ballast; it's a structural component.
Ballasted Racking System
A PV mounting system for flat roofs that uses weighted ballast blocks to secure the array against wind forces, avoiding roof penetrations.
- Primarily used on low-slope or flat commercial roofs.
- Eliminates roof penetrations, preserving roof integrity.
- Requires careful calculation of ballast weight based on wind loads.
Memory trick: Ballast: The 'Weighty Watchman' against wind, saving the roof!