Derating is the reduction of the maximum capacity (or "load") a dimmer can reliably handle when its side-sections (or "fins") are removed.
Traditionally, Designer, and New Architectural style dimmer controls share the same derating requirements. Most dimmers in these styles must be derated, and the fins must be broken.
NovaT and Vareo have seperate derating rules, and Nova requires custom derating and ganging instruction. For details on these dimmers, please see our custom Architectural multi-gang tool
and capacity derating charts