Heavy duty type lamp holders are required on branch circuits having a rating in excess of what amperage?

The requirement for heavy duty type lamp holders on branch circuits is established to ensure safety and reliability in electrical installations. Heavy duty lamp holders are designed to withstand higher electrical loads and physical stresses compared to standard lamp holders. For branch circuits, when the rating exceeds 20 amperes, the use of heavy duty lamp holders becomes necessary. This is primarily because circuits with higher amperages are more likely to experience elevated temperatures, increased wear, or risk of arcing, which can lead to failures or safety hazards. Thus, whenever a circuit is rated for more than 20 amps, implementing heavy duty lamp holders is crucial to accommodate the higher demands and ensure compliance with electrical safety standards.