Final answer:
The missing category in NEC Section 590.6(A) that requires GFCI protection for receptacle outlets is 240V single phase circuits. GFCI protection is required for receptacle outlets in specific locations to enhance electrical safety.
Step-by-step explanation:
The missing category in NEC Section 590.6(A) that requires GFCI protection for receptacle outlets is 240V single phase circuits.
It's important to note that GFCI protection is required for receptacle outlets in specific locations such as bathrooms, kitchens, garages, and outdoor areas to enhance electrical safety. GFCIs can quickly detect electrical imbalances and interrupt the circuit to prevent electric shocks or electrocution.