According to NEC, what must be done for an output voltage higher than 50 VAC?

The National Electrical Code (NEC) stipulates that for systems with an output voltage higher than 50 VAC, proper grounding practices are essential for safety and to mitigate the risk of electrical shock. Connecting both sides of the secondary winding (or output side) to ground is a crucial safety measure. This grounding helps ensure that in the event of a fault, any stray voltage is safely directed to the ground, reducing the risk of electric shock to individuals and preventing potential equipment damage.

Grounding both sides of a secondary circuit also aids in ensuring that voltages do not rise to dangerous levels, maintaining the system's integrity. It's a practice that supports the safety of electrical installations in environments where higher voltages are present, helping to protect both personnel and property. This requirement aligns with the NEC's goal of promoting safe electrical practices in all installations.