Secondary protectors should be used on circuits exposed to potential contact with electric conductors above what voltage?

Secondary protectors are essential for safeguarding low voltage systems from transient voltages or surges that can arise from nearby electrical conductors. When considering the threshold for when these protectors should be employed, it's important to note that the National Electrical Code (NEC) typically identifies a standard level—300 volts—as the point at which secondary protection becomes necessary.

The rationale surrounding this voltage level is based on the increased risk of electrical interference or accidental contact that can occur with circuits exposed to higher voltages. When operating near conductors above 300 volts, the potential for dangerous electrical conditions rises, making it imperative to mitigate those risks.

By utilizing secondary protectors in circuits exposed to voltages above this threshold, one enhances the safety and reliability of low voltage communication systems, helping to prevent damage and ensure regulatory compliance. This understanding highlights why 300 volts is the correct threshold for implementing secondary protection measures effectively.