2025 Complete Texas Fire Alarm License Practice Test

Using an over-current device not rated over 20 Amperes is essential for protecting transformers from power-supply conductors because it ensures that the transformer operates within its safe limits. Transformers are typically designed to handle specific current loads, and over-current devices are integral to preventing damage from excess current.

When an over-current condition occurs, this type of protective device will trip or blow, interrupting the electrical flow before it can cause overheating or other forms of damage to the transformer. Selecting an over-current device rated not greater than 20 Amperes aligns with the capacity of most transformers, which is designed to handle loads safely without allowing excessive current to pass through them.

This approach provides a balance between ensuring adequate protection and allowing the transformer to function correctly under normal operating conditions. Consequently, the correct rating contributes significantly to system reliability and safety.