A 30 A circuit breaker is used to protect a 22 A electrical load. If the circuit is totally enclosed in thermal insulation and has a Ca of 0.88, what is the minimum current carrying capacity (Iz) for this conductor?

To determine the minimum current carrying capacity (\( I_z \)) for the conductor protecting a 22 A electrical load with a 30 A circuit breaker, while considering the thermal insulation factor (\( C_a \)) of 0.88, follow these steps: ### 1. Determine if the Load is Continuous Assuming the 22 A load is **continuous** (operating for three hours or more), the National Electrical Code (NEC) requires that the conductor ampacity be **125%** of the continuous load. This accounts for potential overheating under prolonged use. \[ \text{Adjusted Load} = 1.25 \times \text{Load} = 1.25 \times 22\,\text{A} = 27.5\,\text{A} \] ### 2. Apply the Correction Factor Since the conductor is **totally enclosed in thermal insulation**, a correction factor (\( C_a \)) of 0.88 is applied to the adjusted load to account for reduced heat dissipation. \[ I_z = \frac{\text{Adjusted Load}}{C_a} = \frac{27.5\,\text{A}}{0.88} \approx 31.25\,\text{A} \] ### 3. Select the Appropriate Conductor Size Conductor sizes are standardized. Therefore, round up to the next standard size to ensure safety and compliance. The next standard size after 31.25 A is typically **35 A**. ### **Conclusion** The **minimum current carrying capacity (\( I_z \))** for the conductor should be **at least 31.25 A**. In practice, you would select the next standard conductor size, such as 35 A, to comply with safety standards and ensure adequate protection. **Final Answer:** A minimum conductor capacity of approximately 31.25 A is required.