You are correct, and your concerns are valid. What you described is a clear violation of the NEC and a potential fire hazard. Here's a breakdown of why, and the relevant code sections

Why This is Wrong:
Overcurrent Protection

The 150A breaker is protecting the entire circuit, including the #2 conductor. The NEC dictates that the overcurrent protection device (OCPD) must be sized according to the smallest ampacity of any conductor in the circuit. Since the #2 is rated for 115A (at 75°C, which is the typical termination temperature rating), the breaker should not exceed 115A.

NEC 240.4(B) - Protection of Conductors

This is the core requirement. Conductors must be protected against overcurrent in accordance with their ampacities.

NEC 110.14(C) - Termination Temperature

Equipment terminals are rated for specific temperatures (usually 60°C or 75°C). You must use the correct ampacity column from NEC Table 310.16 based on the termination temperature rating. Typically, you need to use the 75°C column, especially for larger conductors.

Voltage Drop Considerations are Separate

While you can upsize conductors for voltage drop, that doesn't override the requirement for overcurrent protection. The OCPD still must be sized to protect the smallest conductor in the circuit.

Fire Hazard

If the load on the PDU exceeds 115A, the #2 conductor will be overloaded. This will cause it to overheat, potentially melting insulation, creating arcing faults, and starting a fire.

The Scenario Where a Larger Conductor Splices to a Smaller Conductor is Different Because

As you mentioned, in situations where a larger conductor reduces to a smaller conductor, the OCPD is sized to protect the smaller conductor. For example, if you have a #10 conductor (rated for 30A) run a long distance to minimize voltage drop, then splice it to a #14 conductor (rated for 15A) to connect to a 15A outlet, you MUST protect the circuit with a 15A breaker. The larger #10 conductor is safe, but the breaker is sized for the #14.

What to Do


Immediate Action



Contact a qualified electrician immediately. This is a serious safety hazard. Explain the situation, and insist they correct it.2. Reduce the Breaker Size

The simplest (but potentially disruptive) solution is to downsize the breaker to 115A. This will protect the #2 conductor, but it may trip frequently due to existing overloading issues.3.

Replace the #2 with 1/0 or Larger

The proper solution is to replace the #2 conductor with a 1/0 conductor that has a proper ampacity rating for 150A. This is the best long-term fix, but may require more work.4.

Evaluate the Load

Determine the actual load on the PDU. Is it truly exceeding 115A? If so, consider load balancing, more PDUs, or other strategies to reduce the load.5.

Document Everything

Keep a record of the problem, your concerns, and the actions taken to correct it.

Key Takeaways: The OCPD protects the weakest link in the circuit (the conductor with the lowest ampacity). Voltage drop calculations do not override overcurrent protection requirements. Never assume a system is safe. Always verify compliance with the NEC and other applicable codes.You are absolutely correct to be concerned about this situation. It's a dangerous condition that needs to be rectified as soon as possible. Flag for review