You are correct. The PM assistant's assertion that metal boxes in an OR should NOT be bonded to the equipment grounding conductor (EGC) originating from the isolated power panel is almost certainly incorrect and likely a violation of NEC 517.13(B).Here's a breakdown of why and addressing your specific question

Understanding the Requirements - 517.13(B) and Beyond
517.13(A) & (B): General Requirements

These sections of the NEC, including in operating rooms and critical care areas,

mandate a reliable equipment grounding system. Acceptable Wiring Methods

The wiring methods must qualify as an equipment grounding conductor, AND...

Supplemental Grounding Wire

Each branch circuit supplying patient care equipment must include an insulated copper equipment grounding conductor (green or green with yellow stripe). This EGC is connected to the grounding terminals of receptacles, metal boxes, and device enclosures.

Why 517.13(B) Exists

The purpose of a supplemental EGC is to provide a low-impedance path for fault current. This is critical for personnel safety.

Important: Isolated Power Systems are NOT a Waiver

The presence of an isolated power system does not negate the requirement for a properly installed and bonded equipment grounding system. The isolated power system adds a layer of safety, but it doesn't replace the fundamental grounding requirements.

517.19 Isolated Power Systems (Further Clarification)

This section describes the operation of the Isolated Power System

Addressing Your Specific Question: Why Bond Metal Boxes in an Isolated Power System?

Even though an isolated power system is designed to limit the initial fault current and prevent the immediate operation of overcurrent devices, there are several crucial reasons why bonding metal boxes is still essential:1. First Fault Scenario

An isolated power system doesn't eliminate ground faults. It limits the current of the first ground fault. Without a properly bonded grounding system, the enclosure of a device with a first fault will be elevated to a voltage level. This scenario poses a significant shock hazard to anyone who touches the faulty enclosure and a grounded surface (like the operating table).2.

Second Fault = BOLT OF LIGHTNING

While a single fault in an isolated power system won't trip a breaker, a second fault on a different conductor will result in a very large current. The grounding system is vital to provide a low-impedance path for this second fault current, ensuring the overcurrent protection device will operate quickly. Without proper bonding, the high fault current can flow through unintended and potentially dangerous paths.3.

Electrostatic Discharge (ESD)

Properly bonding metal boxes helps to minimize the build-up of static electricity. ESD can be a concern in operating rooms, especially with sensitive electronic equipment.4.

Code Compliance is Mandatory

NEC 517.13(B) doesn't provide exceptions for isolated power systems. You must follow the code.

Why the PM Assistant is (Almost Certainly) Wrong

Disconnecting the EGC pigtails from the metal boxes is a dangerous practice and almost certainly violates NEC 517.13(B). This creates a situation where the metal boxes are not properly grounded, increasing the risk of electrical shock and creating an unreliable fault current path. His reasoning is flawed, and it's crucial to correct this misunderstanding immediately.

What You Should Do1. Document Everything

Document the PM assistant's instructions in writing and the potential safety concerns.2.

Escalate

Escalate this issue to someone with the authority to overrule the PM assistant – a senior engineer, the facility's electrical safety officer, or the hospital's administration. Explain the NEC requirements and the potential safety hazards.3.

Consult with a Qualified Electrical Engineer

If there's any doubt, consult with a qualified electrical engineer experienced in healthcare facilities. They can provide a definitive interpretation of the code and ensure the grounding system is compliant and safe.4.

Insist on Corrective Action

Insist that the metal boxes be properly bonded to the EGC. This may involve re-terminating the ground pigtails.5.

Formal Inspection: Request a formal electrical inspection and evaluation from an independent, qualified authority.In conclusion, you are correct in your assessment. The PM assistant's instruction to disconnect the EGC pigtails from metal boxes in the OR is likely a violation of the NEC and creates a dangerous situation. Immediate corrective action is required. Flag for review