Chapter 5 of the National Electrical Code provides rules for special occupancies that modify or amend the general wiring requirements of chapters 1–7. Electrical installations in special occupancies often require a more amended and restrictive approach to address specific concerns as well as grounding and bonding rules that exceed general requirements. 

It is important to establish a clear comprehension of the electrical wiring that exceeds what would normally be required for electrical systems in general locations. Good examples include restrictive grounding and bonding requirements for healthcare facilities, specifically for branch circuits serving the same patient care spaces and vicinities. The idea here is to establish and maintain redundancy of the grounding and bonding with branch circuits. 

The requirements are to install two and be assured of the required effective ground-fault current path in these locations. Section 517.13 provides the rules to accomplish this redundancy. Reducing differences of potential between conductive equipment or other objects and the earth helps minimize shock hazards in normal circuit operation. 

In patient care spaces, it is essential that overcurrent protective devices operate quickly during ground-fault conditions to minimize the potential (voltage) on conductive parts. These are the main reasons for the more restrictive requirements on equipment grounding conductors (EGCs) for branch circuits that supply patient care spaces in a healthcare facility. This requirement does not apply to the EGCs for feeders that supply the panelboards containing branch circuits for patient care spaces.

With an understanding of the rules in 517.13, it is also important to apply the additional bonding requirements in Section 517.14.

Feeder EGC rules

The general requirements in Section 215.6 mandate that feeders provide an EGC where the feeder supplies branch circuits in which EGCs are required. This requirement applies to all feeders regardless of occupancy. Each feeder supplying branch circuits serving patient care spaces must include an EGC in accordance with the provisions in 250.134 for connection of branch circuit EGCs served by the feeder. Electrical distribution systems in healthcare facilities often require multiple levels of panelboards. 

Specific bonding requirements apply to panelboards containing branch circuits that serve patient care vicinities. The term “patient care vicinity” is defined in Article 100 as, “A space, within a location intended for the examination and treatment of patient, extending 1.8 m (6 feet) beyond the normal location of the bed, chair, table, treadmill, or other device supports the patient during examination and treatment and extending vertically to 2.3 m (7 feet, 6 inches) above the floor.”  

Bonding panelboard requirements

In addition to the feeder EGC rules in 215.6 and 517.19(E), there are bonding requirements for panelboards that provide branch circuits serving patient care vicinities. The Code requires the equipment grounding terminal bars of the normal and essential branch circuit panelboards serving the same patient care vicinity be bonded together.

Section 517.14 specifically requires these components be connected (bonded) together with an insulated copper conductor no smaller than 10 AWG. The bonding conductor installed between the panelboard equipment grounding terminal bars must be continuous, except that it may be broken where it connects to the terminal bar in the panelboard. There is also a new exception in the 2023 NEC that recognizes the 10 AWG insulated copper bonding conductor can be terminated using listed connectors attached to aluminum or copper bus bars not smaller than ¼-inch thick, 2 inches wide and of sufficient length to accommodate all bonding connected conductors. 

This additional bonding applies to all situations in which two or more panelboards supply the same patient care vicinity and are served through separate transfer equipment on the essential system. The reason for this additional bonding is that the normal branch circuits and critical branch circuits serving the same individual patient care vicinity are generally supplied from different separately derived and power sources, usually transformers. This situation creates possible potential differences between the branch circuit EGCs of the normal and essential electrical systems. 

Bonding equipment grounding terminal bars of all panelboards serving the same patient care vicinity helps minimize the possible potential differences. The NEC requires this bonding conductor to be insulated and at least a 10 AWG copper conductor. This is the minimum size, but it may be larger depending on the design and to account for longer distances between the panelboards serving the same patient care vicinity. For example, if the panelboards were located a considerable distance apart, voltage drop could be a problem.

michael johnston