Quick links: | Article 215 | NEC Requirement | NEC 2023 code change/intention | Rationale for change

• 215 Feeders
• 215.15 Barriers

The language in Article 215 in Section 215.15 (Barriers) is very similar to the language that was created for Section 230.62 (Service Equipment Barriers). Similar hazards exist in both of these locations.

These requirements recognize the increased “risk” for equipment fed directly from transformers and tap conductors. Barriers are required for panelboards, switchboards, switchgear, or motor control centers supplied by feeder taps in 240.21(B) or transformer secondary conductors in 240.21(C).

When the disconnecting device, to which the tap conductors are terminated, is in the OPEN position, you cannot have any exposed energized parts.

The intent of this code change is to reduce risk in these areas. The first panelboard on the secondary of a transformer or at the end of a tap conductor has an increased incident energy level, thus increasing the severity should a fault occur. Risk is comprised of likelihood and severity; hence this requirement addresses one portion of risk, which is reducing the likelihood of accidentally coming in contact with energized parts.

The first equipment supplied on the secondary of a transformer or from a tapped feeder have an increased risk through an increased severity of incident energy because the upstream overcurrent protective device has an intentional delay.  In the case of a transformer, the first equipment supplied from the secondary of the transformer has an incident energy value determined by the clearing time of the primary overcurrent protective device.  The primary overcurrent protective device is artificially inflated in the instantaneous pickup value because the breaker must permit the inrush current of the transformer to flow without tripping when the transformer is energized.  This inflated pickup value for instantaneous will cause a long clearing time for faults on the secondary of the transformer resulting in elevated levels of incident energy for that equipment.  Tap conductors that serve equipment present a similar increased level of incident energy because the upstream protecting overcurrent protective device is sized to protect the larger feeder and not the smaller tap conductor.  The following image presents an example of this situation and demonstrates that when the secondary OCPD is separate from the panelboard, it now becomes the protecting OCPD for the panelboard significantly reducing the incident energy because it is not artificially inflated in size due to transformer inrush.