Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Send questions to codefaqs@gmail.com. Answers are based on the 2017 NEC.

NFPA 99 and Article 700

We were surprised to see a new requirement in Article 700 for feeder-circuit fire protection that affects healthcare facilities. It is our understanding that NFPA 99 overrides the NEC with respect to this rule. This is a significant revision, and it could be expensive if we miss it. Which document takes precedence in this case? When we asked our local electrical inspector, he said he enforces the NEC, not NFPA 99.

You have identified a conflict between NFPA 70, the NEC and NFPA 99, Healthcare Facilities Code. NFPA 99 has purview over performance in healthcare facilities. The NEC revision you are referring to occurred in Section 700.10(D), Fire Protection, which provides requirements for fire protection of feeder-circuit wiring, feeder-circuit equipment and generator control wiring. In the 2014 NEC, these fire-protection requirements apply only to assembly occupancies for not less than 1,000 people or in buildings taller than 75 feet.

The 2017 NEC significantly expands this requirement to include healthcare occupancies in which people are not capable of self-preservation and educational occupancies with more than 300 occupants. However, as you have pointed out, there is a conflict between NFPA 99 and the NEC. Section in the 2015 edition of NFPA 99 limits the application of Article 700 to the life safety branch. Additionally, Section mandates that the requirements of NEC 700.10(D) (1) through (3) do not apply. It is likely that this conflict will be resolved through a tentative interim amendment or during the revision cycle for the 2020 NEC.

Connectors for Type TC cable?

What type of connector is required to terminate Type TC cable? We are working in an existing installation, and the TC cable already installed seems to be terminated with connectors commonly used for armored cable and cord.

Section 336.6 requires Type TC cable and all associated fittings to be listed. The UL product category for Type TC cable is (QPOR). Connectors and fittings for use with Type TC cable are covered under power and control tray cable connectors (QPOZ). This connector category also recognizes dual-listed connectors that may be used with Type TC cable as well as armored cable, flexible metal conduit, nonmetallic sheathed cable, cord or service entrance cable where suitability is marked on the carton. Also, it is important to note that the connector itself or the smallest shipping carton will be marked with both the smallest and largest Type TC cable diameters for which the connectors may be used.

Application of 240.87

My electrical inspector said I need to meet 240.87 requirements for all breakers that can be adjusted to 1,200 amperes (A) or higher. The equipment manufacturer said its circuit breakers all ship with instantaneous trip set at minimum, so the breakers meet 240.87 out of the box. Is that true? My inspector disagrees. What if the instantaneous trip gets adjusted up after I leave the job? Shouldn’t I assume the instantaneous trip is set on maximum?

Section 240.87 provides prescriptive requirements for arc-energy reduction. This applies to all circuit breakers where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted is 1,200A or higher. While the manufacturer may ship all of these devices with the instantaneous trip setting at minimum, the actual installation of each circuit breaker will typically involve adjustment to a higher level of clearing time for coordination purposes and may possibly be set to maximum. This requires a review of the circuit-breaker coordination settings provided by the engineer.

As you stated, assuming the instantaneous is set to maximum will always ensure the requirements of 240.87 are met regardless of where the instantaneous pickup is set. However, depending on the system, and the characteristics/settings of the device installed, additional measures may not be required.

We must review the seven permitted methods for arc-energy reduction. Two of those methods may apply, and there would be no need for additional arc-energy reduction because the device will already open as quickly as possible. These methods are (1) where the instantaneous-trip setting on the circuit breaker is less than the available arcing current and (2) an instantaneous override that is less than the available arcing current.

Compliance with Section 240.87 can never be achieved by simply stating that the manufacturer ships devices with instantaneous trip set at the minimum. The actual settings for each circuit breaker must individually be reviewed to comply with one of the seven methods provided to achieve arc-energy reduction.

Equipment openings

Why does the NEC permit electrical equipment to have ventilation openings that would easily permit a metal fish tape to pass through the enclosure and into live parts? I was recently working in a large gear room where we mounted a temporary panelboard. I forgot to blank off a 7⁄8-inch hole on the bottom of the equipment, and the general contractors safety consultant wrote us up because that is an OSHA violation. Directly opposite the temporary panelboard was service equipment and a large transformer. All along the bottom of the transformer, there are ventilation openings that would easily permit a metal fish tape to enter the enclosure and come into contact with both line and load. Why does the inspector permit this?

There are many types of electrical equipment, including transformers that require ventilation to dispose of the heat created under normal operation. Section 90.7 provides general requirements for examination of equipment for safety. Where equipment—such as the transformer you have described—is listed by a qualified electrical testing laboratory in accordance with an applicable product standard, ventilation openings are both necessary and permitted. These ventilation openings must be in place to ensure the heat can be readily disposed of to allow the transformer to function properly. The 7/8-inch hole in the panelboard is an “unused opening,” and Section 110.12(A) requires it to be closed to afford protection “substantially equivalent to the wall of the equipment.”

Where any work is performed in the vicinity of energized equipment, a job-safety analysis should be performed. Justified energized work requires a shock and arc flash risk assessment. Using a metal fish tape where there are ventilation openings in energized electrical equipment, such as transformers, is a recognized hazard. Section 130.7(D) in NFPA 70E addresses requirements for insulated tools and equipment, which includes readily available fiberglass fish tapes.

Accessibility requirements

Are the accessibility requirements in Annex J enforceable? When we need to comply with accessibility requirements, does Annex J contain everything we need to know?

Annexes in the NEC are informational only; they are not an enforceable part of the Code—see Section 90.5 (D). Annex J provides information based on standards for accessible design. The information in sections J.1 through J.7 is just a part of the 2010 Americans With Disabilities Act, Standards for Accessible Design. The referenced requirements include but are not limited to protruding objects such as a panelboard in walkways and unobstructed forward and side reach clearances.

Add up the amp ratings?

I am reviewing a set of electrical plans for a new 1,200A service at 480/277 volts (V). The service conductors enter the building in a wireway, and there are three 400A service disconnects. It is well understood that three disconnects are permitted. What I am struggling with is the requirements for ground-fault protection of equipment (GFPE), doors that open in the direction of egress and large equipment requirements for two doors. This is essentially a 1,200A service with three 400A disconnects. Are these ratings cumulative, and can I add them up to get the 1,200A to invoke other requirements?

No, you cannot add the service disconnect ratings to get to 1,200A to invoke additional requirements. We need to look at each one of these rules in the NEC.

Section 230.95 for GFPE applies only to service disconnects rated at 1,000A or more. Section 110.26(C)(3) for personnel doors that open in the direction of egress with panic hardware is limited to equipment rated at 800A or more. Section 110.26(C)(2), which requires large equipment to have a door at each end of the working space of the equipment, is limited to equipment rated 1,200A or more and at least 6 feet wide.

The NEC requirements are clear, and prescriptive values are provided in each of these sections. The GFPE requirements are intended to protect the equipment. The requirements for doors that open in the direction of egress with panic hardware and for doors at each end of the working space (large equipment) are safety driven and affect everyone that will install and maintain this equipment. I encourage you to get involved and submit public inputs to revise the 2020 NEC.