Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at [email protected]. Answers are based on the 2023 NEC.
Cybersecurity in the NEC
With all of the ransomware thefts, etc., going on, why doesn’t the NEC address cybersecurity? Many systems could be hijacked that might result in serious safety concerns. When will we catch up?
Protection from cyberthreats is primarily considered a design or engineering decision. However, as stated in your question, safety is affected. Facility owners should assess their individual needs for protection. Cybersecurity requirements do exist in Article 708, Critical Operations Power Systems (COPS). These critical systems and Article 708 requirements exist only where they are so classed by municipal, state, federal or other codes by any governmental agency having jurisdiction or by facility engineering documentation establishing the necessity for such a system.
The requirements of Section 708.7, Cybersecurity, mandate that all COPS connected to a communication network and that have the capability to permit control of any portion of the premises must (1) ensure the ability to control the system is limited to a direct connection through a local nonnetworked interface or (2) connect through a network interface with the system, and the associated software is identified as being evaluated for cybersecurity or a cybersecurity assessment has been conducted on the connected system to determine vulnerabilities to cyberattacks.
What can be in the fire pump room?
Engineered drawings show a 480/277V service supplying a listed fire pump controller. The CT cabinet and associated metering were shown in the fire pump room. During plan review, we were informed that the CT cabinet and metering had to be relocated. We cannot find any such requirement. Can you help?
Purview over the performance of fire pumps resides in NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection. Article 695 in the NEC simply extracts performance-based requirements from NFPA 20 into NEC style. The NEC addresses only the electrical installation. Chapter 4 of NFPA 20 contains general requirements, and the general rule in Section 220.127.116.11.5 prohibits rooms containing fire pumps from being used for storage, equipment and penetrations not essential to the operation of the pump and related components.
Locating the CT cabinet and associated metering in the fire pump room is “not essential” to the operation of the pump and related components. Section 18.104.22.168.6 of NFPA 20 does permit equipment related to domestic water distribution in the fire pump room. NFPA 20 Annex material (Informational Annex A) explains that equipment such as boiler or fuel-fired water heaters should not be installed in the fire pump room.
A local inspector is mandating that we install a 6 AWG copper bonding jumper to black-jacketed CSST gas tubing to protect from lightning. I thought no additional bonding (other than an equipment grounding conductor) was required with the new black CSST?
See Section 90.2 in the NEC. The Code’s purpose is the practical safeguarding of persons and property from hazards arising from the use of electricity. We do not use lightning. NFPA 780, Standard for the Installation of Lightning Protection Systems, applies to all conductors and equipment installed to protect from lightning hazards. The black-jacketed CSST gas tubing is commonly called arc-resistant CSST. The international fuel gas code, international residential code and arc-resistant CSST manufacturer’s instructions have all been modified to recognize that the only bonding required is a connection to the equipment grounding conductor for the circuit likely to energize the piping system. No additional bonding is required. See 250.104(B)(1).
An inspector flagged our job and told us that taking a normal and emergency circuit into the same lighting fixture violated 700.10(B). Additionally, the inspector stated that the fixture has to be listed as an emergency one. Is that right?
The general rule in Section 700.10(B) is that wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads must be kept entirely independent of all other wiring and equipment unless specifically permitted in one or more of the six list items provided. Section 700.10(B)(2) prescriptively permits wiring supplied from two sources in exit or emergency luminaires. The NEC does not contain a requirement for luminaires to be listed for use in an emergency system. However, Article 700 does require listing of equipment in some cases, including, but not limited to, transfer equipment. It is important to note that all luminaires must be listed; see 410.6, but Article 700 does not contain an “emergency luminaire” requirement.
Third-floor service equipment?
In a mixed-use new construction building, the client is requesting their service equipment be located on the third floor. The engineer shows RMCs vertically next to a steel column containing service conductors to the third floor. The municipality approved the drawings and said RMC is OK. Can we install service conductors through a building if they are in RMC?
The general rule (230.70(A)(1)) for service conductors is that they terminate in a disconnecting means and overcurrent protection at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors. If there is a desire or need to run service conductors inside a building or structure, the service conductors must be installed in accordance with Section 230.6 requirements. In this case, traveling vertically to the third floor, service conductors must be installed within a building or other structure in a raceway encased in concrete or brick not less than 2 inches thick.
Transformer secondary conductors
Can we install four sets of conductors from a transformer secondary to four different enclosures, each with a main circuit breaker? It is 75 kVA with 480V primary and 208/120V secondary. The circuit breakers are (2) 200A and (2) 60A. Does this meet the requirements of NEC 450.3(B)?
There are multiple NEC requirements involved here and two permitted methods to protect the transformer in 450.3(B). Multiple sets of transformer secondary conductors from a single transformer secondary are specifically permitted in the parent text of 240.21(C). It is important to note that the requirements of 240.21(C) will in most cases limit the length of the transformer secondary conductors to 10/25 feet and will provide minimum sizes without regard to the rating of the overcurrent device where they terminate. If this installation is done in accordance with 450.3(B) for primary protection only, the four sets of conductors comply with 450.3(B). However, if primary and secondary protection are applied (primary at 250%) then Note 2 to Table 450.3(B) applies. This note mandates that where secondary overcurrent protection is required, the secondary overcurrent device is permitted to consist of not more than six circuit breakers or six sets of fuses grouped in one location.
Additionally, we must add the rating of multiple overcurrent devices, and the total of all device ratings cannot exceed the allowed value of a single overcurrent device. When applying primary and secondary protection in accordance with Table 450.3(B), secondary protection must be provided at a value not to exceed 125% of the transformer secondary current.
Note 1 does allow you to round up to the next standard size overcurrent protective device. With a transformer secondary current of 208A: 208 x 1.25 = 260. This is not a standard size according to 240.6, so it can be rounded up to 300A. The total rating of devices in your question is 320A. Therefore, if you protect the transformer with primary and secondary overcurrent protection of the transformer, this installation would be in violation of 450.3(B).
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About The Author
DOLLARD is retired safety coordinator for IBEW Local 98 in Philadelphia. He is a past member of the NEC Correlating Committee, CMP-10, CMP-13, CMP-15, NFPA 90A/B and NFPA 855. Jim continues to serve on NFPA 70E and as a UL Electrical Council member. Reach him at [email protected].