NFPA 110: Standard for Emergency and Standby Power Systems extended Q&A

Q: When is it required to have a 3 pole and 4 pole ATS?

Q: With respect to breaker coordination; what are the preferred electronic trips: LI, LS/I, LSI, or LSIG?

Q: Do you recommend dual hot-standby control PLCs when installing parallel gensets?

Q: Are schools considered to be Level 1 or Level 2 facilities? Typically, Level 1 is needed for health care or mission critical facilities only.

Q: What is the intent/purpose of physically separating the critical branch and life safety branches? Can one have a detrimental impact on the other?

Q: Is mineral-insulated (MI) cable needed for optional standby generator feeder circuits?

Q: Does the 10-second power restoration start time apply to the main service or to the end use device?

Q: Does the emergency system include conductors and other equipment upstream from an ATS on the normal side of the ATS?

Q: Should the emergency service switchboard that feeds the ATSs be in a separate room from the room that contains the ATSs?

Q: If the only important issue is egress lighting, can that be addressed with battery lights, and if so, can my system be standby only?

Q: When referring to the NEC as related to the EPSS, do you need to also consider article 695 elevators and 517 hospitals for additional requirements?

Q: How long does the crank test need to be done on the generator?

Q: Is the use of closed transition transfer switches recommended for Level 1 facilities? Any issues with using closed transition switches?

Q: What are the requirements for the life safety and critical branch systems when the building—specifically a skilled nursing facility—has a full building backup generator? Do you still require separate ATSs, even though we have separate panels and wiring within the building? Contractors feel this is not needed.

Q: If I have a system per Article 701 and Article 702 application, what branches do the battery charger, fuel pump, and dampers get connected to?

Q: If a hospital is to be 100% backed up by Generators, is it a violation of NEC 517.30(B)(4)-Transfer Switches to eliminate all transfer switches by providing Medium Voltage Generators and tie them thru a paralleling gear to a Medium Voltage Distribution Switchgear at the Central Utility Plant? Transfer of power will be at the Medium Voltage switchgear.

Q: Could the 517.34 system be considered as a 701 system?

Q: To test under on-site or portable load bank, do facilities have a TESTING transfer switch to connect the load bank to the system and provide that auto removal of load bank if utility power fails during load bank testing?

Q: Can you combine Article 700-type loads and Article 701-type loads within the same switchgear and on the same OCPD of a generator?

Q: While performing the 2 hour load test per 7.13.4.3, I assume the generator OEM factory can perform only a 2 hour reactive load test at rated power factor to comply with 7.13.4.3.2, correct?

– Edited by Jessica DuBois-Maahs, associate content manager, CFE Media, jdmaahs(a)cfemedia.com.

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