The evolution of NFPA 110

NFPA 110 has changed in the past several years, and electrical engineers should understand the nuances

By David Stymiest November 19, 2021
Courtesy: Smith Seckman Reid


Learning Objectives

  • Understand the evolution of major NFPA 110 changes over time.
  • Learn about the major impacts to NFPA 110-2022 from the new addition of fuel cell systems as an acceptable type of emergency power supply.
  • Know the danger of wet-stacking related to diesel engine exhaust piping.
  • Appreciate the true scope of NFPA 110.

NFPA 110: Standard for Emergency and Standby Power Systems is referenced by NFPA 101: Life Safety CodeNFPA 99: Health Care Facilities CodeNFPA 72: National Fire Alarm and Signaling Code and NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection. NFPA 110 is also referenced by the International Fire Code (IFC), the International Building Code (IBC) and numerous state and local building codes. Additionally, NFPA 70: National Electrical Code mentions NFPA 110 as a resource for further information on performance, testing and maintenance in some of the NFPA 70 Informational Notes.  

Before we consider NFPA 110’s evolution, let’s consider an area that has not evolved. The Chapter 8 inspection, testing and maintenance rules of the entire emergency power supply system have not changed much for decades. The same basic language in 1999 has different bullet symbols now, but is still (with my comments added): 

Chapter 8.1.1: The routine maintenance and operational testing program shall be based on all of the following: 

    1. Manufacturer’s recommendations (this can change with new equipment). 
    2. Instruction manuals (this can change with new equipment). 
    3. Minimum requirements of this chapter (changes may occur on a three-year update cycle). 
    4. The authority having jurisdiction (no comment). 

We all know there is never just one AHJ. Design engineers, contractors and manufacturers should ensure that facility engineering personnel obtain at least two copies each of items 1 and 2 above from the project team whenever new equipment is installed or existing equipment is replaced. NFPA requires those two copies in two different locations. It is the responsibility of the facility engineering personnel to update themselves on NFPA 110 Chapter 8 changes every three years to comply with item 3 above. And finally, someone may need to have a list of the AHJs and find out what they want with respect to Chapter 8. 

What is an EPSS? 

What is this thing called an EPSS? The EPSS is defined by NFPA 110, Subchapter 3.3 General Definitions, as “a complete functioning system of an emergency power supply coupled to a system that can consist of conductors, disconnecting means and overcurrent protective devices, transfer switches and all control, supervisory and support devices up to and including the load terminals of the transfer equipment needed for the system to operate as a safe and reliable source of electric power.”  

In short, using the pre-2022 EPS equipment lists because we will shortly be seeing some new fuel cell system EPSs, that includes the generators, whatever makes them run (including the fuel oil tanks, fuel oil pumps and fuel oil controllers, panelboard powering the fuel oil controller, fuel oil alarms, remote equipment alarms, panelboard powering those EPSS alarm panels, emergency shutdown devices, cooling equipment including skid-mounted or remote radiators, water exchangers if the EPS is city-water cooled, starting batteries, control panels including EPSS power monitoring/control systems), paralleling switchgear if applicable, generator breakers, all panelboards between the EPS and the furthest downstream transfer switches and downstream to the load terminals of every transfer switch. The EPSS stops at the load terminals of each transfer switch (unless of course that transfer switch feeds an EPSS component, in which case an AHJ could argue that particular power source is also part of the EPSS.) 

Figure 1: This generator set is raised above the floor, providing protection from any water leakage potential. Courtesy: Jason O’Rear Photography, Smith Seckman Reid

Examples of the NFPA 110 evolution 

The list below is not all-inclusive. 

The minimum allowable hours of on-site fuel is not mandated by NFPA 110. That requirement is sometimes mandated by other codes and standards or by the federal, state or local governments. In the 2013 edition, the previously mandatory 96-hour fuel supply requirement for seismic categories was deleted from NFPA 110, further clarifying that the need for continued operation and the minimum operational time without refueling is a design consideration or is directed by a code, another standard or an AHJ. 

Fuel quality, fuel testing and fuel storage tanks were addressed in the 1996 edition (types of fuel tanks and spillage considerations), the 2005 edition (new annex material clarifying recommended diesel fuel testing and maintenance procedures), the 2013 edition (adding references to ASTM standards and additional annex material to further address fuel quality and storage issues) and the 2019 edition allowed the testing of fuel in accordance with the manufacturer’s recommendations in lieu of simply invoking an ASTM standard. The 2022 edition included new annex information to help users “understand fuel quality issues, identify applicable standards and types of tests available, as well as provide guidance on how to mitigate deficiencies.” 

The 2010 edition clarified that NFPA 110 does not apply to NEC Article 702 Optional Standby Systems.  

Grouping of related requirements occurred in the 2013 edition when construction requirements were consolidated within Chapter 5 and also when performance requirements were consolidated within Chapter 7.  

A generator fuel line automatic cutoff valve was prohibited starting in the 2016 edition to prevent the inadvertent cutoff of fuel at times when generator operation should not be stopped. 

The 2022 edition clarified the Level 1 energy converter design and testing requirement in subparagraph 5.2.3 Energy Converter Design and Testing to include “phase-to-ground, phase-to-phase and 3-phase bolted faults” within the previous short circuit requirement. 

Many NFPA standards apply only to new installations. In the 2010 edition, NFPA 110 clarified that Chapter 8 — which covers routine maintenance and operational testing as well as regular inspections of all EPSS components — applies to both new and existing EPSSs. The 2010 edition also changed operational test durations, loading conditions and the method of initiating the monthly EPS test. 

Other changes related to current Chapter 8 content included battery maintenance in the 1993 edition, revisions to monthly load testing requirements for generator sets along with discussions of potential wet stacking in the 1996 and 1999 editions. With diesel oil-fueled engines, light loading can create a condition termed “wet stacking,” indicating the presence of unburned fuel or carbon or both, in the exhaust system. Sometimes that unburned fuel will burn, resulting in the potential for equipment damage or much worse. 

The 1999 edition modified monthly testing requirements, which many users used to call 30/50 testing because it reflected the greater of 30% of the generator rating (still remaining) or 50% of the EPSS load (deleted in the 1999 edition), whichever was greater. The only relevant measure was clarified in the 1999 edition change to be the generator nameplate rating because extended generator loading below 30% of the nameplate rating was seen as increasing the likelihood of wet stacking.  

Monitoring that the EPS exhaust temperature meets manufacturer recommendations was added as an option in the 1999 edition because the exhaust temperature is also an acceptable performance measure of EPS loading. In the 2016 edition, paralleling gear acceptance testing and maintenance items were added, along with a requirement to rotate the transfer switch initiating the monthly test when there are multiple transfer switches. New section 8.5 Records was added in the 2016 edition to consolidate record management and define record retention requirements. 

Although not located within Chapter 8, a 2022 edition Annex paragraph A. change updated and clarified several recommendations regarding when to replace lead-acid starting batteries for generators. Those recommendations, based upon ohmic testing as well as the temperature exposure environment, should be reviewed by facility professionals as well as consulting-specifying engineers. 

Another Chapter 5 change in the 2022 edition added the requirement for Level 1 system load shed controls to the control panels portion of 5.6.5 Control Functions. There are also multiple other changes within the 2022 edition subsection 5.6.5. 

The 2022 edition has a few minor changes to 7.4 Mounting, including more specificity added to the traditional requirements. 

Figure 2: Two exterior generator sets with security fencing and below-unit oil tanks, often called belly tanks. This arrangement requires access for generator set maintenance as stipulated by NFPA 110. Courtesy: Smith Seckman Reid

Fuel cell systems  

In a major NFPA 110 change, the 2022 edition introduces requirements for fuel cell systems used for Level 1 or Level 2 standby power. These changes now align with both NFPA 70 and NFPA 99. The new fuel cell system EPS performance requirements were added to parallel with the performance requirements of the historical engine-generator assembly EPSs.  

Important note 1: Any existing documentation (design specifications, design drawings, manufacturer documentation and facility inspection, testing and maintenance documentation) that applied to previous NFPA 110 paragraph numbers should be reviewed against the 2022 edition and updated as appropriate. You are likely to find changes. 

Important note 2: The following discussion is intended to identify the types of major changes within NFPA 110-2022 to reflect fuel cell systems as EPSs. This article is not intended to supplant NFPA 110 as the source of information. In fact, readers who are intending to consider fuel cell systems as a Level 1 EPS or a Level 2 EPS must read, understand and comply with NFPA 110-2022, along with its references. 

Level 1 EPSSs are systems whose equipment failure could result in loss of human life or serious injuries. Level 2 EPSSs are systems whose equipment failure is less critical to human life and safety. NFPA 110 does not direct which EPSSs are Level 1 or Level 2 systems.  

As NFPA 110 states in Annex paragraph A.4.4.1 in part, along with a list of 7 common types of Level 1 systems, “Other NFPA codes and standards such as NFPA 20, NFPA 99, NFPA 101 and NFPA 1221 provide specific requirements on where Level 1 systems are required.” Annex paragraph A.4.4.2 discusses Level 2 systems whose interruption “could create hazards or hamper rescue or fire-fighting operations” along with a list of 6 examples of Level 2 systems. 

Newly referenced publications now include NFPA 2: Hydrogen Technologies Code and NFPA 853: Standard for the Installation of Stationary Fuel Cell Power Systems, along with the International Electrotechnical Commission IEC 62282-3-100, Fuel cell technologies – Part 3-100: Stationary fuel cell power systems – safety, 2019 edition. 

Chapter 3 (Definitions) added extracted text from NEC to define both a fuel cell (new paragraph 3.3.7) and a fuel cell system (new paragraph 3.3.8). Extracted text means that the source document is the only document that can change the extracted language. 

Chapter 4 (Classification of EPSSs) did not change in the 2022 edition. This short chapter defines the Class in hours that the EPSS must operate at its rated load without refueling or recharging, as well as the Type in seconds between the initial loss of power and the EPSS reenergizing the transfer switch load terminals, plus and Level 1 or Level 2 as described above. 

Chapter 5 (EPS: Energy Sources, Converters and Accessories) defines hydrogen gas by adding a new subparagraph 5.1.1(4) within 5.1 Energy Sources along with the related Annex A.5.1.1(4) information regarding NFPA 2 and NFPA 855. Also in Chapter 5, new subparagraph requires Level 1 fuel cell systems to be listed or field labeled, similarly to the existing requirement for Level 1 engine-generator assemblies. The related annex mentions the availability of ANSI/CSA FC1, Stationary Fuel Cell Power Systems for listing or field labeling fuel cells. 

Figure 3: This generator set has protection from nearby activity including potential damage from wheeled carts. Courtesy: Jason O’Rear Photography, Smith Seckman Reid

Chapter 5 differentiates between the historical engine-generator assembly EPSs and the fuel cell system EPSs by renumbering numerous existing paragraphs and subparagraphs and inserting new paragraphs and  subparagraphs reflecting the new fuel cell EPS parameters.  

New subparagraph lists the five allowable types of fuel cell system EPSs: proton exchange membrane, solid oxide, molten carbonate, phosphoric acid and alkaline. A related annex paragraph discusses startup ramp time for different types of fuel cell systems along with a short informational discussion of related compliance approaches. 

Another new subparagraph in 5.2.5 invokes NFPA 853 for fuel cell system EPSs with any NFPA 110 modifications. 

Under 5.3 Energy Converters – Temperature Maintenance; new subparagraphs 5.3.2 and both require a thermal management system for fuel cell system type EPSs to comply with their listings and requirements related to the cold start and load acceptance for the EPSS type. New subparagraph 5.3.6 requires compliance with the listing as well as the fuel cell system EPSs’ manufacturer installation instructions and specifications. 

Under new subsection 5.7 Fuel Cell System Equipment, there are numerous new detailed requirements, with the major topics generally as follows, plus several tables and annexes: 

  • 5.7.1 Fuel Cell System Ratings — derating factors and their effects on ability to meet load requirements. 
  • 5.7.2 Fuel Cell System Accessories — controls, power conditioning, bandwidth, rated frequency, frequency droop, frequency dip.
  • 5.7.3 Fuel Cell System Starting Equipment — manufacturer’s instructions. 
  • 5.7.4 Control Functions — on-site controls, local status notification, remote monitoring system where approved, control and monitoring functions, control and safety panel as part of EPS, equipment and/or characteristics, shutdown/lockout functions, alarms, Level 2/Level 1 priorities, alarm indicators, approvals, remote emergency stop switch, access only by qualified persons, remote common audible alarm. 
  • 5.7.5 Fuel Cell Cooling Systems — forced air, natural convection, liquid-cooled.

Chapter 7 (Installation and Environmental Considerations) has several new subparagraphs related to fuel cell system EPSs. Also, existing paragraph 7.4.4 has a new title “EPS Utilizing Rotating Equipment” and is limited to just that. 7.4.4 was also split into three segments to comply with the NFPA requirement that no paragraph may contain more than one requirement. Some other existing language that does not apply to fuel cell systems was clarified to apply only to rotating equipment systems, similar to the example above. A new paragraph 7.10.2 was inserted to cover fuel cell system exhaust equipment and installations.  

Section 7.9.1 covers fuel tanks. Existing subparagraph was clarified to cover only fuel tanks serving rotating equipment. New paragraphs and were added to cover fuel tanks and systems for use with fuel cell systems. Original paragraphs and became and 

Previous 7.13 Installation Acceptance requirements that still apply to rotating equipment EPSs has been renamed as subsection 7.13.4 Generator-Based EPSS Acceptance Testing. Also under the higher-level 7.13 Installation Acceptance, new subsection 7.13.5 Fuel Cell-based EPSS Acceptance Testing covers those requirements. There are some similarities plus some differences between those two subsections. 

In Chapter 8 (Routine Maintenance and Operational Testing) subsection 8.2.5 requires a maintenance manual complying with Section 7.4.5 of the previously referenced IEC 62282-3-100. Also in Chapter 8, a subparagraph of 8.4.1 (the paragraph requiring weekly inspections and monthly load tests) contains in the related requirements for a continually operating fuel cell system EPS. The existing 8.4.4 cold start requirement for generator load tests does not apply to an EPS that is continually running as an energy source as stated in new paragraph 

Author Bio: David Stymiest is a senior consultant at Smith Seckman Reid Inc. He has 48 years of experience in multiple types of facilities as a consulting electrical engineer, construction management and facility electrical engineering as an owner and now also a facility engineering management consultant. Although David Stymiest is a primary voting member (NFPA Special Expert category) and was previously the 10-year chairman of the NFPA Technical Committee on Emergency Power Supplies, which is responsible for NFPA 110 and 111, all views and opinions expressed in this article are purely those of the author and shall not be considered the official position of NFPA or any of its Technical Committees and shall not be considered to be, nor be relied upon as, a Formal Interpretation. Readers are encouraged to refer to the entire texts of all referenced documents (