NFPA 110 Generator System Equipment Specifications

WhitE PAPEr

iNtrODUCtiON

The National Fire Protection Association (NFPA) maintains several standards that may be invoked for applications of standby generators and automatic transfer switches. One of the most prominent is NFPA 110, Standard for Emergency and Standby Power Systems, which is currently published in a 2005 edition. To develop well written specifications for projects utilizing generator systems, it is important to understand equipment requirements associated with referencing NFPA 110. This White Paper provides guidelines to assist engineers in this task.

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SCOPE OF NFPA 110

NFPA 110 covers construction, installation, maintenance and operational testing requirements as these pertain to performance of an emergency power supply system (EPSS). By NFPA 110 definition (ref. Section 3.3.3), the EPSS consists of an emergency power supply (or engine-driven generator set (EPS) for example) connected to a system of conductors, disconnecting means, overcurrent protective devices, transfer switches and all control, supervisory and support devices up to and including the load terminals of the transfer equipment.

NFPA 110 does not address what facilities or loads within a building require an EPSS, nor does it prescribe required classifications for an EPSS. Ultimately, this responsibility lies with the authority having jurisdiction (AHJ) for the site of the construction project, such as the local building inspection or fire marshal's office. Requirements for NFPA 110 compliance may be included in local laws, ordinances or regulations. Local authorities should always be consulted to determine requirements for specifying NFPA 110 compliance on any project.

CLASSiFiCAtiON OF EMErGENCY POWEr SUPPLY SYStEMS

NFPA 110 identifies three attributes that are used to classify an EPSS – Class, Type and Level. Therefore, stating that a generator "shall meet NFPA 110" is an incomplete specification. EPSS Class, Type and Level need to be defined in the project specification to quote the proper generator configuration. Otherwise, additional clarification will be required which can delay the bidding process.

NFPA 110 does not prescribe what Class, Type and Level an EPSS should be for any given installation. This determination ultimately rests with the AHJ, whom should be consulted when creating the specification. However, the NFPA 110 standard does provide guidelines to assist parties involved in the definition process.

Class – This defines the minimum amount of hours that the EPSS can operate at its rated load without being refueled. Therefore, a Class 48 system must operate for a minimum of 48 hours while a Class 0.25 system must operate for a minimum of 0.25 hours (15 minutes). Selection of class should take into account past outage records and fuel delivery problems due to weather, shortages, and other geographic/environmental conditions (ref. NFPA 110 Annex A4.2). For example, Class 48 (or in some cases Class 72) is being adopted for certain applications such as healthcare.

A primary effect of EPSS Class is on the fuel storage tank of a generator. The fuel storage tank must be sized to meet Class requirements. Refer to the "Generator Equipment & Accessories For NFPA 110 Compliance" section below for further discussion on fuel supply requirements.

Type – This defines the maximum amount of seconds that the load terminals of the EPSS transfer switch can be without acceptable electrical power. In other words, this is the maximum allowable time from the moment of a utility outage until the generator is operating and the EPSS is providing the facility load with electrical power. As an example, a Type 10 EPSS must provide electrical power within 10 seconds. The 10 second start capability is a relatively common performance trait of a good quality generator system that is properly installed and maintained.

In addition, NFPA 110 also defines two letter designations – Type U is uninterruptible, which requires that a UPS (Uninterruptible Power Supply) system be used. Type M is manual operation, which has no time limit requirement.

Level – There are two Levels defined by NFPA 110 for an EPSS. Level 1 is more stringent and is imposed when failureof EPSS equipment could result in loss of human life or serious injuries. Level 2 is used when failure of theEPSS is less critical to human life and safety. NFPA 110 Annex "A" provides guidelines and examples of Level 1and Level 2 systems. Level 1 requires additional generator features as described later in this document.

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iNFOrMAtiON tO BE PrOViDED iN thE PrOJECt SPECiFiCAtiON

When a project specification is being written for an NFPA 110 EPSS, certain information is needed to fully define generator requirements. In addition to equipment and performance requirements, the following should be included in the specification or supporting documents to allow proper quoting of NFPA 110 compliant generator systems:

• Class, Type and Level of EPSS • Project site altitude • Project site maximum and minimum ambient temperatures for generators installed outdoors or equipment room

conditions for indoor installations • Type of fuel supply and local fuel energy content • Building load power quality requirements: – Frequency regulation from no load to full load conditions – Permissible frequency and voltage dip

GENErAtOr EQUiPMENt & ACCESSOriES FOr NFPA 11O COMPLiANCE

Chapter 5 of NFPA 110 defines specific equipment and accessory requirements for generators. The dealer or sales office for each major generator manufacturer can provide quotes on compliant generators. While the standard provides a complete listing of requirements, those that differ between Level 1 and Level 2 systems, and other items of note, are listed below. The specific section of NFPA 110 is referenced in parentheses after each item:

• Level 1 installations in locations with high probability of off-site fuel supply interruption require on-site fuel storage capacity consistent with the EPSS Class, along with provisions for automatic transfer of fuel supplies (5.1).

• Level 1 installations in seismic risk areas (Zones 3 and 4) require a minimum 96 hour on-site fuel supply, i.e. Class 96 EPSS (5.1.2).

• Generators must be separately prototype tested as a complete assembly to prove capabilities consistent with the standard (5.2). This makes it very difficult to ensure that units built by a system packager are compliant with requirements.

• For a Level 1 EPSS, fuel supplies other than natural or synthetic gas cannot be shared with any other purpose (5.5.1). • For a Level 2 EPSS, the fuel supply can be shared, provided the draw-down level for auxiliary equipment always

maintains the quantity needed for EPSS run-time requirements (5.5.1.1). • Low fuel indication is required when the supply is below the quantity needed for EPSS run-time requirements (5.5.2). • Fuel reservoir capacity shall be at least 133% of either the low fuel indication level or the quantity needed to meet run-

time requirements for the EPSS Class (5.5.3). • For Level 1 systems, the automatic battery charger must be sized to provide a 100% charge to a fully discharged

starting battery within 24 hours. The time requirement is 36 hours on Level 2 systems (5.6.4.7 and Table 5.6.4.2). • Both Level 1 and Level 2 systems require a set of local and remote safety indications and shutdowns with the

generator. However, the requirements are much more extensive for Level 1 systems (Table 5.6.5.2) and are typically met by providing a remote annunciation panel with the generator.

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GENErAtOr EQUiPMENt & ACCESSOriES FOr NFPA 11O COMPLiANCE (Continued) • Level 1 installations require the generator control panel to have (5.6.9.9): – an AC voltmeter and ammeter for each phase or a phase selector switch – a frequency meter – a rheostat or controls to allow +5% voltage adjustment

trANSFEr SWitCh EQUiPMENt rEQUirEMENtS

Chapter 6 of NFPA 110 defines specific equipment requirements for transfer switches. The dealer or sales office for each major transfer switch manufacturer can provide quotes on compliant units. This chapter also provides a complete listing of requirements, which are virtually identical for both Level 1 and Level 2 systems. The only exception is section 6.2.7, which requires an adjustable time delay for load transfers to the EPS. This is a feature available on many commercial automatic transfer switches.

iNStALLAtiON, MAiNtENANCE & tEStiNG

Installation, maintenance and testing requirements for Level 1 and Level 2 systems are covered in Chapters 7 and 8 of NFPA 110. Much of the material presented in these chapters is outside the scope of this White Paper, which is dedicated to equipment requirements for generator systems. However, several items that have implications on equipment requirements are presented here and the relevant NFPA 110 section is listed in parentheses after each item.

• For Level 1 systems, ventilation dampers for equipment rooms and generator outdoor enclosures must be spring-open, motor-closed. Fire dampers, shutters or other self-closing devices are not permitted (7.7.5).

• Fuel supply systems must maintain external fuel supplies within the fuel lift and static head pressure limits of the engine's fuel pump (7.9.2 and 7.9.2.1). These are available from the generator manufacturer. If the pressure limits are exceeded, a day tank arrangement is required.

• Integral fuel tanks for generators installed indoors or on rooftops are limited to 660 gallons of diesel fuel or 25 gallons of gasoline (7.9.5).

• Flexible connectors for exhaust piping are typically supplied by the generator manufacturer (7.10.3). • Section 7.13 requires full load testing of the installed system, with 7.13.6.1 allowing the on-site tests to be at unity

power factor, provided that rated power factor (typically 0.8) generator testing has been done by the manufacturer. However, standard factory testing by the generator manufacturer may be at unity power factor. If this is the case, 0.8 power factor testing should be included in the supplier’s bid, either as a factory option or by on-site reactive load bank testing.

NOTICE – The intent of this document is to help familiarize the reader with the scope of NFPA 110 as it relates to engine-driven generators. It is not intended to be a substitute for the actual NFPA 110 Standard. The specifying agent and all other parties involved in the procurement, installation, maintenance and operation of the generator system must reference the current NFPA 110 Standard in effect for the facility to ensure compliance and ultimate approval by the local authority having jurisdiction.

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Bulletin 0173220SBY / Printed in USA 06.06