NFPA 110 Overview
Part 1: Key Requirements for Emergency
and Standby Power Systems
White Paper 125
NFPA 110 Overview
Part 1: Key Requirements for Emergency and Standby Power Systems
NFPA 110 – Standard for Emergency and Standby Power Systems
provides basic requirements for the performance of
backup power systems.1 Often referenced by other standards and regulations, a useful understanding of NFPA 110 is
essential for professionals engaged in the installation and operation of critical power equipment. The first of a two-part
series, this document summarizes key highlights from the standard.
PURPOSE, SCOPE, AND APPLICABILITY
The purpose of NFPA 110 is to provide performance standards for Emergency Power Supply Systems (EPSS). It
addresses the installation, maintenance, operation and testing of emergency and standby power systems. With the
exception of
Maintenance and Operational Testing
Section 8
, the standard applies to newly installed systems. The requirements in
apply to both new and existing systems. Notably, NFPA 110 does not specify
Section 8 - Routine
where backup power systems must be used; other standards provide such requirements.
RELEVANCE TO OTHER CODES
•
International Building Code
power is required. It identifies Emergency Systems (including but not limited to fire alarm, exit signage, and
egress illumination systems) and Standby Systems (including but not limited to smoke control, powered door,
and emergency ventilation systems).
•
NFPA 70 – National Electrical Code® (NEC®)
from electrical hazards.3 Table 1 identifies key sections that relate to backup power systems and the loads
they power.
- The International Building Code is one code that does identify where backup
2
- The purpose of the NEC is to safeguard persons and property
The NEC also specifies requirements for generators and healthcare facilities in Articles 445 and 517,
respectively. For additional information, review the ASCO power Technologies document entitled
Changes for Backup Power
.
2020 NEC
Table 1. NEC Article Summary
Article Focus Type Installation Operation Maintenance Monitoring Control Systems Aected
700
701
702
708
1
NFPA 110 – Standard for Emergency and Standby Power Systems, 2019 Edition
2
International Building Code, 2018 Edition
3
NFPA 70 - National Electrical Code, 2020 Edition
Emergency
Systems
Legally
Required
Standby
Systems
Optional
Standby
Systems
Critical
Operations
Power Systems
Permanent X X X
Permanent X X X
Temporary
or
Permanent
Temporary
or
Permanent
. International Code Council. Washington, DC, USA. 2018.
X X
X X X X X
. National Fire Protection Agency. Quincy, Massachusetts, USA. 2019.
. National Fire Protection Agency. Quincy, Massachusetts, USA. 2018.
Lighting and power for
human safety
Power to eliminate
hazards and aid
rescue/reghting
Power to eliminate
discomfort or damage
to product/process
Power for national
security, economy,
public health/safety
2
•
NFPA 99 – Health Care Facilities Code
- NFPA 99 specifies requirements for mitigating hazards from facilities,
equipment, materials and other sources in healthcare facilities.4 For power systems, it specifies requirements for
loads served by the
personnel; the
Life Safety Branch
Critical Branch
, which addresses systems needed to ensure the safety of patients and
which serves area and functions involved in patient care; and the
Equipment Branch
which serves other systems such as medical air, suction, and smoke control systems.
CATEGORIZATION OF EMERGENCY POWER SUPPLY SYSTEMS
NFPA 110 applies performance standards to Emergency Power Supply Systems (EPSS). The requirements necessarily
vary by application. Section 4 of the standard thus dierentiates systems by
Class, Type
, and
Level
as follows:
,
• Class: Class is identified by the amount of time in hours that a backup power system is designed to operate without
refueling or recharging. The classifications are presented in Table 2.
5
• Type: Types define the maximum time, in seconds, that the EPSS will permit the load terminals of the transfer switch
to be without acceptable electrical power, as listed in Table 3.
6
• Level: Level 1 systems are installed where a failure of backup power could result in loss of human life or serious
injuries.7 Level 2 systems serve systems and equipment that are “less critical” to human life and safety.
Table 2: Classification of EPSSs
Class Minimum Time
Class 0.083 0.083 Hr. (5 Min.)
Class 0.25 0.25 Hr. (15 Min.)
Class 2 2 Hrs.
Class 6 6 Hrs.
Class 48 48 Hrs.
Class X As required by code, application, or user
Type Minimum Time
Type U Basically Uninterruptible (UPS)
Type 10 10 Seconds
Type 60 60 Seconds
Type 120 120 Seconds
Type M
Table 3: Types of EPSSs
Manual Stationary or Nonautomatic
– No Time Limit
8
4
NFPA 99 – Health Care Facilities Code, 2018 Edition
5 NFPA 110. Article 4.2. p. 110-8.
6 Ibid. Article 4.3. p. 110-8.
7 Ibid. Article 4.4.1. p. 110-8.
8 Ibid. Article 4.4.2.p. 110-8.
. National Fire Protection Agency. Quincy, Massachusetts, USA. 2017.
3
ENERGY SOURCES
Section 5 - Emergency Power Supply: Energy Sources, Converters, and Accessories
stipulates that liquified petroleum
fuels (e.g. diesel, gasoline), liquified petroleum gases (e.g. propane), and natural or synthetic gases can be used for
backup power generation. It also states that a utility service can be used for backup power where “the primary power
source is by means of on-site energy conversion.”
9
The standard identifies that the Emergency Power Supply (EPS) must be a generator driven by spark-ignited, diesel, or
gas turbine engines.
that is not associated with the generator or its accessories.
10,11
For Level 1 applications, the prime mover is not permitted to mechanically power any device
12
The Emergency Power Supply must be installed in accordance with NEC requirements, and must be of sucient
capacity to “pickup and carry” the emergency load in the time specified for its type (see Table 3 above).
13,14
The
remainder of Section 5 presents specific requirements for EPSs, including requirements for fuel systems, rotating
equipment, starting batteries, controls, alarms, and important derating factors for certain site conditions.
TRANSFER SWITCHES
Transfer switches
explained in the ASCO Power Technologies
General transfer switch requirements in
• Switch ratings sized for the total load that is designed to be connected
• A separate enclosure or compartment for each switch
transfer electric loads from one power source to another. Their essential functions are further
Technical Brief
Chapter 6 - Transfer Switch Equipment
entitled
Basic Automatic Transfer Switch Functions
of NFPA 110 include:
.15
• Use of switches and their load carrying components listed for all load types to be served
• Switch and load current-carrying components designed to withstand the eects of available fault currents.
• Where available, switches that are listed for emergency service as a completely factory-assembled and
factory-tested unit
9
Ibid. Article 5.1.3. p. 110-8.
10
Ibid. Article 5.2.1. p. 110-8.
11
Ibid. Article 5.2.4. p. 110-9.
12
Ibid. Article 5.2.4.2. p. 110-9.
13
Ibid. Article 5.2.5. p. 110-9.
14
Ibid. Article 5.4, p. 110-9.
15
Basic Automatic Transfer Switch Functions
resources/technical-briefs/basic-automatic-transfer-switch-functions.jsp. Accessed November 25, 2020.
16
NFPA 110. Article 6.1.6 et seq. p. 110-14.
16
. ASCO Power Technologies, Inc. Florham Park, NJ, USA. 2020. https://www.ascopower.com/us/en/
4
Each
Automatic Transfer Switch
to initiate transfer the alternate source.
must be equipped with a test means for simulating a failure of a normal power source
17
Automatic transfer switches sense voltage and frequency on the active power source, then transfer to backup power
when they sense unacceptable aberrations in voltage and frequency. For power source sensing, undervoltage sensing
devices are required for all ungrounded lines of the normal power source, and on one ungrounded line of EPS. When
voltages decrease below the minimum operating voltage of any load, the transfer switch must automatically initiate
engine start and transfer to the alternate power source. However, this function must be inhibited until the voltage and
frequency are within a specified range. Additional Information about power sensing and load transfer is available in the
ASCO Technical Brief entitled
Basic Power Source Synchronization and Paralleling
18
.
When the voltage on all phases of the normal source returns to specified ranges in a specified time, retransfer must be
initiated. Mechanical interlocking must prevent the inadvertent interconnection of power sources. Automatic Transfer
Switches must also provide for manual operation.19 In
mechanically held and operated by direct manual or electrical remote manual control.
non-automatic transfer switches
20
, switching devices must be
Time delays are necessary for the proper operation of transfer switches. NFPA 110 requires specific delays for starting
and transferring loads to an EPS, retransferring loads to the normal source, and engine cooldown. The code also
requires the bypassing of transfer delays if the EPS should fail.21 Additional Information is available about power sensing
and load transfer in the ASCO White Paper entitled
Timing Delays for ATS Transition Modes
22
.
Where transfer switches serve motor loads, NFPA 110 calls for provisions to reduce in-rush currents if they could
damage equipment or cause nuisance trips of overcurrent protective devices.23 For information on four approaches for
mitigating these currents, review the ASCO document entitled
the ASCO video entitled
White Paper Video – Transferring Motor Loads
Transferring Motor Loads Between Power Sources
24, 25
.
and
A power distribution system with a separately derived ground for the EPSS requires provisions for ensuring the continuity,
transfer, and isolation of the primary and EPS neutral conductors.26 Additional information on this topic can be found in
the ASCO Power Technologies document entitled
subject, view the ASCO video entitled
Bypass-Isolation Transfer Switches
When to Separately Ground a Backup Generator
are permitted by NFPA 110. This equipment allows operators to bypass the transfer
Switching the Neutral Conductor
27
.
For additional background on this
.
mechanism without disrupting power flow to loads. This capability enables inspection, service, and replacement of a
transfer switch mechanism without impacting downstream operations. NFPA 110 requires that bypass-isolation switches
have adequate ratings, be listed for emergency use as a factory-assembled and factory-tested unit, and to be able to
function as an independent non-automatic transfer switch. The equipment must also be capable of reconnecting the
transfer switch without interrupting power to loads.
17
Ibid. Article 6.2.12. p. 110-15.
18
Basic Power Source Synchronization and Paralleling
en/resources/technical-briefs/basic-power-source-synchronization.jsp. Accessed November 25, 2020.
19
Ibid. Article 6.2 et seq. p. 110-14.
20
Ibid. Article 6.2.16. p. 110-15.
21
Ibid. Article 6.2.5 et seq., 110-14.
22
Timing Delays for ATS Transition Modes
document/ASC-TS-WP-123-TD-ATS/. Accessed November 25, 2020.
23
Ibid. Article 6.2.14. p. 110-14.
24
Transferring Motor Loads Between Power Sources
download/document/asc-ts-wp-119-motorloads/. Accessed November 25, 2020.
25
White Paper Video - Transferring Motor Loads
watch?v=l75DQDUwvhg. Accessed November 25, 2020.
26
NFPA 110. Article 6.2.15. p. 110-14.
27
Switching the Neutral Conductor
document/TS-WP-NEUTRALCON/. Accessed November 25, 2020.
28
NFPA 110. Article 6.4 et seq. p. 110-115.
. ASCO Power Technologies, Inc. Florham Park, NJ, USA. 2020. https://www.ascopower.com/us/en/download/
. ASCO Power Technologies, Inc. Florham Park, NJ, USA. 2019. https://www.ascopower.com/us/en/download/
. ASCO Power Technologies, Inc. Florham Park, NJ, USA. 2020. https://www.ascopower.com/us/
. ASCO Power Technologies, Inc. Florham Park, NJ, USA. 2020. https://www.ascopower.com/us/en/
. ASCO Power Technologies, Inc. Florham Park, NJ, USA. 2020. https://www.youtube.com/
28
5
SUMMARY
The first of a two-part series, this document highlights NFPA 110 requirements for Emergency Power Supplies and
Emergency Power Supply Systems. In addition to explaining the relationship between NFPA 110 and other selected
standards, this white paper describes how NFPA 110 categorizes back power systems and highlights key requirements
for power sources and transfer switches. Part 2 of this document will review installation, testing, and maintenance of
emergency and standby power systems in accordance with NFPA 110 requirements.
6
ASCO Power Technologies - Global Headquarters
160 Park Avenue
whitepapers.ascopower.com
customercare@ascopower.com
Florham Park, NJ 07932
Tel: 800 800 ASCO
© 2020 ASCO Power Technologies. All Rights Reserved. Life Is On Schneider Electric is a trademark and the property of Schneider Electric SE, its subsidiaries and aliated companies.
Loading...