2. NFPA110 Overview
Purpose
NFPA 110 describes minimum requirements for EPSS system
performance that is necessary for life safety applications.
– A unique requirement, not addressed in most other standards
– EPSS (emergency power supply system) is an electro-
mechanical system
• Standards tend to be either electrical or mechanical
– EPS (emergency power supply) is the source of power in EPSS
Intent of standard is to achieve maximum system reliability
Why is this needed?
– Example: Alternator voltage dip on load application
3. NFPA110 Overview
What’s the voltage dip?
18%, right?
Nope! This is alternator only!
VOLTAGE ROLLOFF
0
20
40
60
80
100
120
45 50 55 60 65
FREQUENCY
%VOLTAGE
4. NFPA110 Overview
Terminology
EPSS: Emergency Power
Supply Systems
EPS: Emergency Power
Supply
Level:
– 1: critical to life safety
– 2:
Class:
– duration of system
operation
Type:
– time period that the load
can be without power
6. NFPA110 Overview
Prototype Test Requirements
Bad news: There’s no common agreement on detailed requirements
for prototype test
Some of the requirements are hardware related
Some of the requirements are installation related
Some requirements depend on proper settings and operation
Best available control is required (especially AVR, governor)
Manufacturer of genset to certify compliance
7. NFPA110 Overview
Prototype, Production, and Site Testing
Prototype tests validate the design
– May be destructive
– Short circuit, life, performance, drop tests, out of phase
paralleling, seismic, overload, starting time, etc.
Production tests validate proper assembly
– Requires good production control (ie, ISO9000)
– Starting, transient performance (gain tuning), full load capability
(0.8 pf), block load capability
Site commissioning tests validate the installation
– Starting, ability to carry full load, accessory installation, black
start test, block load test
Regular exercise and tests verifies proper maintenance
8. NFPA110 Overview
Site Test: Cold Start Requirement
Requires coolant heaters to be continuously
operating
Typical requirement is that genset must be in a 40F
environment in order to start in 10 seconds, and pick
up full load
Alarm when engine temperature too low to start and
pick up load in 10 seconds
9. NFPA110 Overview
Site Test: Full Load Operation
Generator set must be able to carry required loads
for duration of time based on defined Class
Evaluate based on site conditions
Impact of installation problems…
10. NFPA110 Overview
Importance of Starting System
Properly sized
batteries
Proper starting
cycle
– Diesels can be
continuous
crank
Proper charger
– features
– recharge time
11. NFPA110 Overview
Critical Charger Performance
Sufficient capacity to recharge batteries within 24
hours (Level 1)
– 225 amp-hour battery recharges in 22.5 hours with 10A
charger
• Charger designed to charge a fully discharged battery
• Need TWO 10A chargers for most 24V diesels
Critical to get charger that properly “floats” when
battery is fully charged
Proper charge rate depends on temperature
compensation—especially for outdoor gensets
12. NFPA110 Overview
Emissions-controlled engines include these functions by
default, plus many more
Operator panels are cheap
Specify display all engine and alternator data for all
applications
Remote annunciation required
13. NFPA110 Overview
Engine Cooling Systems
How often do you do commissioning at full load
on the hottest day of the year?
Air Flow In
90F 110F 125F
14. NFPA110 Overview
Alternator Requirements
What the heck is
“amortisseur”?
Protects
alternator field
during short
circuit conditions
Common on
larger machines,
not so much on
smaller
Amortisseur Windings
15. NFPA110 Overview
Other Alternator Requirements
Stable with all loads (maybe hard)
– Much of a modern facility load is non-
linear
– Low cost voltage regulators may have
operational problems
Operate at the
correct voltage at
all loads (easy)
Sized to prevent
load drop out due
to voltage dip
– Remember
engine/alternator
volts/hz function
16. NFPA110 Overview
Transfer Switch Requirements
Not very hard to meet…
It’s got to work (duh!)
Separate enclosure for each ATS
Must have commonly available time delays
– Start, stop, transfer, retransfer
– Controlled operation speed for motor loads (my opinion)
Source availability sensing
– All-Phase undervoltage sensing line side
– Single phase undervoltage and frequency sensing on genset side
Mechanical & electrical interlock, except closed transition (???)
Exercisor clock in system, test switch, position indication, switched
neutral pole when required
Labeled as LISTED for use in emergency circuits
Suitable for fault currents…
18. NFPA110 Overview
Selective Coordination (Bonus Info)
Move breakers off generator set to remote switchboard or breaker boxes for each
load type
– Make selective coordination task the responsibility of one party
– Includes Service Entrance requirements for outdoor generators
Overload (ANSI 51 Function) is required but is not necessarily required to be
located on the generator
– A main breaker in the switchboard may provide this function
– See NEC Handbook
19. NFPA110 Overview
Other Installation Points
Dedicated genset room
– Separated from normal
service
Minimize risk of flood
Accessible
Battery lighting, lighting
from ATS
Doesn’t vibrate the
building
20. NFPA110 Overview
Other Installation Points (con’t)
Cooling system properly
designed, including
provisions for service
Probably need alternator
heaters for outdoor
gensets
Ventilation system allows
enough airflow
Don’t do something stupid
with the exhaust system
21. NFPA110 Overview
Fuel System
Perhaps your biggest risk…
– Easiest to do wrong
– 2nd most likely reason for unplanned shutdown
Design depends on somewhat on engine
manufacturer
More sensitive with emission-controlled engines
Many codes and standards to comply with
– Subject to local interpretation
Your generator guy is your friend…
22. NFPA110 Overview
Outdoor Generator Sets (NEW)
Coolant heaters are not sufficient to meet this
requirement
Guideline: enclosures maintained at a minimum
temperature of 40ºF, assuming coolant heaters
designed as in past (now required)
23. NFPA110 Overview
Installation Acceptance Testing
Detailed requirements are in the standard
– Rewritten in 2010 version
– Specify: “System shall be tested as required in
NFPA 110-2010 section 7.13.4.1.”
Cold start test
– Engine(s) in normal mode, with heaters running
– Must start and pick up all emergency loads
2-Hour full load test
– 0.8 pf, unless tested at factory at 0.8 pf
– Parallel gensets can be used for this
Full load step test
– 0.8 pf gives different results than 1.0 pf
Paralleled gensets can be load tested individually
Standard requires testing the engine safeties and cycle
crank
– A bit of a waste, as all engines are emissionized, and have
fail safe sensor circuits; factory test is allowed with report
Documentation Required
– Prototype test certification including torsionals, test
certificate
– Installation certification
24. NFPA110 Overview
A set of manuals and other operating information as
well as recommended spares are required to be
located in the generator room for level 1 systems
(recommended for all)
A routine maintenance and test program must be
implemented for all systems
– Monthly tests under load
• At least 30% of rated load or load sufficient to develop
minimum exhaust temperature recommended by engine maker
– Some exceptions are available for diesel gensets
• ATS must be operated every month, so using the ATS to “test
with load” is a good idea
Annual inspection, cleaning and operational testing of ATS
and breakers is required
A test of the entire EPSS for Level 1 systems, including all
assigned loads is required every 36 months
– Duration of test is based on class, maximum 4 hours
– May be combined with annual test
– Requires minimum of 75% of rated load
Permanent record of test/exercise schedule, test results, and
maintenance/service on the system is required
– Samples are in the standard
sample
Ongoing Maintenance and Testing
25. NFPA110 Overview
NFPA 110
Requirements to achieve
maximum on-site power
system reliability
System Focus
Practical, but not cheap
See appendix for some
practical advice on power
system design and
operation
