Bulletin No. 0613DB9902
June 1999
Cedar Rapids, IA USA
Data Bulletin
ANSI® C37 Standard and UL® 489 Standard Comparison
EVOLUTION OF PRODUCTS AND
MARKETS
Since Ben Franklin discovered electricity, people have been struggling to
harness its energy and use it safely. As the use of electricity spread into
residences and commercial businesses, the need for personal safety and
protection against fires became clear.
People needed products that were safe to use and afforded protection against
the hazards of fire. They used electricity in their homes and businesses but
were not trained to determine the types of products they needed to protect
themselves and their property.
Underwriters Laboratories Inc.® (UL®)
Underwriters Laboratories Inc. (UL), was set up in the late 1800s to test many
products for the insurance industry. Fire safety and prevention were a major
concern. UL, working with electrical manufacturers, developed standards for
electrical products and provided third-party certification assuring that the
products provide safe and intended functionality regardless of manufacturer.
The products began as safety switches evolving into circuit breakers and load
centers.
The molded case circuit breakers designed for this market are Listed to the
UL 489 Standard. UL 489 requires that these circuit breakers meet specific
construction and testing requirements to provide necessary protection while
requiring little or no maintenance. One important feature of these types of
circuit breakers is the enclosed molded case which provides personal safety
as well as assuring proper dielectric clearances.
The American National Standards
Institute® (ANSI®)
As the need and dependence on electricity grew, power generation along with
large industrial users and continuous process industries became a large part
of our industrial complex. Safety and fire prevention were major
considerations but continuity of service and equipment performance were
also primary requirements. These users had highly trained staffs that worked
with manufacturers and the International Electrical and Electronics Engineers,
Inc. (IEEE®) committee to design, test and produce electrical equipment that
provided the safety, performance and continuity of service they required.
The American National Standards Institute (ANSI) compiled these
accumulated design and test documents, provided by IEEE and
manufacturers, into ANSI Standards. These standards then became the basis
for designing and testing low-voltage power circuit breakers (LVPCBs) and
switchgear.
Switchgear is designed with strict standards for compartmentalization,
drawout construction and steel barriers between circuit breaker, bus and
instrument compartments. Because of the compartmentalization and barriers,
LVPCBs were designed with an open construction to allow for strength, heat
dissipation and maintenance that was necessary for long service life.
CIRCUIT BREAKER AND EQUIPMENT
STANDARDS
UL incorporated ANSI Standard C37 into the UL 1558 Standard for
switchgear in 1982 and into the UL 1066 standard for low-voltage power circuit
breakers in 1985. These two UL standards provide the basis for third-party
witnessing and certification to the ANSI Standard.
Circuit Breaker Standards
UL 489
ANSI C37.13 and C37.50 or UL 1066
Equipment Standards
© 1999 Square D All Rights Reserved
UL67 Panelboards
UL 891 Switchboards
ANSI Switchgear or UL1558 Switchgear or UL 891 Switchboards
ANSI® C37 Standard and UL® 489 Standard Comparison
Data Bulletin
DIFFERENCES BETWEEN THE UL 489
STANDARD AND THE ANSI C37
STANDARD
Bulletin No. 0613DB9902
June 1999
The UL and ANSI Standards differ in four basic areas:
Philosophy
Construction
Performance testing
Certification
Philosophy
UL 489 Standard Design and Test Philosophy
The scope of the UL 489 Molded Case Circuit Breaker Standard includes
miniature circuit breakers (MCBs), molded case circuit breakers (MCCBs)
and insulated case circuit breakers (ICCBs). These circuit breakers are
typically rated 10–6000 A and up to 600 Vac and 500 Vdc. Circuit breakers
designed and tested to this standard typically exhibit the following
characteristics:
Sealed molded case
Little or no maintenance
No user replaceable parts
Good performance and reliability
Long service life
ANSI C37 Standard Design and Test
Philosophy
The scope of the ANSI C37 Low Voltage Power Circuit Breaker Standard
includes 2- or 3-pole stationary and drawout circuit breakers. The
specifications of these circuit breakers are 254, 508 or 635 Vac maximum,
fused or unfused, and manually- or power-operated with or without
electromechanical or electronic trip units. These circuit breakers typically
exhibit the following characteristics:
Iron frame—older designs are open, newer designs are closed
Maintainable for long service life
Most parts can be replaced in the field
High performance and reliability
High maintenance costs
Construction
The main construction differences between UL 489 Listed and ANSI C37
Certified circuit breakers are maintainability, ampere interrupting ratings
(AIRs), heat rise and endurance. These construction differences result from
the design and test philosophies outlined above. These differences will be
discussed under Performance Testing.
UL 489 Listed circuit breakers are sealed and require no maintenance for a
long service life. ANSI C37 Certified circuit breakers typically require
maintenance for long life and have been designed with an open case to
facilitate maintenance.
Performance Testing
The UL 489 and ANSI C37 Standards require the same basic tests including
the following:
Dielectric
Calibration
Overload
Temperature
Endurance
Short circuit
Both the UL 489 and ANSI C37 Standards demonstrate the circuit breaker’s
ability to protect conductors under overload or short-circuit conditions. The
major differences in performance testing occur during the details and
sequences of the tests for overload, temperature, endurance and shortcircuit conditions.
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© 1999 Square D All Rights Reserved
ANSI® C37 Standard and UL® 489 Standard Comparison
Data Bulletin
Bulletin No. 0613DB9902
June 1999
Overload Testing
Overload testing is done to demonstrate making
and breaking current values that might be
obtained when initially energizing a motor load.
Each time the circuit breaker is closed and
opened on a high current load (600%), the contact
surfaces are subjected to arcing and heat. This
action simulates an accelerated life test to make
sure the contacts provide adequate conductivity
through many operations. The UL 489 Standard
tests all circuit breaker ratings with significant
operations to ensure the design is capable of a
long service life with no maintenance. The ANSI
C37 Standard tests circuit breakers rated only up
to 2000 A.
Temperature Testing
The UL 489 Standard allows for two types of
ratings. Standard circuit breakers cannot exceed
a maximum of 50°C temperature rise at the wire
terminal connection at 100% current in 40°C open
air. 100% rated circuit breakers may have a
temperature rise of 60°C at the wire terminal
connection in the smallest allowable enclosure if
the circuit breakers are connected with wire rated
at 90°C wiring insulation sized to the 75°C chart
(Table 310-16, National Electric Code®—NEC®).
The ANSI C37 Standard requires a maximum of
55°C temperature rise at 100% in the smallest
enclosure and a maximum of 85°C temperature
rise on the contacts.
Endurance Testing
Circuit breakers tested to the UL 489 Standard
must pass a significant number of operations
without any maintenance. This test verifies that
the design is capable of a long service life. The
ANSI C37 Standard tests circuit breakers for
further operations but then allows for
maintenance of the circuit breaker at relatively
short intervals.
UL 489
Power Factor: 0.50
Frame size
(A)
Frame size
(A)
© 1999 Square D All Rights Reserved
Number of operations at
rated voltage
Number of operations
at rated voltage
50–1600
50
600% current
225–800
50
600% current
1601–2500
25
600% current
1600–2000
38
600% current
2501–6000
3
600% current*
>2000
0
*An additional 25 operations at 200% current.
UL 489
ANSI C37
Temperature
50°C temperature rise at line and load
terminals
55°C temperature rise at line and
load terminal bus connections
and 85°C temperature rise on
circuit breaker contacts
Current
Standard circuit breaker:
100% rated current in open air at 40°C
80% rated current in smallest enclosure
100% rated current in smallest
enclosure
Exceptions
100% rated circuit breaker:
Trip unit defeated
100% rated current in smallest enclosure
Temperature rise may be 60°C if 90°C
wire is used sized to the 75°C chart (NEC)
UL 489
ANSI C37
Power factor: 0.75–0.80
Power factor: 0.85
Maintenance not allowed
Maintenance allowed
Max. frame
size (A)
Number of operations at
rated voltage
Max. frame
size (A)
Number of operations
at rated voltage
100
6000
4000
At rated current
Without current
225
4000
10000
2500
At rated current
Without current
Between maintenance
225
4000
4000
At rated current
Without current
600
2800
9700
1750
At rated current
Without current
Between maintenance
600
1000
5000
At rated current
Without current
800
2800
9700
1750
At rated current
Without current
Between maintenance
800
500
3000
At rated current
Without current
1600
800
3200
500
At rated current
Without current
Between maintenance
2500
500
2000
At rated current
Without current
2000
800
3200
500
At rated current
Without current
Between maintenance
6000
400
1100
At rated current
Without current
3200
400
1100
250
At rated current
Without current
Between maintenance
4000
400
1100
250
At rated current
Without current
Between maintenance
NOTE: No manufacturer currently offers 225 A or
600 A frame circuit breakers tested to ANSI C37.
Short-circuit Testing
The short-circuit tests reflect differences in the
philosophies between the UL and ANSI circuit
breaker standards. The UL 489 Standard requires
that the tests be conducted at several values of
short-circuit current. A separate test sequence
evaluates the maximum interrupting rating
claimed by the manufacturer. Tests are conducted
at the rated voltage(s) of the circuit breaker which
is typically 240, 480 or 600 V.
ANSI C37
Power Factor: 0.45–0.50
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ANSI® C37 Standard and UL® 489 Standard Comparison
Data Bulletin
Three-pole circuit breakers are tested under
three-phase conditions during the maximum
interrupting ability sequence. Each pole is tested
individually at a reduced current level. The circuit
breaker must safely interrupt the short-circuit
current and protect the rated wire in the circuit.
The ANSI C37 Standard requires that a threepole circuit breaker be tested under three-phase
conditions at the maximum interrupting rating and
also that each individual pole be tested at 87% of
the maximum interrupting rating. Both the threephase and the individual-pole tests are conducted
at rated maximum voltages of 254, 508 and 635 V.
The ANSI C37 Standard also includes a separate
sequence to evaluate the short-time withstand
current of the circuit breaker. The short-time
withstand current is a high-level current that can
be maintained for 0.5 seconds without damage to
the circuit breaker.
Certification
Bulletin No. 0613DB9902
June 1999
Short
Circuit
UL 489
ANSI C37
Power factor
≤10,000 A
10,001–20,000 A
≥ 20,000 A
Voltage and
current
Rated voltage with low-, mediumand high-level current
Rated current at the three voltage
levels: 254, 508 and 635 Vac
Operations
Open—close/open on all three
poles
Open—close/open on all three poles.
First open at closing angle to ensure
peak current of 2.3 x rated current in
one phase
0.45–0.50
0.25–0.30
0.15–0.20
Open—close/open on each
individual pole at reduced current
level
0.15 Unfused
0.20 Fused
Open—close/open individual pole at
87% of rated current
Short-time withstand—first ON cycle,
closing angle must ensure a peak
current of 2.3 x rated current in one
phase. Circuit breaker remains
closed, tripping disabled—0.5 sec.
ON, 15 sec. OFF, 0.5 sec. ON
Certification tests to the UL 489 Standard are witnessed by UL engineering
representatives. At the successful completion of the test program, UL permits
circuit breakers to bear a UL Listing mark combined with the product identity
of “CIRCUIT BREAKER” or “CIRCUIT BREAKER FRAME.” These circuit
breakers are then required to undergo subsequent follow-up testing on a
regular basis: quarterly, semiannually or biannually depending on the circuit
breaker size and quantities produced. All follow-up tests are witnessed by UL
field representatives.
Certification tests to the UL 1066 Standard (which include the requirements
of the ANSI C37 Standard) are witnessed by UL engineering representatives.
At the successful completion of both UL test programs, UL permits the circuit
breaker to bear a UL Listing mark combined with the product identity of “LOW
VOLTAGE AC POWER CIRCUIT BREAKER” or “LOW VOLTAGE AC
POWER CIRCUIT BREAKER FRAME.” While UL conducts follow-up
inspections on the UL 1066 Standard tested products to ensure that the
construction has not changed from that which was originally tested, they do
not require subsequent follow-up testing.
Square D Company
PO Box 3069, 3700 Sixth St. SW
Cedar Rapids, IA 52406-3069
Field Services: 1-800-634-2003
www.squared.com
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Square D and
are registered trademarks of Square D/Schneider Electric or related companies.
Underwriters Laboratories Inc. and UL are registered trademarks of Underwriters Laboratories Inc.
ANSI is a registered trademark of American National Standards Institute, Inc.
National Electric Code and NEC are registered trademarks of National Fire Protection Association, Inc.
IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
All other trademarks are the intellectual property of their respective companies.
Bulletin No. 0613DB9902 June 1999 © 1999 Square D All Rights Reserved.