Bulletin No. 0613DB9902 Data Bulletin June 1999 Cedar ...

Data Bulletin Bulletin No. 0613DB9902
June 1999
ANSI® C37 Standard and UL® 489 Standard Comparison
Cedar Rapids, IA USA

EVOLUTION OF PRODUCTS AND Since Ben Franklin discovered electricity, people have been struggling to
MARKETS harness its energy and use it safely. As the use of electricity spread into
residences and commercial businesses, the need for personal safety and
Underwriters Laboratories Inc.® (UL®) protection against fires became clear.

The American National Standards People needed products that were safe to use and afforded protection against
Institute® (ANSI®) 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
CIRCUIT BREAKER AND EQUIPMENT themselves and their property.
STANDARDS
Circuit Breaker Standards Underwriters Laboratories Inc. (UL), was set up in the late 1800s to test many
Equipment Standards products for the insurance industry. Fire safety and prevention were a major
concern. UL, working with electrical manufacturers, developed standards for
© 1999 Square D All Rights Reserved 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.

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.

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.

UL 489
ANSI C37.13 and C37.50 or UL 1066

UL67 Panelboards
UL 891 Switchboards
ANSI Switchgear or UL1558 Switchgear or UL 891 Switchboards

ANSI® C37 Standard and UL® 489 Standard Comparison Bulletin No. 0613DB9902
Data Bulletin June 1999

DIFFERENCES BETWEEN THE UL 489 The UL and ANSI Standards differ in four basic areas:
STANDARD AND THE ANSI C37
STANDARD Philosophy
Construction
Performance testing
Certification

Philosophy The scope of the UL 489 Molded Case Circuit Breaker Standard includes
UL 489 Standard Design and Test Philosophy miniature circuit breakers (MCBs), molded case circuit breakers (MCCBs)
and insulated case circuit breakers (ICCBs). These circuit breakers are
ANSI C37 Standard Design and Test typically rated 10–6000 A and up to 600 Vac and 500 Vdc. Circuit breakers
Philosophy 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

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 short-

circuit conditions.

2 © 1999 Square D All Rights Reserved

Bulletin No. 0613DB9902 ANSI® C37 Standard and UL® 489 Standard Comparison
June 1999 Data Bulletin

Overload Testing UL 489 ANSI C37
Overload testing is done to demonstrate making
and breaking current values that might be Power Factor: 0.45–0.50 Power Factor: 0.50
obtained when initially energizing a motor load.
Each time the circuit breaker is closed and Frame size Number of operations at Frame size Number of operations
opened on a high current load (600%), the contact (A)
surfaces are subjected to arcing and heat. This rated voltage (A) at rated voltage
action simulates an accelerated life test to make
sure the contacts provide adequate conductivity 50–1600 50 600% current 225–800 50 600% current
through many operations. The UL 489 Standard
tests all circuit breaker ratings with significant 1601–2500 25 600% current 1600–2000 38 600% current
operations to ensure the design is capable of a
long service life with no maintenance. The ANSI 2501–6000 3 600% current* >2000 0
C37 Standard tests circuit breakers rated only up
to 2000 A. *An additional 25 operations at 200% current.

Temperature Testing UL 489 ANSI C37
The UL 489 Standard allows for two types of
ratings. Standard circuit breakers cannot exceed Temperature 50°C temperature rise at line and load 55°C temperature rise at line and
a maximum of 50°C temperature rise at the wire Current terminals load terminal bus connections
terminal connection at 100% current in 40°C open Exceptions and 85°C temperature rise on
air. 100% rated circuit breakers may have a circuit breaker contacts
temperature rise of 60°C at the wire terminal
connection in the smallest allowable enclosure if Standard circuit breaker: 100% rated current in smallest
the circuit breakers are connected with wire rated enclosure
at 90°C wiring insulation sized to the 75°C chart 100% rated current in open air at 40°C
(Table 310-16, National Electric Code®—NEC®). 80% rated current in smallest enclosure
The ANSI C37 Standard requires a maximum of
55°C temperature rise at 100% in the smallest 100% rated circuit breaker: Trip unit defeated
enclosure and a maximum of 85°C temperature 100% rated current in smallest enclosure
rise on the contacts. Temperature rise may be 60°C if 90°C

wire is used sized to the 75°C chart (NEC)

Endurance Testing UL 489 ANSI C37
Circuit breakers tested to the UL 489 Standard
must pass a significant number of operations Power factor: 0.75–0.80 Power factor: 0.85
without any maintenance. This test verifies that
the design is capable of a long service life. The Maintenance not allowed Maintenance allowed
ANSI C37 Standard tests circuit breakers for
further operations but then allows for Max. frame Number of operations at Max. frame Number of operations
maintenance of the circuit breaker at relatively size (A) rated voltage
short intervals. size (A) at rated voltage

NOTE: No manufacturer currently offers 225 A or 100 6000 At rated current 225 4000 At rated current
600 A frame circuit breakers tested to ANSI C37. 4000 Without current 10000 Without current
2500 Between maintenance
Short-circuit Testing
The short-circuit tests reflect differences in the 225 4000 At rated current 600 2800 At rated current
philosophies between the UL and ANSI circuit 4000 Without current 9700 Without current
breaker standards. The UL 489 Standard requires 1750 Between maintenance
that the tests be conducted at several values of
short-circuit current. A separate test sequence 600 1000 At rated current 800 2800 At rated current
evaluates the maximum interrupting rating 5000 Without current 9700 Without current
claimed by the manufacturer. Tests are conducted 1750 Between maintenance
at the rated voltage(s) of the circuit breaker which
is typically 240, 480 or 600 V. 800 500 At rated current 1600 800 At rated current
3000 Without current 3200 Without current
500 Between maintenance

2500 500 At rated current 2000 800 At rated current
2000 Without current 3200 Without current
500 Between maintenance

6000 400 At rated current 3200 400 At rated current
1100 Without current 1100 Without current
250 Between maintenance

4000 400 At rated current
1100 Without current
250 Between maintenance

© 1999 Square D All Rights Reserved 3

ANSI® C37 Standard and UL® 489 Standard Comparison Bulletin No. 0613DB9902
Data Bulletin June 1999

Three-pole circuit breakers are tested under Short UL 489 ANSI C37
three-phase conditions during the maximum Circuit
interrupting ability sequence. Each pole is tested Power factor ≤10,000 A 0.45–0.50 0.15 Unfused
individually at a reduced current level. The circuit 0.20 Fused
breaker must safely interrupt the short-circuit Voltage and 10,001–20,000 A 0.25–0.30
current and protect the rated wire in the circuit. current Rated current at the three voltage
Operations ≥ 20,000 A 0.15–0.20 levels: 254, 508 and 635 Vac
The ANSI C37 Standard requires that a three-
pole circuit breaker be tested under three-phase Rated voltage with low-, medium- Open—close/open on all three poles.
conditions at the maximum interrupting rating and and high-level current First open at closing angle to ensure
also that each individual pole be tested at 87% of peak current of 2.3 x rated current in
the maximum interrupting rating. Both the three- Open—close/open on all three one phase
phase and the individual-pole tests are conducted poles
at rated maximum voltages of 254, 508 and 635 V. Open—close/open individual pole at
The ANSI C37 Standard also includes a separate Open—close/open on each 87% of rated current
sequence to evaluate the short-time withstand individual pole at reduced current
current of the circuit breaker. The short-time level Short-time withstand—first ON cycle,
withstand current is a high-level current that can closing angle must ensure a peak
be maintained for 0.5 seconds without damage to current of 2.3 x rated current in one
the circuit breaker. phase. Circuit breaker remains
closed, tripping disabled—0.5 sec.
ON, 15 sec. OFF, 0.5 sec. ON

Certification 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 Square D and are registered trademarks of Square D/Schneider Electric or related companies.
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Cedar Rapids, IA 52406-3069 ANSI is a registered trademark of American National Standards Institute, Inc.
Field Services: 1-800-634-2003 National Electric Code and NEC are registered trademarks of National Fire Protection Association, Inc.
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All other trademarks are the intellectual property of their respective companies.
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Bulletin No. 0613DB9902 June 1999 © 1999 Square D All Rights Reserved.