Suggestion on How to Use

Industry Trainers are encouraged to use this

material in their sessions
Download both the PowerPoint file (.ppt) and
script file (.pdf)
Print the script file (.pdf) and read the script as
you view the PowerPoint presentation in the
Slide Show view. In this way you see the
slides in large format and have animation (if
there is any)
Must have PowerPoint and Adobe Reader
application software on your system.

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2004 Cooper Bussmann

2005 National Electrical Code Changes

Affecting Overcurrent Protection

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409
409.110
430.8
670.3(A)
440.4(B)
230.82(3)
100
700.27
701.18
517.26
240.86(A)
100
240.5(B)
240.60(D)
410.73(G)
430.52(C)(6)
430.83(E)

New Article 409: Industrial Control Panels

SCCR Marking for Industrial Control Panels
SCCR Marking on Motor Controllers
Industrial Machinery SCCR Marking
HVAC Short Circuit Current Rating (SCCR) Marking
SCCR Marking on Meter Disconnects
Definition for Coordination (selective)
Selective Coordination: Emergency Systems
Selective Coordination: Legally Required Standby Sys.
Selective Coordination: Healthcare Essential Circuits
Existing Facilities: Series Rating Engineering Method
Definition for Supplementary OCPD
Appliance and Extension Cord Protection
Renewable Fuses: Replacement ONLY
Disconnecting Means: Electric Discharge Lighting
Self Protected Comb. Ctrl 1 Pole Interrupting Capacity
Motor Controllers Slash Voltage Requirement

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2004 Cooper Bussmann

Summary of Changes Requiring

Marked Short Circuit Current Rating
409
409.110
430.8
440.4(B)

New Article 409 Industrial

Control Panels
Marked on Industrial Control
Panels
Marked on Motor Controllers
Marked on HVAC
Greater than 60A Non Residential

670.3
Marked on Industrial Machinery
230.83(3) Marked on Meter Disconnect
Switches
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Industrial Control Panels

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2002 NEC and Before

Required marking for
interrupting rating of main
Overcurrent Protective
Device on Industrial
machinery (670.3)
Industrial control panels,
HVAC control panels, motor
controllers, and meter
disconnects were not
required to be marked with
SCCR
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Now - 2005 NEC

Required to be marked with short

circuit current rating:
Components
Motor Controllers
Meter Disconnects
Assembly
Industrial Control Panels
Industrial Machinery Electrical
Panels
HVAC Panels above 60A nonresidential
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WHY????

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Short Circuit Current Ratings (SCCR)

What is a Short Circuit Current Rating?

The maximum short circuit current a

component, assembly or equipment can
safely withstand when protected by a
specific overcurrent protective device, or
for a specified time interval
SCCR pertains to protection of
components, multiple component
assemblies or entire control panels
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Short Circuit Current Ratings

Short Circuit Current Rating is not the
same as Interrupting Rating:

Interrupting Rating Maximum

available current a fuse or circuit
breaker can safely interrupt under
standard test conditions
Class H Fuses 10kAIR
Interrupting Rating only pertains to
the overcurrent protective device
Adequate Interrupting Ratings do
not ensure protection of circuit
components, assemblies or
50,000A Fault
equipment
Inadequate Interrupting Rating
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Marked Short Circuit Current Ratings

Why are Marked Short Circuit Current Ratings
Important?
Needed to ensure compliance with NEC
110.10
Helps to eliminate hazards where components
and equipment are applied above their ratings
Simplifies inspection approval process

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Marked Short Circuit Current Ratings

Component Marking Requirements

Short Circuit Current Rating may be established
during testing as part of the listing and labeling
process for individual components or multiple
component assemblies

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Meter Disconnects
Marked Short Circuit Current Rating
230.82(3) Equipment Connected to the
Supply Side of Service Disconnect.
Only the following equipment shall be permitted to be
connected to the supply side of the service disconnecting
means:
(3) Meter disconnect switches nominally rated not in
excess of 600 volts that have a short-circuit current
rating equal to or greater than the available short
circuit current, provided all metal housings and service
enclosures are grounded.

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2004 Cooper Bussmann

230.82(3) Meter Disconnects

Marked Short Circuit Current Ratings
Meter Disconnect Switches:
Must have a marked short circuit current
rating equal to or greater than the
available short circuit currents
Typically achieved by
a fused disconnect
utilizing current-limiting
fuses

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2004 Cooper Bussmann

430.8 Motor Controllers

Marked Short Circuit Current Ratings
430.8 Motor Controllers
A controller shall be marked
with the manufacturers name
or identification, the voltage, the
current or horsepower rating,
the short-circuit current
rating, and such other
necessary data to properly
indicate the applications for
which it is suitable.
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430.8 Motor Controllers

Marked Short Circuit Current Ratings
Exceptions where the Short Circuit Current Rating is
not required on the controller:
1/8HP or less motors which are normally left running and
constructed not to be damaged by overloads
1/3HP or less portable motors where the controller is the
attachment plug and receptacle
The rating is marked elsewhere on an assembly
The assembly into which the controller is to be installed is
marked with a rating
Controller is rated 2HP or less at 300V or less and is listed
exclusively for general purpose branch circuits
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Motor Controllers
Marked Short Circuit Current Ratings
UL 508 has:
Standard fault current test
An optional high available fault current test
Optional Type 2 no damage, high available fault
current (UL 508E)
Standard level:
5kA for 0 - 50HP ratings
10kA for 51 - 200HP ratings, etc.
Current limiting fuses are often used in the optional highavailable fault current tests and Type 2 no damage
tests to achieve high short circuit current ratings

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Marked Short Circuit Current Ratings

Motor Controller Label Example
(from an 80A, 40HP rated controller)
GENERAL PURPOSE SWITCH
INTERRUPTEUR, USAGE GENERAL
Short circuit rating 100kA at 600VAC max
when protected by 100A class J or T
5kA when protected by 150A class H or
RK5 fuses
LISTED 3E73
MAN MTR CNTRL

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Marked Short Circuit Current Ratings

Equipment Marking Requirements

Short Circuit Current Rating can be

established during testing as part of the
Listing and Labeling process

Where testing is not feasible, Short Circuit

Current Ratings can be determined using
approved engineering methods

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Marked Short Circuit Current Ratings

409.110 Industrial Control Panels Marking.
An industrial control panel shall be marked with the
following information that is plainly visible after
installation:
(3) Short-circuit current rating of the industrial
control panel based on one of the following:
a. Short-circuit current rating of a listed and labeled
assembly
b. Short-circuit current rating established utilizing an
approved method
FPN: UL 508A-2001, Supplement SB, is an example of an
approved method
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Industrial Control Panels: Now Marked

with Short Circuit Current Rating
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Marked Short Circuit Current Ratings

670.3 Industrial Machine Nameplate Data.
(A) Permanent Nameplate. shall be attached to
the control equipment enclosure or machine and
shall be plainly visible after installation. The
nameplate shall include the following information:
(4) Short-circuit current rating of the industrial
control panel based on one of the following:
a. Short-circuit current rating of a listed and
labeled assembly
b. Short-circuit current rating established utilizing
an approved method
FPN: UL 508A-2001, Supplement SB, is an example of an
approved method
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Marked Short Circuit Current Ratings

Example: Industrial Machinery Control Panel Label
Plastics Processing Machine

Short

SN2356YUP77
Serial Number
87 Amperes
Current
25 Horsepower
Largest Motor H.P.
60 Ampere
Max OCP Device
460 - 480 volts
Voltage
3ph., 60 Hz
Phase & Freq..
Amperes
RMS
Short Circuit
Current Rating
Circuit
Current
Rating100,000
100,000
Amperes
Diagram Numbers
CM 12.1 THRU CM 12.5

Quality Machine
Tool Somewhere,
USA
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RMS

Marked Short Circuit Current Ratings

440.4(B) Marking on Hermetic Refrigerant
Motor-Compressors and Equipment
(B) Multimotor and Combination-Load Equipment.
Multimotor and combination-load equipment shall be
provided with a visible nameplate marked with the
makers name, the rating in volts, frequency and number
of phases, minimum supply circuit conductor ampacity, the
maximum rating of the branch-circuit short-circuit and
ground-fault protective device, and the short-circuit
current rating of the motor controllers or industrial
control panel.

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Marked Short Circuit Current Ratings

Combination Load and Multimotor HVAC
and Refrigeration Equipment
Exceptions:
Equipment used in one and two family
dwellings
Cord-and-attachment-plug connected
equipment
Equipment supplied by a branch circuit
protected at 60A or less
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Marked Short Circuit Current Ratings

Example of HVAC Label
HVAC Control Panel

Short

Serial Number
Current
Min Circuit Ampacity
Max Fuse Size
Voltage
Phase & Freq..
Short Circuit
CurrentRating
Rating
Circuit
Current

HVDB708429521
72 Amperes

90 Amperes
125 Ampere
460 - 480 volts
3ph., 60 Hz
40,000 Amperes RMS

40,000 Amperes RMS

HVAC Equipment,
Inc. Anytown,
USA
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Ensuring Compliance
For equipment requiring Marked Short Circuit Current
Ratings
Engineer provides:
Available short circuit currents at each
installation point
Short circuit current rating of each piece of
equipment or panel
During site inspection, inspector compares actual
marked short circuit current ratings to the submitted
data: planned SCCRs and available short circuit
currents

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Ensuring Compliance
This method requires proper engineering
and analysis by the design engineers
and proper review by inspectors.

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Ensuring Compliance: Simple Check

For Short Circuit Current Rating
Determine the maximum, worst case
short circuit current available at the
terminals of the supply transformer
Verify that all required equipment is
marked with a short circuit current
rating sufficient for this maximum,
worst case available current
If SCCRs are sufficient: installation
approved. If this SCCRs insufficient
by this quick check method, a
detailed analysis may be required

500 KVA
5%Z
480/277V
1

1500 KVA
2%Z
480/277V
2

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13,222 A

99,165 A

Achieving High Short Circuit Current

Ratings
High Short Circuit Current Ratings Make
Equipment and Controllers:
Easier to specify and install for compliance
More flexible can be moved from location
to location safely

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Achieving High Short Circuit Current

Ratings
Current Limiting Fuses:
Reduce fault energy
Can be used to achieve
high short circuit current
ratings for motor
controllers, assemblies
of multiple components,
disconnects, and
industrial control panels

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2004 Cooper Bussmann

Regulatory - 2005 NEC Changes

Marked Short Circuit Current Ratings
Before

Now Marked

Plastics Processing
Current
Voltage

87 Amperes
Current Rating

460 - 480 volts

Phase & Freq..

3ph., 60 Hz

XYZ Machine Company

Anywhere, USA

Fuses
and
Disc
PDB

Plastics

Processing

Current

87 Amperes

Voltage

460 - 480 volts

Phase & Freq..

Short Circuit
Current Rating

200 kA SCCR

3ph., 60 Hz

200 kA

XYZ Machine Company

Anywhere, USA

400A Class J Fuse Disconnect

Listed 200,000A SCCR
Power Distribution Block Listed
200,000A SCCR Protected by
400A Class J Fuses
Branch circuits with current
limiting fuses, contactors and
overloads
Listed 200,000A SCCR

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2004 Cooper Bussmann

Marked Short Circuit Current Ratings

Summary: The 2005 NEC now requires short
circuit current ratings to be marked on:
Meter Disconnect Switches
Motor Controllers
Industrial Control Panels
Industrial Control Panels for Industrial
Machinery
Combination Load and Multimotor HVAC and
Refrigeration Equipment

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Summary of Changes
Selective Coordination of Overcurrent
Protective Devices
100
700.27
701.18
517.26

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2004 Cooper Bussmann

Definition: Coordination Selective

Required for Emergency Systems
Required for Legally Required
Standby Systems
Required for Essential Electrical
Standby Systems

Selective Coordination
2005 NEC New Article 100 Definition
Coordination (Selective)
Localization of an overcurrent condition to
restrict outages to the circuit or equipment
affected, accomplished by the choice of
overcurrent protective devices and their
ratings or settings.

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What is Selective Coordination?

Selective coordination
Isolates an overloaded or faulted circuit
Only the nearest upstream
overcurrent protective
device opens

Why is it required?
Vital for critical systems
Increase system reliability
OPENS
NOT AFFECTED
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Faul
t

Selective Coordination: Avoids Blackouts

Lacking
Selective Coordination

With
Selective Coordination

Fault
OPENS

Fault
UNNECESSARY
POWER LOSS

NOT AFFECTED

Selective Coordination Requirements

Articles affected
700 Emergency Systems
701 Legally Required Standby Systems
517 Health Care Facilities

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Selective Coordination Requirements

Other supporting requirements
700.4 Maintenance and Testing Requirements
700.9(B) Emergency circuits separated from
normal supply circuits
700.9(C) Wiring specifically located to
minimize system hazards
700.16 Failure of one component must not
result in a condition where a means of egress
will be in total darkness

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Selective Coordination Requirements

700.27 Coordination.
Emergency system(s) overcurrent
devices shall be selectively coordinated
with all supply side overcurrent
protective devices.

Blackout

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Emergency Systems
Required in places of assembly or
where panic control is needed
Hotels, theaters, sports arenas, health care
facilities and similar institutions

Provide power for:

Ventilation, fire detection, alarm systems,
elevators, fire pumps, public safety
communications, and continuous
processes

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Selective Coordination Requirements

701.18 Coordination.
Legally required standby system(s)
overcurrent devices shall be selectively
coordinated with all supply side
overcurrent protective devices.

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Legally Required Standby Systems

Supply power to selected loads when
normal source fails
Serve loads to:
Heating and refrigeration, communications,
ventilation and smoke removal, sewage
disposal, lighting systems, and continuous
processes

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Selective Coordination Requirements

517.26 Application of Other Articles. The
essential electrical system shall meet the
requirements of Article 700, except as
amended by Article 517.
Article 517 covers health care facilities
Selective coordination required in essential electrical
systems

There are no amendments in Article 517 concerning

selective coordination of overcurrent protective
devices

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Essential Electrical Systems

In health care facilities
Designed to ensure service to lighting and
power in critical areas

Essential systems include:

Critical branch, life safety branch, and
equipment systems essential for life safety

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Objectives For These Important Circuits

Keep loads powered in the event of loss of
normal power
Ensure system uptime
Ensure safety to human life in an emergency
Reduce the probability of faults
Provide reliable operation
Minimize the effects of an outage
Selective coordination requirements fit well with
these objectives

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Selective Coordination: Normal Supply

Normal
Source

Emergency
Source

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ATS

Selective Coordination: Normal Supply

Normal
Source

Emergency
Source
Unnecessary Feeder Outage
N

Fault
X1

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ATS
Opens
Not Affected
Unnecessary
Power Loss

Selective Coordination: Normal Supply

Without
Emergency
Source

Normal
Source

c
a
l

t
u
ko

Fault
X1

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s
o
P
s
N

!
e
l
b
si

Unnecessary Main Outage

ATS
Opens
Not Affected
Unnecessary
Power Loss

Selective Coordination: Normal Supply

Without
With
Emergency
Source

Normal
Source

c
a
l

t
u
ko

Fault
X1

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s
o
P
s
N

!
e
l
b
si

Normal
Source

ATS

Emergency
Source

Opens
Not Affected
Unnecessary
Power Loss

ATS

Selective Coordination: Normal Supply

Without
With
Normal
Source

Emergency
Source

b
i
s
s
o
P
s
t
u
ATS
o
ck
N

a
l
B
Fault
X1

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!
e
l

Normal
Source

!
d
e
t
n
e
ev

Emergency
Source

r
P
s
t
u
o
ATS
k
c
N

Opens Bl
Not Affected
Unnecessary
Power Loss

Isolated to
Branch Only
Fault
X1

Selective Coordination: Emergency Supply

Normal
Source

Emergency
Source

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ATS

Selective Coordination: Emergency Supply

Normal
Source

Emergency
Source
Unnecessary Feeder Outage
N

Fault
X1

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ATS
Opens
Not Affected
Unnecessary
Power Loss

Selective Coordination: Emergency Supply

Without
Normal
Source

c
a
l

t
u
ko

Fault
X1

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Emergency
Source

s
o
P
s
N

!
e
l
b
si

ATS

Unnecessary Outage Entire

Emergency Source

Opens
Not Affected
Unnecessary
Power Loss

Selective Coordination: Emergency Supply

Without
Normal
Source

c
a
l

t
u
ko

Fault
X1

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Emergency
Source

s
o
P
s
N

!
e
l
b
si

Normal
Source

ATS

Emergency
Source

Opens
Not Affected
Unnecessary
Power Loss

ATS

Selective Coordination: Emergency Supply

Without
With
Normal
Source

c
a
l

t
u
ko

Fault
X1

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Emergency
Source

s
o
P
s
N

!
e
l
b
si

ATS

Normal
Source

c
a
l
B

Opens
Not Affected
Unnecessary
Power Loss

t
u
ko

Emergency
!
d
Source
te

n
e
v
e
r
P
s
N

ATS

Isolated to
Branch Only
Fault
X1

Selective Coordination
Ensuring Compliance
Requires proper engineering,
specification and installation
Designer must provide proper
documentation of coordination
Site inspection should verify correct
devices are installed per plans to
achieve coordination

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What must to be
considered?

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Selective Coordination - Fuses

MELTING
ENERGY

Short Circuit Region

Selectivity Ratio Guide
(based on I2T)
LINE SIDE

KRP-C-1200SP

LOAD SIDE

Loadside fuse must

clear prior to lineside
fuse melting

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Tm

AVAILABLE
SHORT-CIRCUIT
CURRENT

LPS-RK-600SP

CLEARING
ENERGY

Ta
Tc

Tc

Selective Coordination
Fuses
Published selectivity ratios
Short circuit study unnecessary

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Selective Coordination - Fuses

Circuit Selectively
Coordinated

Low Peak
LPJ-100SP

KRP-C_SP LPJ_SP LPS-RK_SP

Lineside Fuse

Low Peak
KRP-C-800SP

Loadside Fuse

Low Peak
LPS-RK-20SP
Overloads or faults
of any level up to
300,000A
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KRP-C_SP

2:1

2:1

2:1

LPJ_SP

2:1

2:1

LPS-RK_SP

2:1

2:1

800/100 = 8:1 only 2:1 needed

Selective Coordination achieved
100/20= 5:1 only 2:1 needed
Selective Coordination achieved

Selective Coordination Circuit Breakers

Circuit Breakers

Depends on characteristics and settings

Difficult to achieve
May be higher cost
Full short circuit study is necessary
Proper analysis and interpretation a must

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Selective Coordination Circuit Breakers

90A & 400A
Molded Case Circuit Breakers
Inherent long delay between
unlatching and interrupting due to
mechanical means of breaking
current
Upstream breaker can unlatch
before the downstream breaker
can clear the fault
Lack of Selective Coordination in
the Short-Circuit Region
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Selective Coordination Circuit Breakers

Not Coordinated above 900A
800 A. CB
STD @ 0.1 Seconds

1000

800 A w/ STD

100

10

TIME IN SECONDS

100 A. CB
IT Non Adjustable

CURRENT IN AMPERES

100 A

20 A

20 A. CB
IT Non Adjustable
0.10

Coordinated for
overloads and faults
less than 900A
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900A
0.01

10

100

1K

10K

dteate.tcc Ref. Voltage: 480 Current Scale x10^0

100K

Selective Coordination Circuit Breakers

Selectively Coordinated up
to CBs Interrupting Ratings
800 A. CB
STD @ 0.4 Seconds

CURRENT IN AMPERES
1000

20 A. CB
IT Non Adjustable
Overcurrents of any level
up to CBs Interrupting
Ratings
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TIME IN SECONDS

10

100 A. CB
STD @ 0.1 Seconds

800 A w/ STD

100

100 A w/ STD

20 A

0.10

0.01

10

100

1K

10K

dteate.tcc Ref. Voltage: 480 Current Scale x10^0

100K

Summary of Changes
Selective Coordination Required
100

Definition

700

Emergency Systems

701

Legally Required Standby

Systems

517

Health Care Facilities: Essential

Electrical Systems

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Summary of Changes
Series Ratings for Existing Systems

240.86(A)

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Series Ratings

Series Ratings
The 2005 NEC, section 240.86(A), will
now permit selection of series rated
combinations for existing systems when
the selection is made by a licensed
professional engineer.

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Series Ratings
First
What is a Series Rated Combination?
110.22 & 240.86(A) Labeling
Panel
MDP1

Contractor Installed Label

CAUTION
Series Rated Combination
with panel LDP1
Rated 200,000 Amperes
Replace with Only
200 Amp Class J Fuses

Panel Mfrs Label

Contractor Installed Label

CAUTION
Series Rated Combination
with 200 Amp Class J fuses in MDP1
Rated 200,000 Amperes
Replace with Only CB Co.
XYZ Circuit Breaker

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NRTL Listing of Series

Combination Rating of
200,000 amperes when CB Co.
XYZ Circuit Breaker
Protected by Maximum
400 A Class J Fuse

Panel LDP1

Series Rating: Fuse/CB

400 A Class J Fuse
200,000 A Interrupting Rating

Series Rated
Combination
200,000 A. I.R.

20 A XYZ Circuit Breaker

Best CB Company
10,000 A Interrupting Rating
Up to ISC= 200,000 Amp
Available Short Circuit
Up to ISC= 200,000 Amp
Available Short Circuit
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Series Rating: CB/CB

200 A ABC Circuit Breaker
Best CB Company
65,000 A Interrupting Rating

Series Rated
Combination
65,000 A. I.R.
20 A XYZ Circuit Breaker
Best CB Company
10,000 A Interrupting Rating

Up to ISC= 65,000 Amp

Available Short Circuit

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Up to ISC= 65,000 Amp

Available Short Circuit

Background Series Ratings for Existing

System
Building improvements and replacement
transformers may have increased
available short circuit currents to levels
that exceeded existing circuit breakers
interrupting ratings.
Serious safety hazard
Does NOT comply with NEC 110.9
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Background
BEFORE
500 KVA
5%Z
480/277V
12,000 A
Existing
Equipment
Circuit
Breakers
14,000 A
Interrupting
Rating
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Background
BEFORE
500 KVA
5%Z
480/277V

AFTER
500 KVA
2% Z
480/277V

12,000 A

30,000 A

Existing
Equipment

Circuit
Breakers
14,000 A
Interrupting
Rating
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Safety Hazard
Available Short Circuit Current Beyond Circuit
Breaker Interrupting Rating
14,000A IR, 480V, Circuit Breaker
50,000 Available

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2004 Cooper Bussmann

Background Series Ratings for Existing

System
Up until NEC 2005
The only optionremove and
replace the CB panel with a new
CB or fusible switch panel with
overcurrent protective devices
with sufficient Interrupting
ratings.
Costly and Disruptive
2004CooperBussmann

2004 Cooper Bussmann

New Requirement 240.86(A) Series

Rating
240.86(A) Selected Under Engineering Supervision in
Existing Installations.
The series rated combination devices shall be selected
by a licensed professional engineer engaged
primarily in the design or maintenance of electrical
installations. The selection shall be documented and
stamped by the professional engineer. This
documentation shall be available to those authorized
to design, install, inspect, maintain, and operate the
system. This series combination rating, including
identification of the upstream device, shall be field
marked on the end use equipment.

2004CooperBussmann

2004 Cooper Bussmann

Series Ratings for Existing System

With the 2005 NEC 240.86(A):
A licensed professional engineer can
determine if an upgrade of lineside fuses or
circuit breakers can series rate with existing
loadside circuit breakers.
This may save owner significant money
and provide a safer system

2004CooperBussmann

2004 Cooper Bussmann

Ensuring Compliance: Series Ratings for

Existing Systems
Engineer:
Analyzes if lineside fuse or circuit breaker
provides protection to the downstream
circuit breakers
Provides stamped documentation that is
readily available to those involved.

2004CooperBussmann

2004 Cooper Bussmann

Methods For Existing Systems

There may be several analysis options
for a licensed professional engineer to
rectify situations where existing circuit
breakers have inadequate interrupting
ratings.
Note: In some cases, a suitable method may
not be feasible. New methods may surface in
the future.

2004CooperBussmann

2004 Cooper Bussmann

Methods For Existing Systems

1. Check if new fused disconnect can be
installed ahead of existing circuit breakers by
using an existing, recognized series rated
combination.
2. If existing system used series ratings with
Class R fuses (RK5 Umbrella), analyze
whether a specific Bussmann Class RK1,
J or T fuse may provide protection at the
higher short-circuit current.

2004CooperBussmann

2004 Cooper Bussmann

Methods For Existing Systems

3. Supervise short circuit testing of lineside
current-limiting fuses to verify protection is
provided to circuit breakers that are identical
to installed, existing circuit breakers.
4. Perform analysis to determine if currentlimiting fuses installed on lineside of existing
circuit breakers provide adequate
protection for circuit breakers.

2004CooperBussmann

2004 Cooper Bussmann

Suggest Bussmann Low-Peak Fuses

For new installations, owners, designers, and contractors
should consider using fusible switches in fully rated
systems
Low-Peak fuses have 300,000A interrupting rating so
changes to electrical system will not cause the available
short circuit current to increase beyond their interrupting
rating
System reliability: no periodic maintenance and testing
required on fuses to ensure their ability to operate as
intended

2004CooperBussmann

2004 Cooper Bussmann

Solution Using Current Limiting Fuses

BEFORE
500 KVA
5%Z
480/277V

Bussmann Low
Peak Fuse

12,000 A

30,000 A
Existing
Equipment
Circuit
Breakers
14,000 A
Interrupting
Rating

2004CooperBussmann

2004 Cooper Bussmann

AFTER
500 KVA
2% Z
480/277V

Series Ratings for New Systems

For new installations, the process remains
the same as the 2002 NEC:
Tested

Listed
Marked

Use the Tables

www.bussmann.com
and SPD publication

2004CooperBussmann

2004 Cooper Bussmann

Summary of Changes
Series Ratings for Existing Systems

240.86(A)

2004CooperBussmann

2004 Cooper Bussmann

Series Ratings

2005 NEC Article 100 Definition

Supplementary Overcurrent Protective

Device.
A device intended to provide limited overcurrent
protection for specific applications and
utilization equipment such as luminaires
(lighting fixtures) and appliances. This limited
protection is in addition to the protection
provided in the required branch circuit by the
branch circuit overcurrent protective device.

2004CooperBussmann

2004 Cooper Bussmann

Supplementary Overcurrent Protective

Devices
Examples

UL248-14
Supplemental Fuses

2004CooperBussmann

2004 Cooper Bussmann

UL1077
Supplemental Protectors
(Mini-breakers)

Supplementary Overcurrent Protective

Devices
Do not substitute where a branch circuit
overcurrent protective device is required
Capabilities and spacings can be inadequate
compared to branch circuit OCPD
Must be evaluated for appropriate application
in every instance
Must investigate differences and limitations for
the specific application

2004CooperBussmann

2004 Cooper Bussmann

Supplementary Overcurrent Protective

Devices
Example of difference between UL489 circuit
breaker and UL1077 supplemental protector:
Spacings:
UL1077 3/8 thru air, 1/2 over surface
UL489

2004CooperBussmann

2004 Cooper Bussmann

1 thru air, 2 over surface

Supplementary Overcurrent Protective

Devices
Example of difference between UL489 circuit
breaker and UL1077 supplemental protector:
Time current characteristics
UL1077 no standard overload characteristics
UL489 standard overload characteristics

2004CooperBussmann

2004 Cooper Bussmann

Supplementary Overcurrent Protective

Devices
10 reasons why UL1077 supplementary devices can
not be used for branch circuit protection
1. Not intended for, nor evaluated for branch circuit
protection
2. Spacings are inadequate
3. Do not have standard overload characteristics
4. Multipole, 3 phase UL1077 devices not
evaluated for all types of overcurrents
5. Most UL1077 devices tested with and rely upon
upstream branch circuit device for protection
2004CooperBussmann

2004 Cooper Bussmann

Supplementary Overcurrent Protective

Devices
10 reasons why UL1077 supplementary devices can
not be used for branch circuit protection
6. Not required to be tested by closing into fault
7. Not tested for calibration or reusability after fault
interruption
8. Considerable damage allowed after short circuit
interruption test
9. Not intended for branch circuit protection or
disconnecting means
10. Not evaluated for energy let-thru or protection of
conductors under short circuit current tests
2004CooperBussmann

2004 Cooper Bussmann

240.5(B) Protection of Flexible Cords,

Flexible Cables and Fixture Wires
Prior to 2005 NEC, supply cords of listed appliances,
portable lamps, and extension cords assumed protected by
branch circuit device
However, many fires caused by small wire
With 2005 NEC, these supply cords are considered
protected when applied within listing requirements
NRTLs & cord and equipment manufacturers determine
if small wire protected
If specific cords or equipment has poor record,
protection may be required
If protection needed, could be fuse, GFCI, AFCI, LCDI
or combination

2004CooperBussmann

2004 Cooper Bussmann

240.5(B) Protection of Flexible Cords,

Flexible Cables and Fixture Wires
One solution - fused line cords
Cost effective
Good protection
Used extensively in UK and Japan

Fused plug

2004CooperBussmann

2004 Cooper Bussmann

240.60(D) Renewable Fuses

Now Replacement Only
240.86(D) Renewable Fuses.
Class H cartridge fuses of the renewable
type shall only be permitted to be used
for replacement in existing installations
where there is no evidence of overfusing
or tampering.
Not to be used on new installations
Reason: renewable fuses have only
10,000A interrupting rating
2004CooperBussmann

2004 Cooper Bussmann

240.60(D) Renewable Fuses

Now Replacement Only

Supports overcurrent protective devices with high

interrupting rating
For new equipment use:
Low Peak Fuses 300,000A IR
LPJ_SP
KRP_C_SP
LPS-RK_SP & LPN-RK_SP
LP-CC (200,000A IR)

CUBEFusesTM 300,000A IR
TCF
Additional fuse types available with high IR

2004CooperBussmann

2004 Cooper Bussmann

240.60(D) Renewable Fuses

Now Replacement Only
Modern current limiting fuses with high
interrupting rating also provide:
Best equipment protection
Selective coordination
Reliability over life of system
Minimal maintenance
Possible arc flash hazard reduction
Physical size rejecting features
2004CooperBussmann

2004 Cooper Bussmann

410.73(G) Disconnecting Means for

Electric Discharge Lighting (1000V or less)
2005 NEC new section requiring disconnecting means
for certain types of luminaires:
That use double-ended lamps
Indoor other than dwellings
Ballasts that can be serviced in place

Disconnecting means accessible to qualified person

prior to servicing the ballast
Effective Jan. 1, 2008
Rationale: safer system for electricians

2004CooperBussmann

2004 Cooper Bussmann

430.52(C)(6) Self-Protected Combination

Controller Single-Pole Interrupting
Capability Limitation
New 2005 NEC
430.52(C)(6) FPN:
Proper application of self-protected combination
controllers on 3-phase systems, other than
solidly grounded wye, particularly on corner
grounded delta systems, considers the selfprotected combination controllers individual
pole-interrupting capability.
2004CooperBussmann

2004 Cooper Bussmann

430.52(C)(6) Self-Protected Combination

Controller Single-Pole Interrupting
Capability Limitation
This limitation can be a safety hazard
The single-pole interrupting capability is not marked on
the device
Must check UL508 Standard
Device 0 to 200 hp up to 600V: tested only for
8,660A single-pole short circuit current interruption,
even though the device may have a three-phase
short circuit current rating of 65,000A.

2004CooperBussmann

2004 Cooper Bussmann

430.83(E) Slash Voltage Rating for Motor

Controllers
New 2005 NEC
430.83(E) Applications.
A motor controller with a slash rating, such as
120/240V or 480Y/277, shall be permitted to be
applied in a solidly grounded circuit where the
nominal voltage of any conductor to ground
does not exceed the lower of the two values of
the motor controllers voltage rating and the
nominal voltage between any two conductors
does not exceed the higher value of the motor
controllers voltage rating
2004CooperBussmann

2004 Cooper Bussmann

Motor
MotorController
Controller
480Y/277
480Y/277 slash
slashvoltage
voltage rating
rating

480
480volts
volts
Line-to-line
Line-to-line

480Y/277
480Y/277Volt
Volt
Three
phase
Three phase
Four
Fourwire
wire
Solidly
Solidly
grounded
grounded
wye
wyesystem
system

A
B
C
N
Ground
277
277volts
volts
Line-to-ground
Line-to-ground

2004CooperBussmann

2004 Cooper Bussmann

Slash Rated Exercise

Can 480Y/277
Controller Be
Used?

System
Voltage

Secondary
System Type

L-L
Volt

L-G
Volt

480Y/277

Solidly Grounded
WYE

480

277

Yes

No

480

Resistance
Grounded WYE

480

277

Yes

No

480

Delta Corner
Grounded
B Phase

480

480

Yes

No

480

Delta
Ungrounded

480

Yes

No

* Ungrounded delta systems - phase conductors

are capacitively coupled to ground
2004CooperBussmann

2004 Cooper Bussmann

Slash Rated Exercise

Can 480Y/277
Controller Be
Used?

System
Voltage

Secondary
System Type

L-L
Volt

L-G
Volt

480Y/277

Solidly Grounded
WYE

480

277

Yes

No

480

Resistance
Grounded WYE

480

277

Yes

No

480

Delta Corner
Grounded
B Phase

480

480

Yes

No

480

Delta
Ungrounded

480

Yes

No

* Ungrounded delta systems - phase conductors

are capacitively coupled to ground
2004CooperBussmann

2004 Cooper Bussmann

Slash Rated Exercise

Can 480Y/277
Controller Be
Used?

System
Voltage

Secondary
System Type

L-L
Volt

L-G
Volt

480Y/277

Solidly Grounded
WYE

480

277

Yes

No

480

Resistance
Grounded WYE

480

277

Yes

No

480

480

Yes

No

480

Yes

No

Delta Corner

480
480

Grounded
B Phase
Delta
Ungrounded

* Ungrounded delta systems - phase conductors

are capacitively coupled to ground
2004CooperBussmann

2004 Cooper Bussmann

Slash Rated Exercise

Can 480Y/277
Controller Be
Used?

System
Voltage

Secondary
System Type

L-L
Volt

L-G
Volt

480Y/277

Solidly Grounded
WYE

480

277

Yes

No

480

Resistance
Grounded WYE

480

277

Yes

No

480

Delta Corner
Grounded
B Phase

480

480

Yes

No

480

Delta
Ungrounded

480

Yes

No

* Ungrounded delta systems - phase conductors

are capacitively coupled to ground
2004CooperBussmann

2004 Cooper Bussmann

Slash Rated Exercise

Can 480Y/277
Controller Be
Used?

System
Voltage

Secondary
System Type

L-L
Volt

L-G
Volt

480Y/277

Solidly Grounded
WYE

480

277

Yes

No

480

Resistance
Grounded WYE

480

277

Yes

No

480

Delta Corner
Grounded
B Phase

480

480

Yes

No

480

Delta
Ungrounded

480

Yes

No

* Ungrounded delta systems - phase conductors

are capacitively coupled to ground
2004CooperBussmann

2004 Cooper Bussmann

Slash Voltage Rating

System must be solidly grounded

Larger device voltage rating greater
than system L-L voltage
Smaller device voltage rating greater
than system L-G voltage
480Y / 277 V
2004CooperBussmann

2004 Cooper Bussmann

Single-Pole Interrupting Capability and

Slash Voltage Rating Examples
The next seven slides demonstrate the
limitations of single-pole interrupting
capabilities and slash voltage rating.
These are examples with circuit
breakers. The same issues are
applicable to self protected combination
controllers for single-pole interruption
and slash voltage ratings and motor
controllers for slash voltage ratings
2004CooperBussmann

2004 Cooper Bussmann

Solidly Grounded WYE System

SERVICE
PANEL

BRANCH
PANEL

277V

Steel Conduit

27

7V

27
7

480V

480V

2004CooperBussmann

2004 Cooper Bussmann

C
N

Solidly Grounded WYE System

Single Pole Must
SERVICE
BRANCH
Interrupt Fault Current
PANEL
PANEL
277V

Steel Conduit

27

7V

27
7

480V

480V

2004CooperBussmann

2004 Cooper Bussmann

C
N

Fault to
Conduit

Corner Grounded Delta System

SERVICE
PANEL
A

480V

0V
48

48
0V

BRANCH
PANEL

B
C

2004CooperBussmann

2004 Cooper Bussmann

Steel Conduit

Corner Grounded Delta System

Single Pole Must
Interrupt Fault Current
SERVICE
BRANCH
PANEL
PANEL
A

480V

0V
48

48
0V

Steel Conduit

B
C

2004CooperBussmann

2004 Cooper Bussmann

Fault to
Conduit

Single Pole Interrupting Capability

UL 489 Circuit Breaker Procedure
UL Single Pole Short-Circuit Test
CB Frame
Rating
100 A
Maximum
101 800 A.

480/277V

480V

10,000 Amps

8,660 Amps

10,000 Amps

8,660 Amps

Example:
20 A, 480V CB having 65,000 A.I.R. (3
Pole Test). Single pole tested at
8,660 Amps
2004CooperBussmann

2004 Cooper Bussmann

480 Volt, 25,000 Amp

Line to Ground

Single Pole Test

UL489 tests single pole at only 8660A

4 Feet
4/0

225 Amp, 480 V

Circuit Breaker
35, 000 Amp Three Phase
Interrupting Rating
Photos on following slide

2004CooperBussmann

2004 Cooper Bussmann

2004CooperBussmann

2004 Cooper Bussmann

2005 Code Changes

THE END