Transcript 2005 NEC Changes - ICE

2005 National Electrical Code® Changes
Affecting Overcurrent Protection
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
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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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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????
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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
©2004 Cooper Bussmann
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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
©2004 Cooper Bussmann
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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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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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430.8 Motor Controllers
Marked Short Circuit Current Ratings
430.8 – Motor Controllers
A controller shall be marked
with the manufacturer’s 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
“high-available” fault current tests and Type 2 “no
damage” tests to achieve high short circuit current
ratings
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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
©2004 Cooper Bussmann
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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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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
maker’s 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
99,165 A
2
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13,222 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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
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Summary of Changes
Selective Coordination of Overcurrent
Protective Devices
• 100
• 700.27
• 701.18
• 517.26
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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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Fault
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
N
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E
ATS
Selective Coordination: Normal Supply
Normal
Source
Emergency
Source
Unnecessary Feeder Outage
N
Fault
X1
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E
ATS
Opens
Not Affected
Unnecessary
Power Loss
Selective Coordination: Normal Supply
Without
Normal
Source
Emergency
Source
Unnecessary Main Outage
N
Fault
X1
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E
ATS
Opens
Not Affected
Unnecessary
Power Loss
Selective Coordination: Normal Supply
Without
With
Normal
Source
Emergency
Source
N
Fault
X1
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E
Normal
Source
Emergency
Source
N
ATS
Opens
Not Affected
Unnecessary
Power Loss
E
ATS
Selective Coordination: Normal Supply
Without
With
Normal
Source
Emergency
Source
N
Fault
X1
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E
Normal
Source
Emergency
Source
N
ATS
Opens
Not Affected
Unnecessary
Power Loss
E
ATS
Isolated to
Branch Only
Fault
X1
Selective Coordination: Emergency Supply
Normal
Source
Emergency
Source
N
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E
ATS
Selective Coordination: Emergency Supply
Normal
Source
Emergency
Source
Unnecessary Feeder Outage
N
Fault
X1
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E
ATS
Opens
Not Affected
Unnecessary
Power Loss
Selective Coordination: Emergency Supply
Without
Normal
Source
Emergency
Source
N
Fault
X1
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E
Unnecessary Outage Entire
Emergency Source
ATS
Opens
Not Affected
Unnecessary
Power Loss
Selective Coordination: Emergency Supply
Without
Normal
Source
Emergency
Source
N
Fault
X1
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E
Normal
Source
Emergency
Source
N
ATS
Opens
Not Affected
Unnecessary
Power Loss
E
ATS
Selective Coordination: Emergency Supply
Without
With
Normal
Source
Emergency
Source
N
Fault
X1
©2004 Cooper Bussmann
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E
Normal
Source
Emergency
Source
N
ATS
Opens
Not Affected
Unnecessary
Power Loss
E
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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Tm
AVAILABLE
SHORT-CIRCUIT
CURRENT
LPS-RK-600SP
CLEARING
ENERGY
Ta
Tc
Tc
Selective Coordination
Fuses
• Published selectivity ratios
• Short circuit study unnecessary
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Selective Coordination - Fuses
Circuit Selectively
Coordinated
Low Peak
KRP-C-800SP
Low Peak
LPJ-100SP
Loadside Fuse
KRP-C_SP LPJ_SP LPS-RK_SP
KRP-C_SP
2:1
2:1
2:1
LPJ_SP
-
2:1
2:1
LPS-RK_SP
-
2:1
2:1
Low Peak
LPS-RK-20SP
800/100 = 8:1 only 2:1 needed
Selective Coordination achieved
Overloads or faults
of any level up to
300,000A
100/20= 5:1 only 2:1 needed
Selective Coordination achieved
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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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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
©2004 Cooper Bussmann
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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
1
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
©2004 Cooper Bussmann
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900A
0.01
1
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
100 A. CB
STD @ 0.1 Seconds
1
Overcurrents of any level
up to CBs’ Interrupting
Ratings
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©2004 Cooper Bussmann
TIME IN SECONDS
10
20 A. CB
IT Non Adjustable
800 A w/ STD
100
100 A w/ STD
20 A
0.10
0.01
1
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
©2004 Cooper Bussmann
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Summary of Changes
Series Ratings for Existing Systems
240.86(A)
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©2004 Cooper Bussmann
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.
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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 Mfr’s 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
©2004 Cooper Bussmann
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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
©2004 Cooper Bussmann
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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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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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Background Series Ratings for Existing
System
Up until NEC® 2005
The only option…remove and
replace the CB panel with a new
CB or fusible switch panel with
overcurrent protective devices
with sufficient Interrupting
ratings.
• Costly and Disruptive
©2004 Cooper Bussmann
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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.
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Summary of Changes
Series Ratings for Existing Systems
240.86(A)
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Supplementary Overcurrent Protective
Devices
Examples
UL248-14
Supplemental Fuses
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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 1” thru air, 2” over surface
©2004 Cooper Bussmann
©2004 Cooper Bussmann
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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©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.
©2004 Cooper Bussmann
©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 controller’s voltage rating and the
nominal voltage between any two conductors
does not exceed the higher value of the motor
controller’s voltage rating…”
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Motor Controller
480Y/277 slash voltage rating
480 volts
Line-to-line
480Y/277 Volt
Three phase
Four wire
Solidly
grounded
wye system
A
B
C
N
Ground
277 volts
Line-to-ground
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Solidly Grounded WYE System
SERVICE
PANEL
BRANCH
PANEL
277V
Steel Conduit
A
A
480V
B
C
B
480V
C
N
©2004 Cooper Bussmann
©2004 Cooper Bussmann
N
Solidly Grounded WYE System
Single Pole Must
SERVICE
BRANCH
Interrupt Fault Current
PANEL
PANEL
277V
Steel Conduit
A
A
480V
B
C
B
480V
C
N
©2004 Cooper Bussmann
©2004 Cooper Bussmann
N
Fault to
Conduit
Corner Grounded Delta System
SERVICE
PANEL
BRANCH
PANEL
Steel Conduit
A
A
B
C
480V
B
C
©2004 Cooper Bussmann
©2004 Cooper Bussmann
Corner Grounded Delta System
Single Pole Must
Interrupt Fault Current
SERVICE
BRANCH
PANEL
PANEL
Steel Conduit
A
A
B
C
480V
B
C
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©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
©2004 Cooper Bussmann
©2004 Cooper Bussmann
©2004 Cooper Bussmann
©2004 Cooper Bussmann
2005 Code Changes
THE END