Short Circuit Current Ratings

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(No Transcript)
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2005 National Electrical Code Changes Affecting
Overcurrent Protection
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409 New Article 409 Industrial Control
Panels 409.110 SCCR Marking for Industrial
Control Panels 430.8 SCCR Marking on
Motor Controllers 670.3(A) Industrial
Machinery SCCR Marking 440.4(B) HVAC Short
Circuit Current Rating (SCCR) Marking 230.82(3)
SCCR Marking on Meter Disconnects 100
Definition for Coordination (selective) 700.27
Selective Coordination Emergency
Systems 701.18 Selective Coordination
Legally Required Standby Sys. 517.26
Selective Coordination Healthcare Essential
Circuits 240.86(A) Existing Facilities
Series Rating Engineering Method 100
Definition for Supplementary OCPD 240.5(B)
Appliance and Extension Cord Protection 240.60(D)
Renewable Fuses Replacement ONLY 410.73(G)
Disconnecting Means Electric Discharge
Lighting 430.52(C)(6) Self Protected Comb. Ctrl
1 Pole Interrupting Capacity 430.83(E) Motor
Controllers Slash Voltage Requirement
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Summary of Changes RequiringMarked Short Circuit
Current Rating

• 409 New Article 409 Industrial
  Control Panels
• 409.110 Marked on Industrial Control
  Panels
• 430.8 Marked on Motor Controllers
• 440.4(B) 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 non-residential

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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
• Interrupting Rating only pertains to the
  overcurrent protective device

Class H Fuses 10kAIR

• Adequate Interrupting Ratings do not ensure
  protection of circuit components, assemblies or
  equipment

50,000A Fault 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 DisconnectsMarked 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 DisconnectsMarked 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 ControllersMarked 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 ControllersMarked 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

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Marked Short Circuit Current Ratings

• Motor Controller Label Example (from an
  80A, 40HP rated controller)

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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
Short Circuit Current Rating
100,000 Amperes RMS
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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
Serial Number
HVDB708429521
Current
72 Amperes
Min Circuit Ampacity
90 Amperes
Max Fuse Size
125 Ampere
Voltage
460 - 480 volts
Phase Freq..
3ph., 60 Hz
Short Circuit Current Rating
40,000 Amperes RMS
Short Circuit Current Rating
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 CheckFor 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

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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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Regulatory - 2005 NEC ChangesMarked Short
Circuit Current Ratings
Before
Now Marked
200 kA SCCR
Current Rating
Short Circuit Current Rating
200 kA
400A Class J Fuse Disconnect Listed 200,000A SCCR
Fuses
and
Power Distribution Block Listed 200,000A SCCR
Protected by 400A Class J Fuses
Disc
PDB
Branch circuits with current limiting fuses,
contactors and overloads Listed 200,000A SCCR
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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 Definition Coordination Selective
• 700.27 Required for Emergency Systems
• 701.18 Required for Legally Required
  Standby Systems
• 517.26 Required for Essential Electrical
  Standby Systems

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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
Fault
NOT AFFECTED
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Selective Coordination Avoids Blackouts

• Lacking
• Selective Coordination

With Selective Coordination

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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.

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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
Emergency Source
Normal Source
ATS
N
E
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Selective Coordination Normal Supply
Emergency Source
Normal Source
Unnecessary Feeder Outage
ATS
N
E
Opens
Not Affected
Unnecessary Power Loss
Fault X1
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Selective Coordination Normal Supply
Without
Emergency Source
Normal Source
Unnecessary Main Outage
Blackouts Possible!
ATS
N
E
Opens
Not Affected
Unnecessary Power Loss
Fault X1
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Selective Coordination Normal Supply
Without
With
Emergency Source
Emergency Source
Normal Source
Normal Source
Blackouts Possible!
ATS
ATS
N
E
N
E
Opens
Not Affected
Unnecessary Power Loss
Fault X1
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Selective Coordination Normal Supply
Without
With
Emergency Source
Emergency Source
Normal Source
Normal Source
Blackouts Prevented!
Blackouts Possible!
ATS
ATS
N
E
N
E
Isolated to Branch Only
Opens
Not Affected
Unnecessary Power Loss
Fault X1
Fault X1
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Selective Coordination Emergency Supply
Emergency Source
Normal Source
ATS
N
E
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Selective Coordination Emergency Supply
Emergency Source
Normal Source
Unnecessary Feeder Outage
ATS
N
E
Opens
Not Affected
Unnecessary Power Loss
Fault X1
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Selective Coordination Emergency Supply
Without
Emergency Source
Normal Source
Unnecessary Outage Entire Emergency Source
Blackouts Possible!
ATS
N
E
Opens
Not Affected
Unnecessary Power Loss
Fault X1
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Selective Coordination Emergency Supply
Without
Emergency Source
Emergency Source
Normal Source
Normal Source
Blackouts Possible!
ATS
ATS
N
E
N
E
Opens
Not Affected
Unnecessary Power Loss
Fault X1
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Selective Coordination Emergency Supply
Without
With
Emergency Source
Emergency Source
Normal Source
Normal Source
Blackouts Prevented!
Blackouts Possible!
ATS
ATS
N
E
N
E
Isolated to Branch Only
Opens
Not Affected
Unnecessary Power Loss
Fault X1
Fault X1
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Selective CoordinationEnsuring 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
Short Circuit Region Selectivity Ratio Guide
(based on I2T)
Loadside fuse must clear prior to lineside fuse
melting
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Selective Coordination

• Fuses
• Published selectivity ratios
• Short circuit study unnecessary

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Selective Coordination - Fuses

Circuit Selectively Coordinated
Loadside Fuse
Low Peak KRP-C-800SP
Lineside Fuse
Low Peak LPJ-100SP
Low Peak LPS-RK-20SP
800/100 81 only 21 needed Selective
Coordination achieved
Overloads or faults of any level up to 300,000A
100/20 51 only 21 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

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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 _at_ 0.1 Seconds
100 A. CB IT Non Adjustable
20 A. CB IT Non Adjustable
Coordinated for overloads and faults less than
900A
900A
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Selective Coordination Circuit Breakers


Selectively Coordinated up to CBs Interrupting
Ratings
800 A. CB STD _at_ 0.4 Seconds
100 A. CB STD _at_ 0.1 Seconds
20 A. CB IT Non Adjustable
Overcurrents of any level up to CBs Interrupting
Ratings
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Summary of ChangesSelective 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 ChangesSeries Ratings for Existing
Systems

• 240.86(A) Series Ratings

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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?

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Series Rating Fuse/CB
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Series Rating CB/CB
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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
Existing Equipment Circuit Breakers 14,000 A
Interrupting Rating
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Background
BEFORE
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 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

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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.

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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  

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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.

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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.

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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.
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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
  current- limiting fuses installed on lineside of
  existing circuit breakers provide adequate
  protection for circuit breakers.

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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

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Solution Using Current Limiting Fuses
AFTER
BEFORE
Bussmann Low Peak Fuse
Existing Equipment Circuit Breakers 14,000 A
Interrupting Rating
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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

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Summary of ChangesSeries Ratings for Existing
Systems

• 240.86(A) Series Ratings

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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.

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Supplementary Overcurrent Protective Devices

• Examples

UL1077 Supplemental Protectors (Mini-breakers)
UL248-14 Supplemental Fuses
89
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

90
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

91
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

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Supplementary Overcurrent Protective Devices

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

93
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

94
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

95
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
96
240.60(D) Renewable FusesNow 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

97
240.60(D) Renewable FusesNow 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

98
240.60(D) Renewable FusesNow 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

99
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

100
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
  self-protected combination controllers
  individual pole-interrupting capability.

101
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.

102
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

103
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
104
Slash Rated Exercise
Can 480Y/277 Controller Be Used?
L-G Volt
L-L Volt
Secondary System Type
System Voltage
277
480
Solidly Grounded WYE
480Y/277
Yes No
Yes No
277
480
Resistance Grounded WYE
480
Yes No
480
480
Delta Corner Grounded B Phase
480
Yes No

480
Delta Ungrounded
480
Ungrounded delta systems - phase conductors are
capacitively coupled to ground
105
Slash Rated Exercise
Can 480Y/277 Controller Be Used?
L-G Volt
L-L Volt
Secondary System Type
System Voltage
Yes No
277
480
Solidly Grounded WYE
480Y/277
Yes No
277
480
Resistance Grounded WYE
480
Yes No
480
480
Delta Corner Grounded B Phase
480
Yes No

480
Delta Ungrounded
480
Ungrounded delta systems - phase conductors are
capacitively coupled to ground
106
Slash Rated Exercise
Can 480Y/277 Controller Be Used?
L-G Volt
L-L Volt
Secondary System Type
System Voltage
Yes No
277
480
Solidly Grounded WYE
480Y/277
Yes No
277
480
Resistance Grounded WYE
480
Yes No
480
480
Delta Corner Grounded B
Phase
480
Yes No

480
Delta Ungrounded
480
Ungrounded delta systems - phase conductors are
capacitively coupled to ground
107
Slash Rated Exercise
Can 480Y/277 Controller Be Used?
L-G Volt
L-L Volt
Secondary System Type
System Voltage
Yes No
277
480
Solidly Grounded WYE
480Y/277
Yes No
277
480
Resistance Grounded WYE
480
Yes No
480
480
Delta Corner Grounded B Phase
480
Yes No

480
Delta Ungrounded
480
Ungrounded delta systems - phase conductors are
capacitively coupled to ground
108
Slash Rated Exercise
Can 480Y/277 Controller Be Used?
L-G Volt
L-L Volt
Secondary System Type
System Voltage
Yes No
277
480
Solidly Grounded WYE
480Y/277
Yes No
277
480
Resistance Grounded WYE
480
Yes No
480
480
Delta Corner Grounded B Phase
480
Yes No

480
Delta Ungrounded
480
Ungrounded delta systems - phase conductors are
capacitively coupled to ground
109
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

110
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

111
Solidly Grounded WYE System
SERVICE PANEL
BRANCH PANEL
Steel Conduit
A
A
277V
277V
B
277V
B
C
C
N
N
112
Solidly Grounded WYE System
SERVICE PANEL
BRANCH PANEL
Steel Conduit
A
A
277V
277V
B
277V
B
C
C
N
N
113
Corner Grounded Delta System
SERVICE PANEL
BRANCH PANEL
Steel Conduit
A
A
480V
480V
B
C
480V
B
C
114
Corner Grounded Delta System
SERVICE PANEL
BRANCH PANEL
Steel Conduit
A
A
480V
480V
B
C
480V
B
C
115
Single Pole Interrupting CapabilityUL 489
Circuit Breaker Procedure
UL Single Pole Short-Circuit Test
480V
480/277V
CB Frame Rating
8,660 Amps
10,000 Amps
100 A Maximum
8,660 Amps
10,000 Amps
101 800 A.
Example
20 A, 480V CB having 65,000 A.I.R. (3 Pole Test).
Single pole tested at 8,660 Amps
116
480 Volt, 25,000 Amp Line to Ground
Single Pole Test
UL489 tests single pole at only 8660A
225 Amp, 480 V Circuit Breaker 35, 000 Amp Three
Phase Interrupting Rating
4 Feet 4/0
Photos on following slide
117
(No Transcript)
118

• 2005 Code Changes
• THE END