Industrial Control Panel

1
Industrial Control Panel Short-Circuit Current
Rating

2
Industrial Control Panel Definition

• 2008 NEC 409.2
• An assembly of two or more components consisting
  of one of the following
• Power circuit components only
• Control circuit components only
• Combination of power and control circuits
• These components, with associated wiring and
  terminals, are mounted on or contained within an
  enclosure or mounted on a subpanel.
• The industrial control panel does not include the
  controlled equipment.

3
Short-Circuit Current Rating Definition

• 2008 NEC Article 100 UL 508A Definition
• The prospective symmetrical fault current at a
  nominal voltage to which an apparatus or system
  is able to be connected without sustaining damage
  exceeding defined acceptance criteria.

4
SCCR Marking Requirements

• 2005 NEC or Later
• 430.8 Marked on motor controllers.
• 440.4(B) Marked on HVAC equipment.
• 409.110 Marked on industrial control panels
• SCCR not required for panels that contain only
  control circuit components.
• 670.3 Marked on industrial machinery control
  panel.
• UL 508A, Supplement SB is an approved method to
  determine SCCR for industrial control panels.

5
SCCR Marking Requirements

• UL 508A Shops
• Comply with UL 508A the standard for industrial
  control panels
• Requires all industrial control panels listed and
  marked to UL 508A to be marked with the
  short-circuit current rating.
• Includes requirements for specific use panels
  such as industrial machinery, service equipment,
  elevator control, HVAC, etc.

6
How to Determine SCCR

• Short-Circuit Current Rating
• Can be established by testing during the listing
  and labeling process
• OR
• Can be determined using an approved (calculation)
  method
• UL 508A Supplement SB is an approved method
• UL field evaluation can also be used.

7
How to Determine SCCR

• For a detailed presentation on SCCR and how to
  determine SCCR based on UL 508A Supplement SB,
  request quote for four hour training from your
  Cooper Bussmann representative (Part
  CBTR-SCCR-4HP).
• The following slides only highlight the UL 508A
  Supplement SB method.

8
UL 508A Supplement SB

• What Needs to be Analyzed?
• All power circuit components (SB 4.1)
• Feeder and branch circuit components that supply
  power to loads (motors, lighting, heating and
  appliances)
• Includes disconnect switches, fuses, circuit
  breakers, load controllers, overload relays,
  power distribution/terminal blocks, bus bars,
  etc.
• Control circuit components are not required to be
  analyzed
• Pushbuttons, pilot lights, selector switches,
  timers, control relays, etc.

9
UL 508A Supplement SB

• How to Determine Component SCCR (SB4.2.2)?
• The SCCR marked on the component or on
  instructions.
• The SCCR determined by the voltage rating of the
  component and the assumed short circuit current
  from Table SB4.1.
• or
• The SCCR for a load controller, motor overload
  relay, or combination motor controller that has
  been investigated in accordance with the
  performance requirements, including short circuit
  test requirements for standard fault currents or
  high fault currents specified in the Standard for
  Industrial Control Equipment, UL 508, and
  described in the manufacturers procedure.

10
UL 508A Supplement SB

• What are the Rules?
• Lowest component SCCR limits assembly SCCR
  unless
• Combination ratings can be used to increase
  branch circuit component ratings (SB 4.2.2)
• Component with marked/specified OCPD
• Check with component manufacturer for combination
  ratings
• Feeder components are used that limit the
  short-circuit current reducing the need for
  higher branch circuit component SCCR (SB 4.3)
• Current limiting overcurrent protective devices
• Transformers rated 10kVA or less

11
Component Combination Ratings
Component SCCR
OCPD I.R.

• 200kA

• Branch component limiting assembly rating

• 14 kA

• 200 kA

• 200 kA

• 100 kA

• 5 kA

• 100 kA

12
Component Combination Ratings
Component SCCR
OCPD I.R.

• 200kA

• 100 kA

• Use combination ratings with specified/marked
  OCPD to fix low rated branch components

• 200 kA

• 200 kA

• 200 kA

• 100 kA

• 100 kA

• 100 kA

Combination ratings of overcurrent protective
devices and components can be used
13
Component Combination Ratings
Component SCCR
OCPD I.R.

• 200kA

• 10kA

• Feeder Component Limiting Assembly Rating

• 200 kA

• 200 kA

• 200 kA

• 100 kA

• 100 kA

• 100 kA

14
Component Combination Ratings
Component SCCR
OCPD I.R.

• 100 kA

• 200kA

• Use UL Listed power distribution block with high
  SCCR when used with marked or specified current
  limiting fuses

• 200 kA

• 200 kA

• 200 kA

• 100kA

• 100 kA

• 100kA

Combination ratings of PDBs is cost effective fix
15
Current Limitation - OCPD
Component SCCR
OCPD I.R.

• 200kA

• Branch components limiting assembly rating

• 200 kA

• 200 kA

• 200 kA

• 100 kA

• 10 kA

• 100 kA

16
Current Limitation - OCPD
Component SCCR
OCPD I.R.

• 200kA

• Current limiting feeder OCPD can be used that
  limits the short-circuit current below 10kA

• 200 kA

• 200 kA

• 200 kA

• 100 kA

• 100 kA

• 100 kA

Current limitation is cost effective fix
Note To learn how to use feeder let-through -
request Lunch Learn
17
Current Limitation - Transformer
Component SCCR
OCPD I.R.

• 200kA

10 kVA

• Transformers can be used to limit the
  short-circuit current available

• 10 kA

• 5kA

Current limitation is cost effective fix
18
Current Limitation Transformer
Component SCCR
OCPD I.R.

• 200kA

10 kVA

• Transformers can be used to
  
• limit the short-circuit current available
• If 10kVA sec comp 5kA
• If 5kVA/120V sec comp 2kA
• Then assign entire circuit I.R. of primary
  overcurrent device

• 10 kA

• 200 kA

• 5kA

Current limitation is cost effective fix
19
UL 508A Supplement SB

• What are the Rules?
• Lowest overcurrent protective device interrupting
  rating (or SCCR for some devices) always limits
  assembly SCCR
• See SB 4.3.2 and 4.3.3
• Tested series combination ratings or series
  ratings (fuse-circuit breaker or circuit
  breaker-circuit breaker) are also NOT allowed.
  See NEC also 240.86(B).

20
Interrupting Rating
Component SCCR
OCPD I.R.

• 200kA

• Limited by interrupting rating of OCPD in the
  branch

• 10 kA

• 50 kA

• 65 kA

• 50 kA

• 50 kA

• 50 kA

Interrupting rating directly affects assembly
rating
21
Interrupting Rating
Component SCCR
OCPD I.R.

• 200kA

• Only fix is to increase interrupting rating

• 200 kA

• 200 kA

• 200 kA

• 50kA

• 50kA

• 50kA

Series ratings of OCPDs are NOT allowed
22
Interrupting Rating
Component SCCR
OCPD I.R.

• 10kA

• Limited by interrupting rating of OCPD in the
  feeder

• 200 kA

• 200 kA

• 200 kA

• 50kA

• 50kA

• 50kA

Interrupting rating directly affects assembly
rating in all locations
23
Two Sweep Method
24
Two Sweep Method

• Sweep 1 Verify Component Short-Circuit Current
  Ratings
• Determine lowest branch and feeder power circuit
  component SCCR
• Check with component manufacturer for combination
  ratings
• Use current limiting overcurrent protective
  devices or transformers in feeder circuit to
  increase downstream branch circuit components
  with low SCCR.
• Determine assembly SCCR.
• Sweep 2 Modify Assembly SCCR Based on Lowest
  Interrupting Rating of Overcurrent Protective
  Devices

25
SCCR Design Considerations

• Proper Component Use and Limitations
• SCCR and IR
• Combination Ratings
• Voltage limitations (slash ratings)
• Functionality
• Fundamentals of Assembly Calculations (UL 508A
  Supplement SB)

26
SCCR Design Considerations

• Other Considerations
• Customer requirements
• Fault Current Levels
• Flexibility of application
• Multiple installations
• Fault current unknown
• Insufficient SCCR can delay installation

27
SCCR Compliance

• Ensure equipment Is
• Labeled with SCCR per NEC requirements
• SCCR is sufficient for installation
• Fault current calculations/documentation
• Higher rated panels less concern
• System or location changes
• Adequate for system voltage and grounding type

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SCCR Compliance
Isca 12,000A
Motor Controller SCCR 15kA
X
Available Short-Circuit Current (Isca)
54,000A
Isca 28,000A
Industrial Control Panel SCCR 30kA
X
X
Isca 31,000A
X
Industrial Machinery Panel SCCR 35kA
HVAC SCCR 40kA
Isca 38,000A
X
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Solutions fromCooper Bussmann
30
Code Change Document

• Code Change Update
• Provides background information on NEC changes
  including SCCR

Available at www.cooperbussmann.com
31
Simplified Guide to SCCR

• Provides Overview
• SCCR.
• Typical supply, feeder and branch components and
  default ratings (in easy to use interactive
  chart).
• Find-It, Fix-It, Forget-It.

Available at www.cooperbussmann.com
32
Selecting Protective Devices (SPD)

• Industrial Control Panels SCCR
• Overview of SCCR.
• Detailed example of Two Sweep analysis method
  per UL 508A.
• FixIt solutions.

Available at www.cooperbussmann.com
33
Software Programs

• Short-circuit Calculator Program
• Single- or three-phase.
• Transformer calculation.
• Conductor/bus calculation.
• FREE.
• OSCAR SCCR Calculator
• Assembly SCCR calculator.
• Database of 55,000 parts.
• Select devices and calculate.
• Version 2.0 available now.

34
Cooper Bussmann OSCAR 2.0
New layout
35
Cooper Bussmann OSCAR 2.0
Easier part search
36
Cooper Bussmann OSCAR 2.0
Identify weak link
37
Cooper Bussmann OSCAR 2.0
New report
38
Cooper Bussmann OSCAR 2.0

• Available from Cooper Bussmann Website for
  Purchase
• 299.99 per year.
• Free 7-day trial available.

Contact your local Cooper Bussmann sales
representative for further details
39
Find It - Common Weak Links

• Supplemental Protectors
• If unmarked 200A, often 5-10kA with slash
  ratings (480/277V).
• Standard Circuit Breakers and Class H Fuses
• If standard CB 10-14kA.
• Class H fuses 10kA.
• Motor Controllers
• If no combination ratings available 5kA SCCR.
• Power Distribution Blocks
• If unmarked/untested 10kA SCCR.

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Fix It - Solutions

• High I.R. Protective Devices

41
Fix It - Solutions

• High SCCR Components

42
Fix It - Solutions

• Compact Circuit Protector (CCP)
• 200kA SCCR.
• 600V.
• 30A with Class CC fuses.
• 30A or 60A with CUBEFuse.
• Smallest fusible disconnect available.
• Finger-safe design.
• UL 98 branch circuit disconnect.

43
Fix It - Solutions

• CCP
• Relative size comparison with similar devices

UL 489 600V
Circuit Breaker
UL 489 480/277V Circuit Breaker
UL 98 600V Cooper Bussmann CCP
UL 489 240V Circuit Breaker
UL1077 480/277V Supplementary Protector
Small value for the OEM customer
3 pole rating
44
Fix It - Solutions

• Type 2 Ratings (SPD)
• Combination Ratings (UL Website)
• Procedure Described

• 100 kA

Cooper Bussmann LPJ-60SP IR 300kA
A30 contactor SCCR 5kA
TA25DU32 overload SCCR 5kA
Type 2 ratings or http//www.ul.com/controlequipme
nt/shortcircuit.html
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Fix It - Solutions

• Power Distribution Blocks
• High SCCR.
• Larger spacings.
• UL Listed.

46
Forget It - Solution
Benefits of Cooper Bussmann Solutions Example
Industrial Machinery Control Panel Label
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Questions?Comments?