siemens ul and iec ce blended seminar · nec (nfpa 70) 2014 ul508a (industrial control panels) nfpa...

© Siemens Industry Inc. 2014. All rights reserved.

Welcome!


Welcome!

Introduction to Industrial control panels for North America and Europe

Overview about important:- North American standards and regulations- Requirements and approach for the European Market

© Siemens Industry Inc. 2014 All rights reserved.Industry Sector / I IA CE S V

Issue date 10/2013 Agenda UL and IEC/EN CE workshop

Speaker

SIEMENSGerhard FlierlGraduate in Electrical Engineering and Business Administration

Industrial AutomationIndustrial Controls

Application consulting:- North American Standards and Codes- European Directives and international IEC/ISO standards

www.usa.siemens.com/controlpaneldesignwww.usa.siemens.com/planning-efficiency



Note / exclusion of liability

The typical circuit diagrams and interpretations of the standard are not binding and do not claim to be complete regarding configuration, equipment or any other eventuality. They do not represent any client-specific solutions and are only intended to offer assistance for typical tasks.

Each person viewing this presentation is responsible for the correct operation of the products described. This presentation does not relieve you of your responsibility regarding safe handling when using, installing, operating, and maintaining the equipment.

By viewing this presentation you agree that Siemens cannot be made liable for possible damage beyond the above mentioned liability clause.

We reserve the right to make changes and revisions to this informational documentation without prior announcement.

When writing these guidelines, a lot of tables and texts were lifted straight from the relevant standards. All users of this documentation must always check whether the items quoted are still up to date or not.

The final decision about the appropriateness of applying the applicable standards must be made by the user of this documentation.

The reproduction of this presentation and its distribution, utilization or the dissemination of its contents to third parties isnot permitted.



Workshop agenda

Overview on North American requirements

Codes, standards, organizations and recent changes

UL approval, terms and definitions

SCCR – short circuit current ratings

Motor branch circuits

Protective measures acc. UL/NFPA

Introduction to the Seminar / Basic differences between North America and Europe

Helpful tools, efficient planning & documentation Support, further information

Overview on Requirements in Europe

Introduction to European Directives

CE marking and assessment procedure

IEC and EN standards

Required verifications for control panels

Protective measures acc. IEC/EN



Now you certainly have questions ...


Gerhard FlierlSiemens Industry Inc. Industrial Automation

5300 Triangle ParkwayNorcross 30092, Atlanta / GA

Phone: +1 (770) 871-3835Cell Phone: +1 (404) 434-6403

E-mail: [email protected]

Thank you for your attention!


- Introduction to the workshop- Basic differences between North

America and Europe

Why this seminar?Seminar objectivesBasic differences between North America and Europe

© Siemens Industry Inc. 2014. All rights reserved.Industry Sector / I IA CE S VPage 2 01/2013 Introduction, Basic differences

Why this seminar?

Increasing confusion and uncertainty when deciding which European Directives are important for control panel design

Which standards are important for control panel design and how can these be fulfilled?

Uncertainty with regard to the question: "Who holds the responsibility?"

How should the documentation be produced?

What is the distinction between the important Machinery directive [MD] 2006/42/EC and Low-voltage directive [LVD] 2006/95/EC ?

To what extent is the EMC directive 2004/108/EC for control panel design important?


Seminar objectives

Overview and introduction to European Directives and standards

Refresher and update for the relevant North American standards (UL/NFPA)

To provide assistance and support in understanding important European Directives and standards

To clarify the relationships between relevant standards and their significance for control panel design

To perform the required verifications of the control panel as per IEC 61439-1 & -2

Suggestions for practical documentation that conforms to North American and IEC/EN standards and European Directives


The importance of standards

In general, standards are:

Standards are not laws – yet they are followed willingly and strictly. When they are followed they are similar to laws

Reflect rules / the state of technology and are considered a proven method in the respective field of application

A support function used to achieve a minimum level of procedure (in different countries, etc.)

Fulfilling standards is not an achievement – it is the minimum expected

The highest protection objectives of standards are: the safety of people, livestock, and property


OrganizationsThe global use of standards

IEC, e.g.: EN, VDE, BS, NFUL / NFPA / NEMAUL / NFPA / NEMA / IECCSA / UL / NFPA / NEMA


Differences between Europe & North America

+ Operating permission of AHJ

EuropeResponsibility of the equipment manufacturer

Responsibility of the operator/user

Protection targets are defined by directives

Presumption of conformity with the application of harmonized standards (ISO9000 et seqq., self-certification, self-responsibility)

USA / North AmericaResponsibility of the operator/user

Protection targets and requirements are defined by laws

Certification/listing of products

Verification by independent NRTL/AHJ (Electrical Inspector) (third-party certification)


Extracts of the OSHA standards and NEC Ed. 2014

OSHA 1910.303(b)(2) Subpart S – Electrical / General requirements:

Installation and use: Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

Definitions acc. NEC Art. 100:

Equipment: A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation.

Listed: Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specified purpose.

Labeled: Equipment or materials to which has been attached a label, symbol, or other identifying mark ofan organization that is acceptable to the authority having jurisdiction and concerned with product evaluation, that maintains periodic inspection of production of labeled equipment or materials, and by whose labeling the manufacturer indicates compliance with appropriate standards…etc.


Basic differences between U.S. and CE Markets Standards – Comparison between USA and IEC

IEC 60947IEC 61008

IEC 60204-1IEC 61439-1

IEC 60204-1 IEC 61439-1


Significant differences between IEC and UL control panels

Main disconnecting mean

LightingReceptacleGFCI

Enclosure interlocking

MTW conductors

Identification ofconductors

Substitution deviceswithout UL - approvals

EnclosureTerminalBlocks

Motor controllerMax. Control voltage

Protection devices accordingUL508A, UL test report

Power distribution

Transformer protection

1

2 3

4

5

6

78

91011

12

13


Questions?

© Siemens Industry Inc. 2014. All Rights Reserved.

Codes, standards and organizations

OrganizationsStandards and CodesRecent changes in the codes and standards

© Siemens Industry Inc. 2014. All Rights Reserved.Industry SectorPage 2 Issue date 10/2013 Codes, Standards and Organizations

Standard Organizations – extract

NFPA:The National Fire Protection Association publishes diverse regulations and directives such as NEC, NFPA79; NFPA70E; NFPA70B

ANSI:The American National Standards Institute is the highest level national standard authority in the USA. Most regulations are based on the ANSI standard

UL:Underwriter Laboratories publishes standards and certifies products in accordance with its own and other standards (CSA, IEC,...). Headquarter: Northbrook, Illinois. In general, UL certification is not required by law. However, all Authoritiesaccept UL certification without restrictions.

CSA:The Canadian Standard Association publishes standards and certifies products in accordance with its own and other standards (UL, IEC,...). Headquarter: Toronto


OrganizationsThe origin of UL

1893 World Exhibition in Chicago

Outbreak of a fire

1894 Start of UL

William H. Merrill opens the “Underwriters Electrical Bureau”


NFPA Organization

Foundation: 1896, due to increasing sprinkler system installations Headquarters: Quincy, MassachusettsPublication of over 300 standards to date

National Electrical Codeor

NFPA70

NFPA79Electrical Standard for

Industrial Machinery

Standardization organization in the field of fire protection, electrical safety and building safety


NRTLs According to OSHAExcerpt from www.osha.gov/dts/otpca/nrtl


Important Standards for OEMs and Industrial Control Panel Manufacturers

National Electrical Codeor

NFPA70

NFPA79Industrial Machinery

UL508AIndustrial Control Panels

NEC is the only statutory standard in the USA

UL508A and NFPA79 have a quasi-legislative character


Standard References in the USA

NEC (NFPA 70) 2014

UL508A (Industrial Control Panels)

NFPA 79 (Electrical Standard for Industrial Machinery)

Art. 409.1 Scope Safety Standard for Industrial Control Panels

Chapt.65.1 These requirements cover industrial control panelfor industrial machinery.

Art. 670 Electrical Standard for Industrial Machinery


StandardsDefinition “Industrial Control Panels” in acc. with NEC 2011

Definition:

2 or more devices installed in the power circuit including their control circuits and control devices

e.g. motor starterComponents suitable for an Industrial Control Panel UL508A, Table SA1.1


Application of the wrong standard

… includes the following … does not include the following

- Industrial Control Panels

- Flame Control Panels

- Industrial Machinery

- Crane Control

- Air Conditioning and Refrigerating Equipment

- Service Equipment

- Industrial Control Panel Enclosures

- Irrigation Equipment

- Panels for Construction Sites

- Motor Control Center

- Panels for Classified Locations

- Switchgear (UL891)

- Control Panels for Wind Mills or photovoltaic

- Control Panels for Swimming Pools

- Alarmpanels

- Fire Pump Stations

Example: Scope of the UL508A…


Meaning of the NPFA79 2012 Edition…

Scope of the standard:…application standard for electrical equipment and systems with

max. 600 V for operator and system protection…from the electric infeed down to the individual machine modules…for non-hazardous ambient conditions (non-hazardous locations)


Industrial Machinery

Definition of "industrial machinery" according to NFPA79 & NEC70:Motorized machine(s) for material processing (e.g. forming, pressing, cutting)Not transportable by hand during operation With corresponding modules, as the case may be (e.g. conveyor belts, mounting accessories, testing equipment, packing units) Including control technology with PLC controls, actuators / sensors

Definition of "industrial machinery" according to UL508A §65:Metal-processing machinesPlastic-processing machines Wood-processing machinesMounting machinesMaterial-handling machinesMaintenance and testing equipment


Examples of Industrial Machines Covered by NFPA79 – Annex C


Example of the scope of application standards

NEC (NFPA70)

*)

*)

*)

*)

*)

*) UL508A

NFPA79


Definition of TermsAHJ

Authorities Having Jurisdiction (AHJ’s):Compliance with laws and codes is monitored by the responsible authorities of the respective federal states, districts or municipalitiesExample: State Electrical Commission, State Fire MarshalThe current NEC (National Electrical Code) serves as reference in most cases


Extracts from the "Electrical Inspection Manual"

Approved:Acceptable to the authority having jurisdiction. [Approval is a primary responsibility of an electrical inspector. Investigations by a thirdparty and the listing and labeling that result are a great aid to inspectors in this responsibility (see "Labeled„ and"Listed").]

The inspector decides on what is and what is not accepted; UL approvals serve as a great help and reference for the inspector

AHJ function:The key to a successful and correct electrical inspection lies in applying therules of the Code, not the personal preferences of the inspector. To reiterate, if the installation meets the Code requirements (including any local amendments) and is safe, the installation should pass inspection.

The application of standards facilitates acceptance by the inspector


Recent changes - National Electrical Code (NEC) 2014Maximum voltage of an Industrial Control Panels has been changed from 600V to 1000V


Recent changes - National Electrical Code (NEC) 2014Maximum voltage of an Industrial Control Panels has been changed

When it comes to Industrial control panels the NEC 2014 refers still to UL 508A!

Recommendation:

Industrial control Panels should fulfill furthermore the UL 508A

Maximum voltage 600V!

UL 508A is still limited to 600V or less!


UL 508AImportant changes

UL 508A was extended by the following specific use parts:

Fountain control panels

Industrial control panels for irrigation equipment

Enclosures

Industrial machinery

Crane control

Service Equipment Use

Flame Control

Marine Use

Air Conditioning and Refrigeration Equipment

New!!!


Definition of TermsListings / Symbols

UL „listed“ Markfor USA andCanada

UL „classified“Mark for USA and

Canada

UL „enhanced“Mark for USA and

Canada

Notes: - Long transition time (approx. 10 years)- The current “classified” and “listed” marks will not expire


NEC Ed. 2014 Important changes – Spacings for Industrial Control Panels

409.106 SpacingsSpacings in feeder circuits between uninsulated live parts of adjacent components, between uninsulated live parts of components and grounded or accessible non–current-carrying metal parts, between uninsulated live parts of components and the enclosure, and at field wiring terminals shall be as shown in Table 430.97(D).

Exception: Spacings shall be permitted to be less than those specified in Table 430.97(D) at circuit breakers and switches and in listed components installed in industrial control panels.


NEC Ed. 2014 Spacings in branch circuits and control circuits acc. UL508A


NEC Ed. 2014 Spacings in feeder circuits acc. UL508A



Enclosure Air conditioners are not part of short circuit current (SCCR) calculation when cord-and-attachment plug connected or supplied from a branch circuit protected maximum 60A



Main Disconnect

contactor contactor

motor heater

Overload-relay

contactor

motor

Overload-relay

Every Transformer is current limiting

Short circuit protection Short circuit protection Short circuit protection

Feeder circuit

Branch circuit

Current limitingdevice

Transformer peak-let-through currents can be used to protect Branch circuits!



Previous rule:A.) Transformer < 5kVA and max. 120V sec. => max. 2kA at the secondary side

all devices at the secondary side for at least 2kA

B.) Transformer < 10kVA => max. 5kA at the secondary side. all devices at the secondary side for at least 5kA

C.) All other transformers are not considered as current limitingsame short-circuit current at the secondary and primary side

SCCR 2 kA SCCR 5 kA SCCR x kA


New rule:Loads provided by a Transformer with isolated secondary acc. to UL 508A SB4.3.1Possibility 1: For transformer with marked or known impedance (Z acc. To UL 508A), the maximum secondary short circuit current will be calculated as follows:

All devices located at transformer secondary shall be the calculated short circuit current rating (Isc)SCCR of the loads = Interrupting rating of primary overcurrent protection device



New rule:Loads provided by a Transformer with isolated secondary acc. to UL 508A SB4.3.1Possibility 2: For transformer with unknown impedance (Z acc. To UL 508A) or 2,1%, the maximum secondary short circuit current will be calculated as in possibility 1 described (assumption Z = 2,1 %) or determined with Table SB4.3 (single phase) respectively SB4.4 (three phase) as follows:1. Transformer kVA maximum value column 1 and2. Secondary voltage not smaller as values in column 2. If the secondary voltage is between the values, the next smaller voltage shall be used.

Table SB4.3 Table SB4.4




Sizing of branch-circuit protection of a variable speed drive if not specified by the manufacturer instruction

Up to now

As of now



Protection devices in dc control circuits above 32V shall be approved for the rating equal or greater

Excerpt from Certificate of compliance of Siemens supplementary protectors 5SY…


NFPA 79 Ed. 2012Grounding

NFPA79 Ed. 20078.2.3.1 The continuity of the equipment groundling (protective bonding) circuit shall be ensured by effective connections through conductors or structural members.

NFPA79 Ed. 20128.2.3.1 The continuity of the equipment grounding (protective bonding) circuit shall be ensured by effective connections through conductors


Thank you for your attention!Questions?


UL Approvals, Terms and Definitions

DefinitionsTerms and their backgroundMarkings

© Siemens Industry Inc. 2014. All Rights Reserved.Industry SectorPage 2 Issue date 10/2013 UL approvals, Terms and Definitions


Application of these products requires the so-called CoAs (Conditions of Acceptability)

The installer requires "special" instructions = engineering supervision

UL certificates (CoC’s) include the ‘Conditions of Accesptability’ or www.ul.com/database



UL „listed“ Markfor USA andCanada

UL „classified“Mark for USA and

Canada

UL „enhanced“Mark for USA and

Canada


Definition of TermsUL Product Categories

The CCN represents a clear description of the respective productThe respective CCN Guide Information clearly describes how and under which conditions the respective product can or may be applied (www.ul.com/database)Every AHJ or UL inspector can thus verify whether the respective product was correctly configured and appliedThe CCN should be additionally integrated in the parts list

Examples: DIVQ // DIVQ7 // NMTR2 // NMTR8


Definition of TermsUL Product Categories

Definition of the CCN (Category Code Number):Numerical or alphanumerical character string for the exact identification of products according to UL standards!

Product Contactors(magnetic motor controllers)

Overcurrent relays(overload relays)

Standard UL508 – Industrial Control Equipment

UL-ListedNLDX NKCR

UL-RecognizedNLDX2 NKCR2

Example:


SA1 list – UL508A


Definition of Terms

Excerpt from NFPA 79 Mandatory!

Recommendation!

UL terms cannot be converted one to one to IEC standards, they must be questioned!

Factory wiring = internal wiring = all components inside the industrial control panelthe installer works under "engineering" supervision UL508A , § 29

Field wiring = all components inserted from the outsidethe installer implements his own professional know-how UL508A, § 28

Overcurrent = NEC Art. 100overload and/or short circuit current and/or, where applicable, ground fault current


Factory / Field WiringExample – Excerpt from UL Database (www.ul.com/database)

Power distribution block5ST25..CCN: XCFR2E-file: E80027

Code 1: Only factory wiring Code 2: Factory and field wiringUL-listed products always feature a field wiring approval!


Definition of Terms Persons

Electrically instructed personElectr. hazards / risks can be avoided through appropriate instruction or supervision

Electrically skilled personElectr. risks can be detected and hazards avoided through appropriate training and experience

Qualified personKnowledge and skills regarding the design and operation of electrical equipment Safety training on the respective hazards (NEC 2008 Handbook Art. 100)


Overview and Definition

Definitions acc. UL508A:

Feeder circuit:Definition: FEEDER CIRCUIT – The conductors and circuitry on the supply side of the branch circuit

overcurrent protective device.

FCPD’s: UL489 (3WL; 3VL; 3RV17/18; 5SJ4…-.HG)

UL248-4…-12 (3NW; Class CC)

UL98

Branch circuit:Definition: BRANCH CIRCUIT – The conductors and components following the last overcurrent

protective device protecting a load.BCPD’s: Depending on application case


Overview and Definition

-M1 -M2

-DISC

-CON1-OL1

-FU1-FU2

-CON2-OL2

-T

-FU3

Control Circuit

Viewing Direction

Boundary Feeder and Branch


Distance through air and over surface

Depending on voltage up to1 inch – distance through air2 inches – distance over surface

Overview and DefinitionPractical realization

0 – 125 V 126 – 250 V 251 – 600 VIndication of the distances between the current-carrying wires and enclosure and the distances through air and over surface

Feeder circuits:

Branch circuits: see UL 508A table 10.1

or

0 – 50 V 51 – 150 V 151 – 300 V 301 – 600 VIndication of the distances between current-carrying wires and enclosures and the distances through air and over surface

UL 489UL 98UL 248

Distribution

Circuit Breaker

Line Terminals

Load Terminals

Motors Trans-former Heater

Feed

er C

ircui

tB

ranc

h C

ircui

tsee UL 508A table 10.2


NEC 2014 – Spacings for Industrial Control Panels

409.106 SpacingsSpacings in feeder circuits between uninsulated live parts of adjacent components, between uninsulated live parts of components and grounded or accessible non–current-carrying metal parts, between uninsulated live parts of components and the enclosure, and at field wiring terminals shall be as shown in Table 430.97(D).

Exception: Spacings shall be permitted to be less than those specified in Table 430.97(D) at circuit breakers and switches and in listed components installed in industrial control panels.


Spacings in branch circuits and control circuits acc. UL508A


Spacings in feeder circuits acc. UL508A


Overview and requirements

There are different type of power supply networks in North America in regards to their- design (e.g. wye, delta)- grounding (ungrounded, grounded, high impedance grounded)

Generally, all voltages occurring in these network types are indicated (phase to phase / phase to ground)

Also the ground connection and the circuit on the secondary side of the transformer are indicated

Abbreviations and Indictaions of number of wires:Number of phase wires: “phase”, “p”, or “ ”Total number of wires: “wire” or “w”

Example of voltage ratings:slash rating: 480Y/277V; 3 4wstraight rating: 480V; 3p; 3w



UL508A requires:1.) For an industrial control panel with a slash voltage rating, the input terminals shall be marked:

“For use on a solidly grounded wye source only”

2.) The voltage rating of an industrial control panel shall not exceed the voltage rating of any componentconnected to the source of supply. When an industrial control panel contains components marked with aslash voltage rating, such as 120/240, 480Y/277, or 600Y/347, the voltage rating of the industrial controlpanel shall be:

a) The complete slash voltage rating, when intended for connection to the higher voltage; or

b) Not more than the lower voltage rating



NFPA79 requires:

A circuit breaker, self-protected combination motor, controller, or a manual motor controller markedwith a slash rating, such as 120/240V or 480Y/277V, shall be applied in a solidly grounded circuit where:

- the nominal voltage of any conductor to ground does not exceed the lower voltage rating - and the nominal voltage between any two conductors does not exceed the higher voltage rating.

When slash-rated devices are connected to the supply circuit of the machine, the nameplate voltage rating shall not exceed the lower voltage rating or shall include the complete slash rating.


Most Important Network Types in DetailGrounded wye / solidly grounded wye

Slash rating:e.g.: 480Y/277V, solidly grounded wye3 phase; 4 wire3 phase; 3 wire

Possible devices480Y/277V; 600/347V480V; 600V

Note:All devices having a slash rating with the indicated voltage or higher

All devices having a straight rating with at least the higher of both voltages

3p, 4w / grounded

phase-ground

U = 277 Vacross one

contactworst case!

L1L2L3

Transformer

480Y/277V AC

M

Ik


Most Important Network Types in DetailCorner grounded delta

Straight (Delta) rating: e.g.: 480V / 3 phase - 3 wire

Possible devices in this example: 480V; 600V

Do not use: 480Y/277V; 600Y/347V

Note:The devices switch full (=high) voltage at the first single pole short-circuit (phase to ground)

The following applies to this network in principle: Only devices with straight rating must be used!

Phase - Ground

U = 480 Vacross one contact

worst case!!

L1L2L3

Transformer 480V AC

M

Ik


Most Important Network Types in DetailUngrounded delta - Ungrounded wye

Straight rating: e.g.: 480V / 3 phase - 3 wire

Possible devices in this example: 480V; 600V

Do not use: 480Y/277V; 600Y/347V

Note:The devices switch the full (=high) voltage at the second single-pole short-circuit (phase to ground)

The following applies to this network in principle: Only devices with straight rating must be used!

480V ACL1L2L3

Transformer

M

/YBetrieb

Insulation measuring

! Operation requiresInsulation monitoring!Ik

Phase - Phase

U = 480 Vacross one

contactworst case!!


Agreements Between Manufacturer and Customer

The standard offers support in the form of a ready-made questionnaire in Annex B / NFPA79 (only informative!)


SCCR –Short Circuit Current Rating

Definition / Explanations

Procedure for Establishing the SCCR

Possibilities of Increasing the SCCR

Establishment of SCCRs – Examples

Device Data / UL-Reports

UL guidelines, chapter 5.8

© Siemens Industry Inc. 2014. All Rights Reserved.Industry SectorPage 2 Issue 10/2013 SCCR – Short Circuit Current Rating

Definition / Explanations

Requirement of NEC 2005 Art. 409 (mandatory since April 26, 2006)

Re-enforcement of the standards for “industrial control panels” Failures in determining the short-circuit current rating (= SCCR) of an industrial control panel.

For the short-circuit current rating not only the short-circuit breaking capacity of, e.g. the circuit breaker is needed, also the short-circuit current rating of every individual device is as relevant.

SCCR-relevant components in the main circuit, such as:

Circuit-breakers, contactors, soft starters, overload relays, but also

Terminals, busbars,

Supply to an control transformers,

Frequency converters, …

Further current limiting “effects” are not allowed to be considerede.g.: that of wires, cables, busbars, …


Definition / Explanation

What is this value for?The indication of the SCCR value at the industrial control panel is to ensure that this control panel is only connected to power supply where at the point of connection the available max. short-circuit current will not exceed the given value on the nameplate.

The target is fire and personal protection Who specifies this value?This can only be established as part of the agreement between the final user (contractor) and the supplier (OEM).Who determines the short-circuit current of the main power supply at the final user ?

Customer himselfFault Studies to be carried out by accredited institutesLicensed professional engineers

What should this value be?To be agreed between the customer and the contractor

Note: The higher the value, the more expensive the devices (compare devices with 35kA and devices with 100kA)


Procedure for Establishing the SCCR

Determination of the short-circuit current rating (SCCR) acc. to NEC409.110 (4):

Step 1: Has to be!SCCR of the installed and UL-listed components

Step 2: Has to be!Establishment of the SCCR on the basis of standard values(UL508A suppl. SB or UL-guide; chapter 5.8.4).

Step 3: Optional, very helpfull!SCCR of tested industrial control equipment assemblies(series rating = 2 circuit breakers in series or combination tests = motor branch circuits)

Step 4: Optional, not very helpfull!Use of current limiting devices (transformers, fuses, circuit breakers)


Establishment of the SCCR value on the basis of the parameters of installed and UL-listed components

Procedure for Establishing the SCCRStep 1

Excerpt of a method description from the “White Paper” by Siemens Energy & Automation (SE&A)

List the short circuit current ratings of components, marked on components or on instructions provided with the components.


Establishment of the SCCR value using the table in UL508A. These standard values must be used if the technical documents do not provide SCCR values for the applied devices.


List the short circuit current ratings of components, from UL 508A, Table SB 4.1, if no values on the nameplate or on instructions provided with the components (see step 1)


SCCR of tested industrial control equipment assembliesSeries rating testsSeries connection of 2 or more devices, which are able to automatically respond in short circuit cases without delay. SB4.3.2 in UL508A! Current limiting cannot be used here !Combination testsSeries connection of any type of devices, e.g.:

Motor protection circuit breaker and contactor (=fuseless load feeders as type F acc. to UL508)MCCB and terminal block




MCCB3VL

MCB5SJ4..HG4

M

MCCB3VL

3RBmotor protection relay

3RTcontactor

Fuse

Series rating Tested combinations

MCB5SJ4..HG4


Possibilities of Increasing the SCCRStep 4 Use of transformers SB 4.3.1


Possibilities of Increasing the SCCRStep 4 Use of transformers

1.) Single Phase Transformers:Transformer Full-Load Current (IFL) = (Transformer kVA x 1000) / Voltage*

Short Circuit Current (ISC line-to-line) = ((Transformer Full Load Current (IFL )) / Transformer Impedance (Z)

2.) Three Phase Transformers:Transformer Full-Load Current (IFL) = (Transformer kVA x 1000) / (Voltage** x 1.732)

Short Circuit Current (ISC line-to-line-to-line) = ((Transformer Full Load Current(IFL )) / Transformer Impedance (Z)


Possibilities of Increasing the SCCRStep 4

Use of current limiting fuses, when used as feeder elements SB 4.3.3Only fuses listed in UL508A – table SB 4.2 are applicable.Use let-through values from the UL508A – table SB 4.2 ONLY(manufacturer‘s values are NOT permissible)Fuses are also standardized in the geometrical dimensions

manufacturer-independent replacementThe fuse is replaced by the service staff, which is shall not compare the corresponding let-through values (old fuse versus new fuse)

Note:For practical application only partially useable, as, e.g.:

Standard contactor up to 37kW: max. 5kAStandard busbar: max. 10kAStandard terminal block: max. 10kA


Possibilities to Increase the SCCRStep 4

Attention:Here, only the let-through values of UL508A (table SB4.2, §SB4.3.3) have to be used. Let-Through values are peak values. These HAVE TO BE compared with the rms (effective values) of the devices acc. to UL508A.


Possibilities of Increasing the SCCRStep 4

Use of current limiting circuit breakers, listed as “current limiting”, when applied as feeder element SB4.3.2

The circuit breaker must be listed as “current limiting”The circuit breaker must be marked as “current limiting” (UL508A – SB 4.3.2)

The manufacturer has to publish the current limiting characteristics or data and provide them to the user

When replacing the circuit breaker by a different type or manufacturer, the SCCR value must be checked again engineering is required

Note:For practical applications hardly usable, as, e.g.:

Standard contactor up to 37kW: max. 5kAStandard busbar: max. 10kAStandard terminal block: max. 10kA

Siemens “current limiting” breakers


Example:Feeder circuit breaker (MCCB; UL489): rated current 40A / 480V,switching capacity 35kA at 480V

Motoroperating current 10A

Contactor / overload relayrated current 10A / 460Vmax. short circuit current load:5kA / 480V

With circuit breaker:SCCR rating for combinations

SCCR 5kA

3VLcircuit breaker

3RT contactor

3RBoverload relay

BCPD3RV17circuit breaker

BCPD, circuit breaker acc. to UL489: rated current 15A / 480V, switching capacity 35kA at 480VDownstream the feeder circuit breaker (feeder),

several motor branch circuits may be installed.

Establishment of SCCRs Example 1

? What is the SCCR value for this combination ?

M

Establishment of the short circuit current (SCCR) in acc. with NEC409.110 (4): SCCR has to be determined acc. to a specified procedure (UL508A suppl. SB or UL guide; chapter 5.8).


Example:Fuse is current limiting:rated current 20A,switching capacity = 100kAprospective Short Circuit Current = 50kA

let-through value 3kA (class CC)(in acc. with UL508A; table SB4.2)


Contactor / overload relayrated current 10A / 460Vmax. short circuit current load:5kA / 480V


SCCR 35kA

Fuse

3RT contactor

3RBoverload relay

BCPD3RV17circuit breaker

BCPD, circuit breaker acc. to UL489: rated current 15A / 480V, switching capacity 35kA at 480VDownstream the feeder fuse (feeder), several

motor branch circuits may be installed.



M



Example:Circuit breaker in acc. with UL489:rated current 30A / 480V, switching capacity 35kA / 480V

Contactor / overload relay rated current 10A / 460Vmax. short circuit current load:5kA / 480V


SCCR 5kA

Downstream the feeder circuit breaker (feeder), several motor branch circuits may be installed.

Establishment of SCCRsExample 3


M


3RV17circuit breaker

3RT contactor

3RBoverload relay

Fuse


Fuse is current limiting:rated current 20A,switching capacity = 100kAprospective Short Circuit Current = 50kA

let-through value 3kA (class CC)(in acc. with UL508A; table SB4.2)



? What is the SCCR value for this combination ?Example:Feeder circuit breaker (MCCB; UL489)as main disconnecting means: rated current 40A / 480V, switching capacity 100kA / 480V

MotorMotor operating current 20A

3RT2 contactor

3RV20 Motor starter acc. to UL508, type E / Frated current 20A, switching capacity 65kA / 480Y/277V

See UL reportE156943; Vol.1; Sec.18


M


AttentionUp to max. 480Y/277V

MV


SCCR 65kA

3VLcircuit breaker



? What is the SCCR value for this combination ?Example:Feeder circuit breaker (MCCB; UL489)as main disconnecting means: rated current 40A / 480V, switching capacity 100kA / 480V

Motor starter acc. to UL508, type E / Frated current 20A, switching capacity 65kA / 480Y/277V

See UL reportE156943; Vol.1; Sec.18


M


AttentionUp to max. 480Y/277V


SCCR 65kA

3RT2 contactor

3RV20

MV

3VLcircuit breaker

MotorMotor operating current 20A


Device Data / ReportsDevice data

Siemens SIRIUS Contactor 3RT1035

Short Circuit Current 5kA, 600V

ULguidelines; chapter 5.8.2


Device Data / ReportsReports

Type FMagnetic

MotorControl

See report in the annex


Support from Siemens

http://www.usa.siemens.com/sccr


Motor Branch Circuits acc. to UL

Definition of Terms / ExplanationsOverview of Basic DevicesConstruction Types acc. to UL 508Self-Protected Combination Motor ControllerVarious types – Single Installation and Group InstallationSuitable for Tap Conductor Protection in Group InstallationExplanations

UL guidelines, chapter 6.2 / 6.3

© Siemens Industry Inc. 2014. All Rights Reserved.Industry SectorPage 2 Issue 10/2013 Motor Branch Circuits acc. UL508A

Overview – standard devices

Motor Starter Combination – ExampleUL guidelines, chapter 6.2.4

Pos Basic Type UL Norm21 Field wiring Terminal on the device

11 Disconnect switch UL 98

13 Fuse, e.g. Class J UL 98UL 512

3 / 5 Controller UL 508

4 Overload protection UL 508

22 Internal Wiring UL 508ANEC §310

23 Field wiring Terminal UL 1059

24 Motor disconnect (Option) UL 508

25 Motor, 460 V SF 1,15 (name plate)

12 Circuit BreakerOverload & Short Circuit UL 489

3RV3VL

3RT

MCSVB2

3RU / 3RB

3LD

a

b

c

d

8WA

As minimum, the following shall be installed acc. to

UL508A:

Disconnect – (a)

Short Circuit Protection – (b)

Motor Controller – (c)

Overload Protection – (d)


Manual Motor Controller Industrial control equipment rated in hp (horsepower) for manual switching of motors (UL508 Part III)including motor overload protection, i.e. separate overload relay would not be neccessary

Magnetic Motor ControllerIndustrial control equipment rated in hp (horsepower) for remote switching of motors (UL508 Part II)

Inverse-Time Circuit BreakerCircuit breaker with overload and short-circuit protection (UL489)

Instantaneous Trip Circuit BreakerCircuit breaker with short-circuit protection (UL489)

Definition of Terms / Explanations

Solid State Motor ControllerIndustrial control equipment rated in hp (horsepower) for remote switching of motors (UL508)

Overload RelayIndustrial control equipment for motor overload protection, set to motor current FLA (UL508 PART XI)


Construction Types in acc. with UL508 / Table 76.2 Various constructions of combination motor controllers – A / B

M

M


Construction Types in acc. with UL508 / Table 76.2 Various constructions of combination motor controllers – C / D

x

M

x

M


Construction Types in acc. with UL508 / Table 76.2 Various constructions of combination motor controllers – E / F

x

M

x

M


Definition of BCPD acc. UL

Branch Circuit Protection Device (BCPD):A fuse or circuit breaker that has been evaluated to a safety standard for providing overcurrent protection

UL 248-4…12 fuse:FUSE, BRANCH CIRCUIT TYPE – A fuse of Class CC, G, H, J, K, L, R, and T. These fuses are able to provide branch circuit protection

UL 489 Circuit Breaker – inverse time:INVERSE-TIME CIRCUIT BREAKER – A circuit breaker in which a delay is introduced into the tripping action of the circuit breaker. The delay decreases as the magnitude of the current increases. These circuit breakers are able to provide branch circuit protection.


BCPD – Branch Circuit Protection Devices

Inverse time C.B. UL489 C.B. / CSA 22.2 No. 5-09

3RV27/28 3RV17/18 3VL

Class CC Fuses acc. UL248-4 / CSA 22.2 No. 248.4

3NW


Motor Starters vs. Type E combination motor controller

Type E combination motor controlleracc. UL508 / CSA 22.2 No. 14

Approved as branch circuit protection devicefor motor loads only!

Slash voltage rating only!

Manual motor controller / motor starteracc. UL508 / CSA 22.2 No. 14

Approved as motor disconnect and motor overload protectioncan not be used as a branch circuit protection device!

Delta voltage rating!

3RV2

3RV23LD


Definition of Motor Starters

There are two types of Motor Starters certified for use in USA and Canada…Motor Starters and Type E Combination Motor Controllers.Motor Starters do not offer any branch circuit protection.Type E Combination Motor Controllers offer branch circuit protection for motors.

Manual Motor Controller (Motor Starter):A device designed for manual-only control of a motor under normal and locked rotor conditions. A motor controller may incorporate a means to automatically interrupt motor overload currents. Some manual motor controllers are provided with limited short circuit interrupting capabilities; however, the certification report will state that the ability of these devices to open the short circuit currents was not evaluated. A manual motor controller is evaluated to CAN/CSA-C22.2 No. 14.

Type E Combination Motor Controller:A single device designed to control a motor under normal and locked rotor conditions, disconnect the motor branch circuit and interrupt short circuit and overload overcurrents having non-replaceable or integral discriminating overload andshort circuit sensors, and provided with one or more sets of contacts where the contacts cannot be isolated for separate testing. A Type E combination motor controller is evaluated to the requirements of CSA Standard C22.2 No. 14-95.


Definition of Terms / Explanations – Service Factor SF

Note:

SF = 1.0 corresponds to a setting value of 0.92 FLA

SF 1.15 corresponds to a setting value of 1.0 FLA

Definition:

The service factor - SF - is a measure of periodically overload capacity at which a motor can operate without overload or damage.

The NEMA standard Service Factor for fully enclosed motors is SF 1.0

SF: service factor SF 1.0 / SF 1.15 to be used for the overload setting of an overload relais Important parameter for the setting of the Bi-metal relay. Only a Service Factors other than SF1.0 have to be indicated on the nameplate.SF1.0 is normally not indicated on the name plate. NEC 2011 – 430.32 (1)


Assembly Options – Single or Group Installation

UL 508A differentiates between 2 installation variants:Single installation = single motor circuit (chapter 31.3)Group installation = motor groups (chapter 31.4)

1. Single installationsManual self-protected combination motor controller (SPCMC) acc. to UL508 Type E (only 3RV) Manual / magnetic self-protected combination motor controller (SPCMC) acc. to UL508 type F (e.g. 3RA1 load feeder = 3RV+3RT) Manual motor controller (only 3RV)Manual / magnetic motor controller (3RV and 3RT)

2. Group installations / branch circuit protection for motorsGroup installationsGroup installations with additional approval „Suitable for tap conductor protection in group installation“ (additional tests with UL508)


Basic rules for sizing a motor branch circuit – Example


Self-Protected Combination Motor Controller

Solution with SIRIUS

Excerpt from the UL configuration manual with tested combinations (with UL report)


Self-Protected Combination Motor Controller Solution with SIRIUS

UL508 type FType F is a combination of:

self-protected combination motor controller (UL508 type E) )

+magnetic motor controller / solid state motor controller

The completely assembled solution for type F starters: 3RA load feeders (type F magnetic motor controller)Assembly:3RV circuit breaker (with power supply terminal) + 3RT contactor


Assembly OptionsSingle Installation

Manual / magnetic motor controller Solution with SIRIUS

Excerpt from the UL configuration manualwith tested combinations(with UL report)


What is the definition of a Group Installation

Definition of a Group Installation:A group of loads, consisting of two or more motors, or one or more motors and other loads,

are able to be protected by a single set of branch circuit fuses or inverse – time circuit breaker

as specified in Method A, B or C(see the following slides for details)

BCPD

Starter Starter Contactor

Motor Motor Heater


Sizing of Branch Circuit Protection for Motor Groups acc. UL/NECMethod A – General requirements

Branch circuit protection not >20A @125V max., or not > 15A @600VEach motor not >6A FLA, Branch Circuit Protection not greater than any component restrictions, andCoordinated with requirements for any non-motor loads per 31.4.4

31.4.4 For a group that includes other (non-motor) loads, additional branch circuit fuses or inverse time circuit breakers shall be provided in each circuit

Exception: Where the ampere rating of the branch circuit protection determined in 31.4.1 does notexceed the applicable branch circuit protection requirements in 31.5 – 31.8 for a non-motor load in the group, additional branch circuit protection is not required


Sizing of Branch Circuit Protection for Motor Groups acc. UL/NECMethod A – Assembly

BCPD


Motor Motor Heater

Step 3: Branch Circuit Protection Device does not exceed:

20A @ 125V15A @600V

Step 1: Ceck starter for specific instructions (UL certificate)

Step 2: FLA of each motormay not exceed 6A

Step 4: Branch Circuit Protection meets requirements in 31.4.4 for non-motor loads


Sizing of Branch Circuit Protection for Motor Groups acc. UL/NECMethod B – General requirements

BCPD size complies with single motor requirements for each individual motor

Tap conductors not less than 1/3 the ampacity of branch circuit conductor, or not less than 1/10 the amp rating of branch circuit protection if Manual Motor Controller marked “Suitable as Tap Conductor Protection in Group Installations”

Additional branch circuit protection for non-motor loads unless branch circuit protection device also meets 31.5 through 31.8 for non-motor loads in group

C.B. inverse time:400 percent of full-load motor current for an inverse-time circuit breaker not exceeding 100 amperes300 percent of full-load motor current for an inverse-time circuit breaker rated more than 100 amperes;

Fuses:225 percent of full-load motor current for a time delay (dual element) fuse400 percent of full-load motor current for a non-time delay fuse or a Class CC time delay fuse not exceeding 600 amperes;


Sizing of Branch Circuit Protection for Motor Groups acc. UL/NECMethod B – Assembly

BCPD


Motor Motor Heater

Step 1: Select Branch Circuit Protection Device not to exceed

single motor sizing for smallest motor

Step 2: Ampacity of tap conductors not less than 1/3 ampacity, or

1/10 rating of BCPD when manual motor controller is marked as “Suitablefor tap conductor protection in group

installations

Step 3: Check if non-motor loads require additional protection


Sizing of Branch Circuit Protection for Motor Groups acc. UL/NECMethod C – General requirements

All controllers marked for group installation with BCPD sized at the lesser of:- the smallest group installation marking for BCPD, or- the calculated BCPD for the largest motor + FLAS’s of other loads

Tap conductors sized per Method B

Non-Motor loads also protected per Method B

Applies to power conversion equipment with DC converter and inverter sections on “common bus”


Sizing of Branch Circuit Protection for Motor Groups acc. UL/NECMethod C – Assembly

BCPD


Motor Motor Heater

Step 2: Size BCPD based on smaller1.) the size required of the largest motor plus

FLA of all other loadsor

2.) lowest BCPD marking for motor grouping

Step 3: Verify tap conductor size

Step 1: Verify that all load sidedevices are “Suitable for tap conductor

protection in Group Installations

Step 4: Check if non-motor loads require additional protection


How to size the Branch Circuit Protection Device for Motor Groups acc UL/NEC?

BCPD


Motor Motor Heater

Verify if non-motor loads require

additional protection

11 Amps 5 Amps 5 Amps

Example for UL Circuit Breaker:1.) 11 Amps x 250% = 27,5 Amps2.) 27,5A + 5A + 5A = 37,5 Amps

37,5 Amps for the BCPDNext Standard size is 40 Amps

Tap Conductors:125% of the largest motor load + 100% of additional loads = 23,75 Amps

23,75 / 3 = 7.9 AmpsUL508A Table 28.1 for ampacities of conductors:

minimum 14 AWG for Power Circuits


Example with the 3RM1 motor starter

16A max per infeed

X

Y

Ampacity Y 1/3 Amapacity X


Explanations, Notes, Rating Plate Data Motor branch circuit – nameplate of 3RV circuit breakers

Indication of hp ratings for 200-208 V, 230 V, 460 V, 575 V

General safety instructions

Only CU wires for 75°C are allowed

Ratio of 125% of tripping current : setting current

Breaks all phases simultaneously

Max. permissiblemotor‘s full load amps(FLA max.)

Reference to the use in combinations with contactors and soft starters

Manual motor controller, suitable as tap conductor protection, in group installationsmotor disconnect suitable for group installationmax. permissible grouping fuse / CBmax. permissible short circuit current

Self-protected combination motor controller (E / F)with reference to adaptermax. permissible short circuits for 240 V, 480Y/277 V, 600Y/347 V

Example: 3RV10 21


Note: … … are placeholders to be supplemented with the technical data of the product (size-related).

Explanations, Notes, Rating Plate DataMotor branch circuit – rating plate of 3RT contactors

Example: 3RT10 2

Contactor

General purpose values (non-motor operated loads)

Permissible short circuit at 600 V AC, value 5 kA derived from UL508,higher values from report

Indication of hp ratings for motors, at 115 V, 230 V, 460 V, 575 V

Screwdriver specification: Pozidrive 2

Only Cu lines for 75°C are allowed

Breaks all phases simultaneously

Maximum permissible RK5 fuse, maximum permissible circuit breaker

Wire stripping length, permissible wire cross sections in AWG

Permissible torque in pound per inch and Nm


Example: 3RU11 2

Explanations, Notes, Nameplate DataMotor branch circuit – nameplate of overload relays

Maximum permissible RK5 fuse, maximum permissible circuit breaker

Certified for 600 V AC (max.)

Only Cu lines for 75°C are allowed

Note: … … are placeholders to be supplemented with the technical data of the product (size-related).

Ratio of tripping current : setting current = 125%

Safety note for AUTO RESET

Permissible short circuit at 600 V AC,value 5 kA derived from UL508,higher values from report

Permissible torque in pounds per inch and Nm


Changes in the standard for industrial control devices

This change is not addressed to the user of industrial control devices but to the manufacturer of control devices!

Complete transition till Nov. 2017

UL 60947-4-1 is aligned and harmonized

with theIEC 60947-4-1


What does the transition from UL508 to UL60947-4-1 affect?

Type of co-ordination 1 Type of co-ordination 2


Panel MarkingAccording UL508A – § SB5


Predictable Reaction Type of co-ordination “1”

UL 60947-4-1 (excerpt):With type of co-ordination “1”, the contactor or starter must not endanger persons or the installation in the event of a short circuit and need not be suitable for further operation without repair and renewal of parts.

Result for the machine or machine operation:The contactor and/or overload relay might be defectiveThe components might be unsuitable for further operationInsecure personnel and system protection with further operationUncertain functionality of the componentsThe components should be replaced

Consequences: Long downtimesHigh repair efforts


Predictable Reaction Type of Co-Ordination “2”

UL 60947-4-1 (excerpt):With type of co-ordination “2”, the contactor or starter must not endanger persons or the installation inthe event of a short circuit and must remain suitable for further operation. The risk of contact welding is given. In this case, maintenance instructions have to be provided by the manufacturer.

Note: If manufacturer recommendations are not complied with for the application of an SCPD, the type of co-ordination is questionable. The risk of contact welding is given.Manufacturer’s maintenance instruction for opening the contact pieces is required

Result for the machine or machine operationThe contactor and/or overload relay may be slightly welded Easy breaking-open of contacts required in case of welding

Consequences:Short downtimesLow repair effort


Where can I get these values?

Ask your supplier for SCCR ratings for Type 1 and Type 2 co-ordination


Frequency Converters / Variable-Speed Drives / Soft Starting

Load devices with power semiconductors must be assessed separately

This means:Branch circuit protection ONLY according to data in the UL Report Branch circuit protection may be omitted if integrated (UL Report)


SCCR ratings for Siemens VFD’s

All the specified drives have a high SCCR as a result of testing with UL.All drives have internal solid state short circuit protection for protection of the drive output but this has not been evaluated for branch circuit protection (BCP)

Our UL certification allows all drives (which have an integral solid state protection circuit) to adopt a high SCCR equal to the interrupt current rating of the branch-circuit protective device protecting the drive.

Example. If a UL listed combination motor protector (Rated current 40A) with an interrupt current rating of 65kA is used as the branch circuit protection device for a MICROMASTER 440 frame size C 400V 11kW drive, the high SCCR of the drive is equal to that of the combination motor protector, which is 65kA.

Hence by selection of the correct UL listed BCP device, with appropriate interrupt rating for the application, any high SCCR rating can be achieved for the above drives.

Short Circuit Current Ratings (SCCR) for Siemens Standard Drives


Overload Protection NFPA79 §19.1

Drives / amplifiers with integrated, approvedoverload protection may be used for motor protection

Data in the UL Report (e.g. for frequency converter, servo drive, etc.)

In motor groups, each motor must be feature a separate overload protection

Every motor must feature a separate overload protection!


Example – Excerpt from SINAMIC G120/130/150 – UL Report

3NE1

Note:

A semiconductor fuse according to UL248-13 does NOT representa suitable branch circuit protective device (unless specified in the UL Report)

A semiconductor fuse can be ADDITIONALLY installed at any time

3NE1 813 SIEMENS SITOR Fuse

Semiconductor LV HRC design

UL recognized only!


Protection Against Electric Shock

Protection against direct contact

Protection against electric shock in case of indirect contact (fault case)

© Siemens Industry Inc. 2014. All Rights Reserved.Industry SectorPage 2 Issue date 07/2013 Industrial Control Panels and Machinery for North America

Protection Against Direct Contact

Measures:(1) Insulation(2) Enclosure(3) Interlocking of enclosures(4) Restricted access to the enclosure

General:Energized parts must be protected against direct contact when:

- AC: U 50 V- DC: U 60V


Protection Against Direct Contact(1) Insulation

Energized parts must meet the following conditions:

Complete insulation (only removable through disassembly!)

Mechanical, chemical, electrical and thermal resistance

Paints, varnishes and coatings do not offer sufficient protection against electric shock


Protection Against Direct Contact(2) Enclosures

Enclosures and enclosure openings must comply with the requirements according to:

UL508 UL508AUL50 or NEMA 250.

Exception:Unapproved enclosures can be checked by means of a test finger; checking of all openings after disassembly of all parts removable without tools

Touching of energized parts with the test finger must not be possible


Test Finger – NFPA79 6.2.2.1


Protection Against Direct Contact(3) Interlocking of Enclosures

Exceptions:1. Main disconnecting means for industrial control panel lighting inside the industrial control panel 2. Main disconnecting means for memory elements for the retention of information

General: Main disconnecting means of enclosures / industrial control panels must be interlocked with the door when energized parts are contained with - AC 50 V- DC 60 V

Note:Qualified persons may implement measures for defeating the interlocking (see NFPA 70E "Standard for Electrical Safety in Workplaces")


Protection Against Direct Contact(3) Interlocking of Enclosures – Conditions

The interlocking must be defeatable by means of a tool With the door open and the "ON" position, the interlocking must be enabled upon closingWith the door is open, switch-on must be mechanically blocked; defeat must be possible without tools ("deliberate action")

Caution: Devices on the inside of industrial control panels must be protected against unintended contact when U 50 V; either by means of devicecharacteristics or through barriersin a range of 50 mm (2 inches)


Protection Against Direct Contact (3) Interlocking of Enclosures – Solutions

Mechanical solutions:UL-compliant with UL508A, NFPA 79, JIC and NEC

Max-flex driveEnclosure type: 1, 3R, 12

Interlocking module 8UCEnclosure type: 1

Standard references:UL508A: 30.4 / 66.1.5 / 66.6.3NFPA79: 5.3.3 / 6.2.3 / 6.2.5

UL Guideline, Chapter 6.1.4


Protection Against Direct Contact(3) Interlocking of Enclosures – mechanical solutions

Examples for mechanical interlocking solutions provided by Siemens


Protection Against Direct Contact(3) Interlocking of Enclosures – Solutions

Electrical solutions:1 key switch for defeat1 timing relay1 undervoltage release per main disconnecting meansDiverse auxiliary relays1 limit switch per door, preferably with tumblerMotorized operating mechanism

Note:The electrical interlocking must meet the same conditions as the mechanical interlocking!

UL Guideline, Chapter 6.1.4


Protection Against Direct Contact(4) Access to Industrial Control Panels

When qualified skilled persons with respective experience open an industrial control panel without main disconnecting means, the following conditions must apply:

the door can be opened by means of a key or tool,

or

the door can be opened without defeat, key or tool when all energized parts are covered or encapsulated in a finger-safe manner


Protection Against Indirect Contact (Fault Case) NFPA79 §6.3

General:

Protection against indirect contact is to prevent hazardous states in case of faults(e.g. due to insulation faults between energized and exposed parts)

Measures: (1) Protection through double insulation(2) Protection through automatic supply disconnection


Protection Against Indirect Contact(1) Double Insulation

“Double insulation" symbol(protection class 2)

Double insulation is to prevent the occurrence of hazardous touch voltages due to faults in the basic insulation

Operating equipment must be respectively marked (UL approval!)

Operating equipment either must be listed or tested in a comparable manner


Protection Against Indirect Contact(2) Protection Through Automatic Supply Disconnection

Prerequisites for the safety measure:1. Exposed, conductive parts must be grounded

2. Application of overcurrent protective devices for automatic disconnection

General:

Protection through automatic supply disconnection of affected circuits by means of the respective overcurrent protective device in case of faults

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