ul508afor panel builders · for the short-circuit current rating not only the short-circuit...

UL508Afor Panel

Builders Getting Started

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Codes and Regulations for Panel Builders

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 is

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Speaker

Jeff Woolfolk

Bachelor of Science, Electrical Engineering Technology

System Consultant

Digital Factory

Control Products

Application consulting:

- North American Standards and Codes

- European Directives and international IEC/ISO

standards

www.usa.siemens.com/controlpaneldesign

www.usa.siemens.com/planning-efficiency

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

http://www.usa.siemens.com/planning-efficiency






Differences between USA and everywhere else

=




Excerpts 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 of

an 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.

https://www.osha.gov/pls/oshaweb/owalink.query_links?src_doc_type=STANDARDS&src_unique_file=1910_0303&src_anchor_name=1910.303(b)(2)




Relevant standards for panels for the US market




Comparison between USA and IEC standards

IEC 60364-1

IEC 61439-2

IEC 60204-1




UL508A Industrial Control Panels

1893 World Exhibition in Chicago

Outbreak of a fire

1894 Start of UL

William H. Merrill opens the

“Underwriters Electrical Bureau”




National Fire Protection Association

• Foundation: 1896, due to increasing sprinkler system installations

• Headquarters: Quincy, Massachusetts

• Publication of over 300 standards to date

National Electrical Code

or

NFPA70

NFPA79

Electrical Standard for

Industrial Machinery

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

http://www.nfpa.org/index.asp




NFPA (nec) and UL508A work together




NFPA (nec) and UL508A work together

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!



Most Important Network Types in Detail

Grounded wye / solidly grounded wye

Slash rating: • e.g.: 480Y/277V, solidly grounded wye

• 3 phase; 4 wire

• 3 phase; 3 wire

Possible devices

480Y/277V; 600/347V

480V; 600V

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

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

3p, 4w / grounded

phase-ground

U = 277 V

across one

contact

worst case!

L1

L2

L3

Transformer

480Y/277V AC

M

Ik




Corner 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 delta rating must be used!

Phase - Ground

U = 480 V

across one contact

worst case!!

L1

L2 L3

Transformer 480V AC

M

Ik




Ungrounded 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 delta rating must be used!

480V AC

L1

L2 L3

Transformer

M

Δ/Y

Betrieb

Insulation

measuring

! Operation requires

Insulation monitoring! Ik

Phase - Phase

U = 480 V

across one

contact

worst case!!




UL Category Code Numbers

• The CCN represents a clear description of the respective product

• The 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

applied

• The CCN should be additionally integrated in the parts list

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

http://www.ul.com/database




UL508A Table SA1.1

../../../01_UL/02_Standards/02_UL/UL508A/2010_UL508A-1.pdf




(www.ul.com/database)





UL508A Short Circuit Current Rating (SCCR)

• 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 power 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 considered

e.g.: that of wires, cables, busbars, …





NEC Article 409.110 Marking

An industrial control panel shall be marked with the following information that is plainly visible after installation:

….

(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

Informational Note: ANSI/UL 508(A), Standard for Industrial Control Panels, Supplement SB, is an

example of an approved method.

Exception to (4): Short-circuit current rating markings are not required for industrial control panels containing

only control circuit components





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

• Step 1: necessary!

SCCR of the installed and UL-listed components

• Step 2: necessary!

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)





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)

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.

../../../../01_UL/02_Standards/02_UL/UL508A/2010_UL508A-1.pdf



SCCR of tested industrial control equipment assemblies

Series rating tests Series 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 tests Series 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







MCCB

3VL

MCB

5SJ4..HG4

M

MCCB

3VL

3RB

motor protection

relay

3RT

contactor

Fuse

Series rating Tested combinations

MCB

5SJ4..HG4

Series rating for Siemens Breakers www.ul.com/database

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=DKSY2.E10848&ccnshorttitle=Circuit+Breakers,+Series+Connected+-+Component&objid=1073748657&cfgid=1073741824&version=versionless&parent_id=1073748645&sequence=1






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 limiting

device

Transformer peak-let-through currents

can be used to protect Branch circuits!





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)





Class J Fuse, 100 Amps

A.I.C: 100 kA

MCB

A.I.C: 10 kA

@480V

Compact MSP

A.I.C: 30 kA

@480V

MSP

A.I.C: 65 kA

@480V

Contactors

SCCR: 5 kA

@480V

Solid state relay

SCCR: 5 kA

@480V

Terminal Block

SCCR: 10 kA

@480V

Terminal Block

SCCR: 10 kA

@480V

Terminal Block

SCCR: 10 kA

@480V

Terminal Blocks

SCCR: 10 kA

@480V

MSP’s

A.I.C: 65 kA

@480V

Infeed system

SCCR: 65 kA

@480V

Transformer: S = 150 kVA, Z = 4%, 3 Phase, 480/277V

Available secondary Fault Current = 4.6kA @480V

Power Distribution Block

SCCR: 10 kA

@480V

Result:

Overall SCCR = 100kA = A.I.C of the

Class J Fuse on the primary side of

the Transformer since the available

secondary fault current of the

transformer (4.6kA) is less than the

SCCR and A.I.C’s of the components

on the load side of the transformer

3 Ph. 480Y/277V AC





• Use of current limiting fuses, when used as feeder elements SB 4.3.3

• Only 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 replacement

• The fuse is replaced by the service staff, which 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. 5kA

• Standard busbar: max. 10kA

• Standard terminal block: max. 10kA



Use of current limiting fuses, when used as

feeder elements SB 4.3.3

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 replacement

The fuse is replaced by the service staff,

which shall not compare

the corresponding let-through values

(old fuse versus new fuse)

Example: There are 7 different 30A Class R

Fuses, each. with different characteristics







• Use of current limiting circuit breakers, listed as “current limiting”, when applied as feeder element SB

4.3.2

• 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. 5kA

• Standard busbar: max. 10kA

• Standard terminal block: max. 10kA

Siemens “current limiting” breakers

http://www.industry.usa.siemens.com/automation/us/en/industrial-controls/tools-and-resources/sccr/Documents/Siemens Current Limiting Circuit Breakers Peak Let thru Curves 1.pdf





Siemens SIRIUS Contactor 3RT1035

Short Circuit Current 5kA, 600V





Type F

Magnetic

Motor

Control

See report in the annex





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

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

../01_Documents for participants/Siemens UL & IEC CE training for control panels/attachments_UL_North America/SCCR Whitepaper.pdf