Suggestion on How to Use Industry Trainers are

Suggestion on How to Use Industry Trainers are encouraged to use this material in their sessions Download the presentation file Print the Notes pages and read them as you view the presentation in the Slide Show view. In this way you see the slides in large format and have animation (when available) 2015 Eaton. All Rights Reserved.. 1 Interrupting Rating 2015 Eaton. All Rights Reserved.. Interrupting Rating NEC Article 100 defines interrupting rating: The highest current at rated voltage that a device is identified to interrupt under standard test

conditions. 2015 Eaton. All Rights Reserved.. 3 Interrupting Rating NEC 110.9 Equipment intended to interrupt current at fault levels shall have an interrupting rating at nominal circuit voltage sufficient for the current that is available at the line terminals of the equipment. Equipment intended to interrupt current at other than fault levels shall have an interrupting rating at nominal circuit voltage sufficient for the current that must be interrupted. The interrupting rating of the OCPD must be equal to or greater than the short-circuit current available or 2015 Eaton. All Rights Reserved.. 4

Interrupting Rating OCPD with improper Interrupting Rating 10,000A IR, 600V, Class H Fuse 50,000 Available 2015 Eaton. All Rights Reserved.. 5 Interrupting Rating OCPD with improper Interrupting Rating 10,000A IR, 600V, Class H Fuse 50,000 Available 2015 Eaton. All Rights Reserved.. 6 Interrupting Rating OCPD with improper Interrupting Rating

10,000A IR, 600V, Class H Fuse 50,000 Available 2015 Eaton. All Rights Reserved.. 7 Interrupting Rating OCPD with improper Interrupting Rating 10,000A IR, 600V, Class H Fuse 50,000 Available 2015 Eaton. All Rights Reserved.. 8 Interrupting Rating OCPD with improper Interrupting Rating 10,000A IR, 600V, Class H Fuse 50,000 Available

2015 Eaton. All Rights Reserved.. 9 Interrupting Rating OCPD with improper Interrupting Rating 10,000A IR, 600V, Class H Fuse 50,000 Available 2015 Eaton. All Rights Reserved.. 10 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available 2015 Eaton. All Rights Reserved..

11 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available 2015 Eaton. All Rights Reserved.. 12 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available 2015 Eaton. All Rights Reserved.. 13

Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available 2015 Eaton. All Rights Reserved.. 14 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available 2015 Eaton. All Rights Reserved.. 15 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker

50,000 Available 2015 Eaton. All Rights Reserved.. 16 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available 2015 Eaton. All Rights Reserved.. 17 Interrupting Rating OCPD with improper Interrupting Rating 14,000A IR, 480V, Circuit Breaker 50,000 Available

2015 Eaton. All Rights Reserved.. 18 Interrupting Rating Marking the Interrupting Rating of OCPDs NEC 240.60(C) requires marking the interrupting rating of branch-circuit cartridge fuses if other than 10,000A. NEC 240.83(C) requires marking the interrupting rating of branch-circuit circuit breakers if other than 5,000A. Does not apply to supplemental protective devices (glass tube fuses or supplementary protectors). 2015 Eaton. All Rights Reserved.. 19 Interrupting Rating - Fuses Modern current-limiting fuses typically have a minimum interrupting rating of 200,000A

Fuses: 300,000 A.I.R. 2015 Eaton. All Rights Reserved.. Isca = 50,000 A 22 Interrupting Rating - MCCB Circuit breakers can be rated in various increments between 5,000A and 200,000A. Circuit breaker interrupting rating is dependent upon voltage. Interrupting rating at 240V may equal 65,000A. However, the same circuit breaker may have an interrupting rating at 480V of 35,000A. 2015 Eaton. All Rights Reserved.. 23

Interrupting Rating - Example What Interrupting Rating must the fuse have? At least 50,000 amperes. (Class R, J, T, L and CC fuses have an Interrupting Rating of at least 200,000 amperes. The short-circuit current rating of the switch may also be 200,000 amperes. 2015 Eaton. All Rights Reserved.. 24 Interrupting Rating - Example What Interrupting Rating must the CB have? Some value greater than or equal to 50,000 amperes. The interrupting rating for a circuit breaker is dependent upon voltage. Circuit breakers come in a wide variety of interrupting ratings If the choices are 14,000A, 25,000A or 65,000A a 65,000A circuit breaker would need to be selected for the circuit shown.

2015 Eaton. All Rights Reserved.. 25 Interrupting Rating The interrupting rating shown on the label for a 3pole circuit breaker is based upon the three phase bolted fault test which has all three phase conductors connected electrically together. 2015 Eaton. All Rights Reserved.. 26 Single Pole Interrupting Capabilities A circuit breakers ability to safely open an overcurrent at a specified voltage utilizing only one pole of the circuit breaker is the single pole interrupting capability A circuit breakers single pole interrupting capability is typically lower than its multi-pole interrupting rating.

-- -- -- 100A Maximum 251-600V -- 10,000 8,660 10,000 8,660 101-800A 8,660 10,000

8,660 10,000 8,660 801-1200A 12,120 14,000 12,120 14,000 12,120 1201-2000A 14,000 14,000 14,000

14,000 14,000 2001-2500A 20,000 20,000 20,000 20,000 20,000 2501-3000A 25,000 25,000 25,000

25,000 25,000 3001-4000A 30,000 30,000 30,000 30,000 30,000 4001-5000A 40,000 40,000 40,000 40,000

40,000 5001-6000A 50,000 50,000 50,000 50,000 50,000 2015 Eaton. All Rights Reserved.. 28 Single Pole Interrupting Capability UL 489 Circuit Breaker Procedure UL Single Pole Short-Circuit Test CB Frame

UL Single Pole Short-Circuit Test CB Frame Rating 100 A Maximum 101 800 A. 480/277V 480V 10,000 Amps 8,660 Amps 10,000 Amps 8,660 Amps Example: 20 A, 480V CB having 65,000 A.I.R. (3 Pole Test). Single pole tested at 8,660 Amps

2015 Eaton. All Rights Reserved.. 30 2002 NEC Change 240.85 FPN: Proper application of molded case circuit breakers on 3-phase systems, other than solidly grounded wye, particularly on corner grounded delta systems, considers the circuit breakers individual pole interrupting capability. Reprinted Reprinted from from NEC NEC 2002 2002 2015 Eaton. All Rights Reserved.. 31 Ground Fault Current Path 277V

SERVICE PANEL C A 27 7 7V 7 2 BRANCH PANEL Fault Fault to Conduit A 480V

PANEL 277V Steel Conduit C A 27 7 7V 27 A 480V V B B

PANEL 277V Steel Conduit C A 27 7 7V 27 A 480V V B B 480V

37 High Resistance Grounded System SERVICE PANEL Resistor Resistor BRANCH PANEL 277V Steel Conduit C 27 A A 480V

Fault Fault Current Current Low: Low: PANEL 55 Amps Amps or So C 27 A BRANCH PANEL Steel Conduit A 480V 27 7V 7V B B

BRANCH Interrupt Interrupt Fault Fault Current PANEL PANEL 277V Steel Conduit C 27 A A 480V 27 7V 7V B

B 480V C High High Value Value of of Fault Fault Current Current Because Because Ground Resistor No Longer Longer in in Path Second Second Fault Fault to to Enclosure Enclosure

SERVICE PANEL BRANCH PANEL Steel Conduit A A 480V C B B 480V C First Fault Fault to

to Steel Steel Conduit Conduit Low Low Value Value of Fault Fault Current Current Because Because of of Large Large Capacitively Capacitively Coupled Coupled Impedance Impedance to to Ground Ground 2015 Eaton. All Rights Reserved.. 42

Ungrounded System Single Single Pole Must BRANCH SERVICE Interrupt Fault Current PANEL PANEL Steel Conduit A A 480V C B B 480V C High

High Value Value of Fault Current Current Because Large Impedance Impedance is is No No Longer Longer in in Path Path Second Fault to to Enclosure 2015 Eaton. All Rights Reserved.. First Fault Fault to to Steel Steel

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