Circuit Breakers

Catalogs > Industrial Controls Catalog > Control Circuit and Load Protection > Circuit Breakers > Bulletin 1492-MC Circuit Breaker

Bulletin 1492-MC Circuit Breaker

Bulletin 1492-MC Thermal Magnetic Description

Thermal Magnetic Circuit Breakers

Bulletin 1492-MC Circuit Breakers for Branch Circuit protection are available in one (1)-, two (2)-, and three (3)-pole construction in 120/240 and 240 volt rating. Versions are available as Ground Fault Circuit Interrupters and as Ground Fault Equipment Protectors.

The 1492-MC product line consists of Thermal Magnetic Circuit Breakers and Ground Fault Sensing Breakers that are designed, manufactured, and certified to North American standards, UL 489, UL 943, UL1093, and the equivalent CSA standards, CSA 22.2 No. 5.1, 22.2 No. 144.

Bul. 1492-MC Thermal Magnetic Circuit Breakers are general-purpose devices suitable for the majority of industrial, inverse time circuit breaker applications.

They combine thermal and magnetic trip actions and provide accurate overload and short-circuit protection for conductors and connected equipment.

Circuit Breaker Application Information

Selection of a Bul. 1492-MC circuit breaker with appropriate circuit protection includes consideration of:

• Circuit voltage
  
• Circuit frequency
  
• Available short circuit current
  
• Continuous current rating
  
• Application considerations
  
• Special operating conditions
  

The following discussion is based upon National Electric Code and UL requirements. Similar considerations are appropriate for Canadian applications.

Circuit Voltage

Bul. 1492-MC circuit breakers are rated by voltage class. Applications should not exceed the listed voltage range (see Table 1).

Circuit Frequency

Bul. 1492-MC circuit breakers may be applied to frequencies from DC up to 60 Hz without derating. For applications above 60…400 Hz, contact Rockwell Automation with specific application information for the derating of the circuit breakers.

Available Short Circuit Current

Bul. 1492-MC circuit breakers should only be applied in those applications in which the available short-circuit (or fault) current is less than or equal to the interrupting rating shown in the Voltage and Interrupting Ratings table.

Table 1. Voltage and Interrupting Ratings

AC Voltage	DC Voltage ⋆	Interrupting Ratings (rms Symmetrical Amperes)		Cat. No.
		AC Rating	DC Rating ⋆
120/240	24, 48, 62.5	10,000	3,000	1492-MCAA1xx
				1492-MCAA2xx
240	24, 48, 62.5		3,000	1492-MCAA2Hxx
				1492-MCAA3xx
120/240	‡		‡	1492-MCBA1xx
				1492-MCBA2xx
240	‡		‡	1492-MCBA2Hxx
				1492-MCBA3xx
120	‡	10,000	‡	1492-MCEA1xx
120/240				1492-MCEA2xx
120				1492-MCGA1xx
120/240				1492-MCGA2xx
⋆ Rating as supplementary protector.
‡ Consult your local Rockwell Automation sales office or Allen-Bradley distributor for specific rating.

Continuous Current Rating

Bul. 1492-MC circuit breakers are rated in RMS amperes at a 40 °C (104 °F) ambient temperature per UL 489 (CSA 22.2 No. 5.1). This temperature is generally used as the average temperature within an industrial enclosure. If a circuit breaker is applied in a temperature that exceeds the 40 °C (104 °F) ambient, then the circuit breaker should be derated. Contact your local Rockwell Automation sales office or Allen-Bradley distributor for derating information.

The characteristic trip curves are shown on pages …. The trip bands shown for each breaker represent current tripping limits for a circuit breaker and are within the limits established by UL. For a specific current at 40 °C (104 °F), a circuit breaker will open ("clear the circuit") automatically at some total time that will be within the "Minimum" and "Maximum" time shown as the "Minimum" and "Maximum" curves. For example, page shows that a one pole, 15 A, 1492-MC trips in not less than 10 s and not more than 150 s on a 30 A current. Because the UL standard defines this time spread, users should not specify exact tripping time. The lower current portion of the curves (upper left) depict the time to trip due to thermal action and reflect overload protection of the wire and connect load. The higher current portion of the curves (lower right) depicts the trip due to magnetic action of the circuit breaker and reflects protection due to short circuit level currents.

Standard current ratings are, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, and 100 A.

Application Considerations

The selection of a specific ampere rating for a specific application is dependent on the type of load and duty cycle and is governed by the National Electric Code (Canadian Electric Code) and UL/CSA. In general the codes require that overcurrent protection is at the current supply and at points where wire sizes are reduced. In addition the codes state that conductors be protected according to their current carrying capacity. There are specific situations that require application consideration, such as motor circuit, and guidelines for the selection for transformer protection.

Bulletin 1492-MC circuit breakders are "non-100% rated" as defined by UL 489 Part 7.1.4.2. As such the circuit breaker's rating should be loaded to no more than 80%, if used with continuous loads.

Branch Circuits:

Bulletin 1492-MC circuit breakers may be used to protect branch circuits. A branch circuit is the wiring portion of a system extending beyond the final overcurrent device protecting the circuit.

Guidelines established in NEC, CEC, UL, and CSA should be used to determine the specific device. For example:



1) Motor Branch Circuit

Bulletin 1492-MC circuit breakers are not horsepower rated because they are able to safely interrupt currents far in excess of the locked rotor value for a selected motor. This ability is recognized in the codes and standards and is also established by the UL and CSA tests described in UL 489 and CSA C22.2 No. 5.1 standards.

The size of a Bulletin 1492-MC circuit breaker should be determined following the guidelines for an Inverse Time Circuit Breaker.

References: NEC 430.51 and UL 508A. Also see CEC and appropriate Canadian Standards.



2) Transformer Protection

Bulletin 1492-MC circuit breakers may be used for transformer protection following the guidelines established.

References: NEC 450 and UL 508A. Also see CEC and appropriate Canadian Standards.



3) Heater Load, Lighting, and Other Load Protection

Bulletin 1492-MC circuit breakers may be used for protection of heater loads, lighting loads, and other loads following the guidelines established.

References: NEC Article 31 and UL 508A. Also see CEC and appropriate Canadian Standards.



Coordinated Overcurrent Protection

Where an orderly shutdown is required to minimize the hazards to personnel and equipment, a system of coordination based upon the faulted or overloaded circuit is isolated by selective operation of only the overcurrent protective device closest to the overcurrent condition.

The user should select devices that meet this requirement.

References: NEC 240.12. Also see CEC.

Time Current Curve – 1-Pole Circuit Breaker



Time Current Curve – 2-Pole Circuit Breakers



Time Current Curve – 3-Pole Circuit Breakers