NOARK Miniature Circuit Breaker UL 489

Noark UL489 Miniature Circuit Breaker
Noark UL1077 Miniature Circuit Breaker

Miniature circuit breakers have different protection curves to accommodate different applications

C Curve

In Type C curve applications, the magnetic trip is set between 5-10 times the full load current. This is the most common protection used for cables, lighting, resistive loads, general purpose applications and when properly sized, for motors.
typical C curve applications for a Noark UL1077 Miniature Circuit Breaker

D Curve

Type D curve applications have a higher setting of 7-15 times the full load current due to the inrush current of motor loads and the magnetizing current on the primary of a transformer or solenoid. Application for this curve include motor loads, transformer primary and solenoids due to the inrush or magnetizing currents.
typical D curve applications for a Noark UL1077 Miniature Circuit Breaker

B Curve​

Type B curves provide a magnetic trip setting of 3-5 times the full load current. Applications: electronic circuits.
typical B curve applications for a Noark UL1077 Miniature Circuit Breaker
  • UL 489 File Number E355392 / IEC 60947-2
  • UL489 file number E355392 standard for connection terminals which allows the user to apply field wiring directly to the breaker.
  • UL listed to UL489 and CSA Standard C22.2 No. 5 for branch circuit protection.
  • IEC 60947-2 standard for industrial applications of circuit protection.
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UL 489 Circuit Breakers and Branch Circuit Overcurrent Devices

A UL 489 device can be used as branch circuit protection or supplementary protection.

UL 489 products have larger dimensions to provide the necessary phase to phase voltage air gap.

The B1 UL 489 miniature circuit breakers are available in a complete range of amperages from 0.5A to 63A. Standard ratings of 10 kA at 480Y/277 Vac and 10 kA at 125 Vdc. These are suitable for branch circuit protection.

• Breakers mount on standard 35 mm DIN rail
• Can be used in UL 1077 or CSA C22.2 No.235 applications
• Field installable shunt trip and auxiliary switch
• Available with provisions for ring tongue terminals
• Module width of only 0.71 in (18 mm) per pole
• Contact position indicator (red/green)
• Provision for pad locking the toggle in ON or OFF position

National Electrical Code (NEC) defines a branch circuit as the circuit conductors between the final overcurrent device protecting the circuit and the outlets. UL 489 opens automatically on overload and short circuit. It also protects wire and cable against overload and short circuit. UL 489 circuit breaker used for branch circuit protection.

UL 489 Applications

• Receptacles and branch lighting
• Control Panels
• Load circuits leaving the equipment (external)
• Uninterruptible power supply (UPS)
• Relays
• Heating, ventilation, air conditioning and refrigeration equipment (HVAC/R)
• Variable frequency drives (VFD)


• DIN rail mountable
• Stand alone Branch Circuit Protection
• External handle mechanisms available
• Field mounted accessories
• Various levels of protection (curves)

Typical Applications

• Branch Circuit Protection Receptacle and lighting circuits
• Motor control circuits
• Load circuits leaving the equipment (external)
• Heating, ventilation, air conditioning, refrigeration equipment
• Power supplies
• Control instrumentation
• Relays
• Uninterruptible power supply (UPS)
• Power conditioners


Alarm Switch
Auxiliary Contact
Padlock (Lock Off)
Surface Mount Clip
Shunt Trip
Under-Voltage Trip
35 mm DIN rail