NNX3B120 - 1200Amp Circuit Breaker

NNX3B120 - 1200Amp Circuit Breaker

Need a Siemens NNX3B120 circuit breaker for an existing installation? This 1200-amp, 3-pole thermal-magnetic breaker is made for compatible electrical distribution equipment using the NNX3 configuration. It is Type NNG, uses an MG frame, and is rated for 50/60 Hz operation. Depending on system voltage, the NNX3B120 carries an interrupting rating of 25k AIC at 600VAC, 35k AIC at 480VAC, or 65k AIC at 240VAC. Physical fit matters as much as the electrical ratings when working with existing equipment, so it's worth checking the dimensions too: 16 inches high, 7.5 inches wide, and 4.75 inches deep. This configuration includes load-side lug terminals. For maintenance teams, electricians, and facilities working with legacy equipment, the NNX3B120 is primarily about matching the breaker already specified for the system—not changing the system around the breaker. Before installation, check the frame, poles, amperage, AIC rating, dimensions, and connection requirements against your equipment. When the specifications match, this Siemens breaker provides the form, fit, and function needed for its intended application and is built to last.

Key Features and Benefits

• 1200-amp rating for compatible electrical distribution applications.
• 3-pole configuration for systems designed around this pole arrangement.
• Thermal-magnetic circuit breaker design for overcurrent protection within the specified application.
• Interrupting ratings of 25k AIC at 600VAC, 35k AIC at 480VAC, and 65k AIC at 240VAC.
• NNX3 type, NNG designation, and MG frame make it easier to confirm compatibility with existing equipment.
• Rated for 50/60 Hz operation.
• HACR Type designation.
• Measures 16 in. H x 7.5 in. W x 4.75 in. D, important when checking physical fit.
• Supplied with load-side lug terminals.
• Well suited to legacy applications where matching the original breaker specifications is the priority.

Technical Specifications

• Part Number: NNX3B120
  
• Manufacturer: Siemens
  
• Breaker Type: Thermal Magnetic Circuit Breaker
  
• Type: NNX3
  
• Additional Type: NNG
  
• Frame: MG
  
• Amperage: 1200A
  
• Poles: 3
  
• AIC @ 600VAC: 25k
  
• AIC @ 480VAC: 35k
  
• AIC @ 240VAC: 65k
  
• Frequency: 50/60 Hz
  
• HACR: HACR Type
  
• Height: 16.0 in.
  
• Width: 7.5 in.
  
• Depth: 4.75 in.
  
• Terminals: Load-Side Lug Terminals
  
• Trip Unit Amps Dial Setting Range: 3250–6500*

Material Compliance and Certifications

• The available specifications identify the NNX3B120 as HACR Type. The product information did not include additional material-compliance declarations, certification numbers, environmental certifications, or agency listings. If a particular approval or compliance requirement applies to your installation, check the breaker markings and supporting technical documentation before use.

Where It Works Best

• The Siemens NNX3B120 1200A circuit breaker makes the most sense in existing electrical equipment designed for this particular breaker configuration. This may include compatible commercial, industrial, facility, or HVAC electrical systems that require an NNX3 breaker with an NNG designation and MG frame.
• With legacy electrical equipment, small differences can matter. A breaker that looks similar isn't necessarily the right fit. Check the 1200 amp rating, three poles, voltage, AIC rating, NNX3 type, NNG designation, MG frame, dimensions, frequency, terminals, and trip-unit requirements against the existing equipment. The objective is simple: match the required specifications as closely as possible so the breaker provides the intended form, fit, and function.