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Siemens NGB3K050B Molded Case Circuit Breaker

  • 50A
  • 3 Pole
  • Bolt-On
Siemens NGB3K050B
Molded Case Circuit Breaker
Brand Siemens
SKU NGB3K050B
Select Item Condition
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  • 50A
  • 3 Pole
  • Bolt-On

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Siemens NGB3K050B - 50A 3 Pole Molded Case Circuit Breaker

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$854.02 In Stock

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Description

Engineered for commercial power distribution, the Siemens NGB3K050B is a 3-pole, 50A molded case circuit breaker from the Sentron GB2 series. It provides proven thermal-magnetic trip protection for demanding electrical systems. This bolt-on MCCB mounts into Siemens P1, P2, and P3 panelboards. For upgrades, note that this NGB frame is transitioning to the 3VA51 series. Rated at 25kAIC at 480Y/277V, it features HACR and HID ratings, reverse feed capability, and includes load side lugs.

Specifications

Key specifications
Brand Siemens
Series NGB
Amperage 50A
Poles 3
Mounting Style Bolt-On
Voltage 240VAC, 480Y/277VAC, 600Y/347VAC, 125/250VDC
Phase 3
AIC Rating 100kA @ 240VAC, 25kA @ 480Y/277VAC, 14kA @ 600Y/347VAC, 14kA @ 125/250VDC
Fit and installation
Frame Type NGB
Terminal Type Lugs
For Use With Siemens P1, P2, P3 Panelboards
Wire Gauge 8-1/0 AWG (Cu), 8-2/0 AWG (Al)
Max Wire 1/0 AWG (Cu), 2/0 AWG (Al)
Min Wire 8 AWG
Protection and operation
Trip Technology Thermal Magnetic
Trip Function Code LI
Trip Function Long-Time, Instantaneous
Trip Adjustability Fixed Thermal, Fixed Magnetic
Standards and features
Available Options Shunt Trip, Auxiliary Switch, Alarm Switch
Accessories Load Side Lugs
Standards CSA C22.2 No. 5, UL 489, NEMA AB 1
Approval CSA, HACR, HID, UL
Temp Rating 40C
Construction Features HACR Rated, HID Rated, Reverse Feed

Product FAQs

7 answers
Which Siemens panelboards are compatible with the NGB3K050B circuit breaker?

This bolt-on breaker is designed for use in Siemens P1, P2, and P3 panelboards.

What wire sizes are accepted by the lugs on the NGB3K050B?

The factory-installed lugs accept 8 to 1/0 AWG copper (Cu) wire or 8 to 2/0 AWG aluminum (Al) wire.

Is the NGB3K050B rated for direct current (DC) applications?

Yes, this breaker carries a DC interrupting rating of 14kA at 125/250VDC, making it suitable for specific direct current systems.

Can the NGB3K050B be used on ungrounded or corner-grounded delta systems?

No. Because this breaker carries slash voltage ratings like 480Y/277VAC and 600Y/347VAC, it is only suitable for solidly grounded wye systems where the voltage to ground does not exceed the lower value.

Does this breaker snap into place or bolt onto the bus?

The NGB3K050B is a bolt-on circuit breaker. It requires a bolted connection to the panelboard bus, which provides a secure, high-vibration resistant contact compared to plug-in types.

How does the interrupting rating (AIC) change based on system voltage for this breaker?

The interrupting capacity scales down as voltage increases. It provides 100kAIC at 240VAC, 25kAIC at 480Y/277VAC, and 14kAIC at 600Y/347VAC.

What type of trip unit is installed in the NGB3K050B?

It features a fixed thermal-magnetic trip unit with long-time and instantaneous (LI) trip functions to protect against overloads and short circuits.

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Reviews

4.5
Rated 4.5 out of 5 stars
Based on 8 reviews
Rating
Ratings
8 reviews
  • JH
    John H.
    Verified Buyer
    Reviewing
    Siemens NGB3B015B - 15A 3 Pole Molded Case Circuit Breaker
    I recommend this product
    Rated 5 out of 5 stars
    9/16/26
    480v breakers

    The breakers work great

  • BP
    Bland P.
    Verified Buyer
    Reviewing
    Siemens NGB3B100 - 100A 3 Pole Molded Case Circuit Breaker
    I do not recommend this product
    Rated 1 out of 5 stars
    7/22/26
    NO LUGS!!

    I ordered this breaker and it arrived with no lugs. It was advertised as new so we didn't open the box and check until the shutdown we needed it for. When we discovered the lugs were missing we sent an email requesting a set overnighted. We didn't get a response for a couple of days, at which point we had already ordered lugs from their competitor Simply Breakers. They asked for pictures and questioned weather we had ordered the correct breaker asking if we needed lugs on both sides. This is a panel breaker and their is only one configuration that I am aware of which is bolted to bus in panel and wires to the three lugs on the other side. I have never had to order lugs separately for this style of breaker. They asked for pictures of box and what was in it, of course at this point the breaker is already installed and the box is thrown away. I sent a receipt for the overnight lugs from Simply breakers and asked for whatever credit they could provide. I received crickets to date. I have never had a problem with an order in the past from super breakers, but they are to busy to even respond to my request so I will think twice before I order anything from them again. It will be my last option once all others have been exhausted. Use Simply Breakers they have better stock and service.

  • PF
    Paul F.
    Verified Buyer
    Reviewing
    Siemens NGB3B060B - 60A 3 Pole Molded Case Circuit Breaker
    I recommend this product
    Rated 5 out of 5 stars
    6/24/26
    Great service, quick shippin

    Need I say more.I have used SB. When we need it and need it quickly Always have what I need.

  • BP
    BJ P.
    Verified Buyer
    Reviewing
    Siemens NGB3B020B - 20A 3 Pole Molded Case Circuit Breaker
    I recommend this product
    Rated 5 out of 5 stars
    5/11/26
    NGB3B020B

    I recently purchased the NGB3B020B and I’m very satisfied with the quality and performance. The breaker feels solid and well-made, and installation was straightforward. It works exactly as expected and provides reliable protection for my electrical setup. Shipping was fast and the product arrived in excellent condition. I would definitely purchase from this seller again.

  • RS
    Radovan S.
    Verified Buyer
    Reviewing
    Siemens NGB3B050B - 50A 3 Pole Molded Case Circuit Breaker
    I recommend this product
    Rated 5 out of 5 stars
    3/9/26
    Absolutely amazing service.

    On Time