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Manufacturer Resources
Spec Sheet
Product Specs
- Amperage Rating:
- 900A
- Catalog Notes:
- Mark 75 Breaker
- Compliances:
- Contact Manufacturer
- Frame Size:
- Frame J-K
- Number Of Poles:
- Three-pole
- Product Height:
- 17.1 IN
- Product Length Depth:
- 18 IN
- Product Weight:
- 26 LB
- Product Width:
- 10.5 IN
- Voltage Rating:
- 600 V, 250 Vdc
- Department:
- Electrical
- Product Group:
- Electrical Components
- Product Subgroup:
- Circuit Breakers
- Product Type:
- Molded case circuit breaker
- Product Details:
- Molded case circuit breaker
B-LINE HNB3900T – Frequently Asked Questions
1) What amperage and voltage is the Eaton HNB3900T circuit breaker rated for?
The HNB3900T is a 900A three-pole molded case circuit breaker rated 600 V AC and 250 Vdc. That AC/DC dual rating matters if you are feeding a DC bus or a battery plant rather than a standard 480Y/277 or 600V distribution panel.
2) Will a 900A Eaton HNB3900T breaker physically fit the switchboard section I have?
Plan the cavity around 17.1 inches high, 10.5 inches wide and 18 inches deep. At 26 pounds it is a two-hand lift into a vertical section, so check working clearance in front and that your mounting pan is rated for the depth before you commit. It is a J-K frame device, so the section has to be prepped for that frame, not for a smaller F or J-only frame.
3) Is the HNB3900T a Mark 75 frame breaker?
Yes. The HNB3900T is a Mark 75 breaker in the Eaton J-K frame range. If your existing switchboard or panel was built for Mark 75 mounting, this is the family it belongs to; Mark 75 hardware is not interchangeable with Eaton's later Series C mounting, so confirm which generation your gear was built around.
4) Can I use a three-pole 900A breaker like the HNB3900T on a single-phase service?
It is built as a three-pole device, so on a single-phase 240V or 480V service you would be using two of the three poles and leaving one idle. That works electrically for many installations but wastes a pole and may not match what the drawing calls for. If the spec calls for a two-pole 900A device, this is not that part.
5) Do I need to know the interrupting rating (AIC) before I order this 900A Eaton breaker?
Yes, and that is the number to confirm against your short circuit study rather than the ampere rating. What is on record here is the 900A frame rating and the 600 V AC / 250 Vdc voltage rating. Pull the HNB3900T spec sheet linked on the product for the interrupting values at each voltage, and match them to the available fault current at that point in the system.
6) What is the exact part number I should quote for this 900A Eaton breaker?
Order it by the Eaton catalog number HNB3900T. That is the identifier your distributor, the switchboard manufacturer, and the inspector will all recognize. Give the frame designation (J-K) with it if you are matching an existing section.
7) Is this a main breaker or a feeder breaker?
A 900A three-pole molded case breaker at this frame size is typically used as a service main or a large feeder in a switchboard or distribution panel rather than as a branch device. Which role it plays is set by your one-line, not by the breaker itself; the same HNB3900T can be ordered for either position.
How fast can I get the B-LINE HNB3900T delivered?
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Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit,
reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the B-LINE HNB3900T come with a warranty?
Absolutely. The B-LINE HNB3900T is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the B-LINE HNB3900T?
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