Engineered for commercial and industrial power distribution, the Siemens BQ3B040 provides thermal-magnetic protection for 240VAC systems. This 3-pole, 40-amp breaker ensures reliable performance in demanding environments requiring standard interrupting capacities. It mounts into Siemens P1, P2, and P3 panelboards using a secure bolt-on connection. The lug terminal design accommodates 14-6 AWG copper or 12-6 AWG aluminum wire for flexible installation.
It is designed to bolt directly onto the busbars of Siemens P1, P2, and P3 lighting and distribution panelboards. It is commonly used for commercial and industrial branch circuit applications.
Can I install this in a standard Siemens residential load center?
No. Standard residential Siemens load centers require plug-on breakers, such as the QP series. This is a commercial-grade, bolt-on circuit breaker designed exclusively for bolt-on panelboards.
Does the BQ3B040 replace older ITE versions of the same part number?
Yes. Siemens manufactures this breaker as a direct, UL listed replacement for older ITE BQ3B040 models. It shares the exact same physical dimensions and bolt-on connection style.
Will this breaker disconnect all phases if a fault occurs on just one line?
Yes. It utilizes a common-trip mechanism. An overload or short circuit on any single pole will automatically trip all three poles simultaneously, protecting connected three-phase equipment from dangerous single-phasing.
Are the load lugs included on the breaker?
Yes, factory-installed load lugs are included. Always torque the terminal screws to the exact values printed directly on the breaker label to ensure a safe, code-compliant connection.
How much panel space does this breaker require?
The BQ frame has a standard one-inch width per pole. Because this is a three-pole breaker, it requires three inches of continuous mounting space in the panelboard.
How much continuous load can I safely run on this 40-amp breaker?
Standard thermal-magnetic circuit breakers are rated for 80 percent continuous duty unless marked otherwise. For continuous loads operating for three hours or more, the maximum sustained current should not exceed 32 amps to prevent nuisance tripping.
Is this circuit breaker rated for direct current applications?
No. This device is rated exclusively for alternating current systems up to 240VAC. It is not UL listed or approved for use in DC circuits.
Does this breaker offer adjustable trip settings?
No. This BQ frame breaker uses a fixed thermal-magnetic trip unit. It provides a non-adjustable long-time delay for overloads and an instantaneous response for short circuits.
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Reviews
Review summary
Customers rate this product 4.9 out of 5 based on 73 reviews.
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Rated 4.9 out of 5 stars
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Reviews Summary
Generated by AI from 67 most recent customer reviews
Last updated 6/3/26
Customers say these breakers arrive quickly and fit perfectly for their electrical needs. Fast shipping and competitive pricing are frequently mentioned, with many users appreciating the availability of hard-to-find and older-style breakers. The products are well-packaged and arrive in good condition. Most customers report successful installations and reliable performance. A few note missing items from orders or concerns about product condition, though the majority express satisfaction with their purchases and indicate they would order again.