Customer support: 833-B3CHECK (833-232-4325)


How do you know if the panel can support a B3 Bypass?

The interconnection experts at QFE002 are here to help. Just email the pictures listed below, and we will provide expert feedback on whether the B3 Bypass is appropriate for your job.

Email pictures with the info listed below below to:

  • MSP with the deadfront removed

  • Close-up of the cable connected to the main circuit breaker

  • MSP label with catalog number

Frequently Asked Questions

The B3 Bypass is a new type of overcurrent protection device that bypasses the bus bars of a panelboard. Instead, the B3 Bypass connects directly to the main circuit breaker feeder wires (on the line/supply side) and avoids (bypasses) the bus bars. It consists of two separate 2-pole circuit breakers in a 2” wide package. Therefore, the total alternative energy current is only limited by the main breaker rating or 80 continuous amps (whichever is lower), saving the homeowner and installer the cost, time, and effort of replacing the panelboard.

The “B3” in B3 Bypass is a shorthand way of expressing bus bar bypass (B3), which is the defining aspect of this UL Classified Breaker. In fact, B3 type circuit breakers are the ONLY UL Classified breakers that make NO electrical contact whatsoever with the bus bars of the main panelboard.

This bus bar bypassing feature of B3 type breakers represents a significant advance in electrical safety since the most common cause of residential structure fires is arcing from faulty connections between breakers and the bus bar stabs in main panelboards.

UL Classified Breakers are those breakers produced by one manufacturer for use in place of the breakers specified for use in other manufacturers’ panelboards.

To receive the UL Classification Mark, a molded-case circuit breaker must satisfy ALL the testing parameters set out for such breakers in UL 489, the Standard for Molded-Case Circuit Breakers. These tests include calibration, endurance, overload, short-circuit interrupting, and dielectric voltage withstand testing. A UL engineer must witness ALL such tests prior to certification.

In addition, to be UL Classified for use in a manufacturer’s UL Listed panelboards, a molded-case circuit breaker must satisfy ALL the testing parameters set out for the use of such breakers in UL 67, the Standard for Panelboards. Tests include temperature, short circuit, and dielectric withstand testing. A UL engineer must also witness ALL such tests prior to certification.

Please refer to the B3 Bypass Installation Guide, accessible by clicking on the Resources tab at the top of the home page.

A field inspection is not required following the installation of any UL Classified breaker, including the B3 Bypass, provided the UL Classified breaker in question:

  • Has been certified by a recognized qualified electrical testing laboratory (the B3 Bypass is certified by UL),
  • Is for use in the manufacturer’s panelboards in accordance with the B3 Bypass Compatibility List (, and
  • Has been installed in accordance with the manufacturer’s installation instructions (

Please download the new B3 Bypass app (, which has a search function to help determine if the B3 is certified for use with the panelboard in question.

You can also view the B3 Bypass Compatibility List on our website ( The list provides catalog number code generators for panelboards in which the B3 Bypass breaker has been UL Classified for installation.

A B3 Bypass Compatibility List is also included in the packaging of every B3 Bypass.

The Compatibility List is a tabulation of panelboards that UL has found to be suitable for use with B3 Bypass breakers. This list is required by UL 67, the Standard for Panelboards, and was reviewed and approved by UL.

Installing equipment according to the NEC means installing it in accordance with the manufacturer’s instructions.  AHJs, therefore, are satisfied provided that a B3 Bypass has been installed per the manufacturer’s instructions.

The B3 Bypass is rated 120/240V, with a 10kA maximum available short circuit interrupting rating. Each of the two 2-pole circuit breakers can be any of the following ratings: 20, 30, 40 or 50 amps.

Maybe. The B3 Bypass has been tested by UL to provide branch circuit overcurrent protection in either direction, i.e. back-feeding alternative energy to the line side of the main circuit breaker or drawing current from the utility/service side. However, to do so, the service entrance wiring must be sized to accommodate both the ampacity of the main breaker PLUS the additional ampacity of the B3 Bypass that are used to feed other loads, or a load calculation must be made in accordance with the Article 220 of the NEC.

No. The B3 Bypass is presently only designed for use with 1” breakers. Please see our Compatibility List ( for the appropriate panelboards.

The present design is intended only for plug-in main breakers. However, we expect to soon have a solution for top and bottom fed panelboards.

Plug-in main circuit breakers are generally limited to 150 amps thereby requiring 1/0 AWG copper. Ratings more than 150 amps are found in combination meter socket / panelboards and are factory wired to a 4-pole plug-in main circuit breaker. The 4-pole factory wired main breaker allows the manufacturer to parallel two circuit breakers per phase, which allows lower rated breakers (and therefore smaller wires). This is allowed by the UL standards since the NEC limitation of paralleling wires 1/0 AWG and larger only applies to field wiring. Thus, the B3 Bypass can then be connected to 2 poles of the 4-pole breaker, as the wire size is within the range of the B3 Bypass.

Not currently. The B3 Bypass is presently only suitable for use with cable fed plug-in main breakers with a maximum wire size of 1/0 AWG copper or 2/0 AWG aluminum.

While the B3 Bypass does connect to the meter side of the service disconnect, the B3 Bypass is installed inside the customer panelboard and is therefore considered to be outside the jurisdiction of the utility. This connection is allowed by Section 230.82 of the National Electrical Code (NEC).

Yes, since the B3 Bypass connects the output circuit to the line side of the main disconnect.

The easiest way to find B3 Bypass wholesalers is to download the B3 Bypass app (  and click on “Find a Dealer.”