Circuit breakers and service panels, or breaker boxes, are made by many different manufacturers and may come in many different models. To the untrained eye, most breakers and panels may look very similar, so much so that you might be tempted to use any old breaker in your panel, as long as it seems to fit. But this is a very bad idea and can be dangerous because breakers are not designed to be interchangeable.
How Breakers Differ
From time to time, there may be a need to change a breaker or add one to your electrical service panel. Most electrical devices, like switches, outlets, and light fixtures can be swapped out with another brand without any problems. Breakers, however, are brand-specific and require the exact replacement type to function properly in the electrical panel. Breakers can have different mounting systems, and panels can have bus bars of different thicknesses, and you never know whether a breaker will function as designed if it's used in a different manufacturer's panel.
Although a breaker from another manufacturer may even fit in the panel you have, the differences that you don't see may cause an electrical nightmare. Some breakers clamp over the bus bar, while others bolt onto the bus. Some breaker bases clamp onto a mounting bar, while others slide into a groove. The tension that the breaker contacts are set for also may vary from product to product.
Electrical panels also come in different styles for residential, commercial, and industrial installations. While snap-in type breaker panels are used for residential and commercial installations, bolt-in breakers typically are used for industrial installations where vibration may be a concern and continuously tight contact is needed.
Will Another Brand Fit?
In many cases, one brand of breaker can fit in another brand of panel. For example, some Bryant breakers will fit into some GE panels. Breaker manufacturers may even tell you which of their breakers you can use to replace other manufacturers' breakers. However, it's not recommended that amateurs choose this route since it's easy to end up with an incompatible match. Also, breaker manufacturers typically disclaim any responsibility if you use their breakers in a different manufacturer's panel.
Same Manufacturer, Different Breakers
The specific model of breaker also matters. For example, Square D makes both Q0 panels and Homeline panels, but each series of panels uses different breakers. Additionally, panels may specify one line of breakers for its branch circuits and a different type of breaker for its main breaker or service disconnect.
How to Know What Type of Breaker to Use
If you open the door of your service panel and look on the inside cover of the door, there should be a label that specifies the types of breakers to use with the panel. Note that the model or series of breakers for the branch circuits may differ from the model specified for the main breaker or service disconnect.
If there is no label on the panel door (they're made of paper and don't last forever), the easiest way to ensure compatibility is to use the exact same type of new breaker as the existing breakers in the panel. You can even remove one of the old breakers to make sure the panel connections are identical, and you can test-fit the new breaker in the panel before you hook it up.