How Many Tandem or Mini Circuit Breakers Can You Put in a Service Panel?
Of course the answer is as many as you can fit! Actually this is a question that is the subject of much conversation. As you are already aware a tandem or mini circuit breaker is a single pole circuit breaker that is one half the size of a regular circuit breaker. You can fit two tandem breakers in a space designed for one original breaker. Keep in mind that both circuits in the tandem breaker will be on the same hot pole or leg. For this reason it is unacceptable (and dangerous) to make a 240 volt circuit or a multi-branch circuit with two tandem breakers. The only reason to use a tandem breaker is to save room because the service panel is full. So how does a home inspector determine if using tandem breakers are acceptable in the electric panel they are inspecting?
Many modern service panels are manufactured in a manner to prevent the installation of more overcurrent protection devices than the number for which the panel was designed and rated. Most manufacturers list the maximum number of breakers allowed and some provide a feature that will not allow tandem breakers to be installed in certain locations. If you see a tandem breaker, or any breaker for that matter that is not seated properly or appears loose when you remove the cover it should be reported. There should be a wiring diagram in every service panel, usually on the door. Looking at the diagram you can easily see how many tandem breakers are allowed and their position because there will be two lines in the space not one. Looking at the pictures at the beginning of this article; the one on the left indicates that there is not a space allocated for tandem breakers, so none would be allowed. The wiring diagram on the right show double lines where tandem breakers would be acceptable (bottom 5 spaces on each side).
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