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What is the difference between QO* and QOT* type tandem breakers, such as QO2020 and QOT2020?

What is the difference between QO2020 and QOT2020?

Product Line:
Electrical Distribution Equipment

QO Type ​Circuit Breakers


The QOT2020 tandem breaker is designed for use in present series (since 1967) of QO load centers which are rated to accept tandem breakers.  The QO2020 circuit breaker is designed for use in much older "Non-Class CTL" QO load centers, which were manufactured at a time prior to the existence of CTL, or circuit limiting, classification of load centers.  The change to the circuit limiting classification of load centers came about due to a change in the National Electrical Code in 1965.
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