The empty circuit breaker is the one that does not have any tripping mechanism or indicator. It is typically identified by its lack of a trip indicator, which is a feature that shows whether the circuit breaker has been activated or not. In most residential and commercial settings, the empty circuit breaker is often the one that is not currently protecting a circuit, as it has not been installed or is not in use.

The reason for this is that circuit breakers are designed to trip when they detect an overload or a short circuit, which can potentially cause damage to the electrical system or pose a safety hazard. An empty circuit breaker, therefore, has no such protection mechanism in place. This is evident in the absence of a trip indicator, which is a common feature on circuit breakers that have been activated. According to the National Electrical Code (NEC), all circuit breakers must be marked with their amperage rating and trip indicator, making it easy to identify an empty circuit breaker by its lack of these markings.

Data from the NEC specifies that all circuit breakers must be clearly marked with their ratings and trip indicators. For instance, a 20-amp circuit breaker will have a label indicating its 20-amp rating and a trip indicator that shows whether it has been activated. In contrast, an empty circuit breaker will not have these markings, making it stand out in a panel filled with operational circuit breakers. This is a crucial safety feature, as it allows electricians and homeowners to quickly identify which circuit breakers are active and which are not, thereby preventing accidental disconnection of live circuits.