Can Eaton multi-pole MCCBs be used in single-phase, single-pole applications?

Any manufacturer’s multi-pole common trip molded case circuit breaker is built, calibrated, and tested on a pole-by-pole (individual pole) basis.

This means that provided the interrupting rating of the breaker meets or exceeds the value of available fault current in the application, the breaker may be used with only one pole (or two poles, etc.) of a multi-pole breaker wired in the application, providing overcurrent protection for the connected load.  Any remaining poles may be left unused and/or unconnected.

UL 489 is the standard governing molded case circuit breaker construction, testing, and labeling.  There are a number of references in UL 489 to employing multi-pole breakers in single-phase applications.  A decent summary of such use can be found in the definition of a COMMON TRIP CIRCUIT BREAKER: “a multi-pole circuit breaker constructed so that all poles will open when any one or more poles open automatically” (UL 489 Section 2.20).

A common trip molded case circuit breaker is suitable for use in installations where one, two, or three of its protected poles will be unused, and if using the breaker in such a manner it will still operate as required in that application.