Frequently asked questions
Can a 3-pole breaker be used in a 2-pole application?
13 January 2022Issue:
Three pole breaker use in two pole (single-phase) application
Powerpact and Masterpact
- A 3p breaker can be used on a 3 phase system using either 2 or 3 poles.
- A 3p breaker can be used on a 1 phase system only if indicated by the markings as noted below.
- Per NEC article 240.85: "A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker’s voltage rating."
- According to UL's White book, "3–pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, “For 1–phase connections, use two outside poles,” or an equivalent statement. A 3-pole breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked."
- The 3-pole P-frame breaker has a marking on the cover that states "single phase any 2 poles". Therefore on a 120/240Vac system, it is ok to use any 2 poles of a 3 pole P-frame breaker.
- This breaker marking correlates with the wiring diagram markings of the M and P breaker enclosure, which shows both 2p and 3p applications.
- Three-pole Powerpact L frame Micrologic breakers with all trip units (U31X, U33X, U43X, U44X, U53X and U54X) are marked for single-phase use, but on 240Vac circuits only. Use any 2 poles.
- Three-pole Powerpact H and J-frame thermal-magnetic breakers are marked for single phase use, including MCP.
- Three-pole Powerpact H and J-frame Micrologic breakers with standard trip units (U31X and U33X) are marked for single-phase use
- Three pole Powerpact B frame breakers are not marked for single phase use.
- Three-pole Powerpact QB, QD, QG, QJ breakers are not marked for single phase use.
- Three pole legacy breakers are not marked for single-phase use