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Can a 3-pole breaker be used in a 2-pole application?

Issue:
Can a three pole breaker be used in either a two pole or a single phase application?

Product Line:
MCCB

Environment:
Powerpact and Masterpact

Resolution:
  • 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.
For reference:
  • 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."

Powerpact P
  • 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.
Powerpact L
  • The 3-pole L-frame breaker does NOT have a marking for single phase systems. Therefore on the 120/240Vac system, it is NOT ok to use a 3 pole L-frame breaker.
  • This marking correlates with the wiring diagram of the L breaker enclosure, which shows only 3p applications.
Powerpact H and J
  • Three-pole Powerpact H and J-frame thermal-magnetic breakers are marked for single phase use
  • 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 H and J-frame Micrologic breakers with Ammeter and Energy trip units (U43X, U53X and U54X) are NOT marked for single-phase use.
  • Three-pole Powerpact H and J-frame Electronic breakers with Micrologic 6.2A trip units can be used for 2P applications in order to have ground fault protection. Additional metering capabilities will not work properly on the unconnected phase.
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