Technical FAQs

Ask a Question

Can a 3-pole circuit breaker be used in a single-phase application?

Product Line:
MCCB

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."

EXAMPLE:
A 600A breaker in an enclosure is required for use on a 120/240Vac system. Can a 3-pole P-frame be used? Can a 3-pole L-frame be used?

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.
Was this helpful?
What can we do to improve the information ?