Which QO breakers can you use on a high leg delta system?
Issue:
QO breaker for a high leg delta system
Product Line:
Circuit Breakers
Resolution:
A high leg delta system is 240 V phase to phase, 120 V to ground on the center tapped phase (normally designated A to C) and 208 V to ground from the high leg (B phase).
Therefore, you can use a standard, GFI, CAFI, AFI, and DF breaker with a 120/240 V rating, such as QO220 and QO220GFI, only on phases A-C and not on B, since the maximum voltage to ground for this breaker is 120 V.
A breaker connected to B phase (the high leg) requires a breaker with a straight 240 V rating such as QO220H. Standard 3 pole breakers such as QO320 or QO320VH type breakers may also be used.
QO breaker for a high leg delta system
Product Line:
Circuit Breakers
Resolution:
A high leg delta system is 240 V phase to phase, 120 V to ground on the center tapped phase (normally designated A to C) and 208 V to ground from the high leg (B phase).
Therefore, you can use a standard, GFI, CAFI, AFI, and DF breaker with a 120/240 V rating, such as QO220 and QO220GFI, only on phases A-C and not on B, since the maximum voltage to ground for this breaker is 120 V.
A breaker connected to B phase (the high leg) requires a breaker with a straight 240 V rating such as QO220H. Standard 3 pole breakers such as QO320 or QO320VH type breakers may also be used.
Released for: Schneider Electric Canada
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