Overcurrent Protection
PowerPacT Q-frame circuit breakers contain individual thermal (overload) and magnetic (short circuit) sensing elements in each pole. The amperage ratings of the thermal trip elements are calibrated at 40°C (104°F) free air ambient temperature. Per the National Electric Code® (NEC®) standard rated circuit breakers can be applied continuously at a maximum of 80% of their rating.
Operating Mechanism
PowerPacT Q-frame circuit breakers have an over-center toggle mechanism providing quick-make, quick-break operation. The operating mechanism is also trip-free, which allows tripping even when the circuit breaker handle is held in the ON (I) position. An internal cross bar provides common opening and closing of all poles with a single operating handle.
All PowerPacT Q-frame circuit breakers have an integral push-to-trip button in the cover to manually trip the circuit breaker. This should be used as part of a regular preventive maintenance program.
Trip Indication
The PowerPacT Q-frame circuit breaker handle can assume any of three positions, ON (I), tripped (˅), or OFF (O) as shown in Handle Position.
The center tripped position provides positive visual indication that the circuit breaker has tripped. The circuit breaker can be reset by first pushing the handle to the extreme OFF (O) position. Power can then be restored to the load by pushing the handle to the ON (I) position.
Standards
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PowerPacT Q-frame circuit breakers are built in accordance with UL Standard 489 and NEMA Standard AB-1-1999.
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Q-frame circuit breakers are UL Listed for use in the United States and UL approved for use in Canada under UL File E84905 and Canadian Standard C22.2 No. 5–02.
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Circuit breakers are listed for use in Mexico with NOM-003–SCFI (under Mexican ANCE Standard NMX-J-266–ANCE).
Interrupting Ratings
Circuit Breaker Interrupting Ratings
| Catalog Prefix | Ampere Rating | Number of Poles | UL Listed Interrupting Rating | Federal Specification (W-C-375B/GEN) |
||
|---|---|---|---|---|---|---|
| Unit Mount | I-Line | 208/120 Vac | 240 Vac | |||
| QB | 70–250 A | 70–225 A | 2 | 10 kA | 10 kA | 12b |
| 3 | 10 kA | 10 kA | 12b | |||
| QD | 70–250 A | 70–225 A | 2 | 25 kA | 25 kA | 14b |
| 3 | 25 kA | 25 kA | 14b | |||
| QG | 70–250 A | 70–225 A | 2 | 65 kA | 65 kA | 15b |
| 3 | 65 kA | 65 kA | 15b | |||
| QJ | 70–250 A | 70–225 A | 2 | 100 kA | 100 kA | 15b |
| 3 | 100 kA | — | — | |||
Molded Case Switches
Two-pole (QB_2000S22) and three-pole (QB_32000S22) automatic molded case switches are available with a 225 A, 240 Vac, 10 kA rating. Automatic molded case switches contain magnetic tripping elements set high enough not to interfere with normal overload protective device operation but still protect the switch in the event of a short circuit. For Q-frame switches, this trip point is 4500 A. Molded case switches provide no other overcurrent protection and must be protected by an upstream circuit breaker or fuse.