The PowerPact™ J-frame circuit breakers are designed to protect electrical systems from damage caused by overloads and short circuits. H-frame and J-frame circuit breakers are available with either thermal-magnetic or Micrologic™ electronic trip units. L-frame circuit breakers are available with Micrologic™ electronic trip units only. H-frame and J-frame circuit breakers with thermal-magnetic trip units contain individual thermal (overload) and instantaneous (short circuit) sensing elements in each pole. The amperage ratings of the thermal trip elements are calibrated at 104 deg F free air ambient temperature. Per the NEC and the CEC, standard circuit breakers may only be applied continuously at up to 80% of their rating. Circuit breakers rated for 100% operation are available but require specially designed enclosures and 194 deg F rated wire.