Current Rating and Thermal Derating
The 250 A rating holds from 40 °C through 50 °C ambient without derating. Above 50 °C the allowable current steps down: 241 A at 55 °C, 232 A at 60 °C, 222 A at 65 °C, and 213 A at 70 °C. For a panel that runs warm — say a packed enclosure with multiple breakers — the 55 °C figure is the practical design point; the 213 A floor at 70 °C is the absolute limit before the trip unit's thermal memory starts to nuisance-trip on a load that's within the breaker's nameplate. Maximum power loss is 48 W, which factors into the enclosure's thermal budget.
Interrupting Capacity by Voltage
The interrupting capacity varies with system voltage: 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 4.5 kA at 690 V. The steep drop at 690 V is characteristic of a breaker whose arc-chamber and contact geometry are optimized for the 240–500 V range — at 690 V the available fault current must be limited to 4.5 kA, which typically restricts this frame to 480 V or 600 V class systems in practice. The insulation voltage is rated at 800 V, so the breaker itself is insulated for higher potentials, but the interrupting capability at 690 V is the binding constraint.
Environmental and Storage Limits
Operating ambient range is -25 °C to 70 °C; storage range extends from -40 °C to 80 °C. The storage minimum of -40 °C is the handling limit — the breaker can sit in an unheated warehouse through a winter shutdown without damage, but the -25 °C operating floor means the trip unit's electronics may not meet accuracy below that temperature. The auxiliary switch configuration is one auxiliary switch plus one trip alarm switch (HP type), which provides a single set of dry contacts for status feedback to a PLC or annunciator.