Rated current alone is not enough to select or quote a molded case circuit breaker. Start with the system voltage and frequency, number of poles, required frame size and rated current. State the installation country and whether the breaker will serve as a main incomer, feeder or motor-circuit device so application differences can be identified before sampling.

Next, record the required Icu and Ics values at the operating voltage and define the trip-unit type. For a thermal-magnetic MCCB, say whether the settings must be fixed or adjustable. For an electronic trip unit, list the required protection functions and any communication requirement. Do not substitute frame rating for trip rating, and never specify a breaking-capacity value without its voltage.

Finally, list the mounting and operating method plus any auxiliary contacts, alarm contacts, shunt trip, undervoltage release or interlocking accessories. Send the single-line diagram, panel layout, target certification, label language, quantity and packing requirements. The factory can then quote the base breaker and each accessory as separate, verifiable lines.