Typical code letters include Q for circuit breakers, T for transformers, A for assemblies (switchboards), etc. There are specified in more detail in IEC 60617 for each type of device. Generally we number each product in a logical fashion which fits the project (i. -Q1, -Q2 . The IEC publishes a series of documents and rules governing the preparation of documents, drawings and the referencing of equipment. Often when IEC. A guide to the certification, listing, and classification of molded case circuit breakers. They also may require this. This standard describes requirements for numbering and labeling of real property electrical distribution equipment, circuits, and site lighting at Lawrence Livermore National Laboratory. Actual project drawings may vary.
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