The correct answer isBbecausenonmetallic auxiliary guttersrequire marking of theinstalled conductor insulation temperature rating. This requirement exists because nonmetallic systems are more directly affected by thermal limitations of the enclosure material than metallic systems. The marking helps ensure that the conductors installed in the gutter do not exceed the temperature capability of the nonmetallic enclosure, which is a key safety and compliance issue under NFPA 70. By contrast,sheet metallic auxiliary guttersdo not rely on this same temperature-limitation marking in the same way, andbuswaysare governed by different construction and marking requirements related more to voltage, current, short-circuit rating, and system characteristics than to installed conductor insulation temperature.
This aligns with the API Guide for Source Inspection and Quality Surveillance of Electrical Equipment, which places strong emphasis on verifying that equipment markings, nameplates, documentation, and construction details comply with the governing code, approved drawings, and purchase specifications during source inspection and surveillance. The guide also identifieselectrical systemsamong its covered equipment areas and focuses on inspection and quality-surveillance activities rather than detailed design engineering alone.