In interpreting 46 CFR, Subchapter J (Electrical Engineering), what should the ambient temperature rating be on a replacement electric motor to be installed in the engine room of a vessel, assuming that it cannot be proven that the temperature will not exceed 45°C in these spaces?
• 46 CFR Subchapter J requirements for ambient temperature ratings of electrical equipment • Special conditions for equipment installed in machinery spaces/engine rooms • What happens to the required rating when you CANNOT prove the space stays at or below 45°C
• Look in 46 CFR Subchapter J for the section that talks about ambient temperature ratings of motors in machinery spaces—what value is specified when higher temperatures are possible? • Ask yourself: if the engine room might be hotter than 45°C and you don’t have proof it stays below that, does the regulation require you to pick a motor rated equal to 45°C, less than, or higher than that temperature? • Consider why the Coast Guard would require a certain safety margin in temperature rating for equipment in hot spaces like engine rooms.
• Verify in 46 CFR Subchapter J (Part 111 – Electrical Systems) what ambient temperature is assumed for equipment in spaces that may exceed 45°C. • Check whether the rule uses the phrase "unless it can be shown" or similar, and see what default temperature rating is then required. • Confirm that the answer you choose is at or above the minimum ambient temperature rating specified for motors in engine rooms when temperature may exceed 45°C.
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