USCG Exam PracticeMotors and generators
A generator rated for 40 °C ambient service must be installed in a machinery space where the ambient temperature regularly reaches 50 °C. Under 46 CFR §183.320, which corrective action is required?
- A. The generator must be replaced with one rated for 50 °C; derating is not permitted
- ✓ The generator may be used if derated to 80 percent of full load rating, with overcurrent devices reduced accordinglyCorrect
- C. The generator may be used at full rating provided additional ventilation is supplied to the space
- D. The generator may be used at full rating if the overcurrent device is increased to 125 percent
Why B is correct
46 CFR §183.320(b)(2) expressly permits a generator designed for 40 °C to be used in a 50 °C ambient location, provided it is derated to 80 percent of its full load rating and the rating or setting of the overcurrent devices is reduced accordingly. Simply adding ventilation or raising the overcurrent setting is not the prescribed remedy.
Cited:46 CFR §183.320