Which of the following procedures should be used to maintain a large electric motor during periods of inactivity?

Correct Answer: Option B — Space heaters should be used to prevent condensation of moisture.

Space heaters are the standard method for preventing moisture condensation within motor windings during idle periods. By maintaining the internal temperature slightly above the ambient dew point, heaters prevent the formation of water droplets that could lead to insulation breakdown and catastrophic ground faults upon startup.