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Space heating to prevent motor damage from condensation

Publication date: 
July 2013
Jim Bryan, EASA Technical Support Specialist
Type of media: 

From time to time, the subject of space heating comes up to address issues caused by condensation in idle motors (or generators). Many feel that a motor can receive more harm from being idle than if it is in service. This is especially true in humid environments where condensation can have a negative impact on winding insulation material and machined surfaces.

Condensation forms when the temperature falls below the dew point. This meteorological term refers to the amount of water vapor the air can hold. The higher the humidity, the closer the ambient temperature will be to the dew point. This becomes a condensation problem when warm, moist air cools, especially at nightfall.

Space heating is intended to keep the surfaces of the motor at about 10°C (18°F) above the ambient temperature so the dew point is never reached inside the machine. This is an auxiliary heating source that should only be utilized when the motor is idle. Anything that increases the temperature of the motor while it is in operation will decrease the winding life. We will discuss various methods to apply this space heating and their merits and shortcomings.

Space heaters