The term ambient temperature is used to denote the temperature of the air surrounding a motor, a control mechanism, or other devices. As an example, a motor may be guaranteed to deliver its full horsepower under operating conditions when its temperature does not exceed 40 C. (72 F.) over the ambient temperature. This means that the temperature of the motor must not be warmer than 72 F. over the surrounding air if the motor is to maintain its operating efficiency.
Ambient temperature is not usually a constant temperature but it may change day-by-day and hour-by-hour depending on the usage of the space, sunshine, and many other factors.
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Basics of Refrigeration