Another method used is to pass a sufficient amount of air across the body of the compressor. This design is used on many semi-hermetic compressors and the compressor is generally referred to as an air-cooled compressor.
The third method used is to wrap a water jacket around the body of a semi-hermetic compressor and use the water leading to a water-cooled condenser to cool the motor’s windings. These compressors are generally referred to as water-cooled compressors.
Refrigerant-cooled compressors are usually adequately cooled with the returning suction gas down to an evaporating temperature of 0°. Below 0° additional cooling by means of airflow is necessary. Many manufacturers will employ a head-cooling fan to provide the additional cooling for these compressors. It is important for a service technician to realize the importance of these fans. During a service or maintenance inspection, these fans can be overlooked leading to compressor overheating and future service problems.
Air-cooled compressors will generally use the discharge air from an air-cooled condenser to provide the required cooling for a compressor. If the compressor and air-cooled condenser are not located next to each other (as in the case of a remote condenser application), a fan must be provided to pass air over the body of the compressor.
The cfm requirement for ventilation of a machine room can be determined by using the formula:
Here is an example: Suppose we have an air-cooled condensing unit with a refrigerating capacity of 18,000 Btuh with a 5,400-Watt input to the compressor motor, and a ¾-horsepower condenser fan motor located in a machine room and we need to determine the ventilation requirements for this room. (See Table 1.)