Evaporative coolers, also known as swamp coolers, are an alternative to air conditioners in areas where the relative humidity is low enough that the process is effective.
With these units, dry air moves over a media pad saturated with water. The moisture-laden air is blown through the area to be cooled and exhausted through vents or slightly open windows. As moisture evaporates inside the space, a cooling effect occurs. This is the same as the cooling effect on your skin when water evaporates after stepping out of the shower.
Most motors used in home units mount in a resilient base and have the same ring-to-ring dimensions. Replacement motors are often sold without bases since the base doesn't normally fail. Single- and two-speed units are available.
The motors are connected to the blower wheel with a drive belt. Proper belt tension is ½- to ¼- inch deflection at the center of the belt span.
The motor pulley must be the type and size recommended by the cooler manufacturer. If an adjustable pulley is used, the pulley should be set by a technician with the c=necessary electrical test equipment. The adjustable pulley blows the load (blower) to run at a speed compatible with the motor.
To set an adjustable pulley:
• Open pulley to maximum width and adjust the tension belt.
• Look for the recommended motor amp rating at the highest speed.
• Using an ammeter, measure the amps at the highest speed.
• Stop the motor, close the pulley one-half turn and adjust the retention belt.
• Repeat step 4 until the amp reading meets, but does not exceed the motor's rated amperage.
An important note: If the amperage exceeds the motor's rating, the motor will overheat and stop. It's also important to caution that the motor will restart automatically after it cools and the overload resets.
Cooler installations not using duct work will require a smaller diameter pulley than the same cooler using duct work. The duct work creates static pressure or resistance to airflow, which reduces the motor load and amp draw.
Check the motor amperage while it is running on high speed. It should not exceed the nameplate amps. Motors with all copper windings or a combination of copper and aluminum windings are available. With advances in connection methods and winding insulation, there is little difference in the reliability of either type.
Source: A.O. Smith Motor Mastery University
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