pityocamptes
06-22-05, 09:34 AM
Hi all. First at what dew point does a evaporative cooler start to become worthless? I don't know if it is coincidence or not but a few days ago I replaced the aspen pads with those blue fiber looking pads. It seems the house is not getting as cool. Right now the dew point level is around 32. The blue fiber pads said they get 2* cooler than regular aspen pads but I'm not sure. Any thoughts? Maybe its time to kick the AC on :rolleyes: Thanks.
Oh, should I go with a larger sheave? Took this from a web site:
Figure 5. Many evaporative coolers have adjustable-speed belt-driven blower wheels which allow airflow to be changed.
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Increasing Air Flow
Most evaporative coolers that are installed with ducts have a belt drive system with an adjustable pulley (formally called a "sheave") on the motor. This sheave has two bolts--one to secure the sheave to the motor shaft and the other to allow the effective diameter of the sheave to be changed. The motor-belt-blower system is similar to a bicycle drive system: the larger the motor sheave is made, the faster the blower wheel will rotate and the more air the cooler will deliver (see Figure 5).
The motor will run at roughly the same speed no matter what its work load. If it is overworked, it will draw excessive current and overheat, and the thermal circuit breaker in the motor will turn the motor off; as the motor cools down, it will automatically restart and repeat this process. If this occurs, the effective diameter of the motor sheave should probably be made smaller (although failed flex duct or tight bearings could also be contributing to the problem).
By checking the motor current and readjusting the sheave diameter and belt tension, the installer can maximize the cooler air output. This is often not done. In fact, I have never visited a cooler installation (except field test sites) in which the motor was putting out its potential.
If a motor is being replaced, this might be a good time to increase the horsepower, blower speed, and airflow. Whenever blower speed is increased, it is important to make sure that the cooler blower can withstand the new speed, that the increased air flow does not cause water to be pulled into the blower, that the duct air noise is acceptable, and that the circuit and wiring to the cooler are adequate for the increased current draw. Although increasing motor speed can improve cooler performance, the higher operating temperatures will decrease the life of the motor. So increase the blower speed only if the cooler's performance is inadequate.
Oh, should I go with a larger sheave? Took this from a web site:
Figure 5. Many evaporative coolers have adjustable-speed belt-driven blower wheels which allow airflow to be changed.
--------------------------------------------------------------------------------
Increasing Air Flow
Most evaporative coolers that are installed with ducts have a belt drive system with an adjustable pulley (formally called a "sheave") on the motor. This sheave has two bolts--one to secure the sheave to the motor shaft and the other to allow the effective diameter of the sheave to be changed. The motor-belt-blower system is similar to a bicycle drive system: the larger the motor sheave is made, the faster the blower wheel will rotate and the more air the cooler will deliver (see Figure 5).
The motor will run at roughly the same speed no matter what its work load. If it is overworked, it will draw excessive current and overheat, and the thermal circuit breaker in the motor will turn the motor off; as the motor cools down, it will automatically restart and repeat this process. If this occurs, the effective diameter of the motor sheave should probably be made smaller (although failed flex duct or tight bearings could also be contributing to the problem).
By checking the motor current and readjusting the sheave diameter and belt tension, the installer can maximize the cooler air output. This is often not done. In fact, I have never visited a cooler installation (except field test sites) in which the motor was putting out its potential.
If a motor is being replaced, this might be a good time to increase the horsepower, blower speed, and airflow. Whenever blower speed is increased, it is important to make sure that the cooler blower can withstand the new speed, that the increased air flow does not cause water to be pulled into the blower, that the duct air noise is acceptable, and that the circuit and wiring to the cooler are adequate for the increased current draw. Although increasing motor speed can improve cooler performance, the higher operating temperatures will decrease the life of the motor. So increase the blower speed only if the cooler's performance is inadequate.