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Can We Save The World ?Whole house fan control systemA detailed home cooling comparison of a whole house fan with an air conditioning system showed that the whole house fan could be more than 20 times better from the energy used plus cooling efficiency perspective, than the AC system. A whole house fan, motorized shutter, and control system was installed in a medium size home in Ohio to reduce energy use and to increase comfort levels. This article briefly describes the control system. Whole house fan An ‘Air Vent Inc 5M156-5’ whole house fan is fitted in the top floor ceiling of an open passageway in the home. This 36 inch diameter 2 speed fan can move 6.300 cu ft of air per hour at low speed, and 9,700 cu ft per hour at high speed. Motorized shutter Below the whole house fan is a Dayton 4C228 motorized ceiling shutter, this is generally closed when the fan is not operating but can be opened independently to provide a natural flow through of cool air. 
Click for a larger image Whole house fan control system 
Click for a larger image The whole house fan control system provides an energy frugal way to cool your home. It consists of a control panel, a typical residential 2 channel programmable timer thermostat, an inside to outside temperature comparator, and a high current relay interface. The system provides independent manual or automatic control of both the fan and shutter. Control Panel The control panel enables the whole house fan and shutter to be independently switched on, switched off, or set to operate automatically. 
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Click for a larger image 2 channel programmable timer thermostat In automatic mode one channel of the 2 channel programmable timer thermostat controls the time that the whole house fan is enabled, the second independent channel controls the time that the shutter is enabled. The thermostat on the unit is set to turn off both the whole house fan and to close the shutter if the temperature drops below a preset level. Temperature comparator In Automatic mode the temperature comparator ensures that the shutter and fan can only be operated when there is an adequate inside - outside temperature difference. The temperatures are monitored by two thermistors, the inside thermistor is mounted on the top floor near to the whole house fan, the second thermistor is fitted outside on the north side of the home. High current relay interface The high current relay interface switches the 120vac to the whole house fan and the shutter. Whole house fan control system functionality The home is most effectively cooled at night when outside air temperatures are low. The programmable timers were set to be on about 3 hours before dawn to 1 hour after. When the programmable timer is on, the motorized shutter opens provided the inside temperature is more than 4 degrees Fahrenheit above the outside temperature. The whole house fan is turned on provided the inside temperature is more than 8 degrees above the outside temperature. Air flow through the home is controlled by opening windows and doors creating an air flow path to the whole house fan. A La Crosse WS 8610 data logger temperature and humidity logging system was used to compare the air conditioner and whole house fan systems effectiveness. This battery powered unit logs temperature and humidity data every 5 minutes from itself and from up to three remote wireless temperature and humidity detectors. Data files can be uploaded and graphed using Microsoft Excel. Measuring residential temperatures. 
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