| 摘要 |
A method and apparatus for maintaining an acceptable level of outside air exchange rate in a structure. The natural ventilation rate is determined as a function of the outdoor air temperature, and the amount of mechanically induced ventilation that is used to supplement the natural air ventilation is controlled such that the sum of the natural occurring ventilation and the mechanically induced ventilation is maintained by a substantially constant predetermined level. One approach is to use a stepper motor to modulate the position of the damper, while another approach is to use an on/off motor damper and to close the damper at outdoor temperatures below a threshold level and to otherwise leave the damper open and use the regular on/off cycle of the system blower to control the flow of outdoor air, with provision for allowing the fan to remain on for a calculated period of time after the system is cycled off to thereby maintain the desired level of ventilation. Can also vary the speed of the furnace blower or a separate ventilation fan motor.
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