Humidity control and ventilation device

1. A humidity control and ventilation device comprising: an air supply fan configured to supply outdoor air into a ventilation target space; an exhaust fan configured to exhaust air in the ventilation target space out of the target space; a humidity controller configured to control humidity of the air in the ventilation target space; and a controller configured to execute constant airflow rate control to bring airflow rates of the air supply fan and the exhaust fan within respective target airflow rates, the constant airflow rate control including adjusting a rotation speed of the air supply fan and a rotation speed of the exhaust fan, determine when a ventilation device, separate from the humidity control and ventilation device and configured to ventilate air from or to the target space, has turned on, if an increasing variation in the rotation speed of the air supply fan exceeds a first predetermined value or an increasing variation in the rotation speed of the exhaust fan exceeds a second predetermined value while the air supply fan and the exhaust fan are under the constant airflow rate control, and decrease the rotation speed of the air supply fan or the rotation speed of the exhaust fan if it is determined that the separate ventilation device has turned on such that a total air supply rate and a total air exhaust rate in the ventilation target space are equal with each other, wherein if the separate ventilation device determined to be turned on is an air supplying device, the controller is configured to decrease the rotation speed of the air supply fan, while the air supply fan and the exhaust fan are under the constant airflow rate control, the controller is configured to determine that the air supplying device has turned on if a decreasing variation in the rotation speed of the exhaust fan exceeds a third predetermined value simultaneously when the increasing variation in the rotation speed of the air supply fan exceeds the first predetermined value, when determining that the air supplying device is turned on under the constant airflow rate control, the controller is configured to suspend the constant airflow rate control, and execute constant rotation speed control in which the rotation speed of the air supply fan is decreased and the rotation speed of the exhaust fan is increased, and then the rotation speed of the air supply fan and the rotation speed of the exhaust fan are maintained at a constant rotation speed such that the total air supply rate and the total air exhaust rate in the ventilation target space are equal with each other, and when, under the constant rotation speed control, an increasing variation in power consumption of the air supply fan exceeds a fourth predetermined value and a decreasing variation in power of the exhaust fan exceeds a fifth predetermined value, the controller is configured to determine that the air supplying device has turned off, and, when determining that the air device has turned off, the controller is configured to suspend the constant rotation speed control and execute the constant airflow rate control.

2. The humidity control and ventilation device of claim 1 , wherein if the separate ventilation device determined to be turned on is an air exhausting device, the controller is configured to decrease the rotation speed of the exhaust fan.

3. The humidity control and ventilation device of claim 2 , wherein while the air supply fan and the exhaust fan are under the constant airflow rate control, the controller is configured to determine that the air exhausting device has turned on if a decreasing variation in the rotation speed of the air supply fan exceeds a sixth predetermined value simultaneously when the increasing variation in the rotation speed of the exhaust fan exceeds the second predetermined value.