PURPOSE: To display a clogging in an air filter to an outside part as early as possible by a method wherein there are provided a signal outputting means for outputting a desired signal if a current value supplied to a fan motor is less than a threshold value and a clogged state displaying means for displaying a clogged state of ate air filter upon receiving the desired signal.
CONSTITUTION: A rotation control part 5 receives a signal of the number of rotation of a cross-row fan 1, calculates a difference between the signal and a target predetermined number of rotation and supplies a driving signal for use in setting the number of rotation of a DC fan motor 2 to the target number of rotation in response to the difference. A current sensing part 6 measures a current in the DC fan motor 2 and when the current is decreased to less than the threshold value, it sends an illuminating signal to a clogged state informing part 9 having LED or the like. With such an arrangement as above, it is possible to inform the clogged state of the air filter to a user as early as possible.
UJIHIRA SHIGEYUKI
IMAI TADAMITSU
