A single suction type centrifugal includes: a casing; and an impeller housed in the casing and provided with a plurality of blades fixed to an impeller main plate. The casing includes a suction side plate having a suction port, and a motor fixing side plate. A center portion of the impeller main plate is fixed to the motor, and a main plate opening is formed in the impeller main plate between the blades and a center portion of the impeller main plate. A blade end portion imaginary plane passes end portions of the blades on a motor fixing side plate side and is perpendicular to a rotary shaft of the motor. A constriction portion is formed where a distance between the blade end portion imaginary plane and the motor fixing side plate is narrowed between the main plate opening and the blades.
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