The Canarm 300DD Series is a high-efficiency direct drive roof exhauster featuring an ECM (electronically commutated) motor for energy-efficient, low-maintenance operation. ECM motor provides true variable speed operation and up to 70% energy savings over standard PSC motors. Speed can be controlled using the built-in potentiometer on the motor, a 0-10V controller, or a remote potentiometer. Square base allows discharge to be oriented in any of 4 directions. Includes backdraft damper, bird screen, and 1/2" fiberglass insulated cabinet. Can be used as either a rooftop or wall-mount exhaust fan.