Abstract: An arrangement is disclosed for controlling fan motors in fan-powered terminal units which permit the air flow of the terminal units to be factory preset and reset using a voltmeter. The fan motor is responsive to the pulse width of pulses of a pulse width modulated signal to provide an air flow which is proportional to the pulse width. By adjusting the pulse width, the air flow may be set as desired. A pulse width modulated signal having pulses with a set amplitude and frequency is generated. The dc voltage of the pulse width modulated signal is measured using a voltmeter. As the pulses have a set amplitude and frequency, the pulse width of the pulses may be adjusted by controlling the dc voltage of the pulse width modulated signal. The fan motor is programmed to deliver the set air flow over a range of static pressures.

Abstract: A damper is provided which is adapted to be positioned in a building conduit to control the flow of fluid through the conduit. The damper includes a frame and barrier structure coupled to the frame which is movable between open and closed positions. The barrier structure permits fluid to flow through the conduit when positioned in the open position and substantially blocks fluid flow through the conduit when positioned in the closed position. The damper further includes an actuator which is coupled to the barrier structure for effecting movement of the barrier structure. A control circuit is also provided and is connected to the actuator for controlling the operation of the actuator. The control circuit includes a thermal responsive switch which, preferably, is located outside of the conduit. The thermal responsive switch prevents operation of the actuator when the temperature of fluid surrounding the switch exceeds a first predetermined value.

Abstract: An arrangement is disclosed for controlling fan motors in fan-powered terminal units which permit the air flow of the terminal units to be factory preset and reset using a voltmeter. The fan motor is responsive to the pulse width of pulses of a pulse width modulated signal to provide an air flow which is proportional to the pulse width. By adjusting the pulse width, the air flow may be set as desired. A pulse width modulated signal having pulses with a set amplitude and frequency is generated. The dc voltage of the pulse width modulated signal is measured using a voltmeter. As the pulses have a set amplitude and frequency, the pulse width of the pulses may be adjusted by controlling the dc voltage of the pulse width modulated signal. The fan motor is programmed to deliver the set air flow over a range of static pressures.