Abstract: A controller for unit ventilators which include processing means having associated memory that enables control schemes to be used. The controller is modular and compact in its construction, is easily installed in existing unit ventilators and provides not only the controlled pneumatic pressure in the output lines for the controller, but also provides electrical control signals for controlling the operation of the fan. The controller is adapted to control unit ventilators having auxiliary radiation and is also adapted to control ASHRAE cycle 3 type installations.

Abstract: A controller having two cascaded PID control loops in the control of unit ventilators of the type which have a heating coil, a fan, and a damper for admitting outside air into a room in which the unit ventilator is located. The controller utilizes the sensed room temperature and a room temperature set point to generate a set point for the temperature of the air being discharged from the unit ventilator, and utilizes the discharge temperature set point and the sensed discharge temperature to control the damper position and the operation of the heating coils of the unit ventilator.

Abstract: An output pressure control apparatus particularly adapted for HVAC control applications, and being of the general type which admits a higher supply pressure to a controlled output line when it is desired to increase the pressure in the output line and which bleeds pressure from the controlled output line when it is desired to reduce the pneumatic output pressure. The pressure regulating apparatus requires only a single filter means and utilizes bidirectional flow of air through the filter means during normal operation which cleans the filter means.