Abstract: A method and circuit design for establishing the operating status of a direct drive, multiple speed motor. More specifically, the invention furnishes a method for providing feedback to an air distribution system indicating first whether the system motor is operating and second which speed winding has been selected. The circuit design senses the voltage differences between the speed windings of the motor and also between the first speed motor winding and the power supply. The voltage difference sensed by the circuit will determine whether a light emitting diode (LED) illuminates. The illumination of the LED indicates to the system controller whether the motor is operating and the speed winding that has been selected, thus providing the necessary feedback to the air distribution system controller.

Abstract: A control strategy for rejecting supply air temperature disturbances in variable air volume air conditioning units using staged DX cooling. The strategy, and corresponding system, minimizes supply air temperature disturbances by controlling zone air dampers through a mapping of zone heat transfer requirements and damper positions. The mapping maintains a zone temperature setpoint, even with relatively large temperature swings caused by system-supplied conditioned air. The primary parameter that is controlled by the strategy of the present invention is a heat transfer rate associated with a temperature-controlled zone. The control strategy of the present invention estimates the zone heat transfer rate at a particular sampling instant and controls the damper position in response thereto.

Abstract: An apparatus and method indirectly determines the amount of outside air introduced into the ventilation system of a structure to control the indoor air quality in the structure. Test gas concentrations, preferably carbon dioxide concentrations, are measured for return air, outside air and mixed (supply) air. The flow rate of mixed air is measured. The volume of outside air introduced into the system is determined through use of the test gas concentration measurements without directly measuring the volume or flow rate of outside air. Preferably, a single sensor is utilized to measure each of the trace gas concentrations in the return air, outside air and supply air, and the various measurements sequentially multiplexed to a controller. Moreover, for calibrating the apparatus, a return air sensor is calibrated to the outside air and a mixed air sensor is calibrated to the outside air or the return air to eliminate inaccuracy due to sensor drift.