Abstract: A control and method for varying the capacity of a centrifugal chiller system used to cool a liquid to a setpoint temperature. The control permits the user to select the setpoint, the control gain, and two variables that determine a first deadband and a second relatively wider deadband about the setpoint. If the absolute value of the difference (error) between the actual fluid temperature and the septoint is increasing, the control uses the first deadband, and conversely, if the error is decreasing, it uses the second deadband to vary chiller capacity. The control also permits the user to select a limit for various operating parameters associated with protective shutdown of the system to avoid catastrophic failure, and adjusts the chiller capacity according to one of two predefined functions of the deviation of the operating parameter from its limit, dependent on whether that deviation is greater or less than a predefined deadband.

Abstract: A control and method for varying the capacity of a centrifugal chiller system used to cool a liquid to a setpoint temperature. The control permits the user to select the setpoint, the control gain, and two variables that determine a first deadband and a second relatively wider deadband about the setpoint. If the absolute value of the difference (error) between the actual fluid temperature and the setpoint is increasing, the control uses the first deadband, and conversely, if the error is decreasing, it uses the second deadband to vary chiller capacity. The control also permits the user to select a limit for various operating parameters associated with protective shutdown of the system to avoid catastrophic failure, and adjusts the chiller capacity according to one of two predefined functions of the deviation of the operating parameter from its limit, dependent on whether that deviation is greater or less than a predefined deadband.

Abstract: A microprocessor based control for tempering supply air in a multi-stage temperature conditioning system. The temperature conditioning stages are normally controlled in response to a comfort temperature sensor to maintain the zone at a setpoint. However, if a sensor in the supply airstream indicates that the temperature of the supply air is less than a predetermined minimum, the primary control algorithm is overridden and the temperature conditioning stages are controlled to increase the supply air temperature. Tempering the supply air prevents personal discomfort due to excessively cold air being supplied to the zone.

Abstract: A control for a multi-stage heating and cooling system used to temperature conditioning a comfort zone. The control includes a microprocessor responsive to a temperature sensor installed in the comfort zone. Heating and cooling setpoints and a lookup table including a plurality of ranges for deviation of the comfort zone from the setpoint temperature and associated limits for the rate of change of the comfort zone temperature used in determining specific staging control actions are stored in solid state memory accessed by the microprocessor.The stages of temperature conditioning are controlled as a function of both the deviation of the zone temperature from the heating or cooling setpoint (depending on the system operating mode), and the rate of change of zone temperature. The mode of operation, i.e., heating or cooling, is determined by the relative values of the zone temperature and the heating and cooling setpoint.