Abstract: A freeze protection system for a heating, ventilation, or air conditioning (HVAC) system is shown. The freeze protection system includes a temperature sensor positioned at an inlet of a coil within which a liquid is at risk of freezing, and a controller comprising a processor and memory. The memory stores instructions that are executed by the processor. The processor is instructed to obtain a measured temperature of the liquid at the inlet of the coil from the temperature sensor, compare the measured temperature of the liquid at the inlet of the coil with a freeze prevention temperature threshold, engage a freeze prevention action in response to a determination that the measured temperature of the liquid at the inlet of the coil is less than or equal to the freeze prevention temperature threshold.

Abstract: A system for controlling a flow rate of a fluid through a valve is provided. The system includes a valve and an actuator. The actuator includes a motor and a drive device that is coupled to the valve for driving the valve between multiple positions. The system further includes a flow rate sensor and a controller that is communicably coupled with the flow rate sensor and the motor. The controller is configured to receive a first flow rate setpoint, determine a first actuator position setpoint using a proportional variable deadband control technique based on the first flow rate setpoint and a flow rate measurement, and receive a second flow rate setpoint. In response to a determination that certain low flow criteria are satisfied, the controller is configured to determine a second actuator position setpoint using the proportional variable deadband control technique based on a low flow compensation setpoint.

Abstract: A system for controlling a flow rate of a fluid through a valve is provided. The system includes a valve and an actuator. An actuator drive device is driven by an actuator motor and is coupled to the valve for driving the valve between multiple positions. The system further includes a flow rate sensor configured to measure the flow rate of the fluid through the valve and a controller that is communicably coupled with the flow rate sensor. The controller is configured to receive a flow rate measurement from the flow rate sensor, adjust a control deadband based on an actuator command history, and determine a compensated position setpoint using the flow rate measurement, the adjusted control deadband, and a proportional variable deadband control technique. The controller is further configured to operate the motor to drive the drive device to the compensated actuator position setpoint.

Abstract: A method for controlling flow in a heating, ventilation, and air conditioning (HVAC) system includes adjusting a setpoint associated with a valve based on a temperature change across a heating or cooling coil to reduce energy waste. The method includes receiving a first temperature measurement associated with an inlet of the coil, receiving a second temperature measurement associated with an outlet of the coil, calculating a difference between the first temperature measurement and the second temperature measurement, determining that the difference between the first temperature measurement and the second temperature measurement is below a threshold, and adjusting a setpoint associated with the valve. Additional control features may be provided to improve system behavior such as a pulse generation feature, a change-limiting feature, and a reevaluation feature.

Abstract: A method for controlling flow in a heating, ventilation, and air conditioning (HVAC) system that imposes an upper limit on the flow of fluid through a heating or cooling coil. Imposing this limit on the flow rate ensures that a temperature change across the coil remains above a minimum threshold and can significantly reduce energy waste. The method includes receiving a first temperature measurement associated with an inlet of the coil, receiving a second temperature measurement associated with an outlet of the coil, and receiving a flow measurement associated with the valve, applying the first temperature measurement, the second temperature measurement, and the flow measurement as input to a model, determining a maximum flow rate that ensures that a difference between the first temperature measurement and the second temperature measurement is above a threshold using the model, and operating the valve in accordance with the maximum flow rate.

Abstract: A thermostat for a building zone includes at least one of a model predictive controller and an equipment controller. The model predictive controller is configured to obtain a cost function that accounts for a cost of operating HVAC equipment during each of a plurality of time steps, use a predictive model to predict a temperature of the building zone during each of the plurality of time steps, and generate temperature setpoints for the building zone for each of the plurality of time steps by optimizing the cost function subject to a constraint on the predicted temperature. The equipment controller is configured to receive the temperature setpoints generated by the model predictive controller and drive the temperature of the building zone toward the temperature setpoints during each of the plurality of time steps by operating the HVAC equipment to provide heating or cooling to the building zone.

Abstract: A system includes a plurality of thermostats corresponding to a plurality of HVAC systems that serve a plurality of spaces and a computing system communicable with the plurality of thermostats via a network. The computing system is configured to, for each space of the plurality of spaces, obtain a set of training data relating to thermal behavior of the space, identify a model of thermal behavior of the space based on the set of training data, perform a model predictive control process using the model of thermal behavior of the space to obtain a temperature setpoint for the space, and provide the temperature setpoint to the thermostat corresponding to the HVAC system serving the space. The plurality of thermostats are configured to control the plurality of HVAC systems in accordance with the temperature setpoints.

Abstract: A thermostat for a building zone includes at least one of a model predictive controller and an equipment controller. The model predictive controller is configured to obtain a cost function that accounts for a cost of operating HVAC equipment during each of a plurality of time steps, use a predictive model to predict a temperature of the building zone during each of the plurality of time steps, and generate temperature setpoints for the building zone for each of the plurality of time steps by optimizing the cost function subject to a constraint on the predicted temperature. The equipment controller is configured to receive the temperature setpoints generated by the model predictive controller and drive the temperature of the building zone toward the temperature setpoints during each of the plurality of time steps by operating the HVAC equipment to provide heating or cooling to the building zone.

Abstract: A system for controlling a flow rate of a fluid through a valve is provided. The system includes a valve and an actuator. An actuator drive device is driven by an actuator motor and is coupled to the valve for driving the valve between multiple positions. The system further includes a differential pressure sensor configured to measure a differential pressure across the valve and a controller that is communicably coupled with the differential pressure sensor and the motor. The controller is configured to receive a flow rate setpoint and the differential pressure measurement, determine an estimated flow rate based on the differential pressure measurement, determine an actuator position setpoint using the flow rate setpoint and the estimated flow rate, and operate the motor to drive the drive device to the actuator position setpoint.

Abstract: A thermostat for a building zone includes at least one of a model predictive controller and an equipment controller. The model predictive controller is configured to obtain a cost function that accounts for a cost of operating HVAC equipment during each of a plurality of time steps, use a predictive model to predict a temperature of the building zone during each of the plurality of time steps, and generate temperature setpoints for the building zone for each of the plurality of time steps by optimizing the cost function subject to a constraint on the predicted temperature. The equipment controller is configured to receive the temperature setpoints generated by the model predictive controller and drive the temperature of the building zone toward the temperature setpoints during each of the plurality of time steps by operating the HVAC equipment to provide heating or cooling to the building zone.

Abstract: A thermostat includes an equipment controller and a model predictive controller. The equipment controller is configured to drive the temperature of a building zone to an optimal temperature setpoint by operating HVAC equipment to provide heating or cooling to the building zone. The model predictive controller is configured to determine the optimal temperature setpoint by generating a cost function that accounts for a cost operating the HVAC equipment during each of a plurality of time steps in an optimization period, using a predictive model to predict the temperature of the building zone during each of the plurality of time steps, and optimizing the cost function subject to a constraint on the predicted temperature of the building zone to determine optimal temperature setpoints for each of the time steps.

Abstract: A thermostat includes an equipment controller and a model predictive controller. The equipment controller is configured to drive the temperature of a building zone to an optimal temperature setpoint by operating HVAC equipment to provide heating or cooling to the building zone. The model predictive controller is configured to determine the optimal temperature setpoint by generating a cost function that accounts for a cost operating the HVAC equipment during each of a plurality of time steps in an optimization period, using a predictive model to predict the temperature of the building zone during each of the plurality of time steps, and optimizing the cost function subject to a constraint on the predicted temperature of the building zone to determine optimal temperature setpoints for each of the time steps.