Abstract: A device and a method for controlling a display make use of a virtual display buffer that acts as an intermediary between data input and display output. The data stored in the virtual display buffer is in a generic, readable first format. A display software driver translates the data stored in the virtual display buffer to a second format usable by a hardware display driver to control a specific display device.

Abstract: A control for controlling a multi-zone HVAC system, wherein the heating or cooling equipment is operable in multiple stages, takes the demand on the system over time into account when determining an appropriate stage. In particular, a time integral of the system demands is utilized along with a current system demand to determine an appropriate stage. In this manner, a weakness in the prior art of allowing a long-term, small difference between the desired set point and the actual temperature in the various zones is addressed.

Abstract: A control is functional to perform a method of determining a maximum desired airflow for each of a plurality of zones in a multi-zone HVAC system, and an expected airflow to those zones. In part, these determinations are based upon an algorithm that calculates the relative size of the ducts leading to each of the zones. The expected and maximum airflows are compared for each of the zones, and if any zone has an expected airflow that exceeds its maximum airflow, certain steps are taken to reduce airflow to that zone.

Abstract: A thermostat receives setpoint information from a system in communication with the thermostat. The thermostat is operative to modify any locally entered setpoints by a predefined amount dictated by the setpoint information received from the system in communication with the thermostat. The thermostat is preferably operative to continually display the time remaining during which it will be under the control of the system in communication with the thermostat. This affords an occupant of the room viewing the displayed time with an opportunity to elect to either continue or to override the control by the system in communication with the thermostat at any time.

Abstract: A device and method for controlling the conditioning of air in the zones of a forced air HVAC system. The device comprises thermostats located in at least two different zones, air ducts and dampers located therein to control the flow of air to the different zones. The microprocessor receives signals from the thermostats corresponding to perceived temperatures in the zones and compares the perceived temperatures to predetermined temperatures and determines a trajectory for each of the zones. The microprocessor in turn sends signals to the dampers corresponding to a positions between fully open and fully closed to control the amount of conditioned air through the ducts such that each of the zones follows the trajectory and reaches the predetermined temperatures at about the same time. The microprocessor further determines system demand and turns the HVAC system on and off in response to the system demand.

Abstract: A thermostat monitors the indoor air temperature indicated by the thermostat's indoor air temperature sensor. The monitored indoor air temperature must be within a predefined range of acceptable temperatures to be considered valid. In the event the monitored temperature is outside this predefined range, the thermostat proceeds to read the outdoor air temperature and activate a heating system if the outdoor air temperature reading is below a predefined level.

Abstract: An electronic thermostat having a short circuit protection feature has a controller which sends control signals to circuitry used for activating and deactivating a system for conditioning air. Short circuit protection circuitry monitors the circuitry within the thermostat and indicates to the controller when a short circuit has occurred. When a short circuit is detected, the controller sets its control signal to deactivate the system for conditioning air for a predetermined period of time.

Abstract: An electronically controlled thermostat has an emergency power configuration which only provides long term emergency power to a real time clock. All other components of the thermostat function only for a limited period of time following a power outage. Emergency power to the other components is monitored during power outage with appropriate action being taken to assure that control information has been stored in nonvolatile memory before emergency power deteriorates to a critical level.

Abstract: A process is disclosed for controlling the operative setpoint of a thermostat during transition from a currently scheduled setpoint temperature to the next scheduled setpoint temperature. The operative setpoint is changed by small amounts at calculated time intervals. The time intervals are a function of the transition periods allocated for different types of systems for air conditioning air that may be operatively connected to the thermostat as well as the difference between the currently scheduled setpoint temperature and the next scheduled setpoint temperature.

Abstract: A process for activating an air conditioning unit includes checking the unit's compressor for possibly being in a recovery status condition. A message is displayed on a control panel as long as the unit's compressor remains in this condition. The display includes an indication as to the time remaining before the compressor will be activated.

Abstract: A setback control for an HVAC system is selectable by depressing a switch on a control panel associated with a programmed microprocessor. The programmed microprocessor is operative to thereafter change the setpoint temperature by a predefined amount each hour until a predetermined number of hours have passed. The set point temperature is thereafter held for a further hourly count before being returned to the starting setpoint temperature. The directional change in setpoint temperature is a function of whether the HVAC system is in a heating or cooling mode of operation.