Abstract: A method of controlling a multistage heating system so as to minimize the energy required to bring the temperature of a predetermined volume of space to a predetermined temperature level is provided. The multistage heating system includes an energy efficient first heating mechanism and at least a less energy efficient second heating mechanism. First, a time period for the multistage heating system to bring the temperature of the predetermined volume of space to the predetermined temperature level is calculated. This calculated time period is provided into a plurality of zones, each of the plurality of zones having an associated temperature limit. The first and second heating mechanism are controlled in each of the plurality of zones according to a switching logic associated with each respective zone such that the temperature within each zone does not exceed the associated temperature limit.

Abstract: Automatically adjusting the time when control is returned to the operational set-point, in compensation for changing load conditions, is accomplished by measuring the operation of a heating or cooling system controller in its standby mode, and using this measurement to calculate the advance time required to return the system to its operational temperature. The operational factor to be measured depends on the control system: with a bistable or on-off thermal source, such as a household furnace, measurement of the time required to heat the house the few degrees between the set-back on and off set-points will permit calculation of the time required to reheat the house to its operational temperature.

Abstract: This adaptive environment control system provides an HVAC control system that adapts to the continually-changing thermal characteristics of the building in which it operates. The adaptive environment control system periodically estimates the thermal characteristics of the building and uses these estimates to control the operation of the HVAC system. The adaptive environment control system also periodically measures the performance characteristics of the HVAC system to obtain data with which to update these thermal characteristic estimates. These thermal characteristic estimates enable the adaptive environment control system to determine both the length of time it takes the building to heat up and cool down when the HVAC system idles, as well as the amount of time it takes the HVAC system to heat or cool the building.

Abstract: A programmable thermostat for an air conditioning system for a predetermined volume of space is provided which includes a digital memory for storing a plurality of program times and program temperatures corresponding to the program times, a sensor for sensing the ambient temperature within the predetermined volume of space, a timer for generating the current time of day, and a controller for controlling the on/off switching of the air conditioning system in response to (1) a comparison of the current time of day with the program times stored in the digital memory to access the corresponding current control temperature stored in the digital memory and (2) comparison of the current ambient temperature sensed by the sensor with the current control temperature stored in the memory.

Abstract: This invention relates to an electronic flow control circuit for use in the low voltage section of an existing control arrangement of a hydronic heating system that utilizes motorized zone valves, to provide a means for controlling fluid flow through the system in order to eliminate hydrostatic shock (water hammer) associated with fast closing motorized zone valves.

Abstract: This relates to a thermodynamic electronic actuator for intermittently controlling the operation of a heating and/or air conditioning system for any temperature controlled area when a door or window is left open or ajar. The actuator circuit comprises a normally-closed switch (or switches if used for more than one opening), which initiates operation of a count-up timer to interrupt the thermostat line after a predetermined period whenever a door or window is left open. To restore power, all that is required is to shut the window or door. This actuates a count-down timer that will restore the thermostat line after a predetermined period, assuming the window or door is not reopened, interrupting the countdown.

Abstract: To reduce the number of boiler sequences over time executed for a given heating load without adversely affecting boiler efficiency, the call signal applied to the boiler to initiate a sequence in response to a demand for heating is delayed as a function of outside temperature and time elapsed since the end of the previous sequence. Accumulated burn time and sequence count are displayed to monitor boiler performance.

Abstract: A control system for a hydronic heating system for an enclosed structure which includes a boiler and at least one heating zone controlled by a thermostat and having a circulator or zone valve for controlling delivery of heat from the boiler to the heating zone(s). The control system senses the ambient temperature external to the enclosed structure, and also the water temperature of the boiler. Responsive to those two sensed values, it determines an upper temperature for the boiler at which the boiler is shut off. The control system further periodically redetermines the upper temperature for the boiler in accordance with the heating demands of the enclosed structure, and accordingly is heuristic in nature. In the preferred embodiment, a central processing unit forms the heart of the control system, and digitally stores in memory words representative of the sensed temperatures and other pertinent parameters relating to timing.

Abstract: A method and an apparatus of automatically switching between cooling and heating of an air conditioner, has which is a first temperature higher than a desired room temperature, a second temperature which lower than the desired room temperature, a first temperature zone not less than the first temperature, and a second temperature zone not more than the second temperature. The method includes the steps of changing an operation mode from a cooling mode to a heating mode during the cooling mode when the room temperature after duration of a first time remains in the second temperature zone, and changing the operation mode from the heating mode to the cooling mode during the heating mode when the room temperature after duration of a second time remains in the first temperature zone.

Abstract: A temperature setting unit is operated to set a desired temperature. An indoor temperature detector detects an indoor temperature. A timer is operated to set an operation start time. An indoor unit includes at least an indoor heat exchanger, an air duct associated with the indoor heat exchanger, a heat radiation member located in the air duct, a heat accumulator thermally coupled to the heat radiation member, and an electric heater for selectively supplying heat to the heat accumulator. An outdoor unit includes at least a compressor for cooperating with the indoor heat exchanger to constitute a heat pump refrigeration cycle for heating operation, and an outdoor exchanger. A controller outputs a first control signal for preheating the electric heater a predetermined period of time before operation start time by counting preset data of the operation start time from the timer, and a second control signal for setting the heat pump refrigeration cycle in a drive state at the operation start time.

Abstract: The present invention is a technique for operator entry of a time program into a programmable device. An operator adjustable input device having associated time indicia is employed to enter a time signal indicative of a time a selected time. A manual control state input device enables selection of one a control state. When the programmable device is in a program mode the selected control state is stored in a program memory at a location corresponding to the selected time. This program memory stores a program of control states for particular times. When in a control mode a clock signal indicative of the current time permits recall of the control state for the current time, thus permitting control in accordance with the recalled control state. In accordance with the preferred embodiment the programmable device is an electronic thermostat.

Abstract: A compensation circuit for sensor lag uses a sensor temperature signal modification circuit to provide a modified sensor temperature signal for subsequent use in controlling the sensed temperature. The compensation circuit digitally compares a current sensor temperature representative signal and a sensor temperature signal at a last or preceeding sample time to produce a difference signal which is converted to a sensor slope signal and is multiplied by a sensor time constant. The resulting signal is passed through a filter to eliminate transient effects and is summed with the original sensor temperature signal to provide a sensed temperature signal for control of the temperature whereby the sensed temperature is a better estimate of the actual environmental temperature controlled by a thermostat utilizing the sensed temperature signal.

Abstract: A system is described for use with a hot water supply for hotels, apartment buildings and similar multi-unit structures, which controls the temperature T.sub.1 of water at the outlet of a water tank to make it close to a desired temperature DTEMP that is low during times of low demand to save energy and which is high at times of high demand to assure adequate hot water at all times. The desired temperature at the tank outlet, DTEMP, is adjusted according to the sensed demand for hot water during an immediately preceding period of given duration, such as 45 minutes. The circuitry is used in parallel with an existing Aquastat on a commercial tank type water heater.

Abstract: A programmable electronic thermostat is provided for controlling operation of a multistage heating apparatus comprising a heat pump and auxiliary heat. A salient feature is a program which provides for economical recovery from a setback temperature. The program includes logic which determines, at the beginning of the recovery time, whether any or all of the auxiliary stages will be temporarily locked out and thus prevented from being energized. This determination is based on a characteristic which is dependent upon the heating demand that is presently being placed on the heating apparatus. The program also includes logic which determines, near the end of the recovery time, whether any or all of the locked stages are to be unlocked. This determination is based on the magnitude of the difference between the temperature existing at the time of determination and the temperature desired at the end of the recovery time.

Abstract: A controlling system for an air conditioning apparatus includes a controlling apparatus, a main controller and room controller provided in each room.

Abstract: The present invention is a technique for thermostatic control of a temperature modifying apparatus such as a heating unit or an air conditioning unit. This technique involves measuring the ambient temperature, generating an error signal based upon the difference between a set point temperature and the measured ambient temperature, operating the temperature modifying apparatus according to the error signal, and adjusting the set point temperature based upon the time history of the error signal. In accordance with the preferred embodiment of the present invention, the temperature modifying apparatus is operated during the next cycle interval with a duty cycle proportional to the error signal at the start of the cycle interval.

Abstract: Control apparatus for controlling the operation of a gas valve in a gas heating system which includes thermostatic switch means and a source of AC voltage which are connected to form a series circuit with the gas valve is disclosed. The control apparatus comprises switch means which is connected to provide continuity in the series circuit upon receipt of a first control signal and to remove the continuity in the series circuit upon removal of the first control signal. Isolation means receives a second control signal having a high state and an alternate low state and generates the first control signal when receiving the high state of the second control signal. A power supply receives the AC voltage when the thermostatic switch means is closed and provides a DC voltage to a timer means. The timer means then generates the second control signal.

Abstract: A power saving system for a hotel guest room has a keyboard operated control circuit that controls operation of an electrical load, such as a room air conditioner, and arms a door-window security circuit. When the guest enters the room, he disables the load control and security alarm system by actuation of a suitable contact on the keyboard. Prior to leaving the room, in order to secure it, he enables the security alarm system, and also the electrical load control, by making a suitable entry on the keyboard.

Abstract: A controller (8) of air conditioning apparatus (18) with a cycle timer (12) for periodically actuating the apparatus (18) irrespective of temperature combined with a thermostat (10) for actuating the apparatus (18) in accordance with sensed temperature and logic circuitry (FIG. 3) for recycling the timer (12) to prevent excessive actuation of the apparatus (18) while ensuring minimum actuation in accordance with sensed conditions. Both the duration of the cycle period and the duty cycle of the timer are selectively variable over a wide range through means of timer circuitry employing dual electronic timers (12a and 12b) which are controlled to operate in a complementary manner.

Abstract: A delayed response air conditioning/heating control system provides a detector which responds to a door or window left open, after a predetermined period of time, and which automatically resets to start time (maximum) if the door or window is closed prior to time of response; otherwise it disables the air conditioning heating system. The system has a wired, or anternatively a wireless, sensor with built-in delay and reset, and a receiver or detector with latching relay and manual relay reset control. If the air conditioning/heating system was operating at the time of disablement, a flashing light indicates this.

Abstract: A microprocessor-based perimeter thermal energy control system regulates heating and cooling in the perimeter area of a building in accordance with instantaneous and integrated heat flow measurements and instantaneous temperature deviation measurements. Control of heat pumps and air conditioning units is provided as is automatic switching between heating and cooling. The inherent thermal parameters of the space are inductively determined and used by the system to continually self-adapt to the heat flow properties of the space. The gain of the heat flow based control system is varied automatically as a function of the deviation between the actual space temperature and the desired set point temperature. Morning recovery is initiated and regulated in response to instantaneous and integrated heat flow measurements and inductively determined thermal space parameters and produces a near linear stepwise change in the temperature of the space from night setback to occupancy temperature.

Abstract: A two wire line voltage thermostat has first and second terminals for receiving line voltage power and for connection to a load, a transformer having a current primary winding, a voltage primary winding and a secondary winding, a primary controller connecting the current and voltage primary windings to the terminals, the controller having at least first and second states, the controller in the first state energizing both the current and voltage primary windings and in the second state energizing only the current primary winding, and a temperature responsive circuit connected to the secondary winding for controlling the controller between the first and second states in accordance with sensed temperature such that the load can be energized when the controller is in one of the states and can be deenergized when the controller is in the other of the states.

Abstract: A line voltage setback thermostat retrofitable over existing single width electrical wall outlet boxes. A metal deck plate is attached to the box and extends laterally beyond along the wall. The line load switch is mounted to the deck plate back and extends into the box and is covered with a metal cover. A resistor under the metal cover provides heat for setback mode operation of a bi-metal element which operates the load switch. A timer for energizing the resistor and surface wiring are surface mounted on the extended portion of the deck. A plastic cover is attached to the deck plate from the back and covers the timer and surface wiring and also retains the metal switch cover. An outer bezel with adjustment knobs extending therethrough provides indicia for setting the thermostat and timer.

Abstract: An electronic system and method are disclosed for controlling a measured temperature during a sequence of time intervals, in accordance with a sequence of selected reference temperatures, each corresponding to one of the intervals. The values of the reference temperatures are programmable and changeable by the user. The system and method can be used to establish thermostatic control in conformity with a referenced temperature that varies throughout the day, for example, hour by hour. The system also provides for using different sequences of reference temperatures on different days.

Abstract: The present invention is a technique for thermostatic control of a temperature modifying apparatus such as a heating unit or an air conditioning unit. This technique involves measuring the ambient temperature, generating an error signal based upon the difference between a set point temperature and the measured ambient temperature, operating the temperature modifying apparatus according to the error signal, and adjusting the set point temperature based upon the time history of the error signal. In accordance with the preferred embodiment of the present invention, the temperature modifying apparatus is operated during the next cycle interval with a duty cycle proportional to the error signal at the start of the cycle interval.

Abstract: A thermostat construction for controlling the output effect of a heat exchanger means, a system utilizing such a construction and a method of making such a construction are provided, the thermostat construction having a unit for sensing room temperature that is the result of the output effect, having a set-point unit for selecting a desired room temperature to be provided by the heat exchanger, having a changing unit for changing the effective set-point setting of the set-point unit to change the duty-cycle of the heat exchanger, and having a unit for sensing the current duty-cycle of the heat exchanger and for causing the changing unit to change the effective set-point setting to a different temperature setting thereof as the duty-cycle approaches a peak duty-cycle of the heat exchanger so that the current duty-cycles is reduced.

Abstract: A method for randomly delaying a restart of electrical equipment following an availability of power for energizing the equipment includes the steps of measuring an environmental temperature, e.g., the room where the electrical equipment is located, converting a predetermined fractional portion of the value of the sensed temperature to a number and using the number following an availability of power for energizing the equipment after a time period having a duration restarting the equipment. An apparatus employing this method includes a restart control, a temperature sensor and an equipment start programmer responsive to the temperature sensor and connected to the restart control for producing a restart control energizing signal dependent on a predetermined fractional portion of the value of the sensed temperature.

Abstract: A zone control apparatus for central heating and/or cooling systems having a central fluid heating and/or cooling plant conduits for directing the heated or cooled fluid to the rooms in a house or other building being serviced by the system. The zone control apparatus comprises one or more flow control devices operatively with respective fluid conduits in the central heating and/or cooling system, and a cycle controller for cycling the flow control device or devices between high and low (or no) flow conditions at times strategically selected to correspond to periods of high and low use of the room or rooms with which the flow control devices are respectively associated. Accordingly, the apparatus operates automatically to eliminate unnecessary heating or cooling of individual rooms or zones during cyclical periods of low or no use whereby substantial energy savings and other benefits may be obtained with minimal compromise in comfort.

Abstract: The present invention is an electronic thermostat having correction for the self heating due to the semiconductor switching device used to switch a temperature modifying apparatus on. This invention includes a semiconductor power switching device disposed on an upper portion of a vertically oriented circuit board, a first thermistor disposed on the circuit board at a lower portion thereof remote from the semiconductor power switching device, and a second thermistor disposed on the circuit board at a portion intermediate between the semiconductor power switching device and the first thermistor. A corrected ambient temperature is generated from the temperature indicated by the first thermistor and the difference in indicated temperature between the second thermistor and the first thermistor. The state of the semiconductor power switching device is then controlled based upon the relationship between the corrected temperature and a desired temperature.

Abstract: An electronic thermostat including a stored program of desired temperatures and predetermined maximum and minimum temperatures. The stored program of desired temperatures is selectable as either a program of heating temperatures or a program of cooling temperatures. When in the heating mode controlled by a program of desired heating temperatures, the cooling mode is entered and the air conditioner is energized if the actual temperature exceeds a predetermined temperature. The control temperature in this cooling mode has a predetermined relationship to the programmed temperature in the heating mode. Similarly, if the thermostat is in a cooling mode and the actual temperature falls below another predetermined temperature which is lower than the first predetermined temperature, then the thermostat enters the heating mode and energizes the furnace. The control temperature in this case bears a predetermined relationship to the programmed cooling temperature.

Abstract: Environmental heating/cooling systems are controlled by an interactive microprocessor and have continuous on-time and adaptive cycling modes wherein continuous on-time brings the temperature to a programmed set point and cycling precisely maintains that temperature rather than causing the temperature to oscillate between limits of a dead zone. Minimum pause and on-time intervals of the cycling mode are established in accordance with optimum thermal transfer efficiency and/or equipment limitations. The initial cycle pause interval is a function of the degree transition time (i.e., time required for system to change temperature one degree as measured during continuous on-time mode); the initial cycle on-time interval becomes the established minimum interval. Cycle intervals are modified as necessary to maintain the temperature at the set point with preference given to minimizing the cycle on-time interval.

Abstract: A controller (8) of air conditioning apparatus (18) with a cycle timer (12) for periodically actuating the apparatus (18) irrespective of temperature combined with a thermostat (10) for actuating the apparatus (18) in accordance with sensed temperature and logic circuitry (FIG. 3) for recycling the timer (12) to prevent excessive actuation of the apparatus (18) while ensuring minimum actuation in accordance with sensed conditions. Both the duration of the cycle period and the duty cycle of the timer are selectively variable over a wide range through means of timer circuitry employing dual electronic timers (12a and 12b) which are controlled to operate in a complementary manner.

Abstract: A time variable thermostat comprising, a housing, a clock connected to the housing and having a shaft which is rotatable with time and a disc connected to the shaft for rotation with the shaft. The disc has a plurality of circumferentially spaced slots each extending radially of the disc. A temperature responsive switch has an actuator movable with a change of temperature and the switch includes contacts which are closed and open depending on a position of the actuator. A double control arm is connected to the actuator and is movable with respect to the housing about a center of rotation and a pin slidably mounted to each slot and having a stop portion extending beyond the disc against which the control arm is engageable to influence closing and opening of the contacts. One arm includes a pin engagement portion movable in an arc with movement of the arm about the center of rotation.

Abstract: A central heating control system includes a control panel housing a timer. The timer has three programme sequences for controlling three groups of radiators each group being independently controlled. The control panel also includes switch units which are selectively operable to isolate each radiator. The switch units are triggered by infrared signals transmitted by a portable control unit. The signals may be received directly by the panel or indirectly through spaced windows coupled to the control panel by an optical fibre network. The system provides an exceptionally convenient method of modifying a programmed heating system.

Abstract: The temperature of a serviced area or zone is cost efficiently maintained within a prescribed range by establishing a prescribed fan cycle period, during which period the fan is both operative and non-operative at variable intervals. The temperature of the serviced area is monitored and averaged for each given cycle. The fan run time is then determined by a CPU for the succeeding cycle dependent upon the difference between the average measured temperature and a prescribed balance temperature.

Abstract: An air duct type multizone air conditioning system having air dampers and corresponding thermostats in respective zones under the control of a main controller. The main controller can override desired temperatures selected by the corresponding thermostats in any of the zones and automatically detects the number of the number of zones, the presence of an auxiliary heater, and a heat pump, and the presence of an air damper and corresponding thermostat properly located in the same zone. The main controller also receives information regarding the operating cost of the heat pump and the auxiliary heater to ensure their cost-effective use.

Abstract: A heating system and air conditioning system incorporating a duty cycling control switch are disclosed. The duty cycling control switch for either the furnace or air conditioning system is mounted within the supply side duct of the system, i.e., the hot air duct for a furnace or cold air duct for an air conditioner. The duty cycling control is a bi-metal switch totally enclosed within a case having a metal base whereby the heat from the air in the duct contacts the metal base which is transferred to a bi-metallic element which in turn opens or closes a switch. This makes the switch particularly responsive to gradual changes in the temperature of the output air but prevents the duty cycling switch from responding to rapid fluctuations of air temperature within the duct.

Abstract: An optimum start system for determining the optimum start time of a temperature control system within a building so that energy can be conserved by operating the temperature control system at reduced energy levels during periods of non-occupancy of the building and by starting the temperature control system an amount of lead time prior to the beginning of occupancy of said building wherein the amount of lead time is selected to bring space temperature within the building within a comfort range by the start of occupancy, the optimum start system including a space temperature sensor for sensing space temperature within the building, an outdoor air temperature sensor for sensing outdoor air temperature external to the building, and a controller connected to the space temperature sensor, the outdoor air temperature sensor and the temperature control system for determining the lead time as a function of an accuracy factor based upon the accuracy of a prior lead time and as a function of both outdoor air temperatur

Abstract: A heating control apparatus for exciting the heating element of a kiln or the like. The heating control apparatus includes an interval timer that produces a pulse of electricity having a predetermined duration of time, a fixed timer adapted to open and close an electrical path, and a power relay connected to the heating element and which is adapted to excite the heating element for selected periods of time in response to the operation of the fixed and interval timers.

Abstract: An improved zone control apparatus having mode selectors which allow a user to select any one of a variety of operating modes for individual fluidically actuated flow control devices. The invention further provides for a smoke damper which upon automatic or manual activation causes all of the flow control devices to restrict flow of conditioned fluid through respective ducts or pipes so as to help minimize smoke contamination and the formation of a "chimney" effect. The invention further provides for the utilization of vibration type diaphragm pumps to create a source of pressure and vacuum, a pressure test device to quickly check the pressure in the apparatus, and a flow indicator for determining the location of leaks in the apparatus.

Abstract: A temperature control system for a multiplant environmental unit such as a heat pump with auxiliary heat is disclosed. The control system utilizes a thermostat having a microprocessor and memory that allows for energy savings through setback functions. The setback functions return the temperature control from a setback temperature to a normal comfort temperature along a ramped rate that is modified from day to day. The purpose of this variable ramp is to minimize the operation of the auxliary heat and maximize shell savings (by starting as late as possible). This is basically accomplished by locking the heat pump on in certain cases.

Abstract: A furnace is operated such that the air-fuel ratio and the temperature rise are maintained constant so that the efficiency remains constant over the range of operation.

Abstract: A temperature offset control system having a central control station wherein temperature limits can be set for the desired amount of offset for both heating and air conditioning systems. A centrally located temperature sensor reads the ambient temperature within the house. A comparator compares this sensed temperature with the offset temperatures and produces a control signal responsive to the comparison. The control signal is then transmitted through the existing house wiring to receivers associated with each heating and/or air conditioning unit, whereby the heating unit will receive the control signal and will respond when that control signal resulted from a sensed temperature crossing the lower end of the temperature limits set at the central control station to thereby turn on and off.

Abstract: For use in a radiator space heating system, a thermostatic valve for controlling the flow of heating agent to the radiator is provided with a bypass and at least two auxiliary valves. One auxiliary valve is disposed in the bypass and controlled by the thermostat. The other auxiliary valve is timer-controlled and disposed in series with the thermostatic valve. When temperature reduction is desired, such as during nighttime operation, the timer-controlled auxiliary valve closes, but the bypass auxiliary valve can open when the set-back temperature is reached.

Abstract: In an operation mode controller wherein a sensor for sensing a quantity of a variable to be controlled is provided and a plurality of operation modes are changed from one to another in accordance with the sensed quantity to set any desired mode, the controller includes; a memory for setting and storing change conditions of the plural operation modes; apparatus preset for determining a set of threshold values for each of the plurality of operation modes, selecting apparatus for choosing the set of threshold values corresponding to a preset operation mode; an switching device for changing the operation modes in accordance with the change conditions when the sensed quantity of the variable that is to be controlled exceeds the chosen set of threshold values corresponding to the preset operation mode.

Abstract: A microcomputer based clock operated thermostat is operated to adjust a ramprate of a setpoint temperature upon a setpoint change. The microcomputer in the thermostat is capable of determining the amount of overshoot or undershoot between the air temperature and the desired setpoint temperature by utilizing a sensor temperature of the thermostat, and computing a variation in the pickup ramprate to bring the overshoot within an acceptable level.

Abstract: A control method uses a room thermostat for generating an output signal representative of an energy demand and an energy source which can be cyclically switched on and off and includes the steps of determining within a switching cycle of the energy source the actual switch on period, comparing the actual switch on period with an adjustable desired switch on period within the cycle to produce a control signal representative of the energy demand and controlling the energy source in accordance with the control signal.

Abstract: An electronic programmable thermostat for the control of a furnace or air conditioner is useful as a replacement for a conventional non-programmable thermostat and mounts on the non-programmable thermostat's wall plate to achieve support, electrical connection with the load and power supply, and the use of certain manual controls supported on the wall plate. The programmable thermostat employs a circular printed circuit board supporting its electronic components, which include a potentiometer for operator adjustment of desired temperature. A flat circular knob supported on the potentiometer shaft and an annular bezel cover the thermostat and allow access to the manual controls supported on the wall plate. The potentiometer and a temperature sensing thermistor control the frequency of a pulse generator which provides input to a counter.

Abstract: This invention regards a control arrangement for heating systems for localities. Heat is given off continuously and the control may take place by changing the temperature (t.sub.w) of the heat carrier medium, thereby sensing the interior temperature (t.sub.i) in the locality and the outdoor temperature (t.sub.u) outside of the locality. A function controller (33) is fed with a known functional relation between the outdoor temperature (t.sub.u) and the temperature (t.sub.w) of the heat carrier medium. The difference between the existing inside temperature (t.sub.i) and the desired inside temperature (t.sub.r) is stated, and the functional relation between the outdoor temperature (t.sub.u) and the temperature of the heat transfer medium (t.sub.w) is divided up into a number of zones, limited from each other dependent upon the difference between the desired inside temperature (t.sub.r) and the inside temperature proper (t.sub.i).

Abstract: A thermostat for generating control signals for a furnace, air conditioner, or the like, employs a constant frequency, periodically alternating electrical source and an oscillator incorporating an element having a thermal-sensitive electrical characteristic so the oscillator frequency varies as a function of the ambient temperature. A comparator receives the two outputs and generates a signal representative of the ambient temperature. The stable output is also provided to dividing circuits to generate a signal representative of the time that is used to interrogate a digtal memory storing a desired temperature-time period, such as a week or month. The ambient temperature signal is compared with the desired temperature signal to generate an output control signals. A display provides a read-out of time and temperature and is used along with a keyboard or the like in programming the memory.