Abstract: A control system for an automatic vending machine functions to operate a refrigerator, for example, continuously during a first mode after a power interruption or restocking occurs, and then switches to a non-continuous mode which may be controlled thermostaticly or by cyclicly switching the refrigerator on and off at selected intervals of time. Also, a timer may be set to turn off the refrigerator and other accessories such as lights altogether during selected times of day.

Abstract: A thermostat used to control a temperature conditioning system to heat or cool a comfort zone to a heating setpoint and a cooling setpoint. The thermostat is microcomputer based and includes both a digital keypad and display for setpoint entry by an operator. Control means in the thermostat automatically insure that at least a predetermined minimum offset is maintained between the heating and cooling setpoints stored in memory, and the control means are further operative to adjust one of the setpoints if the operator enters a value for the other setpoint that is in error.

Abstract: A selected segment heating system including: means for heating a fluid; conduit means for conducting the fluid from the outlet to the return inlet of the means for heating through a plurality of areas; means, interconnected with the conduit, for moving the fluid through the conduit; gauging means for operating the means for moving to move a segment of the heated fluid in the conduit as far as the return point of the farthest area to be heated; and delay means for suspending operation of the means for moving for permitting a predetermined heat exchange to occur between the heating fluid and the air in the area to be heated.

Abstract: An electronically controlled programmable wall thermostat provides better control of comfort temperature and permits improved energy-saving temperature setback at selected intervals of the day or night in multistage heating and cooling systems and is particularly useful in achieving improved energy savings for systems having heat pump means in the main temperature conditioning stage of the system. The thermostat includes clock means, temperature sensing means, means for displaying desired parameters of time and temperature, data entry and storage means for programming the thermostat to maintain desired temperatures during selected time intervals, and a processing means with a memory incorporating a permanently stored program instruction sequence which responds to signals from the temperature sensing means for controlling the heating and cooling systems in accordance with the time-temperature sequence programmed into the thermostat by the user.

Abstract: A preheating process and apparatus for determination and utilization of a quantity of preheating energy so as to automatically achieve a desired temperature at a given location prior to a predetermined period of usage, especially for preheating an automotive vehicle. In accordance with the process, the respective preheating times required to achieve a desired temperature for various possible actual conditions at the location of usage are determined and stored, at a predetermined point of time prior to the usage commencement time, the correct preheating time is determined from the stored preheating times based upon actual temperature conditions and application of heat to the location is automatically commenced at a time prior to the usage commencement time that corresponds to the difference between the usage commencement time and the correct preheating time determined previously.

Abstract: A line voltage thermostat is replaced by a low voltage clock-controlled thermostat without the need to install a switching relay in the basement of a house. Instead, a transformer-controller adapter unit is mounted within an electrical outlet box at which the thermostat is mounted. The adapter unit can be wired to the hot and the load wires at the outlet box without requiring any connection to a neutral wire.

Abstract: A microcomputer controlled digital thermostat is powered by supply voltage derived from a large capacitance (e.g. 3.3 farad) voltage supply capacitor. The voltage supply capacitor is normally charged by an AC voltage which is derived from the furnace and which is rectified by a full wave rectifier bridge. Time and temperature data are stored in read/write RAM storage. The microcomputer controls operation of the thermostat as a function of sensed temperature and the stored time and temperature data. A voltage sensing circuit senses the supply voltage from the voltage supply capacitor and prevents the supply voltage from being provided to the microcomputer and other portions of the thermostat control circuitry when a prolonged interruption of AC power causes the supply voltage to decrease to a predetermined value. The supply voltage continues to be supplied to the read/write RAM to retain the stored time and temperature data.

Abstract: A programmable thermostat has an associated electronic control circuit. There is a coding matrix and a multiplicity of programs which may be selected via the matrix. The user may select two set points to cause two programs to work in an interrelated manner, one for high heat requirements and one for low heat requirements. A clock may call in the two programs in any pre-selected manner such as: high heat in the morning, low heat as soon as the house has heated, high heat in the evening when the outside temperature falls, and low heat at night.

Abstract: The apparatus includes a first triac having terminals to which the control wire of a heater gas inlet valve solenoid or other heating element is connected and the apparatus further includes a second triac to which the control wire of an air conditioner compressor or other cooling element is connected. The triacs are actuated by respective optical coupling devices. One or the other of the optical coupling devices is selected by a switch to indicate whether the heater or air conditioner mode is selected. Whichever optical coupling device, and thus whichever mode, is selected, a timer circuit provides a selectable timing signal to cause the selected optical coupling device to periodically actuate or deactuate the associated triac to thereby activate or deactivate the solenoid or compressor (or other element) associated with the triac.

Abstract: A system for the control of a load such as a heating or cooling plant in response to changes in an external parameter, specifically ambient temperature, comprises a loop circuit with two conductors connected at an input end across a power supply and at an output end across a switching network, the load being inserted in one of these conductors. A high-impedance voltage multiplier connected across these conductors downstream of the load, in parallel with the switching network, supplies the necessary operating voltage to a parameter sensor such as a thermostat even when that network is in a low-impedance state so as to draw a maximum load current. The switching network may include a voltage clamp provided with a source of reference potential, e.g. a primary battery, which upon failure of the normal power supply can act as a standby supply insuring continued operation of a timer serving for a periodic switchover between different temperature thresholds for the thermostat.

Abstract: In a climatization system the influence of the outside air temperature is fed to a comparator which is also fed with a comparation voltage, successively variable during the starting time and obtained from a pulse generator of variable pulse-time-relation, and the climatization process is started at a balance point between the two voltages.

Abstract: A thermostat with a single control to establish the quantity of set back during heating and set up during cooling.

Abstract: A controller for a space heating system employs a room thermostat and a furnace thermostat responsive to the temperature of a room and a furnace, respectively, for firing the furnace. This controller has a power input terminal for receiving primary electrical power. The controller also has a timed switch and a switching means. The timed switch can connect and disconnect the power input terminal to the furnace. Disconnecting this terminal disables the furnace thermostat. The switching means responds to the room thermostat and can connect and disconnect the power input terminal to the furnace.

Abstract: An electric thermostat operative to be connected to a furnace or other temperature modifying apparatus to control its state of operation includes means for generating a desired temperature set-point signal and means for measuring ambient temperature at the thermostat. When the ambient temperature falls sufficiently below this set-point, the furnace is energized until the ambient temperature rises to a stored temperature level, also below the set-point. The system then monitors the peak ambient temperature reached during the following temperature overshoot resulting from the inertia of the furnace. The temperature differential between this limiting temperature obtained and the set-point is then added to the stored temperature value if the system did not obtain the set point temperature or substracted from the stored temperature value if the system exceeded the set-point value.

Abstract: An energy saving thermostat having a selected offset temperature time period previously programmed with means to shift the time period ahead or backward.

Abstract: A heating system control device is responsive to the drop in outside temperature to below a predetermined weatherhead set point for turning on a heating system to be controlled. Upon the establishment of the heat in the heating system, a defined heating cycle is carried out consisting of a heat-on portion and a heat-off portion having a duty cycle dependent on the outside temperature. The heating cycle does not start until there is an establishment of heat in the heating system. The start of consecutive heating cycles is delayed in response to a check for heat loss in the system. When heat is established and the set point has not been reached, as noted by the means for determining the establishment of heat in the heating system, the next cycle will be delayed to save energy.

Abstract: An optimal start programmer for starting a heating or cooling cycle for an intermittently occupied building includes a digital counter which is enabled at the start of a pre-occupancy "search" period and accumulates counts from a timing source. A digital to analog converter is responsive to the cumulative output count of the counter circuit for generating a staircase or ramp signal which provides a time-variable set point signal during the search period. In the heating mode, the reference signal to the digital to analog converter is a signal representative of the outdoor ambient temperature; and in the cooling mode the reference is a constant signal. The operating mode of the system during the search period is determined by a mode selection circuit which is responsive to a heating mass signal and a cooling mass signal to automatically determine whether the system is to operate in a heating mode, a cooling mode or an inhibit mode in which neither the boilers nor the chillers are actuated.

Abstract: An electronic digital programmable wall thermostat system for controlling heating and cooling systems supplying an indoor area or space. The thermostat includes a digital clock, a display for displaying desired parameters of time and temperature and a data entry keyboard for programming the thermostat to maintain desired temperatures during selected time intervals. The heart of the system is a digital processor with memory, which responds to signals from a temperature sensing means which includes an analog to digital converter for controlling the heating and cooling systems in accordance with the sequence programmed therein. An output from the processor gates a triac on and off which in turn activates or deactivates the heating and cooling systems. In a preferred embodiment, a single chip digital processor is used to control the operation of the thermostat system, the keyboard, display and temperature sensing means being selectively scanned from output terminals of the digital processor.

Abstract: A programmable thermostatic control device for controlling the temperature within a preselected zone of an enclosed environment. The device can be readily installed and utilizes an interface unit through which the heating, ventilation and cooling system of a building and/or residence are connected to the device outputs. An operator is guided through the programming of the device by cueing or prompting lights which sequentially indicate the information to be entered on the keypad. The device is processor-based and controls the heating and cooling systems to maintain a preselected temperature range, and to establish a preselected temperature within the controlled zone at a predetermined time. The temperature within the control zone is established and/or maintained with maximum efficiency by controlling the stage and duration of energization of the heating and air conditioning units.

Abstract: A time controlled thermostat provides the setting up or setting down of space temperature during certain selected time periods depending on whether it is controlling heating or cooling apparatus as selected by a changeover lever. The normal control temperature as determined by a temperature responsive switch is set by a first selection lever and the setback temperature set by a second selection lever, during heating operation, as selected by the changeover lever the normal temperature is selected by the second selection lever and the setup temperature by the first selection lever during cooling operation as selected by the changeover lever. Limit stops are provided for limiting the position of the first lever during heating to a maximum temperature and the position of the second lever during cooling for a minimum temperature.

Abstract: An electronic system and method including a user programmable thermostat for measuring temperature at the situs of the measurement unit and for signaling and controlling a remotely located energy controller which is connected to the programmable thermostat. By utilizing a multiplexed signal communication channel between the programmable thermostat and the energy controller, the energy controller activates preselected energy using units which may, for example, include a furnace and air conditioning units for controlling the temperature at the measurement unit situs and a power shedder unit for shedding energy usage to conserve energy all in accordance with a user provided program.

Abstract: An integrated, microprocessor-based primary control system for a building heating system. The control system includes in one unit a microprocessor and associated circuitry for (1) establishing the high limit of heat exchanger operation, (2) establishing the low-limit of heat exchanger operation for systems having a summer/winter coil, (3) modulating heat exchanger temperature as a function of outdoor temperature, (4) detecting alarm conditions, providing audio-visual signals while locking out heat exchanger operation in response thereto, and (5) providing an override time period for domestic hot water production in systems having a summer/winter coil.

Abstract: A microprocessor based control for a heat pump system providing at least two setback temperature settings individually selected by the system user to be effective during different time periods of the day, also individually selectable by the user. In the event of conflicting setback temperature settings during an overlap in the selected time periods, the microprocessor is programmed to implement the setback temperature that provides the most energy efficient operation of the system. Additionally, the microprocessor automatically assures that any setback temperature settings are at least a minimum temperature differential away from the normal temperature setting in the more energy efficient direction. This override provision is effective whether the invalid setback temperature settings are initially inserted by the user or are the result of a subsequent change in the normal temperature setting.

Abstract: Apparatus is provided for a wall mounted thermostat to accept and convert manually generated instructions to binary encoded electronic impulses to control ambient air conditions in the environment in which the thermostat is located. The parameters of operation include a building heating control which reduces the desired ambient temperature at night, beginning at a prescribed time and returning to a higher daytime level at a different prescribed time. The system may also adjust desired temperature depending upon humidity conditions and alter the timing of heating and air conditioning control by predicting when a desired temperature will be reached in order to avoid overshoot. The system includes a liquid crystal or light emitting diode display and communicates with a power source and with heating and air conditioning switches such as relays or contactors.

Abstract: A kiln temperature controller is provided comprising a circuit for providing a first signal representative of a selectable kiln temperature and a temperature detection circuit for providing a second signal representative of the detected kiln temperature. The temperature detection circuit comprises first and second thermocouples disposed in the kiln and in the temperature controller, respectively. The first and second thermocouples are coupled in series and in opposite polarity. A solid state temperature sensing circuit is provided in the kiln temperature controller, the temperature sensing circuit being coupled in series with the first and second thermocouples and providing an output signal having a polarity opposite that of the second thermocouple to nullify ambient temperature variations of the kiln temperature controller.

Abstract: A system for alternately activating and deactivating a load comprises a high-resistance d-c circuit branch connected across a power supply downstream of a load-operating impedance, this branch including a voltage limiter and a voltage multiplier in series with each other and with a switching stage responsive to commands from a timer and/or a parameter sensor such as a thermostat. The junction of the voltage limiter and the voltage multiplier is connected to one input of a differential amplifier whose other input is energized with either of two potentials, respectively higher and lower than that of the junction, by the switching stage.

Abstract: The disclosure relates to a system for providing central control for appliances connected to the electrical power distribution network of a building. In one embodiment the systems may be used for conserving energy used by temperature regulating units, such as space heaters and air conditioning units, by overriding local thermostatic control therefor, to prevent operation of the units during preselected time periods. The system includes a transmitter for transmitting control pulses over the electrical power distribution network of the building. Receivers, connected to the local thermostatic controls, detect the pulses and shut off the electrical power provided to the thermostatic controls responsive to the detected pulses to thereby prevent operation of the associated temperature regulating units. In one embodiment the control pulse transmitter operates responsively to signals transmitted over a coaxial cable such as employed in cable television systems.

Abstract: An adapter converts a conventional thermostat to effectively approximate a setback thermostat. A conventional thermostat includes a mercury switch which is actuated by a bi-metallic coil. The attachment is interposed between the thermostat and its standard base plate and operates to tilt the entire thermostat under control of the timing mechanism to thereby effectively change the setpoint of the thermostat.

Abstract: A temperature control system for a building has a temperature responsive means or thermostat in the space for controlling a temperature conditioning apparatus furnishing temperature condition medium to the space. A time control apparatus provides for a reduction or deviation of the space temperature during certain time periods for the purpose of energy conservation and/or comfort. The space temperature is restored to the normal temperature by a pickup operation. The magnitude of temperature setback initially selected or to be maintained during the setback time period is automatically adjusted by responding to the actual building heat load, so as to keep the time and heating capacity needed to restore the space to the normal temperature within certain limits.

Abstract: A timed rate control applies to a system having a device 12 for varying a medium 14, a sensor 13 for detecting variation in the medium, and a pneumatic line 11 for varying the device 12 in response to the sensor. This includes many pneumatic control systems that the invention can effectively stabilize to reduce fluctuation and improve operating accuracy and efficiency. The pneumatic line is opened and closed by a solenoid valve 17, and a setable timer 18 variably determines both closed and open intervals for the solenoid valve. The timer is connected to the solenoid valve to control alternate operation between the closed and open intervals while the system operates. This limits each adjustment to a brief duration separated by inactive periods that allow the system to stabilize.

Abstract: In control of an air conditioner, a first deviation corresponding to the rate of change of the actual air temperature in a compartment is detected such that an expected value of the actual air temperature to be obtained as a stable value under the control of the air conditioner is detected to detect a second deviation in relation to a desired temperature. When the second deviation is larger than a predetermined value, a third deviation is also detected in relation to the second deviation to adjust the temperature of air flow supplied from the air conditioner and to eliminate undesired temperature deviation caused by fluctuation of the heat load in the compartment.

Abstract: In control of an air conditioner, the rate of change of the actual temperature of air in a compartment is detected to detect a deviation between the actual temperature of air and a desired temperature of air. When the detected deviation is larger than a predetermined value, another deviation is also detected to adjust the temperature of air flow supplied from the air conditioner and to eliminate undesired temperature deviation caused by fluctuation of the heat load in the compartment.

Abstract: A method and apparatus for the control of power consumption in individual space-conditioning loads fed by an electric power network utilizes a commandable, programmable temperature control device which gradually, substantially continually changes the control setpoint in response to an external signal to reduce power consumption such that temperature changes go relatively unnoticed by the occupants. A radio receiver or the like is utilized to receive a signal from the power utility company and, in response to the signal, the setpoint function of the thermostat associated with the load becomes an electronically simulated function in accordance with the invention and the user-control setpoint is removed from the control loop. The effective load shedding is also greatly enhanced by the provision of an integral reset function in addition to the conventional proportional control within the temperature control system.

Abstract: A low dissipation two wire thermostat for connection to an alternating current source and a load to be controlled wherein, on alternate half cycles of the source, a rechargeable DC source, is recharged and, on the opposite half cycles, a capacitor is charged to control a comparator's output so as to cause a switching action that prevents high power dissipation in the thermostat for both the "on" and "off" conditions.

Abstract: The present invention discloses an energy conserving thermostat for controlling the supply of energy within a commercial or industrial building during unoccupied periods and for providing additional energy to the building when required. The present system includes: a night thermostat for establishing a low temperature necessary for the maintenance of the building during a non-occupancy period; a seven-day timer clock calibrated for every hour of each day, with manually adjustable pins on the clock settable for a time interval within each day during which a normal comfort condition is required; mechanical switch means responsive to such pins of the clock; electrical switch means including a relay energized by operation of the mechanical switch; and an override timer including a time meter and a manually operable switch to increase the time setting for any day wherein an unusual supply of energy is required within a zone of the building. The extra time of such setting is recorded on a time clock meter.

Abstract: An improvement for a thermostatic control system of the type in which a heater having two electrical terminals is turned on when a conductive path is established between the two terminals and is turned off when the conductive path is opened, and in which first thermostat is used to open and close the conductive path. The improvement is a series combination of a remotely controlled electrical switch and a second thermostat, the series combination being connected to the heater terminals in parallel with the first thermostat. The second thermostat is normally set to a temperature greater than the temperature to which the first thermostat is set. The first thermostat controls the heater to standby temperature until a signal is applied to the remotely controlled electrical switch. Upon receipt of a predetermined signal, control is passed to the second thermostat which thereafter maintains a higher temperature.

Abstract: An electronic multiple-setback thermostat for residential and commercial use includes an internal clock having a week-long cycle. The thermostat is programmed by the operator, usually manually actuable input devices, to control the furnace/air conditioning system to achieve a schedule of temperatures over the weekly period by simply inputting the temperature desired to be attained at the time of entry. Each temperature entry may be programmed to reoccur on a daily basis or to modify the program on a once-a-week basis. The thermostat employs an internal clock which controls memory addresses so that each memory location is representative of a short time period during the weekly cycle. A desired temperature signal is entered in a memory location determined by the clock state at the time of entry and is read out to the control system each time that time state reoccurs.

Abstract: A thermostat control for a heat pump thermostat allows the heat pump to change its temperature setting automatically and systematically minimizing the use of resistive heating with the heat pump as a backup to accomplish the temperature change. A cam having a smooth and gradually varying cam surface changes the position of the thermostat control on the heat pump thermostat to move the control through a desired temperature differential at a rate less than the rate at which resistive heating will be used as a backup to aid the change unless the heat pump is operating at full capacity.

Abstract: A power supply circuit for a temperature control system is switchable between a low input impedance mode and a high input impedance mode, so that a temperature control system having this power supply can directly replace a bimetallic switch and the power supply will look to the rest of the system like the replaced bimetallic switch.

Abstract: Controls for lights in a room with a swinging door for entry into and exit from the room, providing a main circuit for the lights, including a main switch normally closed to close the circuit, a time delay relay adapted, when energized, to hold the main switch in closed position for a preset time period and then shift the same to its open position, and a relay circuit, including a featured master switch of push button type having its push button in the form of a latch bolt, with this switch being mounted on the door so that the push button may serve as a latch bolt by being projectible into and retractible from an associated catch on the door jamb inside the room, with the master switch being closed to close the relay circuit when the latch bolt is retracted, and being open to open the relay circuit when the latch bolt is projected.

Abstract: A multistage thermostat is operated by comparing the thermostat setpoint and the sensed temperature over a continuous series of discrete intervals of time. When a sudden change occurs between the sensed temperature and the setpoint, the magnitude of this change is evaluated in a comparator means and if necessary the system is reset to compensate for the change to operate in the most efficient manner. The adjustment of a constant supplied to an integrating circuit that forms part of a signal processing circuit means for the thermostat means provides the adjustment when the predetermined level of change is made.

Abstract: A control arrangement is provided for a heating system having heat outlets each controlled by a solenoid valve (210). Each heat outlet is connected to a pair of thermostatic switches (411, 413) operative at different temperatures. A time switch included in a central control means (108) is operative to selectively energize a pair of bus-bars (530, 532) at different times, thereby to provide common output signals for actuating the heat outlets via different thermostatic switches (411, 413) at different times to provide different heat outputs during different parts of a predetermined period of time (e.g. 24 hours). The central control means (108) includes a plurality of manual switches (540) each connecting the time switch output bus-bars (530, 532) to the thermostatic switches (411, 413) of an associated one of the heat outlets to manually set the heat output of the heat outlet.

Abstract: The invention relates to an electric temperature setback device which is placed in proximate relation to a conventional thermostat and is operatively controlled by a timing device for providing local warmth to the thermostat at pre-determined times and for pre-determined intervals. The setback device includes spades with integral female lamp connectors for arraying a plurality of incandescent lamps in series across an electrical circuit. By so doing, the voltage to each lamp is proportionally reduced, decreasing the filament temperature of each lamp and thereby increasing the amount of heat energy produced proportional to the amount of light energy produced.

Abstract: Apparatus is provided for a wall mounted thermostat to accept and convert manually generated instructions to binary encoded electronic impulses to control ambient air conditions in the environment in which the thermostat is located. The parameters of operation include a building heating control which reduces the desired ambient temperature at night, beginning at a prescribed time and returning to a higher daytime level at a different prescribed time. The system may also adjust desired temperature depending upon humidity conditions and alter the timing of heating and air conditioning control by predicting when a desired temperature will be reached in order to avoid overshoot. The system includes a liquid crystal or light emitting diode display and communicates with a power source and with heating and air conditioning switches such as relays or contactors.

Abstract: An energy saving thermostat adapted to be connected to a remote temperature conditioning apparatus for controlling the temperature of air in a space maintains a first temperature during a first time period and a second energy saving temperature during other time periods of the day. The thermostat has a visual indicating means so that when a manually settable switch is pushed, a time interval counter means is energized for indicating and storing a series of pulses each indicative of an hour of setback time into a storage means. The thermostat also has a review button for reviewing the stored time by pulsing the visual indicating means for the number of hours of the time period energy saving temperature.

Abstract: A microcomputer controlled digital thermostat has separate, independent registers for storing heating control information and cooling control information. On a periodic basis, the microcomputer determines whether the furnace should be turned on, based upon a temperature signal indicative of room temperature, a time-of-day value indicative of the present time of day, and the stored heating control information. If the furnace is already off and the microcomputer determines that it should remain off, the microcomputer then determines whether air conditioning is needed, based upon the temperature signal, the time-of-day value, and the stored cooling control information.

Abstract: A temperature control and monitoring device for a heater of a building having a plurality of separate areas comprising, a motor having a shaft rotatable at constant speed, a disc connected to the shaft having a pluraliity of radially extending slots, a pin slidably mounted in each of the slots, a temperature indicator having a shaft rotatable by a change in temperature and responsive to a temperature sensed by temperature sensing members, a plurality of temperature sensing members, each in one of the separate areas, for sensing the temperature in each of the areas respectively connected to the temperature indicator and a selector device connected between each of the temperature sensing members and the temperature indicator for selectively connecting one of the sensing members at a time for a predetermined time period and at predetermined intervals to the temperature indicator.

Abstract: A thermostat range control device for maintaining a thermostat temperature that has a substantially constant difference with respect to room temperature, and which allows the thermostat to respond quickly and accurately to changes in room temperature. The device includes a detachable enclosure for substantially enclosing the thermostat, a distributed heater within the enclosure having multiple openings therein for providing generally uniform heat within the enclosure, means for allowing room temperature air to enter the enclosure at a level below the thermostat, and means for allowing heated air within the enclosure to exit from the enclosure at a level above the thermostat, in a manner such that substantially only heated air passes the thermostat.

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 digital memory storing a desired temperature-time program for the thermostat for a repetitive period, such as a week or month. The ambient temperature signal is compared with the desired temperature signal to generate an output conrol signal. A display provides a read-out of time and temperature and is used along with keyboard or the like in programming the memory.

Abstract: A control system (12) for environmental units (10) such as air conditioners or heaters is disclosed.A control panel (14) accommodates a control module (16) associated with each unit. First and second temperature reference circuits (58 and 60) are located in each module for setting first and second reference temperatures. A circuit (64) responsive to a clock (62) selects the first reference temperature during a first predetermined time period and the second reference temperature during a second predetermined time period. Each unit is thermostatically controlled according to the selected reference temperature.