Abstract: A system and method for automatically controlling cabin air temperature T.sub.CBN in an aircraft having a cabin and a mixed air delivery system. The mixed air delivery system provides a flow of mixed air having an actual mixed air temperature into the cabin. The mixed air delivery system comprises a hot bleed air sub-system for providing a flow of hot bleed air, a cool air sub-system for providing a flow of cool air, and an ambient air sub-system for providing a flow of ambient air. The method comprises the steps of defining a selected cabin air temperature T.sub.CBN SEL, and then controlling the flow of hot bleed air, the flow of cool air, and the flow of ambient air such that the mixed air temperature is driven toward a target mixed air temperature defined as k(T.sub.CBN SEL -T.sub.CBN)+T.sub.CBN SEL, wherein k is a gain factor.

Abstract: A system is disclosed for conveying network identifications of HVAC master controllers within an HVAC communication network to their respective zone controllers. Each master controller addresses and transmits its network identification to zone controllers within a predefined range of network addresses unless it encounters another master controller. The network identifications are used by the zone controllers to identify messages from their respective master controllers.

Abstract: A space comfort system controls humidity in a space by applying heat to air recirculated to the space when the humidity is excessive and cooling of the air is not required. In a preferred embodiment, the call for heat occurs from the time the humidity increases to a level above a differential band within which is the humidity set point until humidity falls to below the differential band. Heat is applied to the air only when there is no demand for cooling of the air.

Abstract: A climate control system having a control means for receiving cool call signals and heat call signals from a plurality of thermostats. The control means blocking action by conflicting calls when the system is in a heat mode or cool mode. The system also preventing a single zone from dominating the mode of the control system and allow a conflicting call to be received after the control system has been in a particular mode for a maximum period or the conflicting call has been waiting for longer than a maximum period. The control system also properly adjusting the dampers to allow purging of ducts after heating and cooling mode and to allow zone or system ventilation upon request.

Abstract: This document describes an energy management system in which microprocessor based thermostats are used to control individual room temperatures in a multiple room building in accordance with the known occupancy status of the room. The occupancy status information, as well as other control parameters, are transmitted to the thermostats from a central computer program. The control of a heating and cooling appliances is performed by an algorithm running on the electronic thermostat, which performs this function in accordance with these downloaded parameters. The system, allows room occupants to control the temperature of an occupied room within preset limits, automatically limits energy usage in unoccupied rooms, and provides additional facilities for energy management and general building management.

Abstract: There is disclosed herein a machine for performing nucleic acid amplification under computer control. The machine utilizes any one of a number of heating and cooling systems under control of a host computer which directs the heating and cooling systems to heat and cool a reaction-chamber-containing heat exchanger at appropriate times in the process. The reaction chambers are pre-loaded with the nucleic acid(s) to be amplified, a thermostable enzyme to catalyze polymerization, specific oligonucleotide primers, and four different nucleotide triphosphates. Also disclosed is the process for the amplification chain reaction implemented by the machine, which utilizes a thermostable enzyme.

Abstract: An electronic thermostat having high and low voltage control capability and varied functional capabilities. The thermostat is particularly suited for use with fan coil heating and cooling units. Specifically the thermostat uses relays to actuate external devices such as heating and cooling equipment, fans and dampers. The use of relays permits control voltages for these external devices to be different (e.g. 24 VAC, 208-230 VAC or 277 VAC).

Abstract: The difference between the zone temperature and the scheduled setpoint, or .DELTA.t, is the basic data from each zone. Communication between the air handler control and the air terminal control is provided via the air system control so that the system is temperature, rather than pressure, responsive.

Abstract: A temperature control system for a building structure such as a household is divided into a plurality of zones. A controller acts between temperature sensing devices in each of the zones and an adjustable thermostat which allows the desired temperature in the building structure to be selected. The controller allows individual zones to be selected to receive conditioned air and allows one of the selected zones to be designated as a control zone. A heating or cooling decision for the temperature control system for all of the selected zones is made based on the difference between the thermostat setting and the output of the temperature sensing device in the control zone. The control zone can be changed manually to the next available selected zone. Different visual indications are given for the control zone and the selected zones. Zones with faulty temperature sensing devices cannot be control zones or selected zones.

Abstract: A thermostat capable of accommodating primary and secondary loads is taught. Preferably a hydronic valve actuator is the primary load and a fan coil of variable speed is the secondary load. Temperature sensing is electronic and both heating and cooling as well as multiple fan modes are accommodated.

Abstract: An improved micro-computer operated control device for an air conditioning system which is specially characterized in that the air volume produced by the air conditioning system can be automatically varied in correspondence to the temperature of a closed space is disclosed. A number of temperature sensing components are constantly monitored by a processing unit of the temperature data thereof which are compared with predefined temperatures provided by a function setting unit; the results of the comparisons are transformed into corresponding signals which are then transmitted to an output control unit; and a voltage regulator is actuated in accordance to the signals to adjust the voltage of the motor of a fan supplied by a power source so that the operation speed of the fan can be constantly varied in correspondence to the external temperatures, resulting in the air volume delivered by the fan varied accordingly.

Abstract: A thermostat is disclosed having a bimetallic strip actuating a single pole, double throw switch, one throw to sense temperatures below the lower limit of a set point range and the other throw to sense temperatures above the upper limit of the set point range. In typical applications one throw for actuating heating and the other throw for actuating cooling. The bimetallic strip is provided with typically a cantilever support at one end and extends between dimensional spaced double throw contacts at the opposite end. Spacing of the contacts determines magnitude of the set point range. An intermediate beam type support is provided between the cantilever support and double throw contacts. This beam support consists of an adjustment screw acting on one side of the bimetallic strip and a spring directly opposing the adjustment screw.

Abstract: A system and method for controlling the operation of a Heating, Ventilation and Air Conditioning (HVAC) system for use primarily in a building having more than two controllable temperature zones. Rooms having a priority for heating or cooling are identified as such in a controller. The controller sums Temperature Differences from all controlled spaces and causes the HVAC system to operate in a first mode (e.g. heating) if the sum has a first relationship to a preselected value (e.g. sum>=0) and causes the HVAC system to operate in a second mode (e.g. cooling) otherwise.

Abstract: A control system for a fan coil of an air-conditioner having a fan for heat exchange, and a coil unit through which cool or hot water circulates to cool or heat the room by heat exchange with the room air, wherein an automatic change is carried out between a cooling operation and a heating operation, referring to the temperature of distributed cool or hot water detected by a water temperature sensor, and a room temperature is controlled by opening or closing an electromagnetic valve disposed in a water distribution system, referring to a room temperature detected by a room temperature sensor. When the system is turned on from its inoperative state, the electromagnetic valve is forcibly opened for a predetermined period of time for the control system for a fan coil to sufficiently detect the temperature of cool or hot water, and to prevent an erroneous change of operation.

Abstract: An air conditioner for a building having a plurality of rooms has heating and cooling modes. A duct system connects the air conditioner to the individual rooms. A plurality of control valves are coupled to the duct mens for individually controlling the flow of air to each room. A first circuit is provided for generating a heating or cooling request signal from each room. A second circuit is provided for summing the number of the heating and cooling requests and providing summation signals of each. A third circuit is provided for sensing the greater of the two summation signals and activating the air conditioners to the mode corresponding to the greater of the summation signals. A fourth circuit is provided for activating the control valves controlling flow to the rooms which do not provide a part of the greater summation signal to the closed position.

Abstract: A single bimetal automatic changeover thermostat has heating, cooling and changeover switches mounted to the bimetal. A single control point adjustment lever for rotating the bimetal has separate shaped heat and cool set point indicators which are movable along a temperature scale.

Abstract: A control device for energizing and de-energizing temperature changing devices having a primary control unit and a secondary control unit is provided. The primary control unit includes means for sensing an external temperature and generating a signal (Ps) having a value proportional to the external temperature, means for generating a set point signal (Psp), representing one end of a predetermined primary temperature range, and means for generating a differential signal (Pd), representing the difference between signal Psp and the other end of the predetermined primary temperature range are included. Additionally, the primary unit includes a primary switch for connecting power to at least one temperature changing device which is opened and closed in response to combinations of signals Ps, Psp and Pd.

Abstract: An air conditioning for a room of a high-rise building, for example, is carried out in consideration of the difference in temperatures in a central interior zone and a circumferential perimeter zone of the room changeably to heating and cooling in accordance with an operation mode and a room temperature set point. In the actual air conditioning, a room temperature in the interior zone is first set and an actual room temperature in the perimeter zone is detected. The set room temperature in the interior zone is compared with the detected room temperature in the perimeter zone to thereby select an operation mode (heating or cooling) of air conditioning of the perimeter zone by an operation mode selecting unit.

Abstract: The programmable thermostat includes a sensor for sensing the ambient temperature within the predetermined volume of space, a timer for generating the current time of day, and a memory for storing a plurality of program times, and a heating and a cooling control temperature corresponding to each program time. The memory also stores a first temperature span associated with the heating control temperatures and a second temperature span associated with the cooling control temperatures. The current ambient temperature is compared to a first temperature above the heating control temperature, a second temperature below the heating control temperature, a third temperature above the cooling control temperature, and a fourth temperature below the cooling control temperature. These comparisons generate a switching control signal for controlling the on/off state of the heating and cooling systems. The first, second, third, and fourth temperatures are fixed by the first and second temperature spans.

Abstract: A heating and cooling apparatus wherein either or both the heating apparatus and cooling apparatus are two-stage is controlled by a thermostat through four connecting wires. A signal on one of the wires enables the functions of controlling operation of the circulator fan and controlling second-stage operation of whichever apparatus is two-stage.

Abstract: An improved monitoring and control system for a heating, ventilating and air conditioning (HVAC) unit which provides zone control in plural zones in which each zone includes a thermostat which controls a damper for its zone. One thermostat is selected and programmed to function as a monitor or master thermostat for selective actuation of the HVAC unit as well as controlling its zone damper. The other thermostats are programmed to function as slave thermostats and are interfaced with the master thermostat thereby allowing for independent zonal control in a multiple zone system which uses a single zone HVAC unit. The master thermostat may also receive control signals and data from higher intelligence such as a computer. Each thermostat is microcomputer-controlled with provision for both local and manufacturer programming via supplemental memory devices. The master thermostat contains a real time clock for time-basing the entire system with attendant advantages.

Abstract: A refrigeration system for temperature conditioning several comfort zones includes several VAV (variable air volume) valves each having a hot water coil conveying water whose flow rate is regulated by a PWM (pulse-width modulated) solenoid valve. Each VAV valve is connected to a supply air duct conveying cool supply air. When a zone's temperature is above a set point temperature, the opening of the VAV valve is modulated to meet the cooling demand, and the water coil is shut off. When a zone's temperature is below the set point, the VAV valve is opened to provide a predetermined constant airflow rate and the hot water coil's solenoid valve is cycled open and closed in a pulse-width modulated manner to meet the heating demand.

Abstract: There is disclosed a thermostat controlled apparatus which controls the operation of a heating system and a cooling system in response to temperature variations in a given environment. The thermostat has a three-electrode mercury switch which is coupled to a single bimetallic element which rotates the switch in response to temperature variations. The switch has a housing containing a pool of mercury and three electrodes extending within. A common electrode is connected to a voltage source. A second electrode is connected to the cooling system. A third electrode is connected to the heating system. Tilting the switch clockwise causes the mercury to connect the second and common electrodes, thereby energizing the cooling system; tilting the switch counterclockwise causes the mercury to connect the third electrode and common electrode, thereby energizing the heating system.

Abstract: A valve is provided with one inlet and two outlets with one of the outlets being normally closed by a valve in the form of a film disc carried by a flexible blade. A magnetic pad secured to the blade is attracted by the proximity of an actuator carrier magnetic element to cause the flexing of the blade to open the normally closed outlet and to close the normally open outlet. The actuator may be either thermally or electrically actuated and is suitable to override a bleed thermostat to permit warm-up of an overcooled area or to cause a switchover in operation between a heating and cooling mode by connecting the appropriate bleed thermostat so as to control the inflation of the bellows.

Abstract: An HVAC system for a plurality of zones comprising an air handling unit including a blower, a plurality of heating stages and a plurality of cooling stages. The air handling unit is connected via ducts to each of the zones, each zone having an air outlet provided with a two-position damper which is either open or closed and a thermostat for providing an input signal to a microprocessor. The microprocessor has outputs for activating motors to move the dampers and outputs for activating the heating and cooling stages. The system includes an automatic mode of operation in which the microprocessor controls the number of stages of heating or cooling which are energized in dependence on the difference between the number of zone therostats calling for heating and the number of zone thermostats calling for cooling.

Abstract: Apparatus for controlling reaction temperatures in a chemical analyzer comprises a thermoelectric element operating in response to a temperature sensor, and control means capable of predicting a setpoint deviation for a future time period, and, when an overshoot is predicted, reducing a control signal for the element by an amount proportional to a current setpoint deviation. The apparatus includes at least one reaction cell and a buffer unit for thermally stabilizing a fluid that is fed, on demand, into the reaction cell, the cell and the buffer unit having separate thermoelectric elements and sensors. A microcomputer control system generates independent control signals for the elements.

Abstract: A valve is provided with one inlet and two outlets with one of the outlets being normally closed by a valve in the form of a film disc carried by a flexible blade. A magnetic pad secured to the blade is attracted by the proximity of an actuator carrier magnetic element to cause the flexing of the blade to open the normally closed outlet and to close the normally open outlet. The actuator may be either thermally or electrically actuated and is suitable for use in a VAV system with thermostatically controlled bellows to override a bleed thermostat to permit warm-up of an overcooled area or to cause a switch over in operation between a heating and cooling mode by connecting the appropriate bleed thermostat so as to control the inflation of the bellows.

Abstract: There is disclosed a thermostat controlled apparatus which operates to control operation of a heating system and a cooling system in response to the temperature detected in a given environment. The thermostat has a pair of mercury switches which are coupled to a single bimetallic element which switches are inclined, one with respect to the other. The circuit configuration is such that one switch controls the heating operation while the other switch controls a cooling operation. Heating and cooling occurs within a predetermined range which is adjustable by means of the angular positions of the switches with respect to the bimetallic coil. In this manner one switch will control the heating operation and the other switch controls the cooling operation. There is an area between the setting of the thermostat wherein neither switch operates but during this mode a separate fan is energized to provide air circulation for the given environment.

Abstract: A housing contains two thermostats which thermostats are interwired so as to enable one thermostat to control a heating operation and the other thermostat to control a cooling operation. The housing contains at least one AC power receptacle coupled to the heating thermostat and one AC power receptacle coupled to the cooling thermostat. In this manner a heater would be plugged into the one receptacle while an air conditioner would be plugged into the other receptacle. The individual thermostats would be set for a temperature heating range being the difference between the settings. The wiring between the thermostats causes the heating thermostat to come on when the temperature falls below the values set. This in turn causes the plugged in heater to operate. When the temperature is above a value set by the heating thermostat, the unit removes power from all AC receptacles.

Abstract: A building air conditioning and heating system includes an air handling system set up to separately control different zones of a building. The air handling system has a blower connected to an air duct system in the building. At least two thermostats are positioned in different portions of the building for separately controlling the heating or the air conditioning in that portion of the building. A plurality of dampers are positioned in the air duct system, with each damper adapted to be opened and closed by gravity or air pressure. A damper locking means locks each damper in a closed position responsive to actuation by an electrical switch so that one zone of the building can be air conditioned or heated as desired. The thermostat can acutate the dampers and can control the temperature in one zone portion of the building while the other thermostat is disabled. Each damper has an electrical solenoid for locking the damper in one position.

Abstract: An electrical heating system for buildings is described in which the output voltage to a resistance heater is varied in accordance with outside temperature. The disclosure includes system means for compensating for solar radiation and wind effects. Also, night setback and morning start up are provided. The heat present on the interior of the building is provided in accordance with the building characteristics and without regard to interior temperatures.

Abstract: A monitoring and control system for a heating, ventilating and air conditioning (HVAC) unit which provides zone control in plural zones in which each zone includes a control thermostat that is interfaced with the monitoring system so that each zone thermostat controls the HVAC unit as well as a damper unit for that particular zone thereby enabling independent zonal control in a multiple zone system which uses a single zone HVAC unit. The monitor considers individual zone needs, damper positions, amount of demand in the zone, mode of the zone damper and other factors which affect the comfort of zone occupants and, in response to signals from the thermostats, decides how and when to control the HVAC unit so that, in effect, a single zone HVAC unit becomes a multiple zone system.

Abstract: An improved thermally actuated diffuser is disclosed. The diffuser comprises three thermal sensor actuators. A first thermal sensor actuator is responsive to changes in the room air temperature and is engaged when cool air is supplied through the duct into the room. A third thermal sensor actuator is responsive to changes in the room air temperature and is engaged when warm air is supplied to the room. A second thermal sensor actuator is responsive to changes in the duct air temperature and brings either the first or second thermal sensor actuator into engagement with the diffuser when the appropriate temperature of air is supplied through the duct and disengages the thermal actuator not being used with that duct air temperature.

Abstract: An improved thermally actuated diffuser is disclosed. The diffuser comprises four thermal sensor actuators. A first thermal sensor actuator is responsive to changes in the room air temperature when cool air is supplied through the duct into the room. A second thermal sensor actuator is responsive to the duct air and is adapted to engage the first thermal sensor actuator when cool air is supplied through the duct and to disengage the first thermal sensor actuator when warm air is supplied through the duct. A third thermal sensor actuator is responsive to changes in the room when warm air is supplied through the duct. A fourth thermal sensor actuator is responsive to changes in the duct air temperature and brings the third thermal sensor actuator into engagement when warm air is supplied through the duct and to disengage the third thermal sensor actuator when cool air is supplied through the duct.

Abstract: In a control system for an air conditioner of a motor vehicle, which includes an automatic control circuit arrangement for controlling the air conditioner to enable it to operate at a desired level of the heating or cooling performance thereof, there is provided an emergency circuit arrangement which is adapted, in case the automatic control circuit arrangement fails to work properly, for example, to cause it to be disconnected from the air conditioner and enable the latter to operate only at the maximum level of the heating or cooling performance thereof. There is also provided a switch device which is connected to selectively render operative a desired one of the above two circuit arrangements, and provided with means for preventing the emergency circuit from being unintentionally rendered operative.

Abstract: A thermostat for controlling heating and cooling apparatuses has a temperature control point adjustment knob connected to a temperature responsive switch means for adjusting the control point thereof. A single lever changeover switch is connected to the temperature responsive switch for selectively connecting either heating or cooling apparatus to the temperature responsive switch. Temperature control point limit stops are connected to the temperature control point adjustment. Upon selecting by the single lever changeover switch either a heating or a cooling operation, the temperature control point limit stops limit the movement of the temperature control point adjustment to a first range of movement when heating is selected and a second range of movement when cooling is selected.

Abstract: A method and apparatus for proving a demand for air conditioning or heating upon startup of an air conditioning unit before the unit is allowed to effect heat transfer. A separate thermal sensing unit is provided in the return air to prove a demand for cooling prior to the conventional thermostat of the unit being energized to operate the unit in the normal manner. This method and apparatus prevents energy waste and unnecessary cycling at startup and low load conditions.

Abstract: A control system for regulating the flow of water to the condenser to maintain most effective loading of the compressor in a water-to-air heat pump arrangement. The system incorporates a temperature sensitive valve which has a thermal transfer contact with the refrigerant flowing through the heat pump compressor which upon sensing the heat in the refrigerant rising or falling correspondingly variably opens and closes the water line to the heat exchanger so as to maintain the temperature at the compressor within a predetermined range, and maintain proper loading on the compressor during heating and cooling cycles of the heat pump.

Abstract: A system for controlling the temperature of an enclosed volume includes a pneumatic thermostat, heating means and cooling means. The thermostat has two entirely independent controls: a heating control and a cooling control. Both controls remain independently operative at all temperatures and each control has an independent set point. Whenever the temperature of the enclosed volume sensed by the thermostat raises above the cooling-control set point, the cooling control generates a first pneumatic signal which activates, adjusts and operates cooling means. Whenever the temperature of the enclosed volume sensed by the thermostat falls below the heating-control set point, the heating control generates a second pneumatic signal which activates, adjusts and operates heating means. The heating-control set point is lower than the cooling-control set point such that there is defined a range of sensed temperatures at which neither heating means nor cooling means is activated, adjusted or operated by the thermostat.

Abstract: A pneumatically operated system having a control unit provided with a single inlet interconnected to a one pressure level pneumatic source and having an outlet arrangement interconnected to a pneumatically operated heating and cooling heat exchanger to control the same in either its heating mode or its cooling mode in relation to the pressure value of the pneumatic signal being directed thereto from the control unit through the outlet arrangement thereof, the control unit having a temperature sensing arrangement for controlling the value of the signal in relation to the sensed output temperature of the heat exchanger by operating a bleed arrangement of the control unit.

Abstract: An electronic thermostatic control for a heat/cool air conditioning unit and with variable temperature anticipation useful when the unit is located above or below the room's normal zone to compensate for different effects of air stratification as between heat and cool operating modes. A comparator circuit output switches the compressor on and off and a portion of the comparator output is fed back to one of the comparator inputs to effect a degree of temperature anticipation. The feedback is altered by a load impedance switch and into and out of the comparator output circuit to vary the voltage swing on the comparator output and thus to vary the feedback. The amount of alteration of the feedback is selected to achieve the desired variation of temperature anticipation between heating and cooling operating modes.

Abstract: A thermostat adapted for controlling heating and cooling apparatuses has a temperature control point adjustment means connected to a temperature responsive switch means for adjusting the control point thereof. A changeover switch means is connected to the temperature responsive switch means for selectively connecting either heating or cooling apparatus to the temperature responsive switch means. A temperature control point limit means is connected to the temperature control point adjustment means so that upon selecting by means of the changeover switch means either a heating or a cooling operation, the temperature control point limit means limits the movement of the temperature control point adjustment means to a first range of movement when heating is selected and a second range of movement when cooling is selected.

Abstract: Means for air conditioning a building interior so as to afford optimum comfort to all its occupants in terms of their physical characteristics. An automatic control mechanism monitors devices for measuring humidity, air velocity, bulb temperature, and the weight and body temperature of humans or animals occupying the said interior. The mechanism comprises a calculator assembly comprising a computer and a comparator. Control is effected by comparing in the comparator the ideal temperature calculated by the computer with the actual measured temperature. The transmitted error signal imposes the control either on a heater or on a ventilator 1 in response to a command signal from a thermostat.

Abstract: A multi-stage condition control system of the time proportional type is shown. The control system utilizes a counting means as part of the anticipation for system control. The counting means counts during the time the control system is within its proportional band. When the control system moves outside of the proportional band, the counting stops. A count detection circuit senses the absence of counts thereby indicating that the system is outside of the proportional band. The absence of counts is then used to increase or decrease multiple stages of condition control equipment to bring the system back within the proportional band.

Abstract: A condition responsive time proportional control means which has a relatively fast time constant when operating in its proportional band has the time constant expanded by means of a digital counter. The counter is a resettable unidirectional type counter that has two counting channels. The main counting channel provides for the counting function during the normal cycling of the system when in the proportional band. A second channel in the counter acts to enable to the counter rapidly in the event that there is a disruption of the counter when the condition responsive system has been outside of the proportional band.

Abstract: A thermally actuated phase change operated control valve particularly adapted for use with heat pump systems has a valve body having a bore therein defining a fluid flow chamber, said valve body having an inlet port at one end and spaced and sized outlet ports in the medial wall thereof so that a valve head slidably disposed in the fluid flow chamber will in the calibrated position of the valve head maintain a predetermined minimum flow of fluid from said inlet port through the respective outlet ports.

Abstract: A temperature control is disclosed for a variable volume air conditioning system of the type wherein electric motor-operated air valve means are provided for varying the volume and relatively warm or relatively cool conditioned air supplied to a conditioned zone. The control includes zone thermostat means for producing an electrical error signal having a magnitude which varies in a predetermined relationship with respect to a deviation in zone temperature, and changeover circuit means for varying said predetermined relationship in order to accommodate changeover between heating and cooling, as sensed by duct temperature sensing means. The control further includes flow limit circuit means for imposing limits upon the maximum and minimum desired flow of conditioned air through the air valve means.

Abstract: A thermostat adapted for controlling heating and cooling apparatuses has a temperature control point adjustment means connected to a changeover switch means whereby upon the adjustment of the temperature control point adjustment means in a first range to select a cooling control point, the changeover switch means only connects the thermostat to the cooling apparatus and when the temperature control point adjustment means is in the heating range, the changeover switch means only connects the thermostat to the heating apparatus. The limited range of temperature selection in the first and second range is an energy conservation feature of the thermostat.

Abstract: A combination thermostat and blower speed control for use with an air conditioner for both heating and cooling air which is circulated through an enclosure by a multi-speed blower.The control has a system switch for selecting either a heating or cooling mode of operation and a blower speed switch for selecting either automatic blower operation or continuous low speed or high speed operation. The combination thermostat and blower speed control has a built-in override such that when the thermostat senses a cooling need and the control is in the cooling mode of operation the blower will operate at high speed notwithstanding the selection of the blower speed at the blower speed switch.

Abstract: A package terminal air conditioning system as disclosed having a room air-circulating blower, an air-cooling device, an air-heating device, and a thermostatic control which governs operation of the air-cooling and air-heating devices in response to the temperature of room air which is circulated by the blower.The control unit senses the temperature of the air which is returned to the unit from the room and the air which is discharged from the unit to the room and operates an appropriate electrical switch to enable and disable the respective air-heating and cooling devices. The operation of the unit is such that when the temperature of the discharged air differs substantially from the temperature of the return air, the differential in the sensed room air temperature between the cut-in and cut-out of the heating or cooling device is reduced which results in minimizing the possibility of overheating or undercooling the room.