Showing papers on "Thermostat published in 1992"

Control system and methods for a multiparameter electronically commutated motor

Abstract: A system which drives a component of a heating, ventilating, and/or air conditioning (HVAC) system in response to a system control signal such as a temperature signal provided by a thermostat. The system includes a motor having a stationary assembly and a rotatable assembly. The rotatable assembly is in magnetic coupling relation to the stationary assembly and is in driving relation to the component. The motor drives the component in response to a control signal generated by a microprocessor. The microprocessor is responsive to parameters representative of the system and to the system control signal. The parameters are stored in a memory and are defined in response to a parameter select signal. The control signal provided by the microprocessor controls the speed and torque of the motor. The system further includes an instruction memory for storing instructions controlling the operation of the microprocessor.

Energy fluctuations induced by the Nosé thermostat

Abstract: The Nos\'e thermostat is a method for simulating a canonical ensemble in molecular-dynamics calculations. It is generally agreed that for large values of Q, the parameter determining the response of the thermostat to the system, the approach to equilibrium is slow and for intermediate values it is rapid. However, for small Q Nos\'e found the thermostat oscillates rapidly and does not equilibrate with the system; we found it equilibrates but yields incorrect values for energy fluctuations, whereas Cho and Joannopoulos found it equilibrates very slowly, eventually yielding correct energy fluctuations. Here we demonstrate how these differences arise.

Interactive elecronic thermostat with minimum and maximum temperature thermal limit switches.

Abstract: An interactive electronic thermostat (100) incorporates a safety backup system (130) to automatically activate the HVAC system (23, 24, 25) in the event that normal operation of the thermostat (100) is interrupted and the temperature in the conditioned area falls or rises beyond a predetermined range. The thermostat (100) operates to communicate with an installer through an audible or visual display (106) and keypad (104) to instruct the installer to perform tasks and enter observations to effect proper connections at the thermostat (100) of HVAC system (23, 24, 25) wires even in the absence of labels indentifying the functions of those wires. The thermostat (100) requires entry of coded indicia representing operator-observed conditions in the system in response to displayed instructions carried out by the operator.

Control for dual heating system including a heat pump and furnace

Abstract: A programmable thermostat is provided for the selective operation either of a fossil fuel furnace or a heat pump. The thermostat is programmed to operate the fossil fuel furnace when the outside temperature is below a preselected temperature range, and to operate the heat pump when the outside temperature is above the preselected temperature range. Within the preselected temperature range, the fossil fuel furnace may be operated during certain time periods and the heat pump may be operated during other time periods.

Electronic time thermostat with a temporary next period adjustment means

Abstract: A thermostat having a temporary "now" and "next" functions The temporary "next" function allows the user to program a temporary deviation from a preprogrammed schedule used to control the temperature within a space The combination temporary "now" and "next" function allows a user to temporarily set a current setpoint which will be held until a temporary next setpoint becomes the control setpoint, after which the thermostat returns to the preprogrammed setpoints

Methods and apparatus for monitoring the operation of a transport refrigeration system

Abstract: A transport refrigeration unit, and methods and apparatus for monitoring the operation thereof, with the unit conditioning a load to a selected set point temperature via commanded cooling and heating cycles. A thermostat provides a digital signal as a function of the load temperature and the selected set point temperature, with each toggling of the least significant bit (LSB) thereof indicating a predetermined change in load temperature. A timer initiates a predetermined timing period with each toggling of the LSB, with the timing period being a dynamic function of the selected set point temperature. Expiration of the timing period before the next bit toggle initiates an alarm signal indicating the rate-of-change of load temperature is not within an acceptable limit for the selected set point temperature. A comparison of successive digital signals also results in an alarm signal when the direction of temperature change is not consistent with the commanded operating cycle.

Modulated temperature control for environmental chamber

Abstract: A temperature-controlled environmental chamber includes a resistance heater powered through a first solid state relay and a refrigeration unit including an electrically powered thermally controlled suction throttling valve connected in the refrigerant line between the evaporator and the inlet of the compressor, and including a bimetal motor and a heating element therefor powered through a second solid state relay. A thermostat senses the temperature in the chamber and compares it to a set point temperature and outputs a pulse-width modulated control signal indicative of the difference between the two temperatures. The control signal directly controls the heater relay for substantially continuous variation of the heater between minimum and maximum heating conditions. The control signal also directly controls the throttling valve relay by controlling the power to its heating element for substantially continuous variation of the valve between maximum and minimum cooling conditions, so that the amount of cooling provided is inversely proportional to the amount of heating provided.

Thermostat providing electrical isolation therein between connected heating and cooling transformers

Abstract: A low voltage space thermostat adaptable for controlling a heating-only apparatus or a heating and cooling apparatus. The thermostat includes a DC power supply and a voltage step-up transformer having two primary windings and a secondary winding for supplying electrical power to the DC power supply when there is a demand for heating, cooling, or fan operation. The thermostat also includes circuit means for supplying electrical power to the DC power supply when there is no demand for heating, cooling, or fan operation. The thermostat further includes circuit means, responsive to the existence of electrical power at a particular one of its wiring terminals, for providing electrical isolation, from each other within the thermostat, of two transformers incorporated in a two-transformer heating and cooling apparatus.

Hot water storage system

Abstract: A hot water system for connection to a water supply and a local hot water usage system, comprising a plurality of series-connected reserve tanks (1) and demand tanks (3) for receiving water from the water supply, heating the received water to a desired temperature within the reserve and demand tanks, and supplying the heated water to the local hot water usage system as it is demanded. A controlling device (13) is provided for sequencing the operation of the reserve (1) and demand tanks relative to peak power consumption hours and off-peak hours. Specifically, each of the tanks is provided with one or more thermostats (17, 19) which are selectively enabled or disabled by the controlling device at predetermined times. The one or more thermostats are, in turn, connected to one or more heating coils (21, 23) or maintenance coils (41). The reserve tanks and demand tanks may be operated under control of the controlling device in any of three modes, as follows: maintenance mode, enable mode, and disable mode. In maintenance mode, the water is maintained at a desired temperature either via enabling a thermostat which is connected to a low-power maintenance coil and disabling the heating coil thermostats, or via cycling power through the heating coil thermostats if no maintenance coil is provided. In enable mode, the heating coil thermostats are enabled so that the water temperature may be increased in a tank via activation of the heating coils under thermostat control, and if a maintenance coil is provided then the maintenance coil thermostat is disabled. In disable mode, the heating coil thermostats, and associated heating coils, are disabled to minimize power consumption. If the tank is provided with a maintenance coil, then the maintenance coil thermostat and associated maintenance coil are also disabled when the tank is operating in disable mode.

Temperature and temperature control in nonequilibrium-molecular-dynamics simulations of the shear flow of dense liquids.

Abstract: Methodological problems of the temperature control (thermostat) in nonequilibrium-molecular-dynamics simulations of dense liquids undergoing a stationary planar shear flow are addressed. They arise in connection with a transition into a shear-induced ordered state at high shear rates which goes along with inhomogeneities of the fields of density, temperature, and velocity gradient (shear rate) on the length scale of a particle diameter. We demonstrate that a meaningful local description of the thermodynamic fields can be achieved by a smoothing procedure. In particular, the local temperature is related to the width of a local Maxwellian velocity-distribution function. These results are employed for a formulation of a so-called profile-unbiased thermostat which fulfills the criterion of the local-equilibrium hypothesis.

Increased diameter detachable thermostat knob allowing easier thermostat use

Abstract: A knob accessory for a round thermostat of the type having a centrally located thermostat adjustment knob, has a relatively large diameter which allows easier adjustment of the thermostat setting for people who have difficulty in rotating an adjustment knob having detents to indicate thermostat settings. The knob accessory latches onto the standard adjustment knob with a detent mechanism which also allows removing the knob.

Recoverable domestic ice maker

Abstract: An ice making apparatus includes a mold in which water is frozen to form an ice body. Also included are an electric motor and an ejector blade for ejecting the ice body from the mold. An electric heater in heat transfer association with the mold is operable to free the ice bodies from the mold prior to the ejector blade ejecting the ice bodies. A control circuit includes a thermostat responsive to temperature of water in the mold. A thermostat switch is controlled by the thermostat to initiate operation of the motor for ejecting the ice body upon complete freezing thereof and concurrently energizing the heater. An electric circuit includes the thermostat switch, the motor and a second switch controlled by the operation of the motor for maintaining energization of the motor independently of the first switch and causing the thermostat switch to control further energization of the heater whereby the thermostat switch de-energizes the heater within a single revolution of the ejector blade. The motor also drives a cam and cam follower for controlling a sensing arm for sensing a full ice condition. The ice maker includes structure for suspending operation of the ice maker in the event that the sensing arm is obstructed.

Method and apparatus for interior space conditioning with improved zone control

Abstract: An interior thermal conditioning method and apparatus with improved zone control is disclosed. The thermal conditioning apparatus, such as a heat pump assembly, generates a desired thermal condition which is conveyed by a thermal distribution medium to a number of zones within a multiple zone building. Each zone includes a heat exchange device for receiving the thermal distribution medium. Each zone also includes a thermostat which is used to set a desired temperature range and to indicate the prevailing temperature. When the prevailing temperature is inconsistent with the desired temperature range, a conditioning request is generated. Rather than immediately responding to the conditioning request, the heat pump controller assesses the temperature of the thermal distribution medium to determine whether it is within a target range. If the thermal distribution medium is not within the target range, execution of the conditioning request is delayed while the heat pump is modulated to produce the desired thermal distribution temperature. Additional conditioning requests may be generated during this modulation period. Conditioning requests are processed after the desired thermal distribution temperature is established. Various criteria may be used to establish conditioning request priorities. Conditioning requests may be swapped with former conditioning requests which are executing. The controller establishes a steady and efficient operation of the heat pump.

Ergodicity and dynamical properties of constant-temperature molecular dynamics.

Abstract: The assumption of ergodicity in Nos\'e's original formulation of the constant-temperature molecular dynamics is tested for a Lennard-Jones-potential system. With the performance of very long simulations, it is shown that the extended system of a Lennard-Jones-potential system is ergodic for all values of thermostat parameters tested. It is also shown, however, that the rate of convergence to the canonical ensemble strongly depends on the value of thermostat effective mass Q. The dynamical properties of the extended system are also studied using the velocity autocorrelation function and the power spectral density. From the analysis of the simulations, it is found that the dynamical properties are not correctly represented for arbitrary values of thermostat parameters. A prescription and a set of quantitative criteria are introduced to generate physically meaningful dynamics. Thus the results of this work show that with a special choice of thermostat parameters it is possible to obtain both the correct canonical ensemble and physically meaningful dynamical behavior of the physical system.

Multitemperature responsive coolant coil fan control and method

Abstract: A cooling system (10) with a control temperature sensor (24) for sensing the temperature of a coolant coil (14) for control of a coolant coil fan (18) in cooperation with ambient temperature sensed by a thermostat (30) to obtain optimum utilization of residual cooling power of the coolant coil (14) after the condenser (28) has been deactivated and to protect against overcooling and consequent icing of the coolant coil (14) in the event of inadvertent failure of the thermostat (30) to turn off the condenser(28).

Continuous flow heater control system for an apparatus for making infusion beverages

Abstract: An electrically heated continuous flow heater control system includes an electric switching element that has an open and a closed switching position and is electrically connected in series to a thermostat. Switching element (26) is always closed in the brewing process while it can be opened and closed again in the keep-warm process by a control circuit. The control circuit includes a temperature sensor which is in good heat contact with the infusion beverage. When in the initial phase of the keep-warm process the sensor temperature is in excess of a definable switching temperature, the control circuit keeps the switching element in its open position for as long as the sensor temperature remains higher than the switching temperature in the course of the consequently occurring cooling of the infusion beverage. When the sensor temperature is below or equal to the temperature of the switching element in the keep-warm process, the control circuit keeps the switching element in its closed position for a predefinable first time interval (heating cycle) irrespective of the sensor temperatures produced during the heating cycle.

Electronic thermostat having correction for internally generated heat from load switching

Abstract: The apparatus controlling operation of a digital thermostat mounted in an enclosure corrects the internally measured temperature for heat generated within the thermostat enclosure by the switching element controlling operation of the load, typically a HVAC unit. The actual ambient temperature is derived by subtracting from the internal temperature a correction value which follows the fraction of total time the switching element conducts power for the HVAC unit (duty cycle). The duty cycle is preferably multiplied by a scale factor and the difference between the ambient temperature as currently calculated and the internal temperature to form the correction value.

Motor vehicle radiator having a fluid flow control device

Abstract: A cooling radiator for the engine of a motor vehicle includes two movable masking members associated with the same fluid manifold of the radiator and actuated by a common actuator in response to the engine temperature. A first of these masking members closes the inlet of the manifold to prevent any flow in the radiator when the engine is cold. The second masking member controls an aperture in an intermediate bulkhead in the fluid manifold so that a variable fraction of the fluid flow in the radiator is diverted (when the manifold inlet is open) through the aperture, so that it does not pass through the tubes of the radiator. This radiator performs the function of a thermostat and also regulates the cooling function at the correct efficiency according to the power being produced by the engine.

Relay contact monitoring system

Abstract: A switching system for switching on and off heating and air conditioning units in an environmental control system. The switching system includes a thermostat and a relay conductively coupled to the thermostat. The relay has a contact, which is responsive to a change signal for changing its position. The system further includes a programmable monitor having predetermined positions stored in a memory. The monitor is conductively coupled to the contact and to the thermostat for continually determining the position of the contact, and for sending a change signal to the relay for switching the position of the contact, as needed, to be in conformance with a predetermined position stored in the memory.

Hvac low power usage circulation blower

Abstract: A field installable device for a conventional heating and air conditioning system (HVAC) is provided which operates a blower fan (5) in conjunction with a standard thermostat (7). Presently, HVAC systems operate in four modes: heating, cooling, off and fan "on". The device includes a multi-pole, multi-speed motor (23) and a control operatively connected between the thermostat and the motor. With the fan switch in the "on" position and heating or cooling called for, the control causes the blower to operate at a high speed, which may be different for heating or cooling. When the pre-selected temperature is reached the particular thermal operation (i.e., heating or cooling) is stopped. The control switches the motor to a speed substantially slower than the operating condition speed to provide continuing air circulation until the thermostat again calls for thermal operation. With the switch in "auto" position, the blower operates similarly to present systems.

Energy saving apparatus and method

Abstract: To save energy in hotel and motel rooms, apartments and temporarily occupied rooms generally, an apparatus for saving energy includes a temperature control circuit that overrides a thermostat for controlling an air conditioning unit in a hotel room and a switching circuit to disconnect power to lights when the room is not being occupied. The temperature control circuit maintains the temperature of the room at a higher temperature to save energy, but not so high as to return the temperature of the room to a comfortable temperature. To return power to lights and control of the air conditioning unit to the thermostat, a tag attached to a key necessary for entering the room must be inserted into a switch included with the apparatus. A delay circuit permits the person sufficient time to leave the room after removing the tag before the thermostat is overridden and power to the lights disconnected.

Single pole double throw thermostat for narrow range temperature regulation

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. The adjustment screw moves the bimetallic strip relative to the contacts for operating excursion of the thermostat thus positioning the mid-point of the set point range between subfreezing and incubation temperature ranges. The spring is selected to act with respect to the adjustment screw to both bias the strip against the adjustment screw as well as provide a non linear vibrational damping to the bimetallic strip. Circuitry is disclosed for passing minimal current through the mechanical portions and amplifying and driving a heater or cooler, preferably electrical heaters and coolers. There results a thermostat which cannot thermally lockup, is resistant to vibration, and can be adjusted to narrow band operation over a wide range to temperatures.

Domestic refrigerator and freezer combination - has thermostat switch monitoring external temp. in series with heating device

Abstract: The domestic refrigerator and freezer combination has respective freezer and refrigerator compartments (5, 6) held at different temps. The temp. within the refrigerator compartment (6) is controlled via a single heat regulating device (15, 16) allowing the required temp. to be maintained via alternate operating and resting phases of the refrigeration circuit. A thermostat switch (21) for the external temp. lies in series with a heating device (17), in parallel with the thermostat heat regulating device (15, 16) for the refrigeration compartment (6). Pref. the thermostat switch (21) lies immediately adjacent the condenser (12) of the refrigeration circuit and is closed upon the measured temp. dropping below a given value. ADVANTAGE - Optimum temp. regulation; energy saving.

IC engine cooling installation with engine-driven pump - has electrically driven second pump with external line contg. two thermostatic valves

Abstract: A cooling system for an i.c. engine (2) provides cooling after the engine has been switched off using a secondary cooling system connected to the engine heating system. The secondary circuit ensures effective cooling of a hot engine after use via a direct connection (17) from a second thermostat (15) to the radiator (3). A first thermostatic valve (6) switches in a bypass to the cooler (3) when the temp. falls below a lower threshold. This valve diverts the coolant to the external line (7,9,14) when the temp. is above the upper threshold and the engine is switched off. A second thermostatic valve (15) switches between the running and off condition cooling circuits. ADVANTAGE - Low constructive change requiring few components increasing wt. and space required.

Thermostat for temperature independant valve command, specially for heating valves.

Abstract: of EP0280891The innovation is a thermostat for a temperature-dependent valve control such as is used for heating valves. The thermostat consists of a sleeve-type housing, a guide element forming the first end wall of the housing, a plunger mounted movably in the guide element, a disc forming the second end wall of the housing, a heat-expandable material packed into the housing and a resistance-type heating element acting on the heat-expandable material. The electrical lead to the resistance-type element is mounted in an insulated manner in the second end wall of the housing. The object of the innovation is to place the resistance-type heating element so that it is exposed as little as possible to external effects and the heating power is rapidly transferred to the heat-expandable material with as high an efficiency as possible. This object is achieved in that the disc forming the second end wall is produced from a castable, electrically insulating material having as good thermal conductivity as possible and the resistance-type heating element is embedded therein.

Trip free thermostat

Abstract: A manually resettable trip free thermostat that has simple construction and a pivotable stationary contact arm that enables the thermostat to be reset while maintaining the contacts in an open condition.

The Gaussian thermostat, phase space compression and the conjugate pairing rule

Abstract: We recently proposed a possible variational principle for ergodic, non-equilibrium steady states (NESS) far from equilibrium (1991, Phys. Rev. Lett., 67, 2597). We provided computer simulation results in support of the hypothesis that in NESS with fixed internal energy, volume, number of particles and applied external field, the decrease of the volume of phase space which is accessible to the system is a local minimum with respect to variations in endogenous variables. This hypothesis is a microscopic and nonlinear generalization of the principle of minimum entropy production which is valid only for NESS close to equilibrium where both the local thermodynamic equilibrium and the Onsager reciprocal relations are valid. In the present paper, we point out that for a wide class of possible thermostatting mechanisms, the Gaussian thermostat minimizes the phase space compression. With respect to our variational principle, the Gaussian thermostat is therefore the optimal thermostat. Further, for this class of po...

Method and apparatus for heating a spa

Abstract: A method and apparatus for heating water in a spa which has a plurality of venturi jets, a hosing which includes a plurality of venturi jets and a high speed pump which circulates water through the housing and the venturi jets in the spa and a water thermostat. The thermostat is positioned in the water of the spa and connected to the high speed pump such that the high speed pump is activated to propel water through the venturi jets at high speed and thus heat it whenever the water temperature falls below a preset level.