Abstract: The apparatus and method control preheating temperature of equipment having a device to be preheated and a preheating device for start-up which includes a heat source and a heat source control device which has a plurality of heating patterns to control said heat source. The apparatus includes a temperature measuring device for measuring current temperature of the device to be preheated within the equipment, a computing device for calculating a predicted time that is required by the preheating device to preheat the device from the current temperature to a preset temperature, a comparison device by which the predicted time as calculated by the computing device is compared with a specified start-up time and a selecting device for selecting from the plurality of heating patterns within the heat source control device a heating pattern that makes the predicted time shorter than the start-up time.

Abstract: A heating element and a process for conducting the operating heat of a semiconductor switch to a heating cell which is triggered by the semiconductor switch via first and second heat and current conducting material strips and a frame terminal with an interposed heat-conducting insulating film. The semiconductor switch is provided with a cooling fin and is applied directly to a surface of the first heat and current conducting material strip.

Abstract: On an electric cooker the sensor circuit (1) detects the presence of a pan (2) on each heater (F1-F4) and comprises a microcontroller (4) and a generator (6,7) that supply a high-frequency current (Ig) to a respective sensor loop (E1-E4) of each heater which generates a magnetic field, and two maximum and minimum reference signals (Vr0,Vr1) for all the heaters (F1-F4) obtained in the working temperature condition and a circuit (9-13) for measuring and evaluating the voltage (Vs) produced in each sensor loop, with a circuit part (11,11′) for demodulation into low frequency of the measuring and reference signals (Vs,Vr0,Vr1), and their differential amplification (Vm,Vrr).

Abstract: There is provided a batch type heat treatment system, control method and heat treatment method capable of appropriately coping with a multi-product small-lot production.

Abstract: The heater control apparatus comprises an exhaust gas sensor 6 for detecting an oxygen concentration in exhaust gases of an internal combustion engine, a heater 5 for heating this exhaust gas sensor 6 to a predetermined temperature, a power source including a battery 2 for supplying electric power to this heater 5 and a charging generator 4 for charging this battery 2, a switching element 19 inserted into a circuit for supplying electric power to the heater 5 from the power source, control means 12 for performing current-carrying control of the switching element 19 so as to maintain a temperature of the exhaust gas sensor 6 at a predetermined value, and an overvoltage detection element 28 for outputting an abnormal detection signal when a voltage of the power source exceeds a predetermined value, and it is constructed so that the switching element 19 is broken to stop the passage of current to the heater 5 by the abnormal detection signal of the overvoltage detection element 28 when a voltage of the charging

Abstract: A current-limiting resistor is connected between a power-supply line and a heater provided near the oxygen-detecting element of limiting-current type oxygen sensor. A power MOSFET is connected between the heater and a ground line. The resistor and the heater have such resistances that a current I2 flowing through the resistor and the heater when the heater has a resistance R2 is about I1{square root}{square root over ((R1/R2))}, where I1 is a current flowing through the resistor and the heater when the heater has a resistance R1.

Abstract: A semiconductor device has an oscillator for generating an oscillating signal whose frequency is dependent on temperature, a frequency tester for determining whether or not the frequency of the oscillating signal is normal, a heater for generating heat if the frequency tester determines that the frequency is abnormal, and a first hard macro core that is shifted to a normal operation mode if the frequency tester determines that the frequency is normal. The oscillator, heater, and first hard macro core are put under the same temperature condition. The frequency tester employs a lower limit of an operating temperature range of the first hard macro core as a reference to determine whether or not the frequency of the oscillating signal is normal.

Abstract: An overheat event location module for use with an existing overheat detection system in an aircraft. The module is non-intrusively connected to the overheat detection system, yet senses currents in the system. The module, by way of the sensed currents is able to distinguish true overheat events from false events (normally created in a test mode) and normal non-overheat conditions. The module is able to respond to the occurrence of an overheat event by measuring the currents in the sensing cable loop, then using the measured currents to produce an estimate of the position in the loop at which the overheat event occurred. Conveniently the module records both the fact of the event and its location, such that subsequent maintenance actions are facilitated.

Abstract: A circuit configuration for driving an ignition coil includes a first semiconductor switch having a load path connected in series with a primary winding of the ignition coil, and having a control electrode, which is driven in accordance with a first drive signal. The circuit configuration further includes a second semiconductor switch having a load path connected in parallel with the primary winding and having a control electrode, which is driven in accordance with a second drive signal.

Abstract: On an electric cooker the sensor circuit (1) detects the presence of a pan (2) on each heater (F1-F4) and comprises a microcontroller (4) and a generator (6,7) that supply a high-frequency current (Ig) to a respective sensor loop (E1-E4) of each heater which generates a magnetic field, and two maximum and minimum reference signals (Vr0,Vr1) for all the heaters (F1-F4) obtained in the working temperature condition and a circuit (9-13) for measuring and evaluating the voltage (Vs) produced in each sensor loop, with a circuit part (11,11′) for demodulation into low frequency of the measuring and reference signals (Vs,Vr0,Vr1), and their differential amplification (Vm,Vrr).

Abstract: In order to ensure that a vehicle seat, having a supporting face and incorporating microcapsules of phase-change material having a phase transition temperature between 15 and 37° C., is comfortable to use in terms of temperature, the support face is heated or cooled before the seat is used so that the phase-change material is at its transition temperature when a user subsequently sits on the seat.

Abstract: A water heater having a water tank and multiple electric resistance heating elements extending into the water tank for heating water in the tank. The water heater includes a proportional band temperature controller for conducting electric power to the electric resistance heating elements in bursts. Each burst of electric power is followed by a period during which the temperature controller does not conduct power to the electric resistance heating element. In one embodiment, each burst of electrical power lasts for about 95% or less of a cycle comprised of one burst of electric power followed by the period during which the temperature controller does not conduct electric power. Further, activation of the heating elements by the controller is carried out in a sequential or other timed or controlled fashion to permit uniform heating of the water in the tank.

Abstract: A temperature control system includes an integrated circuit that combines magnetic sensitive elements and infrared sensors to detect user temperature settings and measure temperature, respectively. Integration of the various sensors results in a very cost-effective and reliable temperature control system suitable for consumer applications.

Abstract: The invention relates to a device for heating a seat, comprising a heating element arranged in connection to the seat and connected to a control unit, which comprises current feeding organs for feeding a current (I) through the heating element in order to heat it, a temperature sensor connected to said control unit for detecting the temperature (T) at said heating element, with the control unit being arranged for feeding said current (I) if said measured temperature (T) falls below a predetermined set temperature value (TB). The invention is characterized in that the control unit comprises a communication unit for receiving information regarding said set temperature value (TB) from an external unit via a transmission channel for the transfer of said information. The invention also relates to a method for heating a seat. By means of the invention, an improved temperature control for a heatable seat is provided, particularly intended for motor vehicles.

Abstract: An electric arc furnace includes a container for receiving metal, an electrode spaced apart from the container, and an electrical power source coupled to the electrode and the container for generating an electrical discharge between the electrode and the container for melting the metal in the container. The arc furnace includes a flicker controller for reducing flicker induced in the power source by the electric arc furnace. The flicker controller consists of a switch electrically connected between the power source and the electrode, and a control system coupled to the switch. The switch includes a gating input for controlling a conduction interval of the switch, and the control system applies gating signals to the gating input for maintaining a magnitude of reactive current flow through the arc furnace substantially constant.

Abstract: A main heater consisting of first and second fever areas and auxiliary heater arranged on an insulator substrate to maintain a precise sensing temperature. Grounded first fever area is contiguous with second fever area and grounded auxiliary heater, with the resistance ratio of first fever area and second fever area identical to that of the third resistor and the second resistor in bridge circuit control. Pyro-sensor or limit current type oxygen sensor capable of maintaining a high temperature, for example 400° C., operates within the high temperature maintained by the main heater, and DC—DC converter for isolating a first power supply, which supplies electric power to the heater from second power supply. Leakage current of the insulator substrate will not be generated as the insulator substrate deteriorates, thereby protecting the sensor cell leakage current from the heater.

Abstract: An improved control method variably activates an electric resistance heating element in a vehicle heating system so as to maximize the heating performance without overloading the vehicle generator or discharging the vehicle storage battery. A desired activation level for the heating element is determined based at least in part on the ability of the engine driven generator to develop electrical current, and when enabled, the heating element is activated based on the desired activation level. If a load condition for which the generator is unable to charge the storage battery is detected, the activation level is progressively reduced, and when the load condition is no longer detected, the activation level is progressively increased toward the desired level.

Abstract: The invention provides a device (11) for switching an electric heater (12) with at least two heating areas (25, 27, 29), which can be variably supplied with electric power by at least one power setter (22) and having control means (19) for the at least one power setter (22, 23) and with functionally separate switching means (14, 16) for operating the at least one power setter. On operating a first switching means (14), a heating area (27) associated therewith can be set by means of a power setter via the control means and on operating a further switching means (16) a heating area (29) associated therewith is settable by means of a power setter. Preferably, precisely one heating area (27, 29) is associated with each switching means (14, 16). The heating areas can be areally extensive heating zones or different power levels of a heater.

Abstract: This reflow soldering apparatus comprises a heater tip 10 for soldering sites to be soldered of a workpiece W by reflow method, a power supply unit for supplying an electric power for heat generation or heating to the heater tip, a control unit for providing a control of the supplied current in the power supply unit, and a pressing unit 16 for pressing the heater tip against the sites to be soldered of the workpiece W. An inverter of the power supply unit has four transistor switching elements. By the control unit by way of a driving circuit, the first set of switching elements and are simultaneously switching (ON/OFF) controlled at a predetermined inverter frequency (e.g., 10 kHz) in response to in-phase inverter control signals G1 and G3, whereas the second set of switching elements are simultaneously switching controlled at the inverter frequency in response to in-phase inverter control signals G2 and G4.

Abstract: An adaptive temperature control circuit includes a first circuit for producing an error signal representing the difference between a preset temperature and an actual temperature and a second circuit coupled to the first circuit for producing a pulse width modulated output signal having a frequency greater than one hertz, wherein the width of the pulses is proportional to the error signal.

Abstract: A mechanism for controlling temperature of the at least one heated fuser element of a fuser, for a reproduction apparatus having a heater for the fuser element, operating at a desired temperature to permanently fix a marking particle image to a receiver member. The temperature controlling mechanism includes a temperature sensing element producing a signal corresponding to a sensed temperature of the fuser element. A temperature sensing face member defines a cavity for receiving the temperature sensing element therein. The temperature sensing face member has a surface configured to correspond to the configuration of the fusing element. A housing is provided having an interior chamber for receiving the temperature sensing face member at one end. Air is substantially trapped in the interior chamber adjacent to the temperature sensing face member.

Abstract: A control system for delivering a constant fuser temperature despite variations in the line voltage. In general, this is effected by a control circuit which employs closed loop feedback control to control the rms voltage across the load. This is accomplished by a circuit and method which functionally provides a continuous solution to the equation which describes the relationship between the temperature of the fuser and the temperature of a desired control setpoint. Briefly, the solution of this equation is obtained by monitoring, i.e. sampling, the temperature of the fuser, subtracting the desired control temperature, and then integrating the difference over time. The resultant time integral is used to control the operating point of a pulse width modulated power controller. The integrator has a time constant sufficiently long and the power controller operates at a frequency sufficiently high so as to render lighting flicker imperceptible.

Abstract: A heater control apparatus wherein a voltage level of the power supply is discriminated by an input voltage discrimination circuit, and in case that an input voltage applied by an AC power supply is the lowest level, the heater is excited by a current corresponding to a full-wave of the input voltage. In case that the input voltage applied by an AC power supply is a level other than the lowest level, the heater is excited by a current substantially equal to that in the case of the input voltage of the lowest level. The exciting current control circuit is composed of a bridge diode, a current limiting resistor for limiting a current flow from the AC power supply, a Zener diode for setting an input voltage discrimination standard value for discriminating a level of the input voltage, a photo coupler for generating an input voltage discrimination signal, and an exciting current signal generating circuit for generating an exciting current signal.

Abstract: A cycle-skipping power control algorithm provides control signal patterns based on generating a number of core patterns corresponding to main power levels and alternating between the core patterns to generate finer control levels. Advantageously, such a cycle-skipping control scheme provides fine power control resolution, and perceptible flicker due to pulsating AC line current is minimized, both in visibly radiant loads and in electric illumination devices in close proximity to the load.

Abstract: A cooking range with an acoustic sensing system for determining the boil state of the contents of a cooking utensil. The acoustic sensing system, which includes at least one acoustic sensor, is positioned on or in the cooking appliance to detect acoustic emissions in one or more specific ranges of frequencies that are characteristic of emissions resulting from the heating and boiling of liquids in a variety of cooking utensils or vessels.

Abstract: The present invention provides both a process and apparatus for rapidly warming and delivering relatively high volumes of a physiological fluid. Unique to this invention is the ability to warm and infuse physiological fluids at a rate of up to about 1000 ml/min without causing damage to the fluid components, e.g. lysing or rupture of cells, or upsetting the normothermic equilibrium of the patient. Further unique to this invention is the utilization of a 12 VDC source, e.g. a battery source, as an amperage supplement to be used simultaneously with an AC power source, thereby enabling the heating of physiological fluids at a rate which surpasses that normally attainable through the sole use of facility provided AC power.

Abstract: A temperature control system for a thermal reactor is disclosed that addresses many of the problems in the art. In accordance with one aspect of the disclosed control system, a plurality of temperature controllers are employed. Each temperature controller employs one or more dynamic models that are optimized for a given temperature range. The temperature range over which a particular controller is optimized is preferably generally exclusive of the temperature ranges over which other controllers of the plurality of temperature controllers are optimized. In accordance with another aspect of the control system the control system employs enhanced ramp trajectory logic. In accordance with another aspect of the control system, the control system employs a virtual temperature sensor in the event of a hardware failure of the corresponding non-virtual temperature sensor.

Abstract: An electric blanket includes a heating element extending through the blanket so that, upon receiving electric current from a power source, the element heats the blanket. A regulator circuit is connected to the element. It is configured to measure the resistance of the element and to control delivery of the electric current from the power source to the element responsively to the resistance so that the element heats to a desired temperature.

Abstract: An ice and snow melting system includes at least one sensor configured for sensing a temperature or moisture associated with an ambient environment and providing a signal indicative thereof. A heater for melting the ice and snow includes a heater wire, a layer of insulation substantially surrounding the heater wire, and a conductive shield substantially surrounding the layer of insulation. A ground fault circuit interrupter is coupled with the shield of the heater. The ground fault circuit interrupter detects a ground fault condition between the heater wire and the conductive shield and provides a signal indicative thereof. An automatic controller is connected to the at least one sensor. The controller includes heater control circuitry receiving each of the sensor signal and the ground fault circuit interrupter signal. The heater control circuitry selectively controls operation of the heater dependent upon the sensor signal and the ground fault circuit interrupter signal.

Abstract: A power supplying apparatus for automotive parts can prevent not only wasteful power consumption even if an electric heater is short-circuited, but also any adverse effects on engine operation during an engine start-up operation. To this and, a heater 3 is connected to a power supply means P for heating the automotive parts. A switch 5 is connected between the power supply means P and the heater 3 for selectively switching on and off the power supply from the power supply means P to the heater.

Abstract: A nonlinear model-based predictive temperature control system is described for use in thermal process reactors. A multivariable temperature response is predicted using a nonlinear parameterized model of a thermal process reactor. The nonlinear parameterized model is implemented using a neural network. Predictions are made in an auto-regressive moving average fashion with a receding prediction horizon. Model predictions are incorporated into a control law for estimating the optimum future control strategy. The high-speed, predictive nature of the controller renders it advantageous in multivariable rapid thermal processing reactors where fast response and high temperature uniformity are needed.

Abstract: A temperature control system for a thermal reactor is disclosed that addresses many of the problems in the art. In accordance with one aspect of the disclosed control system, a plurality of temperature controllers are employed. Each temperature controller employs one or more dynamic models that are optimized for a given temperature range. The temperature range over which a particular controller is optimized is preferably generally exclusive of the temperature ranges over which other controllers of the plurality of temperature controllers are optimized. In accordance with another aspect of the control system, the control system employs enhanced ramp trajectory logic. In accordance with another aspect of the control system, the control system employs a virtual temperature sensor in the event of a hardware failure of the corresponding non-virtual temperature sensor.

Abstract: A toaster broiler oven with an NTC temperature probe located within the oven chamber and a controller that controls the heater of the oven in a thermostat operation for non-toasting modes and in a variable toasting interval length operation in the toasting mode. When the toaster start switch is activated in the toast mode, the controller determines if the oven chamber temperature is greater than a predetermined temperature, such as room temperature. If not, a first toast interval is selected. If so, a second shorter toast interval is selected. The length of the second interval is chosen so that the toaster oven consistently produces toast of a selected color from one toast cycle to the next, regardless of the elapsed time between consecutive toast cycles.

Abstract: An initial power feed quantity to be provided at the start to an electric heater equipped to an air-fuel ratio sensor is set corresponding to the temperature of a sensor element, and at the same time, the increase control time for increasingly changing the power feed quantity from said initial power feed quantity to the maximum power feed quantity is set corresponding to the temperature of the sensor element, and according to said initial power feed quantity and said increase control time, the power feed quantity to said electric heater is increased gradually from the start.

Abstract: An image heating apparatus has a heater for generating heat when an electric power is supplied from a commercial power source to the heater, a temperature detecting element for detecting a temperature of the heater, a control wave number setting circuit for setting a control wave number of the electric power to be supplied to the heater, and an electric power controlling circuit for controlling the electric power supplied to the heater in accordance with a detected temperature from the temperature detecting element and the control wave number set by the control wave number setting circuit.

Abstract: A supplemental controller for a fiber glass bushing actively performs heating and cooling of a connected segment of the bushing which is otherwise controlled by a primary controller. In one embodiment, the supplemental controller performs heating by means of current injection into a connected bushing segment and cooling by means of current diversion from or around the connected bushing segment. Initial start-up and balancing operations can be performed without activation of the supplemental controller. In another embodiment of the invention, the supplemental controller heats a bushing segment by injecting current in-phase with current from the primary bushing controller and cools the bushing segment by injecting current out-of-phase with current from the primary bushing controller.

Abstract: A heater having selective power rating includes a source of electric current, at least one heating unit and at least one electric conductor having an input and an output. Each conductor is permanently fixed at its input and its output so that the conductor is in electric communication with the source. Each conductor is in one of two states. In a conducting state, the conductor is electrically continuous between its input and its output. In a nonconducting state, the conductor is severed between its input and its output. A first conductor is disposed with respect to the source and a first heating unit so that the first heating unit operates at a power level that is dependent on the state of the first conductor. The source and the at least one heating unit are configured to produce one of a plurality of a desired power levels depending on the state of the first conductor.

Abstract: A steering wheel heating system (10) includes a modular controller (18) electrically connected to a heating element (12) and temperature sensor (20) disposed beneath the surface of a rim portion (14) of a steering wheel (16). Controller (18) includes a cabin temperature sensor (26), a remote control receiver (30), a temperature adjustment control (34), and an on/off/reset switch (36). Steering wheel heating system (10) receives electric current from power system (42) and allows this current to pass through heating element (12) to heat steering wheel (16). Controller (18) controls the flow of current to heating element (12) using control inputs from one or more of steering wheel temperature sensor (20), cabin temperature sensor (26), temperature adjustment control (34), and vehicle climate control system (44). A timing module automatically shuts off the flow of current after a predetermined period of time.

Abstract: A heater control device that prevents a flickering by driving a fixing heater in a phase controlling at a fixed phase angle for predetermined duration when an image forming apparatus starts power supplying to the fixing heater.

Abstract: Due to a bimetallic contact point, a fine control is out of sight. Further, dispersion of bimetal characteristics and poor durability of a contact point cause problems, particularly in maintenance work. In order to overcome these problems, a controller for extending a service life of the contact point can provide a fine control, so that a maintenance-free electric cooker can be provided. The ON/OFF of the contact point of relay is controlled to operate at zero potential of commercial power, and a short-pulse-signal-switch that allows the relays to remove deposition by itself even if the contact point encounters deposition, are prepared and applied to plural heaters for controlling thereof.

Abstract: Apparatus is described for controlling an electric heater incorporating at least one electric heating element (2A, 2B, 2C) and energized from a single voltage alternating current supply (8). The apparatus includes a control knob (15) for manually selecting any one of a predetermined number of power settings for the heater from the voltage supply (8), the power settings varying progressively between a minimum power setting and a maximum power setting. The apparatus further includes a controller (10) adapted and arranged to supply to the electric heater within a predetermined constant time interval in each power setting a first dissipated power level and a second dissipated power level. The first dissipated power level comprises a first selected proportion of half cycles in a predetermined number of half cycles of the voltage supply and the second dissipated power level comprises a second selected proportion of half cycles in a predetermined number of half cycles of the voltage supply.

Abstract: The present invention provides a method of determining the boil states of a liquid as measured by an acoustic sensor which measures the acoustic signal generated by the liquid as it is heated. The acoustic signal is smoothed and a first derivative of the acoustic signal is calculated. Also the frequency of the acoustic signal is measured. Derivative inflection points, zero slope points, and acoustic signal frequencies are utilized to determine the pre-simmer, simmer, pre-boil, boil, boil dry, and boil over states of the liquid.

Abstract: An improved control method is provided that combines conventional ON-OFF control and conventional phase-angle control to reduce the AC inrush current to an electrical load, such as a tungsten halogen lamp used as a heating element in a laser printer, so that the power control circuit can satisfy both the European flicker and European harmonic requirements. Phase-angle control is applied to the load for a very short time period when it is initially energized, then the control circuit quickly switches from phase-angle control to standard ON-OFF control to reduce the harmonics generated by conventional phase-angle control methodologies. The electrical load exhibits three possible states: power full OFF, power ramp-up, and power full ON. During the power ramp-up state, power supplied to the load is adjusted by delaying the phase angle of the firing pulse relative to the start of each AC half cycle.

Abstract: A power factor correction system includes a sensing device in communication with a power supply to measure the line voltage on conventional service lines and detect any voltage fluxuations. A temperature controller receives power from the service lines and supplies an output voltage, based on the line voltage input, to one or more resistive loads, such as heater members. The heater members in turn are used to keep material in a molding device in a molten condition and within a certain temperature range. Fluctuations in the line voltage are detected by the sensing device which prevents corresponding changes in the voltage supplied to the resistive loads from the temperature controller.

Abstract: An electric clothes iron with circuitry for automatically disabling power to the iron when the iron is left unattended for a certain period of time. The circuitry includes a circuit for controlling two timing periods, one for controlling the shut off when the iron is in the horizontal position, and one for controlling the shut off when the iron is in the vertical position. When the user grasps the handle of the iron, the timing circuits are disabled. However, once the user removes his hand from the iron, one of the two timer periods starts to expire. If the timer reaches its prescribed limit before the handle is again grasped, the iron will automatically shut off. If the user grasps the iron during the timing process, the timer will be disabled, and will start the counting from zero the next time the hand is removed from the handled.

Abstract: A control device includes both a heating element and a temperature sensor. The control device has the form of a Wheatstone bridge which applies sensing current to the heating element. When the bridge is unbalanced, the control device may apply heating current to the heating element. In one embodiment, the sensing current is switched, so that it flows only for a relatively small part of the electrical cycle. The circuit also includes a provision for reduction or elimination of electrical spikes. The circuit further includes a calibration arrangement, which enables the user to adjust the bridge without passing heating current through the heating element. Another feature of the invention enables the set point of the bridge to be remotely controlled, by adjusting a level of analog current applied to the bridge. The circuit also includes an arrangement for compensating for temperature-induced changes in its components.

Abstract: An aquarium water temperature controller, which includes a glass casing, an inner tube mounted within the glass casing, an electric heating element mounted in the glass casing and connected to the inner tube, and a circuit board mounted in the inner tube and electrically connected to the electric heating element, wherein the circuit board includes a bridge circuit having a thermistor, a comparator circuit controlled by the bridge circuit to output high/low potential subject to temperature detecting status of the thermistor, a bias voltage generating circuit connected to the bridge circuit and the comparator circuit, an analog switching circuit controlled by the bias voltage generating circuit, a thyristor, and a voltage following circuit and an integrating circuit controlled by the analog switching circuit to turn on the thyristor when the bridge circuit outputs low potential, or to turn off the thyristor when the bridge circuit outputs high potential.

Abstract: The present invention relates to driving of a heater of a fixing unit in an image process apparatus. In case of driving first and second heaters by using a constant voltage output control circuit, when the first or second heater is switched from an ON state to an OFF state, an operation of the constant voltage output control circuit is stopped, thereby preventing destruction of circuit elements. Also, when the first heater is in the ON state and the second heater is switched from the OFF state to the ON state, the operation of the constant voltage output control circuit is stopped.

Abstract: The invention relates to a system for reducing radial leaks in an air heater for thermal equipment, the heater being of the type including a rotor fitted with a plurality of heater elements supported by diaphragms, a stator constituted by a leakproof metal case, and radial sealing means including hinged sector plates positioned over the heater elements together with radial gaskets provided on the diaphragms.

Abstract: A heater assembly for use with spas, hot tubs and the like, includes a control circuit which controls the application of electrical power to the heater. A control circuit controls application of power to the heater in response to a thermostat setting, the flow of water in the spa system and in response to a high limit temperature. When the high limit temperature is exceeded, electrical power to the heater is removed. Electrical power to the heater cannot be restored until power to the entire system is turned off and then back on. The control circuit is mounted on the heater and includes spring-loaded standoffs which maintain the temperature sensors in good thermal contact with the body of the heater.